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”.
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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 6.9. 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)); };
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.
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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));};Note the following points when reading kernel messages on various platforms.
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The kernel usually sends log messages to a special file (
/dev/kmsgon BSDs,/proc/kmsgon Linux). Thefile()driver reads log messages from such files. The syslog-ng application can periodically check the file for new log messages if thefollow-freq()option is set. -
On Linux, the
klogddaemon can be used in addition to syslog-ng to read kernel messages and forward them to syslog-ng.klogdused to preprocess kernel messages to resolve symbols and so on, but as this is deprecated byksymoopsthere is really no point in running bothklogdand syslog-ng in parallel. Also note that running two processes reading/proc/kmsgat the same time might result in dead-locks. -
When using syslog-ng to read messages from the
/proc/kmsgfile, syslog-ng automatically disables thefollow-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));
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:
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size: size of the file
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position: file position the message was read from
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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
The file() driver has the following options:
| 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.
| 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)
| 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”.
| 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.
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assume-utf8: The
assume-utf8flag 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 thevalidate-utf8flag. -
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
msgin 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 thedont-store-legacy-msghdrflag. -
empty-lines: Use the
empty-linesflag to keep the empty lines of the messages. By default, syslog-ng PE removes empty lines automatically. -
expect-hostname: If the
expect-hostnameflag 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 theno-hostnameflag by default. -
kernel: The
kernelflag makes the source default to theLOG_KERN | LOG_NOTICEpriority if not specified otherwise. -
no-hostname: Enable the
no-hostnameflag 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-lineflag 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 therltp,syslog(),network(),unix-dgram()drivers support multi-line messages. -
no-parse: By default, syslog-ng PE parses incoming messages as syslog messages. The
no-parseflag 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 sinceflags(no-parse)disables message parsing, it interferes with other flags, for example, disablesflags(no-multi-line). -
syslog-protocol: The
syslog-protocolflag 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 thesyslogdriver, which handles only messages that have a frame header. -
validate-utf8: The
validate-utf8flag 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.
| 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.
| 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.
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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.
| 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.
| 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.
| 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).
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”.
| 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.
| 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.
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Caution:
If the |
| 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.
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TIP:
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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.
| 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
| 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.
| 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.
| 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)
);};| 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.
| 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.
| 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.
[4] The byte order mark (BOM) is a Unicode character used to signal the byte-order of the message text.