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syslog-ng Open Source Edition 3.38 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng The syslog-ng OSE quick-start guide The syslog-ng OSE configuration file source: Read, receive, and collect log messages
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files wildcard-file: Collecting messages from multiple text files kubernetes: Collecting and parsing the Kubernetes CRI (Container Runtime Interface) format linux-audit: Collecting messages from Linux audit logs mqtt: receiving messages from an MQTT broker network: Collecting messages using the RFC3164 protocol (network() driver) nodejs: Receiving JSON messages from nodejs applications mbox: Converting local email messages to log messages osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes pacct: Collecting process accounting logs on Linux program: Receiving messages from external applications python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources snmptrap: Read Net-SNMP traps sun-streams: Collecting messages on Sun Solaris 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— OBSOLETE unix-stream, unix-dgram: Collecting messages from UNIX domain sockets stdin: Collecting messages from the standard input stream
destination: Forward, send, and store log messages
amqp: Publishing messages using AMQP collectd: sending metrics to collectd discord: Sending alerts and notifications to Discord elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED) elasticsearch-http: Sending messages to Elasticsearch HTTP Bulk API file: Storing messages in plain-text files graphite: Sending metrics to Graphite Sending logs to Graylog hdfs: Storing messages on the Hadoop Distributed File System (HDFS) Posting messages over HTTP http: Posting messages over HTTP without Java kafka: Publishing messages to Apache Kafka (Java implementation) kafka-c(): Publishing messages to Apache Kafka using the librdkafka client (C implementation) loggly: Using Loggly logmatic: Using Logmatic.io mongodb(): Storing messages in a MongoDB database mqtt() destination: sending messages from a local network to an MQTT broker network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) osquery: Sending log messages to osquery's syslog table pipe: Sending messages to named pipes program: Sending messages to external applications pseudofile() python: writing custom Python destinations redis: Storing name-value pairs in Redis riemann: Monitoring your data with Riemann slack: Sending alerts and notifications to a Slack channel smtp: Generating SMTP messages (email) from logs snmp: Sending SNMP traps Splunk: Sending log messages to Splunk sql: Storing messages in an SQL database stomp: Publishing messages using STOMP Sumo Logic destinations: sumologic-http() and sumologic-syslog() 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) Telegram: Sending messages to Telegram unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal: usertty() destination Write your own custom destination in Java or Python Client-side failover
log: Filter and route log messages using log paths, flags, and filters Global options of syslog-ng OSE TLS-encrypted message transfer template and rewrite: Format, modify, and manipulate log messages parser: Parse and segment structured messages
Parsing syslog messages Parsing messages with comma-separated and similar values Parsing key=value pairs JSON parser XML parser Parsing dates and timestamps Python parser Parsing tags Apache access log parser Linux audit parser Cisco parser Parsing enterprise-wide message model (EWMM) messages iptables parser Netskope parser panos-parser(): parsing PAN-OS log messages Sudo parser MariaDB parser Websense parser Fortigate parser Check Point Log Exporter parser Regular expression (regexp) parser db-parser: Process message content with a pattern database (patterndb)
Correlating log messages Enriching log messages with external data Statistics of syslog-ng Multithreading and scaling in syslog-ng OSE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages Creative Commons Attribution Non-commercial No Derivatives (by-nc-nd) License The syslog-ng Open Source Edition Documentation License Glossary

redis() destination options

The redis() driver sends messages as name-value pairs to a Redis key-value store.

The redis() destination has the following options:

auth()
Type: hostname or IP address
Default: N/A

Description: The password used for authentication on a password-protected Redis server. Available in syslog-ng OSE version 3.10 and later.

batch-lines()
Type: number
Default: 1

Description: Specifies how many lines are flushed to a destination in one batch. The syslog-ng OSE 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.

For example, if you set batch-lines() to 100, syslog-ng OSE waits for 100 messages.

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

Note that if the batch-timeout() option is enabled and the queue becomes empty, syslog-ng OSE flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-lines().

For optimal performance, make sure that the syslog-ng OSE source that feeds messages to this destination is configured properly: the value of the log-iw-size() option of the source must be higher than the batch-lines()*workers() of the destination. Otherwise, the size of the batches cannot reach the batch-lines() limit.

batch-timeout()
Type: time in milliseconds
Default: -1 (disabled)

Description: Specifies the time syslog-ng OSE waits for lines to accumulate in the output buffer. The syslog-ng OSE application sends batches to the destinations evenly. The timer starts when the first message arrives to the buffer, so if only few messages arrive, syslog-ng OSE sends messages to the destination at most once every batch-timeout() milliseconds.

command()
Type: comma-separated list of strings ("<redis-command>", "<first-command-parameter>", "<second-command-parameter>", "<third-command-parameter>")
Default: empty string

Description: The Redis command to execute, for example, LPUSH, INCR, or HINCRBY. Using the HINCRBY command with an increment value of 1 allows you to create various statistics. For example, the command("HINCRBY" "${HOST}/programs" "${PROGRAM}" "1") command counts the number of log messages on each host for each program.

Note the following points when using the redis() destination:

  • You can use macros and templates in the parameters of the Redis command.

  • Currently you can use only one command in a redis() destination.

  • The syslog-ng OSE application ignores the return value of the command. If the Redis server returns an error, syslog-ng OSE closes the connection.

disk-buffer()

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

reliable()
Type: yes|no
Default: no

Description: If set to yes, syslog-ng OSE cannot lose logs in case of reload/restart, unreachable destination or syslog-ng OSE 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 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, the messages stored in the disk-buffer will be lost.

compaction()
Type: yes|no
Default: no

Description: If set to yes, syslog-ng OSE prunes the unused space in the LogMessage representation, making the disk queue size smaller at the cost of some CPU time. Setting the compaction() argument to yes is recommended when numerous name-value pairs are unset during processing, or when the same names are set multiple times.

NOTE: Simply unsetting these name-value pairs by using the unset() rewrite operation is not enough, as due to performance reasons that help when syslog-ng OSE is CPU bound, the internal representation of a LogMessage will not release the memory associated with these name-value pairs. In some cases, however, the size of this overhead becomes significant (the raw message size can grow up to four times its original size), which unnecessarily increases the disk queue file size. For these cases, the compaction will drop unset values, making the LogMessage representation smaller at the cost of some CPU time required to perform compaction.

dir()
Type: string
Default: N/A

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

Caution:

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

syslog-ng OSE 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 OSE will look for or create disk-buffer files in their old location. To ensure that syslog-ng OSE 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.

NOTE: If the dir() path provided by the user does not exist, syslog-ng OSE creates the path with the same permission as the running instance.

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

Description: This is a required option. The maximum size of the disk-buffer 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. 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.
qout-size()
Type: number (messages)
Default: 64
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 already exists, the change will take effect when the disk-buffer becomes empty.

Options reliable() and disk-buf-size() are required options.

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")
        )
    );
};

truncate-size-ratio()

Type: number (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 the disk IO operations, but it saves disk space, so syslog-ng only truncates the file, if the possible disk gain is more than truncate-size-ratio() times disk-buf-size().

Caution:

One Identity does not recommend you to change truncate-size-ratio(). Only change its value if you know the performance implications of doing so.

batch-bytes()
Accepted values: number [bytes]
Default: none

Description: Sets the maximum size of payload in a batch. If the size of the messages reaches this value, syslog-ng OSE sends the batch to the destination even if the number of messages is less than the value of the batch-lines() option.

Note that if the batch-timeout() option is enabled and the queue becomes empty, syslog-ng OSE flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-bytes().

Available in syslog-ng OSE version 3.19 and later.

batch-lines()
Type: number
Default: 1

Description: Specifies how many lines are flushed to a destination in one batch. The syslog-ng OSE 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.

For example, if you set batch-lines() to 100, syslog-ng OSE waits for 100 messages.

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

Note that if the batch-timeout() option is enabled and the queue becomes empty, syslog-ng OSE flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-lines().

For optimal performance, make sure that the syslog-ng OSE source that feeds messages to this destination is configured properly: the value of the log-iw-size() option of the source must be higher than the batch-lines()*workers() of the destination. Otherwise, the size of the batches cannot reach the batch-lines() limit.

batch-timeout()
Type: time in milliseconds
Default: -1 (disabled)

Description: Specifies the time syslog-ng OSE waits for lines to accumulate in the output buffer. The syslog-ng OSE application sends batches to the destinations evenly. The timer starts when the first message arrives to the buffer, so if only few messages arrive, syslog-ng OSE sends messages to the destination at most once every batch-timeout() milliseconds.

hook-commands()

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

NOTE: The syslog-ng OSE application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable syslog-ng OSE to execute external applications.

Using the hook-commands() when syslog-ng OSE starts or stops

To execute an external program when syslog-ng OSE starts or stops, use the following options:

startup()
Type: string
Default: N/A

Description: Defines the external program that is executed as syslog-ng OSE starts.

shutdown()
Type: string
Default: N/A

Description: Defines the external program that is executed as syslog-ng OSE stops.

Using the hook-commands() when syslog-ng OSE reloads

To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:

setup()
Type: string
Default: N/A

Description: Defines an external program that is executed when the syslog-ng OSE configuration is initiated, for example, on startup or during a syslog-ng OSE reload.

teardown()
Type: string
Default: N/A

Description: Defines an external program that is executed when the syslog-ng OSE configuration is stopped or torn down, for example, on shutdown or during a syslog-ng OSE reload.

Example: Using the hook-commands() with a network source

In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as syslog-ng OSE is started/stopped.

The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the syslog-ng OSE created rule is there, packets can flow, otherwise the port is closed.

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};
host()
Type: hostname or IP address
Default: 127.0.0.1

Description: The hostname or IP address of the Redis server.

port()
Type: number
Default: 6379

Description: The port number of the Redis server.

retries()
Type: number (of attempts)
Default: 3

Description: If syslog-ng OSE cannot send a message, it will try again until the number of attempts reaches retries().

If the number of attempts reaches retries(), syslog-ng OSE will wait for time-reopen() time, then tries sending the message again.

throttle()
Type: number
Default: 0

Description: Sets the maximum number of messages sent to the destination per second. Use this output-rate-limiting functionality only when using disk-buffer as well to avoid the risk of losing messages. Specifying 0 or a lower value sets the output limit to unlimited.

time-reopen()
Accepted values: number [seconds]
Default: 60

Description: The time to wait in seconds before a dead connection is reestablished.

workers()
Type: integer
Default: 1

Description: Specifies the number of worker threads (at least 1) that syslog-ng OSE uses to send messages to the server. Increasing the number of worker threads can drastically improve the performance of the destination.

Caution:

Hazard of data loss. When you use more than one worker threads together with disk-based buffering, syslog-ng OSE creates a separate disk buffer for each worker thread. This means that decreasing the number of workers can result in losing data currently stored in the disk buffer files. Do not decrease the number of workers when the disk buffer files are in use.

If you are using load-balancing (that is, you have configured multiple servers in the url() option), increase the number of worker threads at least to the number of servers. For example, if you have set three URLs (url("site1", "site2", "site3")), set the workers() option to 3 or more.

riemann: Monitoring your data with Riemann

The riemann() driver sends your data (for example, metrics or events) to a Riemann monitoring system.

For the list of available parameters, see riemann() destination options.

Declaration:
riemann(
	server("<riemann-server-address>")
	port("<riemann-server-port>")
	metric("<the-metric-or-data-to-send-to-riemann>")
);
Example: Using the riemann() driver

The following destination sends the value of the SEQNUM macro (the number of messages sent to this destination) as a metric to the Riemann server.

@version: 3.38

source s_network {
	network(port(12345));
};

destination d_riemann {
	riemann(
		server("localhost")
		port(5555)
		ttl("300.5")
		metric(int("$SEQNUM"))
		description("syslog-ng riemann test")
		state("ok")
		attributes(x-ultimate-answer("$(+ $PID 42)")
				   key("MESSAGE", rekey(add-prefix("x-")) )
				   )
	);
};

log {
	source(s_network);
	destination(d_riemann);
	flags(flow-control);
};

For a detailed use-case on using syslog-ng OSE with the Riemann monitoring system, see the article A How to Guide on Modern Monitoring and Alerting by Fabien Wernli.

riemann() destination options

The riemann() driver sends metrics or events to a Riemann monitoring system.

The riemann() destination has the following options:

attributes()
Type: parameter list of the value-pairs() option
Default:

Description: The attributes() option adds extra metadata to the Riemann event, that can be displayed on the Riemann dashboard. To specify the metadata to add, use the syntax of the value-pairs() option. For details on using value-pairs(), see Structuring macros, metadata, and other value-pairs.

description()
Type: template, macro, or string
Default:

Description: The value to add as the description field of the Riemann event.

disk-buffer()

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

reliable()
Type: yes|no
Default: no

Description: If set to yes, syslog-ng OSE cannot lose logs in case of reload/restart, unreachable destination or syslog-ng OSE 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 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, the messages stored in the disk-buffer will be lost.

compaction()
Type: yes|no
Default: no

Description: If set to yes, syslog-ng OSE prunes the unused space in the LogMessage representation, making the disk queue size smaller at the cost of some CPU time. Setting the compaction() argument to yes is recommended when numerous name-value pairs are unset during processing, or when the same names are set multiple times.

NOTE: Simply unsetting these name-value pairs by using the unset() rewrite operation is not enough, as due to performance reasons that help when syslog-ng OSE is CPU bound, the internal representation of a LogMessage will not release the memory associated with these name-value pairs. In some cases, however, the size of this overhead becomes significant (the raw message size can grow up to four times its original size), which unnecessarily increases the disk queue file size. For these cases, the compaction will drop unset values, making the LogMessage representation smaller at the cost of some CPU time required to perform compaction.

dir()
Type: string
Default: N/A

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

Caution:

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

syslog-ng OSE 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 OSE will look for or create disk-buffer files in their old location. To ensure that syslog-ng OSE 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.

NOTE: If the dir() path provided by the user does not exist, syslog-ng OSE creates the path with the same permission as the running instance.

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

Description: This is a required option. The maximum size of the disk-buffer 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. 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.
qout-size()
Type: number (messages)
Default: 64
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 already exists, the change will take effect when the disk-buffer becomes empty.

Options reliable() and disk-buf-size() are required options.

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")
        )
    );
};

truncate-size-ratio()

Type: number (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 the disk IO operations, but it saves disk space, so syslog-ng only truncates the file, if the possible disk gain is more than truncate-size-ratio() times disk-buf-size().

Caution:

One Identity does not recommend you to change truncate-size-ratio(). Only change its value if you know the performance implications of doing so.

event-time()
Type: template, macro, or string
Default: ${UNIXTIME}

Description: Instead of the arrival time into Riemann, syslog-ng OSE can also send its own timestamp value.

This can be useful if Riemann is inaccessible for a while, and the messages are collected in the disk buffer until Riemann is accessible again. In this case, it would be difficult to differentiate between messages based on the arrival time only, because this would mean that there would be hundreds of messages with the same arrival time. This issue can be solved by using this option.

The event-time() option takes an optional parameter specifying whether the time format is in seconds or microseconds. For example:

event-time("$(* $UNIXTIME 1000000)" microseconds)
event-time("12345678" microseconds)
event-time("12345678" seconds)
event-time("12345678")

In case the parameter is omitted, syslog-ng OSE defaults to the seconds version. In case the event-time() option is omitted altogether, syslog-ng OSE defaults to the seconds version with $UNIXTIME.

Note that the time format parameter requires:

  • riemann-c-client 1.10.0 or newer

    In older versions of riemann-c-client, the microseconds option is not available.

    In case your distribution does not contain a recent enough version of riemann-c-client and you wish to use microseconds, install a new version from .

    If you installed the new version in a custom location (instead of the default one), make sure that you append the directory of the pkg-config file (.pc file) to the environment variable export PKG_CONFIG_PATH=....

    After calling configure, you should see the following message in the case of successful installation:

    [...]
     Riemann destination (module): yes, microseconds: yes
    [...]
  • Riemann 2.13 or newer

    Older versions of Riemann cannot handle microseconds. No error will be indicated, however, the time of the event will be set to the timestamp when the message arrived to Riemann.

Example: Example event-time() option
destination d_riemann {
   riemann(
   server("127.0.0.1")
   port(5555)
   event-time("${UNIXTIME}")
   [...]
   );
};
batch-bytes()
Accepted values: number [bytes]
Default: none

Description: Sets the maximum size of payload in a batch. If the size of the messages reaches this value, syslog-ng OSE sends the batch to the destination even if the number of messages is less than the value of the batch-lines() option.

Note that if the batch-timeout() option is enabled and the queue becomes empty, syslog-ng OSE flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-bytes().

Available in syslog-ng OSE version 3.19 and later.

batch-lines()
Type: number
Default: 1

Description: Specifies how many lines are flushed to a destination in one batch. The syslog-ng OSE 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.

For example, if you set batch-lines() to 100, syslog-ng OSE waits for 100 messages.

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

Note that if the batch-timeout() option is enabled and the queue becomes empty, syslog-ng OSE flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-lines().

For optimal performance, make sure that the syslog-ng OSE source that feeds messages to this destination is configured properly: the value of the log-iw-size() option of the source must be higher than the batch-lines()*workers() of the destination. Otherwise, the size of the batches cannot reach the batch-lines() limit.

If an error occurs while sending the messages to the server, syslog-ng OSE will try to resend every message from the batch. If it does not succeed (you can set the number of retry attempts in the retries() option), syslog-ng OSE drops every message in the batch.

batch-timeout()
Type: time in milliseconds
Default: -1 (disabled)

Description: Specifies the time syslog-ng OSE waits for lines to accumulate in the output buffer. The syslog-ng OSE application sends batches to the destinations evenly. The timer starts when the first message arrives to the buffer, so if only few messages arrive, syslog-ng OSE sends messages to the destination at most once every batch-timeout() milliseconds.

hook-commands()

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

NOTE: The syslog-ng OSE application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable syslog-ng OSE to execute external applications.

Using the hook-commands() when syslog-ng OSE starts or stops

To execute an external program when syslog-ng OSE starts or stops, use the following options:

startup()
Type: string
Default: N/A

Description: Defines the external program that is executed as syslog-ng OSE starts.

shutdown()
Type: string
Default: N/A

Description: Defines the external program that is executed as syslog-ng OSE stops.

Using the hook-commands() when syslog-ng OSE reloads

To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:

setup()
Type: string
Default: N/A

Description: Defines an external program that is executed when the syslog-ng OSE configuration is initiated, for example, on startup or during a syslog-ng OSE reload.

teardown()
Type: string
Default: N/A

Description: Defines an external program that is executed when the syslog-ng OSE configuration is stopped or torn down, for example, on shutdown or during a syslog-ng OSE reload.

Example: Using the hook-commands() with a network source

In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as syslog-ng OSE is started/stopped.

The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the syslog-ng OSE created rule is there, packets can flow, otherwise the port is closed.

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};
host()
Type: template, macro, or string
Default: ${HOST}

Description: The value to add as the host field of the Riemann event.

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

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

metric()
Type: template, macro, or string
Default:

Description: The numeric value to add as the metric field of the Riemann event. If possible, include type-hinting as well, otherwise the Riemann server will interpret the value as a floating-point number. The following example specifies the SEQNUM macro as an integer.

metric(int("$SEQNUM"))
port()
Type: number
Default: 5555

Description: The port number of the Riemann server.

retries()
Type: number (of attempts)
Default: 3

Description: If syslog-ng OSE cannot send a message, it will try again until the number of attempts reaches retries().

If the number of attempts reaches retries(), syslog-ng OSE will wait for time-reopen() time, then tries sending the message again.

server()
Type: hostname or IP address
Default: 127.0.0.1

Description: The hostname or IP address of the Riemann server.

service()
Type: template, macro, or string
Default: ${PROGRAM}

Description: The value to add as the service field of the Riemann event.

state()
Type: template, macro, or string
Default:

Description: The value to add as the state field of the Riemann event.

tags()
Type: string list
Default: the tags already assigned to the message

Description: The list of tags to add as the tags field of the Riemann event. If not specified syslog-ng OSE automatically adds the tags already assigned to the message. If you set the tags() option, only the tags you specify will be added to the event.

throttle()
Type: number
Default: 0

Description: Sets the maximum number of messages sent to the destination per second. Use this output-rate-limiting functionality only when using disk-buffer as well to avoid the risk of losing messages. Specifying 0 or a lower value sets the output limit to unlimited.

time-reopen()
Accepted values: number [seconds]
Default: 60

Description: The time to wait in seconds before a dead connection is reestablished.

timeout()
Type: number [seconds]
Default:

Description: The value (in seconds) to wait for an operation to complete, and attempt to reconnect the Riemann server if exceeded. By default, the timeout is disabled.

ttl()
Type: template, macro, or number
Default:

Description: The value (in seconds) to add as the ttl (time-to-live) field of the Riemann event.

type()
Type: tcp | tls | udp
Default: tcp

Description: The type of the network connection to the Riemann server: TCP, TLS, or UDP. For TLS connections, set the ca-file() option to authenticate the Riemann server, and the cert-file() and key-file() options if the Riemann server requires authentication from its clients.

Declaration 1:
destination d_riemann {
	riemann(
		server("127.0.0.1")
		port(5672)
		type(
		   "tls"
		   ca-file("ca")
		   cert-file("cert") 
		   key-file("key")
		)
	);
};

An alternative way to specify TLS options is to group them into a tls() block. This allows you to separate them and ensure better readability.

Declaration 2:
destination d_riemann {
	riemann(
		server("127.0.0.1")
		port(5672)
		type("tls")
		tls(
			ca-file("ca")
			cert-file("cert") 
			key-file("key")
		)
	);
};

Make sure that you specify TLS options either using type() or using the tls() block. Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

ca-file()

Type: path to a CA certificate in PEM format
Default:

Description: Path to the CA certificate in PEM format that signed the certificate of the Riemann server. When establishing TLS connection, syslog-ng OSE verifies the certificate of the Riemann server using this CA.

Alternative 1:

type(
	"tls"
	ca-file("/opt/syslog-ng/etc/syslog-ng/riemann-cacert.pem")
	)

Alternative 2:

riemann(
	.
	.
	type("tls")
	tls(
          	ca-file("/opt/syslog-ng/etc/syslog-ng/riemann-cacert.pem")
	)

This option was called cacert() up until (and including) syslog-ng OSE version 3.12.

cert-file()

Type: path to a certificate in PEM format
Default:

Description: Path to the a certificate file in PEM format. When establishing TLS connection, syslog-ng OSE authenticates on the Riemann server using this certificate and the matching private key set in the key-file() option.

Note that you have to set the cert-file() and key-file() options only if the Riemann server requires authentication from the clients.

Alternative 1:

type(
	"tls"
	cert-file("/opt/syslog-ng/etc/syslog-ng/riemann-client-cert.pem")
	key-file("/opt/syslog-ng/etc/syslog-ng/riemann-client-cert.key")
	)

Alternative 2:

riemann(
	.
	.
	type("tls")
        tls(
              cert-file("/opt/syslog-ng/etc/syslog-ng/riemann-client-cert.pem")
              key-file("/opt/syslog-ng/etc/syslog-ng/riemann-client-cert.key")
       )

This option was called cert() in syslog-ng OSE version 3.7.

key-file()

Type: path to a private key file
Default:

Description: Path to the private key of the certificate file set in the cert-file() option. When establishing TLS connection, syslog-ng OSE authenticates on the Riemann server using this private key and the matching certificate set in the cert-file() option.

Note that you have to set the cert-file() and key-file() options only if the Riemann server requires authentication from the clients.

Alternative 1:

type(
	"tls"
	cert-file("/opt/syslog-ng/etc/syslog-ng/riemann-client-cert.pem")
	key-file("/opt/syslog-ng/etc/syslog-ng/riemann-client-cert.key")
	)

Alternative 2:

riemann(
	.
	.
	type("tls")
        tls(
              cert-file("/opt/syslog-ng/etc/syslog-ng/riemann-client-cert.pem")
              key-file("/opt/syslog-ng/etc/syslog-ng/riemann-client-cert.key")
       )

This option was called key() in syslog-ng OSE version 3.7.

slack: Sending alerts and notifications to a Slack channel

The slack() destination driver sends messages to a Slack channel using the Slack Web API. For the list of available optional parameters, see Slack destination options. This destination is available in version 3.19 and later.

Declaration:
destination d_slack {
  slack(
    hook-url("https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX")
  );
};

The driver allows you to modify nearly every field of the HTTP request. For details, see the Slack API documentation.

You can use the proxy() option to configure the HTTP driver in all HTTP-based destinations to use a specific HTTP proxy that is independent from the proxy configured for the system.

By default, the throttle() option is set to 1, because Slack has a 1 message/second limit on Webhooks. It can allow more message in short bursts, so you can set it to 0, if you only expect messages in a short period of time. For details, see the Web API rate limiting in the Slack documentation.

To use this destination, the scl.conf file must be included in your syslog-ng OSE configuration:

@include "scl.conf"

The slack() driver is actually a reusable configuration snippet configured to send log messages using the http() driver. For details on using or writing such configuration snippets, see Reusing configuration blocks. You can find the source of this configuration snippet on GitHub.

Prerequisites

To send messages and notifications from syslog-ng OSE to Slack, you must create a Slack app and a Webhook that syslog-ng OSE can use. For details, see the Slack documentation.

Example: Using the slack() driver

The following example sets the colors and the author of the message.

@include "scl.conf"

destination d_slack1 {
  slack(
    hook-url("https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX")
    colors("#000000,#222222,#444444,#666666,#888888,#AAAAAA,#CCCCCC,#EEEEEE")
    color-chooser(7)
    author-name("syslog-ng BOT")
    author-link("https://www.syslog-ng.com/products/open-source-log-management")
    author-icon("https://raw.githubusercontent.com/MrAnno/vscode-syslog-ng/master/images/syslog-ng-icon.png")
  );
};
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