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syslog-ng Premium Edition 6.0.18 - Administration Guide

Preface Chapter 1. Introduction to syslog-ng Chapter 2. The concepts of syslog-ng Chapter 3. Installing syslog-ng Chapter 4. The syslog-ng PE quick-start guide Chapter 5. The syslog-ng PE configuration file Chapter 6. Collecting log messages — sources and source drivers Chapter 7. Sending and storing log messages — destinations and destination drivers Chapter 8. Routing messages: log paths, reliability, and filters Chapter 9. Global options of syslog-ng PE Chapter 10. TLS-encrypted message transfer Chapter 11. FIPS-compliant syslog-ng Chapter 12.  Reliable Log Transfer Protocol™ Chapter 13. Reliability and minimizing the loss of log messages Chapter 14. Manipulating messages Chapter 15. Parsing and segmenting structured messages Chapter 16. Processing message content with a pattern database Chapter 17. Statistics and metrics of syslog-ng Chapter 18. Multithreading and scaling in syslog-ng PE Chapter 19. Troubleshooting syslog-ng Chapter 20. Best practices and examples

Collecting internal messages

All messages generated internally by syslog-ng use this special source. To collect warnings, errors and notices from syslog-ng itself, include this source in one of your source statements.

internal()

The syslog-ng application will issue a warning upon startup if none of the defined log paths reference this driver.

Example 6.6. Using the internal() driver

source s_local { internal(); };

The syslog-ng PE application sends the following message types from the internal() source: 

  • fatal: Priority value: critical (2), Facility value: syslog (5)

  • error: Priority value: error (3), Facility value: syslog (5)

  • warning: Priority value: warning (4), Facility value: syslog (5)

  • notice: Priority value: notice (5), Facility value: syslog (5)

  • info: Priority value: info (6), Facility value: syslog (5)

internal() source options

The internal() driver has the following options:

host-override()
Type: string
Default:

Description: Replaces the ${HOST} part of the message with the parameter string.

log-iw-size()
Type: number (messages)
Default: 1000

Description: The size of the initial window, this value is used during flow control. If the max-connections() option is set, the log-iw-size() will be divided by the number of connections, otherwise log-iw-size() is divided by 10 (the default value of the max-connections() option). The resulting number is the initial window size of each connection. For optimal performance when receiving messages from syslog-ng PE clients, make sure that the window size is larger than the flush-lines() option set in the destination of your clients.

Example 6.7. Initial window size of a connection

If log-iw-size(1000) and max-connections(10), then each connection will have an initial window size of 100.


normalize-hostnames()
Accepted values: yes | no
Default: no

Description: If enabled (normalize-hostnames(yes)), syslog-ng PE converts the hostnames to lowercase.

program-override()
Type: string
Default:

Description: Replaces the ${PROGRAM} part of the message with the parameter string. For example, to mark every message coming from the kernel, include the program-override("kernel") option in the source containing /proc/kmsg.

tags()
Type: string
Default:

Description: Label the messages received from the source with custom tags. Tags must be unique, and enclosed between double quotes. When adding multiple tags, separate them with comma, for example tags("dmz", "router"). This option is available only in syslog-ng 3.1 and later.

use-fqdn()
Type: yes or no
Default: no

Description: Add Fully Qualified Domain Name instead of short hostname. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

use-syslogng-pid()
Type: yes or no
Default: no

Description: If the value of this option is yes, then the PID value of the message will be overridden with the PID of the running syslog-ng process.

Collecting messages from text files

Collects log messages from plain-text files, for example from the logfiles of an Apache webserver.

The syslog-ng application notices if a file is renamed or replaced with a new file, so it can correctly follow the file even if logrotation is used. When syslog-ng is restarted, it records the position of the last sent log message in the /opt/syslog-ng/var/syslog-ng.persist file, and continues to send messages from this position after the restart.

The file driver has a single required parameter specifying the file to open. For the list of available optional parameters, see the section called “file() source options”.

Caution:

Hazard of data loss! If your log files are on an NFS-mounted network file system, see the section called “NFS file system for log files”.

Declaration: 

file("filename");

Example 6.8. Using the file() driver

source s_file { file("/var/log/messages"); };

Example 6.9. Tailing files

The following source checks the access.log file every second for new messages.

source s_tail { file("/var/log/apache/access.log"
            follow-freq(1) flags(no-parse)); };

NOTE:

If the message does not have a proper syslog header, syslog-ng treats messages received from files as sent by the kern facility. Use the default-facility() and default-priority() options in the source definition to assign a different facility if needed.

Wildcards and file sources. 

In syslog-ng PE, the filename (but not the pathname) may include wildcard characters (for example *). Note that when using wildcards in filenames, always set how often syslog-ng PE should check the file for new messages using the follow-freq() parameter.

Caution:

If you use wildcards in multiple file sources, make sure that the files and folders that match the wildcards do not overlap. That is, every file and folder should belong to only one file source. Monitoring a file from multiple wildcard sources can lead to data loss.

To use wildcards in the file source if your log files are on an NFS file system, set the force-directory-polling() option to yes to detect newly created files. Note that wildcard file sources are available only in syslog-ng PE version 6.0.3 and newer versions of the 6.x branch, and are not yet available in syslog-ng PE version 7.

When using wildcards, syslog-ng PE monitors every matching file, and can receive new log messages from any of the files. However, monitoring (polling) many files (that is, more than ten) has a significant overhead and may affect performance. On Linux this overhead is not so significant, because syslog-ng PE uses the inotify feature of the kernel.

Also, by default, the operating system notifies syslog-ng PE when an application modifies a logfile. However, in some cases this does not happen, because the file-monitoring API of the operating system does not notice that the file has changed. In such cases, enable the force-directory-polling() option. Note that enabling this option decreases the performance of syslog-ng PE if you monitor lots of logfiles.

Example 6.10. Using wildcards in the filename

The following example monitors every file with the .log extension in the /var/application directory for log messages. Note that only syslog-ng PE supports wildcards in the file and pathnames.

source s_file { file("/var/application/*.log" follow-freq(1));};

Notes on reading kernel messages

Note the following points when reading kernel messages on various platforms.

  • The kernel usually sends log messages to a special file (/dev/kmsg on BSDs, /proc/kmsg on Linux). The file() driver reads log messages from such files. The syslog-ng application can periodically check the file for new log messages if the follow-freq() option is set.

  • On Linux, the klogd daemon can be used in addition to syslog-ng to read kernel messages and forward them to syslog-ng. klogd used to preprocess kernel messages to resolve symbols and so on, but as this is deprecated by ksymoops there is really no point in running both klogd and syslog-ng in parallel. Also note that running two processes reading /proc/kmsg at the same time might result in dead-locks.

  • When using syslog-ng to read messages from the /proc/kmsg file, syslog-ng automatically disables the follow-freq() parameter to avoid blocking the file.

  • To read the kernel messages on HP-UX platforms, use the following options in the source statement:

    file("/dev/klog" program-override("kernel") flags(kernel) follow-freq(0));

File sources and the RFC5424 message format

When reading messages from a file and forwarding them in IETF-syslog (RFC5424) format, syslog-ng PE automatically adds all file-related information to the file@18372.4 SDATA block. When the source is file and the transport protocol is syslog or syslog-protocol flags were used in the destination side, the message will contain the following source file-related information:

  • size: size of the file

  • position: file position the message was read from

  • name: name of the file

Example 6.11. File-related information in message

309 <38>1 2010-10-19T15:50:45.018203+02:00 server1 localprg 1234 - [timeQuality isSynced="0" tzKnown="0"][file@18372.4 size="184567" pos="1024" name="/var/tmp/msg.txt"] seq: 0000000001, runid: 1287496244, stamp: 2010-10-19T15:50:45 messagetext


file() source options

The file() driver has the following options:

default-facility()
Type: facility string
Default: kern

Description: This parameter assigns a facility value to the messages received from the file source, if the message does not specify one.

default-priority()
Type: priority string
Default:

Description: This parameter assigns an emergency level to the messages received from the file source, if the message does not specify one. For example, default-priority(warning)

encoding()
Type: string
Default:

Description: Specifies the characterset (encoding, for example UTF-8) of messages using the legacy BSD-syslog protocol. To list the available character sets on a host, execute the iconv -l command. For details on how encoding affects the size of the message, see the section called “Message size and encoding”.

flags()
Type: assume-utf8, empty-lines, expect-hostname, kernel, no-multi-line, no-parse, dont-store-legacy-msghdr, syslog-protocol, validate-utf8
Default: empty set

Description: Specifies the log parsing options of the source.

  • assume-utf8: The assume-utf8 flag assumes that the incoming messages are UTF-8 encoded, but does not verify the encoding. If you explicitly want to validate the UTF-8 encoding of the incoming message, use the validate-utf8 flag.

  • dont-store-legacy-msghdr: By default, syslog-ng stores the original incoming header of the log message. This is useful of the original format of a non-syslog-compliant message must be retained (syslog-ng automatically corrects minor header errors, for example, adds a whitespace before msg in the following message: Jan 22 10:06:11 host program:msg). If you do not want to store the original header of the message, enable the dont-store-legacy-msghdr flag.

  • empty-lines: Use the empty-lines flag to keep the empty lines of the messages. By default, syslog-ng PE removes empty lines automatically.

  • expect-hostname: If the expect-hostname flag is enabled, syslog-ng PE will assume that the log message contains a hostname and parse the message accordingly. This is the default behavior for TCP sources. Note that pipe sources use the no-hostname flag by default.

  • kernel: The kernel flag makes the source default to the LOG_KERN | LOG_NOTICE priority if not specified otherwise.

  • no-hostname: Enable the no-hostname flag if the log message does not include the hostname of the sender host. That way syslog-ng PE assumes that the first part of the message header is ${PROGRAM} instead of ${HOST}. For example:

    source s_dell { network(port(2000) flags(no-hostname)); };
  • no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line. Note that this happens only if the underlying transport method actually supports multi-line messages. Currently the rltp, syslog(), network(), unix-dgram() drivers support multi-line messages.

  • no-parse: By default, syslog-ng PE parses incoming messages as syslog messages. The no-parse flag completely disables syslog message parsing and processes the complete line as the message part of a syslog message. The syslog-ng PE application will generate a new syslog header (timestamp, host, and so on) automatically and put the entire incoming message into the MSG part of the syslog message. This flag is useful for parsing messages not complying to the syslog format.

    If you are using the flags(no-parse) option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, syslog-ng PE generates a new syslog header (timestamp, host, and so on) automatically. Note that since flags(no-parse) disables message parsing, it interferes with other flags, for example, disables flags(no-multi-line).

  • syslog-protocol: The syslog-protocol flag specifies that incoming messages are expected to be formatted according to the new IETF syslog protocol standard (RFC5424), but without the frame header. Note that this flag is not needed for the syslog driver, which handles only messages that have a frame header.

  • validate-utf8: The validate-utf8 flag enables encoding-verification for messages formatted according to the new IETF syslog standard (for details, see the section called “IETF-syslog messages”). If theBOM[4]character is missing, but the message is otherwise UTF-8 compliant, syslog-ng automatically adds the BOM character to the message.

follow-freq()
Type: number (seconds)
Default: 1

Description: Indicates that the source should be checked periodically. This is useful for files which always indicate readability, even though no new lines were appended. If this value is higher than zero, syslog-ng will not attempt to use poll() on the file, but checks whether the file changed every time the follow-freq() interval (in seconds) has elapsed. Floating-point numbers (for example 1.5) can be used as well.

force-directory-polling()
Type: yes or no
Default: no

Description: Specifies whether syslog-ng should force the polling of the logfiles that match the wildcarded filenames specified in the file() driver.

NOTE:

Enabling this option decreases performance if you monitor lots of logfiles.

To use wildcards in the file source if your log files are on an NFS file system, set the force-directory-polling() option to yes to detect newly created files. Note that wildcard file sources are available only in syslog-ng PE version 6.0.3 and newer versions of the 6.x branch, and are not yet available in syslog-ng PE version 7.

keep-timestamp()
Type: yes or no
Default: yes

Description: Specifies whether syslog-ng should accept the timestamp received from the sending application or client. If disabled, the time of reception will be used instead. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

Caution:

To use the S_ macros, the keep-timestamp() option must be enabled (this is the default behavior of syslog-ng PE).

log-fetch-limit()
Type: number (messages)
Default: 10

Description: The maximum number of messages fetched from a source during a single poll loop. The destination queues might fill up before flow-control could stop reading if log-fetch-limit() is too high.

log-iw-size()
Type: number
Default: 1000

Description: The size of the initial window, this value is used during flow control. Make sure that log-iw-size() is larger than the value of log-fetch-limit().

When using wildcards in the filenames, syslog-ng PE attempts to read log-fetch-limit() number of messages from each file. For optimal performance, make sure that log-iw-size() is greater than log-fetch-limit()*(the-number-of-matching-files).

Example 6.12. Initial window size of file sources

If log-fetch-limit() is 10, and your wildcard file source has 200 files, then log-iw-size() should be at least 2000.


log-msg-size()
Type: number (bytes)
Default: Use the global log-msg-size() option, which defaults to 65535.

Description: Specifies the maximum length of incoming log messages. Uses the value of the global option if not specified. For details on how encoding affects the size of the message, see the section called “Message size and encoding”.

log-prefix() (DEPRECATED)
Type: string
Default:

Description: A string added to the beginning of every log message. It can be used to add an arbitrary string to any log source, though it is most commonly used for adding kernel: to the kernel messages on Linux. NOTE: This option is deprecated. Use program-override() instead.

multi-line-garbage()
Type: regular expression
Default: empty string

Description: Use the multi-line-garbage() option when processing multi-line messages that contain unneeded parts between the messages. Specify a string or regular expression that matches the beginning of the unneeded message parts. If the multi-line-garbage() option is set, syslog-ng PE ignores the lines between the line matching the multi-line-garbage() and the next line matching multi-line-prefix(). See also the multi-line-prefix() option.

When receiving multi-line messages from a source when the multi-line-garbage() option is set, but no matching line is received between two lines that match multi-line-prefix(), syslog-ng PE will continue to process the incoming lines as a single message until a line matching multi-line-garbage() is received.

Caution:

If the multi-line-garbage() option is set, syslog-ng PE discards lines between the line matching the multi-line-garbage() and the next line matching multi-line-prefix().

NOTE:

Starting with syslog-ng PE version 3.2.1, a message is considered complete if no new lines arrive to the message for 10 seconds, even if no line matching the multi-line-garbage() option is received.

multi-line-prefix()
Type: regular expression
Default: empty string

Description: Use the multi-line-prefix() option to process multi-line messages, that is, log messages that contain newline characters (for example, Tomcat logs). Specify a string or regular expression that matches the beginning of the log messages. Use as simple regular expressions as possible, because complex regular expressions can severely reduce the rate of processing multi-line messages. If the multi-line-prefix() option is set, syslog-ng PE ignores newline characters from the source until a line matches the regular expression again, and treats the lines between the matching lines as a single message. See also the multi-line-garbage() option.

NOTE:

Starting with syslog-ng PE version 3.2.1, a message is considered complete if no new lines arrive to the message for 10 seconds, even if no line matching the multi-line-garbage() option is received.

TIP:
  • To make multi-line messages more readable when written to a file, use a template in the destination and instead of the ${MESSAGE} macro, use the following: $(indent-multi-line ${MESSAGE}). This expression inserts a tab after every newline character (except when a tab is already present), indenting every line of the message after the first. For example:

    destination d_file {
        file ("/var/log/messages"
            template("${ISODATE} ${HOST} $(indent-multi-line ${MESSAGE})\n") );
    };

    For details on using templates, see the section called “Templates and macros”.

  • To actually convert the lines of multi-line messages to single line (by replacing the newline characters with whitespaces), use the flags(no-multi-line) option in the source.

Example 6.13. Processing Tomcat logs

The log messages of the Apache Tomcat server are a typical example for multi-line log messages. The messages start with the date and time of the query in the YYYY.MM.DD HH:MM:SS format, as you can see in the following example.

2010.06.09. 12:07:39 org.apache.catalina.startup.Catalina start
SEVERE: Catalina.start:
LifecycleException:  service.getName(): "Catalina";  Protocol handler start failed: java.net.BindException: Address already in use<null>:8080
       at org.apache.catalina.connector.Connector.start(Connector.java:1138)
       at org.apache.catalina.core.StandardService.start(StandardService.java:531)
       at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
       at org.apache.catalina.startup.Catalina.start(Catalina.java:583)
       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
       at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
       at java.lang.reflect.Method.invoke(Method.java:597)
       at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
       at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
       at java.lang.reflect.Method.invoke(Method.java:597)
       at org.apache.commons.daemon.support.DaemonLoader.start(DaemonLoader.java:177)
2010.06.09. 12:07:39 org.apache.catalina.startup.Catalina start
INFO: Server startup in 1206 ms
2010.06.09. 12:45:08 org.apache.coyote.http11.Http11Protocol pause
INFO: Pausing Coyote HTTP/1.1 on http-8080
2010.06.09. 12:45:09 org.apache.catalina.core.StandardService stop
INFO: Stopping service Catalina

To process these messages, specify a regular expression matching the timestamp of the messages in the multi-line-prefix() option. Such an expression is the following:

source s_file{ file("/var/log/tomcat6/catalina.2010-06-09.log" follow-freq(0) multi-line-prefix("[0-9]{4}\.[0-9]{2}\.[0-9]{2}\.") flags(no-parse));
};

Note that the flags(no-parse) is needed to avoid syslog-ng PE trying to interpret the date in the message.

pad-size()
Type: number (bytes)
Default: 0

Description: Specifies input padding. Some operating systems (such as HP-UX) pad all messages to block boundary. This option can be used to specify the block size. (HP-UX uses 2048 bytes). The syslog-ng PE application will pad reads from the associated device to the number of bytes set in pad-size(). Mostly used on HP-UX where /dev/log is a named pipe and every write is padded to 2048 bytes. If pad-size() was given and the incoming message does not fit into pad-size(), syslog-ng will not read anymore from this pipe and displays the following error message:

Padding was set, and couldn't read enough bytes
program-override()
Type: string
Default:

Description: Replaces the ${PROGRAM} part of the message with the parameter string. For example, to mark every message coming from the kernel, include the program-override("kernel") option in the source containing /proc/kmsg.

read-old-records()
Type: yes|no
Default: yes

Description: If set to yes, syslog-ng PE will start reading the records from the beginning of the file, if the file has not been read yet. If set to no, syslog-ng PE will read only the new records. If the source has a state in the persist file, this option will have no effect.

recursive

Type: yes or no
Default: no

Description: When enabled, syslog-ng PE monitors every subdirectory of the directory set in the path of the file parameter, and reads log messages from files with the set filename. The recursive option can be used together with wildcards in the filename.

Example 6.14. Monitoring multiple directories

The following example reads files having the .log extension from the /var/application/ directory and its subdirectories. Note that only syslog-ng PE supports recursive directory handling and wildcards in the file and pathnames.

source s_file_subdirectories { file("/var/application/*.log"
                    recursive(yes)
                    follow-freq(1)
                    log-fetch-limit(100)
                    );};

replace-null-characters()
Type: yes|no
Default: no

Description: If set to yes, syslog-ng PE replaces the '\0' characters in the file input data with spaces ' '. Available in version 6.0.8 and later.

tags()
Type: string
Default:

Description: Label the messages received from the source with custom tags. Tags must be unique, and enclosed between double quotes. When adding multiple tags, separate them with comma, for example tags("dmz", "router"). This option is available only in syslog-ng 3.1 and later.

time-zone()
Type: name of the timezone, or the timezone offset
Default:

Description: The default timezone for messages read from the source. Applies only if no timezone is specified within the message itself.

The timezone can be specified as using the name of the (for example time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format (for example +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.

use-syslogng-pid()
Type: yes or no
Default: no

Description: If the value of this option is yes, then the PID value of the message will be overridden with the PID of the running syslog-ng process.



[4] The byte order mark (BOM) is a Unicode character used to signal the byte-order of the message text.

Collecting messages using the RFC3164 protocol (network() driver)

The network() source driver can receive syslog messages conforming to RFC3164 from the network using the TCP, TLS, and UDP networking protocols.

You can use the RLTP™ protocol as well. For details about the RLTP™ protocol, see Chapter 12, Reliable Log Transfer Protocol.

  • UDP is a simple datagram oriented protocol, which provides "best effort service" to transfer messages between hosts. It may lose messages, and no attempt is made to retransmit lost messages. The BSD-syslog protocol traditionally uses UDP.

    Use UDP only if you have no other choice.

    For details on minimizing message loss when using UDP, see Collecting log messages from UDP sources.

  • TCP provides connection-oriented service: the client and the server establish a connection, each message is acknowledged, and lost packets are resent. TCP can detect lost connections, and messages are lost, only if the TCP connection breaks. When a TCP connection is broken, messages that the client has sent but were not yet received on the server are lost.

  • The syslog-ng application supports TLS (Transport Layer Security, also known as SSL) over TCP. For details, see the section called “Encrypting log messages with TLS”.

When you send your log messages from a syslog-ng PE client through the network to a syslog-ng PE server, you can use different protocols and options. Every combination has its advantages and disadvantages. The most important thing is to use matching protocols and options, so the server handles the incoming log messages properly. For details, see the section called “Things to consider when forwarding messages between syslog-ng PE hosts”.

Declaration: 

network([options]);

By default, the network() driver binds to 0.0.0.0, meaning that it listens on every available IPV4 interface on the TCP/601 port. To limit accepted connections to only one interface, use the localip() parameter. To listen on IPv6 addresses, use the ip-protocol(6) option.

Example 6.15. Using the network() driver

Using only the default settings: listen on every available IPV4 interface on the TCP/601 port.

source s_network {
    network();
};

UDP source listening on 192.168.1.1 (the default port for UDP is 514):

source s_network {
    network(
        ip("192.168.1.1")
        transport("udp")
    );
};

TCP source listening on the IPv6 localhost, port 2222:

source s_network6 {
    network(
        ip("::1")
        transport("tcp")
        port(2222)
        ip-protocol(6)
    );
};

A TCP source listening on a TLS-encrypted channel.

source s_network {
    network(
        transport("tcp")
        port(2222)
        tls(peer-verify("required-trusted")
            key-file("/opt/syslog-ng/etc/syslog-ng/syslog-ng.key")
            cert-file("/opt/syslog-ng/etc/syslog-ng/syslog-ng.crt")
            );
    );
};

A TCP source listening for messages using the IETF-syslog message format. Note that for transferring IETF-syslog messages, generally you are recommended to use the syslog() driver on both the client and the server, as it uses both the IETF-syslog message format and the protocol. For details, see the section called “Collecting messages using the IETF syslog protocol (syslog() driver)”.

source s_tcp_syslog {
    network(
        ip("127.0.0.1")
        flags(syslog-protocol)
    );
};

For details on the options of the network() source, see the section called “network() source options”.

network() source options

The network() driver has the following options.

encoding()
Type: string
Default:

Description: Specifies the characterset (encoding, for example UTF-8) of messages using the legacy BSD-syslog protocol. To list the available character sets on a host, execute the iconv -l command. For details on how encoding affects the size of the message, see the section called “Message size and encoding”.

flags()
Type: assume-utf8, empty-lines, expect-hostname, kernel, no-multi-line, no-parse, dont-store-legacy-msghdr, syslog-protocol, validate-utf8
Default: empty set

Description: Specifies the log parsing options of the source.

  • assume-utf8: The assume-utf8 flag assumes that the incoming messages are UTF-8 encoded, but does not verify the encoding. If you explicitly want to validate the UTF-8 encoding of the incoming message, use the validate-utf8 flag.

  • dont-store-legacy-msghdr: By default, syslog-ng stores the original incoming header of the log message. This is useful of the original format of a non-syslog-compliant message must be retained (syslog-ng automatically corrects minor header errors, for example, adds a whitespace before msg in the following message: Jan 22 10:06:11 host program:msg). If you do not want to store the original header of the message, enable the dont-store-legacy-msghdr flag.

  • empty-lines: Use the empty-lines flag to keep the empty lines of the messages. By default, syslog-ng PE removes empty lines automatically.

  • expect-hostname: If the expect-hostname flag is enabled, syslog-ng PE will assume that the log message contains a hostname and parse the message accordingly. This is the default behavior for TCP sources. Note that pipe sources use the no-hostname flag by default.

  • kernel: The kernel flag makes the source default to the LOG_KERN | LOG_NOTICE priority if not specified otherwise.

  • no-hostname: Enable the no-hostname flag if the log message does not include the hostname of the sender host. That way syslog-ng PE assumes that the first part of the message header is ${PROGRAM} instead of ${HOST}. For example:

    source s_dell { network(port(2000) flags(no-hostname)); };
  • no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line. Note that this happens only if the underlying transport method actually supports multi-line messages. Currently the rltp, syslog(), network(), unix-dgram() drivers support multi-line messages.

  • no-parse: By default, syslog-ng PE parses incoming messages as syslog messages. The no-parse flag completely disables syslog message parsing and processes the complete line as the message part of a syslog message. The syslog-ng PE application will generate a new syslog header (timestamp, host, and so on) automatically and put the entire incoming message into the MSG part of the syslog message. This flag is useful for parsing messages not complying to the syslog format.

    If you are using the flags(no-parse) option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, syslog-ng PE generates a new syslog header (timestamp, host, and so on) automatically. Note that since flags(no-parse) disables message parsing, it interferes with other flags, for example, disables flags(no-multi-line).

  • syslog-protocol: The syslog-protocol flag specifies that incoming messages are expected to be formatted according to the new IETF syslog protocol standard (RFC5424), but without the frame header. Note that this flag is not needed for the syslog driver, which handles only messages that have a frame header.

  • validate-utf8: The validate-utf8 flag enables encoding-verification for messages formatted according to the new IETF syslog standard (for details, see the section called “IETF-syslog messages”). If theBOM[5]character is missing, but the message is otherwise UTF-8 compliant, syslog-ng automatically adds the BOM character to the message.

host-override()
Type: string
Default:

Description: Replaces the ${HOST} part of the message with the parameter string.

ip() or localip()
Type: string
Default: 0.0.0.0

Description: The IP address to bind to. By default, syslog-ng PE listens on every available interface. Note that this is not the address where messages are accepted from.

If you specify a multicast bind address and use the udp transport, syslog-ng PE automatically joins the necessary multicast group. TCP does not support multicasting.

ip-protocol()
Type: number (IP version)
Default: 4

Description: Determines the internet protocol version of the given driver (network() or syslog()). The possible values are 4 and 6, corresponding to IPv4 and IPv6. The default value is 4.

ip-tos()
Type: number (type of service)
Default: 0

Description: Specifies the Type-of-Service value of outgoing packets.

ip-ttl()
Type: number (hops)
Default: 0

Description: Specifies the Time-To-Live value of outgoing packets.

keep-alive()
Type: yes or no
Default: yes

Description: Specifies whether connections to sources should be closed when syslog-ng is forced to reload its configuration (upon the receipt of a SIGHUP signal). Note that this applies to the server (source) side of the syslog-ng connections, client-side (destination) connections are always reopened after receiving a HUP signal unless the keep-alive option is enabled for the destination.

keep-hostname()
Type: yes or no
Default: no

Description: Enable or disable hostname rewriting.

  • If enabled (keep-hostname(yes)), syslog-ng PE assumes that the incoming log message was sent by the host specified in the HOST field of the message.

  • If disabled (keep-hostname(no)), syslog-ng PE rewrites the HOST field of the message, either to the IP address (if the use-dns() parameter is set to no), or to the hostname (if the use-dns() parameter is set to yes and the IP address can be resolved to a hostname) of the host sending the message to syslog-ng PE. For details on using name resolution in syslog-ng PE, see the section called “Using name resolution in syslog-ng”.

NOTE:

If the log message does not contain a hostname in its HOST field, syslog-ng PE automatically adds a hostname to the message.

  • For messages received from the network, this hostname is the address of the host that sent the message (this means the address of the last hop if the message was transferred via a relay).

  • For messages received from the local host, syslog-ng PE adds the name of the host.

This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

NOTE:

When relaying messages, enable this option on the syslog-ng PE server and also on every relay, otherwise syslog-ng PE will treat incoming messages as if they were sent by the last relay.

keep-timestamp()
Type: yes or no
Default: yes

Description: Specifies whether syslog-ng should accept the timestamp received from the sending application or client. If disabled, the time of reception will be used instead. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

Caution:

To use the S_ macros, the keep-timestamp() option must be enabled (this is the default behavior of syslog-ng PE).

log-fetch-limit()
Type: number (messages)
Default: 10

Description: The maximum number of messages fetched from a source during a single poll loop. The destination queues might fill up before flow-control could stop reading if log-fetch-limit() is too high.

log-iw-size()
Type: number (messages)
Default: 1000

Description: The size of the initial window, this value is used during flow control. If the max-connections() option is set, the log-iw-size() will be divided by the number of connections, otherwise log-iw-size() is divided by 10 (the default value of the max-connections() option). The resulting number is the initial window size of each connection. For optimal performance when receiving messages from syslog-ng PE clients, make sure that the window size is larger than the flush-lines() option set in the destination of your clients.

Example 6.16. Initial window size of a connection

If log-iw-size(1000) and max-connections(10), then each connection will have an initial window size of 100.


log-msg-size()
Type: number (bytes)
Default: Use the global log-msg-size() option, which defaults to 65535.

Description: Specifies the maximum length of incoming log messages. Uses the value of the global option if not specified. For details on how encoding affects the size of the message, see the section called “Message size and encoding”.

max-connections()
Type: number (simultaneous connections)
Default: 10

Description: Specifies the maximum number of simultaneous connections.

multi-line-garbage()
Type: regular expression
Default: empty string

Description: Use the multi-line-garbage() option when processing multi-line messages that contain unneeded parts between the messages. Specify a string or regular expression that matches the beginning of the unneeded message parts. If the multi-line-garbage() option is set, syslog-ng PE ignores the lines between the line matching the multi-line-garbage() and the next line matching multi-line-prefix(). See also the multi-line-prefix() option.

When receiving multi-line messages from a source when the multi-line-garbage() option is set, but no matching line is received between two lines that match multi-line-prefix(), syslog-ng PE will continue to process the incoming lines as a single message until a line matching multi-line-garbage() is received.

Caution:

If the multi-line-garbage() option is set, syslog-ng PE discards lines between the line matching the multi-line-garbage() and the next line matching multi-line-prefix().

NOTE:

Starting with syslog-ng PE version 3.2.1, a message is considered complete if no new lines arrive to the message for 10 seconds, even if no line matching the multi-line-garbage() option is received.

multi-line-prefix()
Type: regular expression
Default: empty string

Description: Use the multi-line-prefix() option to process multi-line messages, that is, log messages that contain newline characters (for example, Tomcat logs). Specify a string or regular expression that matches the beginning of the log messages. Use as simple regular expressions as possible, because complex regular expressions can severely reduce the rate of processing multi-line messages. If the multi-line-prefix() option is set, syslog-ng PE ignores newline characters from the source until a line matches the regular expression again, and treats the lines between the matching lines as a single message. See also the multi-line-garbage() option.

NOTE:

Starting with syslog-ng PE version 3.2.1, a message is considered complete if no new lines arrive to the message for 10 seconds, even if no line matching the multi-line-garbage() option is received.

TIP:
  • To make multi-line messages more readable when written to a file, use a template in the destination and instead of the ${MESSAGE} macro, use the following: $(indent-multi-line ${MESSAGE}). This expression inserts a tab after every newline character (except when a tab is already present), indenting every line of the message after the first. For example:

    destination d_file {
        file ("/var/log/messages"
            template("${ISODATE} ${HOST} $(indent-multi-line ${MESSAGE})\n") );
    };

    For details on using templates, see the section called “Templates and macros”.

  • To actually convert the lines of multi-line messages to single line (by replacing the newline characters with whitespaces), use the flags(no-multi-line) option in the source.

Example 6.17. Processing Tomcat logs

The log messages of the Apache Tomcat server are a typical example for multi-line log messages. The messages start with the date and time of the query in the YYYY.MM.DD HH:MM:SS format, as you can see in the following example.

2010.06.09. 12:07:39 org.apache.catalina.startup.Catalina start
SEVERE: Catalina.start:
LifecycleException:  service.getName(): "Catalina";  Protocol handler start failed: java.net.BindException: Address already in use<null>:8080
       at org.apache.catalina.connector.Connector.start(Connector.java:1138)
       at org.apache.catalina.core.StandardService.start(StandardService.java:531)
       at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
       at org.apache.catalina.startup.Catalina.start(Catalina.java:583)
       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
       at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
       at java.lang.reflect.Method.invoke(Method.java:597)
       at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
       at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
       at java.lang.reflect.Method.invoke(Method.java:597)
       at org.apache.commons.daemon.support.DaemonLoader.start(DaemonLoader.java:177)
2010.06.09. 12:07:39 org.apache.catalina.startup.Catalina start
INFO: Server startup in 1206 ms
2010.06.09. 12:45:08 org.apache.coyote.http11.Http11Protocol pause
INFO: Pausing Coyote HTTP/1.1 on http-8080
2010.06.09. 12:45:09 org.apache.catalina.core.StandardService stop
INFO: Stopping service Catalina

To process these messages, specify a regular expression matching the timestamp of the messages in the multi-line-prefix() option. Such an expression is the following:

source s_file{ file("/var/log/tomcat6/catalina.2010-06-09.log" follow-freq(0) multi-line-prefix("[0-9]{4}\.[0-9]{2}\.[0-9]{2}\.") flags(no-parse));
};

Note that the flags(no-parse) is needed to avoid syslog-ng PE trying to interpret the date in the message.


Caution:

If you receive messages using the UDP protocol, do not use multi-line processing. If every line of a multi-line message is received in the same UDP packet, everything is fine, but if a multi-line message is fragmented into multiple UDP packets, the order they are received (thus the way how they are processed) cannot be guaranteed, and causes problems.

pad-size()
Type: number (bytes)
Default: 0

Description: Specifies input padding. Some operating systems (such as HP-UX) pad all messages to block boundary. This option can be used to specify the block size. (HP-UX uses 2048 bytes). The syslog-ng PE application will pad reads from the associated device to the number of bytes set in pad-size(). Mostly used on HP-UX where /dev/log is a named pipe and every write is padded to 2048 bytes. If pad-size() was given and the incoming message does not fit into pad-size(), syslog-ng will not read anymore from this pipe and displays the following error message:

Padding was set, and couldn't read enough bytes
port() or localport()
Type: number (port number)
Default:

In case of TCP transport: 601

In case of UDP transport: 514

Description: The port number to bind to.

program-override()
Type: string
Default:

Description: Replaces the ${PROGRAM} part of the message with the parameter string. For example, to mark every message coming from the kernel, include the program-override("kernel") option in the source containing /proc/kmsg.

so-broadcast()
Type: yes or no
Default: no

Description: This option controls the SO_BROADCAST socket option required to make syslog-ng send messages to a broadcast address. For details, see the socket(7) manual page.

so-keepalive()
Type: yes or no
Default: no

Description: Enables keep-alive messages, keeping the socket open. This only effects TCP and UNIX-stream sockets. For details, see the socket(7) manual page.

so-rcvbuf()
Type: number (bytes)
Default: 0

Description: Specifies the size of the socket receive buffer in bytes. For details, see the socket(7) manual page.

Caution:

When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the syslog-ng PE server or relay receiving the messages). Note that on certain platforms, for example, on Red Hat Enterprise Linux 5, even low message load (~200 messages per second) can result in message loss, unless the so-rcvbuf() option of the source is increased. In such cases, you will need to increase the net.core.rmem_max parameter of the host (for example, to 1024000), but do not modify net.core.rmem_default parameter.

As a general rule, increase the so-rcvbuf() so that the buffer size in kilobytes is higher than the rate of incoming messages per second. For example, to receive 2000 messages per second, set the so-rcvbuf() at least to 2 097 152 bytes.

so-sndbuf()
Type: number (bytes)
Default: 0

Description: Specifies the size of the socket send buffer in bytes. For details, see the socket(7) manual page.

tags()
Type: string
Default:

Description: Label the messages received from the source with custom tags. Tags must be unique, and enclosed between double quotes. When adding multiple tags, separate them with comma, for example tags("dmz", "router"). This option is available only in syslog-ng 3.1 and later.

time-zone()
Type: name of the timezone, or the timezone offset
Default:

Description: The default timezone for messages read from the source. Applies only if no timezone is specified within the message itself.

The timezone can be specified as using the name of the (for example time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format (for example +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.

transport()
Type: rltp, udp, tcp, or tls
Default: tcp

Description: Specifies the protocol used to receive messages from the source.

Caution:

When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the syslog-ng PE server or relay receiving the messages). Note that on certain platforms, for example, on Red Hat Enterprise Linux 5, even low message load (~200 messages per second) can result in message loss, unless the so-rcvbuf() option of the source is increased. In such cases, you will need to increase the net.core.rmem_max parameter of the host (for example, to 1024000), but do not modify net.core.rmem_default parameter.

As a general rule, increase the so-rcvbuf() so that the buffer size in kilobytes is higher than the rate of incoming messages per second. For example, to receive 2000 messages per second, set the so-rcvbuf() at least to 2 097 152 bytes.

tls()
Type: tls options
Default: n/a

Description: This option sets various options related to TLS encryption, for example, key/certificate files and trusted CA locations. TLS can be used only with tcp-based transport protocols. For details, see the section called “TLS options”.

use-dns()
Type: yes, no, persist_only
Default: yes

Description: Enable or disable DNS usage. The persist_only option attempts to resolve hostnames locally from file (for example from /etc/hosts). The syslog-ng PE application blocks on DNS queries, so enabling DNS may lead to a Denial of Service attack. To prevent DoS, protect your syslog-ng network endpoint with firewall rules, and make sure that all hosts which may get to syslog-ng are resolvable. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

NOTE:

This option has no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname.

use-fqdn()
Type: yes or no
Default: no

Description: Add Fully Qualified Domain Name instead of short hostname. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

NOTE:

This option has no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname.

use-syslogng-pid()
Type: yes or no
Default: no

Description: If the value of this option is yes, then the PID value of the message will be overridden with the PID of the running syslog-ng process.



[5] The byte order mark (BOM) is a Unicode character used to signal the byte-order of the message text.

Collecting messages from named pipes

The pipe driver opens a named pipe with the specified name and listens for messages. It is used as the native message delivery protocol on HP-UX.

The pipe driver has a single required parameter, specifying the filename of the pipe to open. For the list of available optional parameters, see the section called “pipe() source options”.

Declaration: 

pipe(filename);

NOTE:

As of syslog-ng Open Source Edition 3.0.2, pipes are created automatically. In earlier versions, you had to create the pipe using the mkfifo(1) command.

Pipe is very similar to the file() driver, but there are a few differences, for example pipe() opens its argument in read-write mode, therefore it is not recommended to be used on special files like /proc/kmsg.

Caution:
  • It is not recommended to use pipe() on anything else than real pipes.

  • By default, syslog-ng PE uses the flags(no-hostname) option for pipes, meaning that syslog-ng PE assumes that the log messages received from the pipe do not contain the hostname field. If your messages do contain the hostname field, use flags(expect-hostname). For details, see the section called “flags()”.

Example 6.18. Using the pipe() driver

source s_pipe { pipe("/dev/pipe" pad-size(2048)); };

pipe() source options

The pipe driver has the following options:

flags()
Type: assume-utf8, empty-lines, expect-hostname, kernel, no-multi-line, no-parse, dont-store-legacy-msghdr, syslog-protocol, validate-utf8
Default: empty set

Description: Specifies the log parsing options of the source.

  • assume-utf8: The assume-utf8 flag assumes that the incoming messages are UTF-8 encoded, but does not verify the encoding. If you explicitly want to validate the UTF-8 encoding of the incoming message, use the validate-utf8 flag.

  • dont-store-legacy-msghdr: By default, syslog-ng stores the original incoming header of the log message. This is useful of the original format of a non-syslog-compliant message must be retained (syslog-ng automatically corrects minor header errors, for example, adds a whitespace before msg in the following message: Jan 22 10:06:11 host program:msg). If you do not want to store the original header of the message, enable the dont-store-legacy-msghdr flag.

  • empty-lines: Use the empty-lines flag to keep the empty lines of the messages. By default, syslog-ng PE removes empty lines automatically.

  • expect-hostname: If the expect-hostname flag is enabled, syslog-ng PE will assume that the log message contains a hostname and parse the message accordingly. This is the default behavior for TCP sources. Note that pipe sources use the no-hostname flag by default.

  • kernel: The kernel flag makes the source default to the LOG_KERN | LOG_NOTICE priority if not specified otherwise.

  • no-hostname: Enable the no-hostname flag if the log message does not include the hostname of the sender host. That way syslog-ng PE assumes that the first part of the message header is ${PROGRAM} instead of ${HOST}. For example:

    source s_dell { network(port(2000) flags(no-hostname)); };
  • no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line. Note that this happens only if the underlying transport method actually supports multi-line messages. Currently the rltp, syslog(), network(), unix-dgram() drivers support multi-line messages.

  • no-parse: By default, syslog-ng PE parses incoming messages as syslog messages. The no-parse flag completely disables syslog message parsing and processes the complete line as the message part of a syslog message. The syslog-ng PE application will generate a new syslog header (timestamp, host, and so on) automatically and put the entire incoming message into the MSG part of the syslog message. This flag is useful for parsing messages not complying to the syslog format.

    If you are using the flags(no-parse) option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, syslog-ng PE generates a new syslog header (timestamp, host, and so on) automatically. Note that since flags(no-parse) disables message parsing, it interferes with other flags, for example, disables flags(no-multi-line).

  • syslog-protocol: The syslog-protocol flag specifies that incoming messages are expected to be formatted according to the new IETF syslog protocol standard (RFC5424), but without the frame header. Note that this flag is not needed for the syslog driver, which handles only messages that have a frame header.

  • validate-utf8: The validate-utf8 flag enables encoding-verification for messages formatted according to the new IETF syslog standard (for details, see the section called “IETF-syslog messages”). If theBOM[6]character is missing, but the message is otherwise UTF-8 compliant, syslog-ng automatically adds the BOM character to the message.

follow-freq()
Type: number (seconds)
Default: 1

Description: Indicates that the source should be checked periodically. This is useful for files which always indicate readability, even though no new lines were appended. If this value is higher than zero, syslog-ng will not attempt to use poll() on the file, but checks whether the file changed every time the follow-freq() interval (in seconds) has elapsed. Floating-point numbers (for example 1.5) can be used as well.

keep-timestamp()
Type: yes or no
Default: yes

Description: Specifies whether syslog-ng should accept the timestamp received from the sending application or client. If disabled, the time of reception will be used instead. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

Caution:

To use the S_ macros, the keep-timestamp() option must be enabled (this is the default behavior of syslog-ng PE).

log-fetch-limit()
Type: number (messages)
Default: 10

Description: The maximum number of messages fetched from a source during a single poll loop. The destination queues might fill up before flow-control could stop reading if log-fetch-limit() is too high.

log-iw-size()
Type: number (messages)
Default: 1000

Description: The size of the initial window, this value is used during flow control. If the max-connections() option is set, the log-iw-size() will be divided by the number of connections, otherwise log-iw-size() is divided by 10 (the default value of the max-connections() option). The resulting number is the initial window size of each connection. For optimal performance when receiving messages from syslog-ng PE clients, make sure that the window size is larger than the flush-lines() option set in the destination of your clients.

Example 6.19. Initial window size of a connection

If log-iw-size(1000) and max-connections(10), then each connection will have an initial window size of 100.


log-msg-size()
Type: number (bytes)
Default: Use the global log-msg-size() option, which defaults to 65535.

Description: Specifies the maximum length of incoming log messages. Uses the value of the global option if not specified. For details on how encoding affects the size of the message, see the section called “Message size and encoding”.

log-prefix() (DEPRECATED)
Type: string
Default:

Description: A string added to the beginning of every log message. It can be used to add an arbitrary string to any log source, though it is most commonly used for adding kernel: to the kernel messages on Linux. NOTE: This option is deprecated. Use program-override() instead.

optional()
Type: yes or no
Default:

Description: Instruct syslog-ng to ignore the error if a specific source cannot be initialized. No other attempts to initialize the source will be made until the configuration is reloaded. This option currently applies to the pipe(), unix-dgram, and unix-stream drivers.

pad-size()
Type: number (bytes)
Default: 0

Description: Specifies input padding. Some operating systems (such as HP-UX) pad all messages to block boundary. This option can be used to specify the block size. (HP-UX uses 2048 bytes). The syslog-ng PE application will pad reads from the associated device to the number of bytes set in pad-size(). Mostly used on HP-UX where /dev/log is a named pipe and every write is padded to 2048 bytes. If pad-size() was given and the incoming message does not fit into pad-size(), syslog-ng will not read anymore from this pipe and displays the following error message:

Padding was set, and couldn't read enough bytes
pipe()
Type: filename with path
Default:

Description: The filename of the pipe to read messages from.

program-override()
Type: string
Default:

Description: Replaces the ${PROGRAM} part of the message with the parameter string. For example, to mark every message coming from the kernel, include the program-override("kernel") option in the source containing /proc/kmsg.

tags()
Type: string
Default:

Description: Label the messages received from the source with custom tags. Tags must be unique, and enclosed between double quotes. When adding multiple tags, separate them with comma, for example tags("dmz", "router"). This option is available only in syslog-ng 3.1 and later.

time-zone()
Type: name of the timezone, or the timezone offset
Default:

Description: The default timezone for messages read from the source. Applies only if no timezone is specified within the message itself.

The timezone can be specified as using the name of the (for example time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format (for example +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.

use-syslogng-pid()
Type: yes or no
Default: no

Description: If the value of this option is yes, then the PID value of the message will be overridden with the PID of the running syslog-ng process.



[6] The byte order mark (BOM) is a Unicode character used to signal the byte-order of the message text.

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