syslog-ng Open Source Edition 3.18 - Administration Guide

kafka: Publishing messages to Apache Kafka

Starting with version 3.7, syslog-ng OSE can directly publish log messages to the Apache Kafka message bus, where subscribers can access them.

• This destination is only supported on the Linux platform.

• Since syslog-ng OSE uses the official Java Kafka producer, the kafka destination has significant memory usage.

• The log messages of the underlying client libraries are available in the internal() source of syslog-ng OSE.

@module mod-java
@include "scl.conf"

kafka(
    client-lib-dir("/opt/syslog-ng/lib/syslog-ng/java-modules/:<path-to-preinstalled-kafka-libraries>")
    kafka-bootstrap-servers("1.2.3.4:9092,192.168.0.2:9092")
    topic("${HOST}")

);

@module mod-java
@include "scl.conf"

destination d_kafka {
  kafka(
    client-lib-dir("/opt/syslog-ng/lib/syslog-ng/java-modules/KafkaDestination.jar:/usr/share/kafka/lib/")
    kafka-bootstrap-servers("1.2.3.4:9092,192.168.0.2:9092")
    topic("${HOST}")
  );
};

• To install the software required for the kafka destination, see Prerequisites.

• For details on how the kafka destination works, see How syslog-ng OSE interacts with Apache Kafka.

• For the list of options, see Kafka destination options.

The kafka() driver is actually a reusable configuration snippet configured to receive log messages using the Java language-binding of syslog-ng OSE. For details on using or writing such configuration snippets, see Reusing configuration blocks. You can find the source of the kafka configuration snippet on GitHub. For details on extending syslog-ng OSE in Java, see the Getting started with syslog-ng development guide.

Prerequisites

To publish messages from syslog-ng OSE to Apache Kafka, complete the following steps.

How syslog-ng OSE interacts with Apache Kafka

When stopping the syslog-ng OSE application, syslog-ng OSE will not stop until all Java threads are finished, including the threads started by the Kafka Producer. There is no way (except for the kill -9 command) to stop syslog-ng OSE before the Kafka Producer stops. To change this behavior set the properties of the Kafka Producer in its properties file, and reference the file in the properties-file option.

The syslog-ng OSE kafka destination tries to reconnect to the brokers in a tight loop. This can look as spinning, because of a lot of similar debug messages. To decrease the amount of such messages, set a bigger timeout using the following properties:

retry.backoff.ms=1000
reconnect.backoff.ms=1000

For details on using property files, see properties-file(). For details on the properties that you can set in the property file, see the Apache Kafka documentation.

Kafka destination options

The kafka destination of syslog-ng OSE can directly publish log messages to the Apache Kafka message bus, where subscribers can access them. The kafka destination has the following options.

@module mod-java
@include "scl.conf"

frac-digits()

Description: The syslog-ng 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 that syslog-ng can add the fractions to non-ISO8601 timestamps as well.

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.

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:

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:

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};

jvm-options()

Description: Specify the Java Virtual Machine (JVM) settings of your Java destination from the syslog-ng OSE configuration file.

For example:

jvm-options("-Xss1M -XX:+TraceClassLoading")

You can set this option only as a global option, by adding it to the options statement of the syslog-ng configuration file.

on-error()

Description: Controls what happens when type-casting fails and syslog-ng OSE cannot convert some data to the specified type. By default, syslog-ng OSE drops the entire message and logs the error. Currently the value-pairs() option uses the settings of on-error().

• drop-message: Drop the entire message and log an error message to the internal() source. This is the default behavior of syslog-ng OSE.

• drop-property: Omit the affected property (macro, template, or message-field) from the log message and log an error message to the internal() source.

• fallback-to-string: Convert the property to string and log an error message to the internal() source.

• silently-drop-message: Drop the entire message silently, without logging the error.

• silently-drop-property: Omit the affected property (macro, template, or message-field) silently, without logging the error.

• silently-fallback-to-string: Convert the property to string silently, without logging the error.

log-fifo-size()

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

acks=all
compression.type=snappy

retries()

Description: The number of times syslog-ng OSE attempts to send a message to this destination. If syslog-ng OSE could not send a message, it will try again until the number of attempts reaches retries, then drops the message.

throttle()

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-zone()

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 by using the name, 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()

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