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syslog-ng Premium Edition 7.0.29 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng PE The syslog-ng PE quick-start guide The syslog-ng PE configuration file Collecting log messages — sources and source drivers
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files google-pubsub: collecting messages from the Google Pub/Sub messaging service wildcard-file: Collecting messages from multiple text files linux-audit: Collecting messages from Linux audit logs mssql, oracle, sql: collecting messages from an SQL database network: Collecting messages using the RFC3164 protocol (network() driver) office365: Fetching logs from Office 365 osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes program: Receiving messages from external applications python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources snmptrap: Read Net-SNMP traps syslog: Collecting messages using the IETF syslog protocol (syslog() driver) system: Collecting the system-specific log messages of a platform systemd-journal: Collecting messages from the systemd-journal system log storage systemd-syslog: Collecting systemd messages using a socket tcp, tcp6, udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol udp-balancer: Receiving UDP messages at very high rate unix-stream, unix-dgram: Collecting messages from UNIX domain sockets windowsevent: Collecting Windows event logs
Sending and storing log messages — destinations and destination drivers
elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED) elasticsearch-http: Sending messages to Elasticsearch HTTP Event Collector file: Storing messages in plain-text files google_pubsub(): Sending logs to the Google Cloud Pub/Sub messaging service hdfs: Storing messages on the Hadoop Distributed File System (HDFS) http: Posting messages over HTTP without Java kafka(): Publishing messages to Apache Kafka (Java implementation) (DEPRECATED) kafka-c(): Publishing messages to Apache Kafka using the librdkafka client (C implementation) logstore: Storing messages in encrypted files mongodb: Storing messages in a MongoDB database network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) pipe: Sending messages to named pipes program: Sending messages to external applications python: writing custom Python destinations sentinel(): Sending logs to the Microsoft Azure Sentinel cloud snmp: Sending SNMP traps smtp: Generating SMTP messages (email) from logs splunk-hec: Sending messages to Splunk HTTP Event Collector sql(): Storing messages in an SQL database stackdriver: Sending logs to the Google Stackdriver cloud syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng(): Forward logs to another syslog-ng node tcp, tcp6, udp, udp6: Sending messages to a remote log server using the legacy BSD-syslog protocol (tcp(), udp() drivers) unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal — usertty() destination Client-side failover
Routing messages: log paths, flags, and filters Global options of syslog-ng PE TLS-encrypted message transfer Advanced Log Transfer Protocol Reliability and minimizing the loss of log messages Manipulating messages parser: Parse and segment structured messages Processing message content with a pattern database Correlating log messages Enriching log messages with external data Monitoring statistics and metrics of syslog-ng Multithreading and scaling in syslog-ng PE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages Glossary

file() destination options

The file() driver outputs messages to the specified text file, or to a set of files. The file() destination has the following options:

Caution:

When creating several thousands separate log files, syslog-ng might not be able to open the required number of files. This might happen for example, when using the ${HOST} macro in the filename while receiving messages from a large number of hosts. To overcome this problem, adjust the --fd-limit command-line parameter of syslog-ng or the global ulimit parameter of your host. For setting the --fd-limit command-line parameter of syslog-ng see the The syslog-ng manual page manual page. For setting the ulimit parameter of the host, see the documentation of your operating system.

create-dirs()
Type: yes or no
Default: no

Description: Enable creating non-existing directories when creating files or socket files.

dir-group()
Type: string
Default: Use the global settings

Description: The group of the directories created by syslog-ng. To preserve the original properties of an existing directory, use the option without specifying an attribute: dir-group().

dir-owner()
Type: string
Default: Use the global settings

Description: The owner of the directories created by syslog-ng. To preserve the original properties of an existing directory, use the option without specifying an attribute: dir-owner().

Starting with version 7.0.93.16, the default value of this option is -1, so syslog-ng PE does not change the ownership, unless explicitly configured to do so.

dir-perm()
Type: number
Default: Use the global settings

Description: The permission mask of directories created by syslog-ng. Log directories are only created if a file after macro expansion refers to a non-existing directory, and directory creation is enabled (see also the create-dirs() option). For octal numbers prefix the number with 0, for example, use 0755 for rwxr-xr-x.

To preserve the original properties of an existing directory, use the option without specifying an attribute: dir-perm(). Note that when creating a new directory without specifying attributes for dir-perm(), the default permission of the directories is masked with the umask of the parent process (typically 0022).

disk-buffer()

Description: This option enables putting outgoing messages into the disk-buffer file of the destination to avoid message loss in case of a system failure on the destination side. It has the following options:

dir()
Type: string
Default: N/A

Description: Defines the folder where the disk-buffer files are stored.

Note that changing the value the dir() option will not move or copy existing files from the old directory to the new one.

Caution:

When creating a new dir() option for a disk-buffer file, or modifying an existing one, make sure you delete the persist file.

syslog-ng PE creates disk-buffer files based on the path recorded in the persist file. Therefore, if the persist file is not deleted after modifying the dir() option, then following a restart, syslog-ng PE will look for or create disk-buffer files in their old location. To ensure that syslog-ng PE uses the new dir() setting, the persist file must not contain any information about the destinations which the disk-buffer file in question belongs to.

disk-buf-size()
Type: number [bytes]
Default:

Description: This is a required option. The maximum size of the disk-buffer file in bytes. The minimum value is 1048576 bytes. If you set a smaller value, the minimum value will be used automatically. It replaces the old log-disk-fifo-size() option.
mem-buf-length()
Type: number [messages]
Default: 10000
Description: Use this option if the option reliable() is set to no. This option contains the number of messages stored in overflow queue. It replaces the old log-fifo-size() option. It inherits the value of the global log-fifo-size() option if provided. If it is not provided, the default value is 10000 messages. Note that this option will be ignored if the option reliable() is set to yes.
mem-buf-size()
Type: number [bytes]
Default: 163840000
Description: Use this option if the option reliable() is set to yes. This option contains the size of the messages in bytes that is used in the memory part of the disk-buffer file. It replaces the old log-fifo-size() option. It does not inherit the value of the global log-fifo-size() option, even if it is provided. Note that this option will be ignored if the option reliable() is set to no.
quot-size()
Type: number [messages]
Default: 1000

Description: The number of messages stored in the output buffer of the destination. Note that if you change the value of this option and the disk-buffer file already exists, the change will take effect when the disk-buffer file becomes empty.

reliable()
Type: yes|no
Default: no

Description: If set to yes, syslog-ng PE cannot lose logs in case of reload/restart, unreachable destination or syslog-ng PE crash. This solution provides a slower, but reliable disk-buffer option. It is created and initialized at startup and gradually grows as new messages arrive. If set to no, the normal disk-buffer option will be used. This provides a faster, but less reliable disk-buffer option.

Caution: Hazard of data loss!

If you change the value of reliable() option when there are messages in the disk-buffer file, the messages stored in the disk-buffer file will be lost.

truncate-size-ratio()
Type: number (for percentage) between 0 and 1
Default: 0.1 (10%)

Description: Limits the truncation of the disk-buffer file. Truncating the disk-buffer file can slow down disk I/O operations, but it saves disk space. As a result, syslog-ng PE only truncates the file if the possible disk gain is more than truncate-size-ratio() times disk-buf-size().

Caution:

One Identity recommends that you do not modify the value of the truncate-size-ratio() option unless you are fully aware of the potential performance implications.

Example: Examples for using disk-buffer()

In the following case, reliable disk-buffer() is used.

destination d_demo {
    network("127.0.0.1"
        port(3333)
        disk-buffer(
            mem-buf-size(10000)
            disk-buf-size(2000000)
            reliable(yes)
            dir("/tmp/disk-buffer")
        )
    );
};

In the following case normal disk-buffer() is used.

destination d_demo {
    network("127.0.0.1"
        port(3333)
        disk-buffer(
            mem-buf-length(10000)
            disk-buf-size(2000000)
            reliable(no)
            dir("/tmp/disk-buffer")
        )
    );
};
flags()
Type: no-multi-line, syslog-protocol, threaded
Default: empty set

Description: Flags influence the behavior of the destination driver.

  • no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line.

  • syslog-protocol: The syslog-protocol flag instructs the driver to format the messages according to the new IETF syslog protocol standard (RFC5424), but without the frame header. If this flag is enabled, macros used for the message have effect only for the text of the message, the message header is formatted to the new standard. Note that this flag is not needed for the syslog driver, and that the syslog driver automatically adds the frame header to the messages.

  • threaded: The threaded flag enables multithreading for the destination. For details on multithreading, see Multithreading and scaling in syslog-ng PE.

    NOTE: The file destination uses multiple threads only if the destination filename contains macros.

flush-lines()
Type: number
Default: Use global setting.

Description: Specifies how many lines are flushed to a destination at a time. The syslog-ng PE application waits for this number of lines to accumulate and sends them off in a single batch. Increasing this number increases throughput as more messages are sent in a single batch, but also increases message latency.

The syslog-ng PE application flushes the messages if it has sent flush-lines() number of messages, or the queue became empty. If you stop or reload syslog-ng PE or in case of network sources, the connection with the client is closed, syslog-ng PE automatically sends the unsent messages to the destination.

For optimal performance when sending messages to a syslog-ng PE server, make sure that the flush-lines() is smaller than the window size set using the log-iw-size() option in the source of your server.

flush-timeout() (DEPRECATED)
Type: time in milliseconds
Default: Use global setting.

Description: This is a deprecated option. Specifies the time syslog-ng waits for lines to accumulate in its output buffer. For details, see the flush-lines() option.

frac-digits()
Type: number
Default: 0

Description: The syslog-ng PE application can store fractions of a second in the timestamps according to the ISO8601 format. The frac-digits() parameter specifies the number of digits stored. The digits storing the fractions are padded by zeros if the original timestamp of the message specifies only seconds. Fractions can always be stored for the time the message was received.

NOTE: The syslog-ng PE application can add the fractions to non-ISO8601 timestamps as well.

NOTE: As syslog-ng PE is precise up to the microsecond, when the frac-digits() option is set to a value higher than 6, syslog-ng PE will truncate the fraction seconds in the timestamps after 6 digits.

fsync()
Type: yes or no
Default: no

Description: Forces an fsync() call on the destination fd after each write.

NOTE: Enabling this option may seriously degrade performance.

group()
Type: string
Default: Use the global settings

Description: Set the group of the created file to the one specified. To preserve the original properties of an existing file, use the option without specifying an attribute: group().

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

Description: Sets the timezone used when expanding filename and tablename templates.

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.

log-fifo-size()
Type: number
Default: Use global setting.

Description: The number of messages that the output queue can store.

mark-freq()
Accepted values: number [seconds]
Default: 1200

Description: An alias for the obsolete mark() option, retained for compatibility with syslog-ng version 1.6.x.

The number of seconds between two MARK messages. MARK messages are generated when there was no message traffic to inform the receiver that the connection is still alive. If set to zero (0), no MARK messages are sent. The mark-freq() can be set for global option and/or every MARK capable destination driver if mark-mode() is periodical or dst-idle or host-idle. If mark-freq() is not defined in the destination, then the mark-freq() will be inherited from the global options. If the destination uses internal mark-mode(), then the global mark-freq() will be valid (does not matter what mark-freq() set in the destination side).

mark-mode()
Accepted values: internal | dst-idle | host-idle | periodical | none | global
Default:

internal for pipe, program drivers

none for file, unix-dgram, unix-stream drivers

global for syslog, tcp, udp destinations

host-idle for global option

Description: The mark-mode() option can be set for the following destination drivers: file(), program(), unix-dgram(), unix-stream(), network(), pipe(), syslog() and in global option.

  • internal: When internal mark mode is selected, internal source should be placed in the log path as this mode does not generate mark by itself at the destination. This mode only yields the mark messages from internal source. This is the mode as syslog-ng PE 3.xsyslog-ng PE 3.3 worked. MARK will be generated by internal source if there was NO traffic on local sources:

    file(), pipe(), unix-stream(), unix-dgram(), program()

  • dst-idle: Sends MARK signal if there was NO traffic on destination drivers. MARK signal from internal source will be dropped.

    MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

  • host-idle: Sends MARK signal if there was NO local message on destination drivers. For example, MARK is generated even if messages were received from tcp. MARK signal from internal source will be dropped.

    MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

  • periodical: Sends MARK signal perodically, regardless of traffic on destination driver. MARK signal from internal source will be dropped.

    MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

  • none: Destination driver drops all MARK messages. If an explicit mark-mode() is not given to the drivers where none is the default value, then none will be used.

  • global: Destination driver uses the global mark-mode() setting. Note that setting the global mark-mode() to global causes a syntax error in syslog-ng PE.

NOTE: In case of dst-idle, host-idle and periodical, the MARK message will not be written in the destination, if it is not open yet.

Available in syslog-ng PE 4 LTSsyslog-ng PE 3.4 and later.

overwrite-if-older()
Type: number (seconds)
Default: 0

Description: If set to a value higher than 0, syslog-ng PE checks when the file was last modified before starting to write into the file. If the file is older than the specified amount of time (in seconds), then syslog-ng removes the existing file and opens a new file with the same name. In combination with for example, the ${WEEKDAY} macro, this can be used for simple log rotation, in case not all history has to be kept. (Note that in this weekly log rotation example if its Monday 00:01, then the file from last Monday is not seven days old, because it was probably last modified shortly before 23:59 last Monday, so it is actually not even six days old. So in this case, set the overwrite-if-older() parameter to a-bit-less-than-six-days, for example, to 518000 seconds.

owner()
Type: string
Default: Use the global settings

Description: Set the owner of the created file to the one specified. To preserve the original properties of an existing file, use the option without specifying an attribute: owner().

pad-size()
Type: number
Default: 0

Description: If set, syslog-ng PE will pad output messages to the specified size (in bytes). 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).

Caution:

Hazard of data loss! If the size of the incoming message is larger than the previously set pad-size() value, syslog-ng will truncate the message to the specified size. Therefore, all message content above that size will be lost.

perm()
Type: number
Default: Use the global settings

Description: The permission mask of the file if it is created by syslog-ng. For octal numbers prefix the number with 0, for example, use 0755 for rwxr-xr-x.

To preserve the original properties of an existing file, use the option without specifying an attribute: perm().

suppress()
Type: seconds
Default: 0 (disabled)

Description: If several identical log messages would be sent to the destination without any other messages between the identical messages (for example, an application repeated an error message ten times), syslog-ng can suppress the repeated messages and send the message only once, followed by the Last message repeated n times. message. The parameter of this option specifies the number of seconds syslog-ng waits for identical messages.

template()
Type: string
Default: A format conforming to the default logfile format.

Description: Specifies a template defining the logformat to be used in the destination. Macros are described in Macros of syslog-ng PE. Please note that for network destinations it might not be appropriate to change the template as it changes the on-wire format of the syslog protocol which might not be tolerated by stock syslog receivers (like syslogd or syslog-ng itself). For network destinations make sure the receiver can cope with the custom format defined.

template-escape()
Type: yes or no
Default: no

Description: Turns on escaping for the ', ", and backspace characters in templated output files. This is useful for generating SQL statements and quoting string contents so that parts of the log message are not interpreted as commands to the SQL server.

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

Description: Convert timestamps to the timezone specified by this option. If this option is not set, then the original timezone information in the message is used. Converting the timezone changes the values of all date-related macros derived from the timestamp, for example, HOUR. For the complete list of such macros, see Date-related macros.

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.

ts-format()
Type: rfc3164, bsd, rfc3339, iso
Default: rfc3164

Description: Override the global timestamp format (set in the global ts-format() parameter) for the specific destination. For details, see ts-format().

google_pubsub(): Sending logs to the Google Cloud Pub/Sub messaging service

From syslog-ng Premium Edition (syslog-ng PE) version 7.0.21, you can use the the google_pubsub() destination to generate your own messaging Google Pub/Sub infrastructure with syslog-ng PE as a "Publisher" entity, utilizing the HTTP REST interface of the service.

Similarly to syslog-ng PE's stackdriver() destination, the google_pubsub() destination is an asynchronous messaging service connected to Google's infrastructure.

For more information about Google Pub/Sub's messaging service, see What Is Pub/Sub?. The rest of this section and its subsections assume that you are familiar with the Google Pub/Sub messaging service, and its concepts and terminology.

Limitations

The current implementation of the google_pubsub() destination has the following limitations:

No message-based acknowledgement: While Google Pub/Sub acknowledges the batch of received messages, it also sends individual acknowledgement ID's to each message. However, we currently do not track individual messages inside Google Pub/Sub. Under normal operation circumstances, the lack of tracking individual messages has no effect on message delivery, and even allows flow control to work properly. However, in case of an error, the only solution is to repeat the entire batch, which can lead to message duplication in case Google Pub/Sub acknowledged part of the previous batch despite indicating an overall error.

NOTE: This behavior, called At-Least-Once delivery, means that if an error occurs, it is more acceptable to duplicate messages than to lose any of them.

NOTE: Typically, only the central syslog-ng PE server uses this destination. For more information on the server mode, see Server mode.

NOTE: The google_pubsub() destination can not fetch logs, only serve as a "Publisher" entity in the Google Pub/Sub service.

Configuring the google_pubsub() destination

From syslog-ng Premium Edition (syslog-ng PE) version 7.0.21, you can use the the google_pubsub() destination to generate your own messaging Google Pub/Sub infrastructure with syslog-ng PE as a "Publisher" entity, utilizing the HTTP REST interface of the service.

Similarly to syslog-ng PE's stackdriver() destination, the google_pubsub() destination is an asynchronous messaging service connected to Google's infrastructure.

For more information about Google Pub/Sub's messaging service, see What Is Pub/Sub?. The rest of this section and its subsections assume that you are familiar with the Google Pub/Sub messaging service, and its concepts and terminology.

Prerequisites

To configure the google_pubsub() destination, you must have each of the following:

For more information, see Quickstart: building a functioning Pub/Sub system.

Declaration
destination d_google_pubsub {
  google_pubsub(
    credentials("<path-to-your-credentials-file>")
    gcp_auth_header_params(ca_file(<path-to-your-systems-root-certificate>))
    project(<the-name-of-your-pub-sub-project>)
    topic(<the-name-of-your-pub-sub-topic>)
  );
};
Configuration

The following example is a sample configuration for the google_pubsub() destination.

Example: configuring the google_pubsub() destination

In your syslog-ng PE configuration, you can use the google_pubsub() destination like this:

destination d_google_pubsub {
  google_pubsub(
    credentials("/home/user/service-account-key.json")
    gcp_auth_header_params(ca_file(<path-to-your-systems-root-certificate>))
    project(mypubsubproject)
    topic(mytopic)
  );
};

NOTE: Similarly to the stackdriver() destination, while using the the gcp_auth_header_params parameter in the google_pubsub() destination, you must use underscore (_) in the options that syslog-ng PE passes directly to Google Pub/Sub).

NOTE: The google_pubsub() destination is a customized http() destination. As a result, the google_pubsub() destination accepts every http() option and its parameters (for example, the stackdriver destination options, with the exception of the Stackdriver-specific options). While using the options of the http() destination and their parameters with the google_pubsub()destination, the hyphen (-) and underscore (_) characters are interchangeable.

Required options and parameters

The google_pubsub() destination has the following required options and parameters:

  • gcp_auth_header_params()
  • the ca-dir() parameter of the gcp_auth_header_params() option

    or

  • the ca-file() parameter of the gcp_auth_header_params() option

NOTE: Specifying at least one of the ca-dir() or ca-file() parameters of the gcp_auth_header_params() option is mandatory. As a result, the gcp_auth_header_params() option is a required option.

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