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 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

mqtt: receiving messages from an MQTT broker

From syslog-ng OSE version 3.35, you can use the mqtt() source to fetch messages from MQTT brokers.

The mqtt() source builds on the MQTT protocol, and uses its client and broker entities.

NOTE: The rest of this chapter and its sections build on your familiarity with the MQTT protocol, the concept of client and broker entities, and how these entities function within an MQTT system.

source s_mqtt{
Example: Using the mqtt() source in your configuration

The following example illustrates an mqtt() source configured to fetch messages from the MQTT broker running on localhost:4444 using the test/test topic, and send them to the localhost:4445 address.

@version: 3.35
@include "scl.conf"
source s_mqtt {
destination d_network {
log {

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Prerequisites to using the mqtt() destination

Using the current implementation of the mqtt() destination has the following prerequisites:

  • Installing the eclipse-paho-mqtt-c library.

    NOTE: The default package manager for some Linux operating systems contains the eclipse-paho-mqtt-c library, but depending on your OS, you may have to install the library manually. For more information about how you can download and install the eclipse-paho-mqtt-c library, see Eclipse Paho on the Eclipse Foundation website.

  • Having a broker entity in a functional MQTT system.

    NOTE: In your configuration, you will specify the broker entity of your MQTT system in the address() option of your mqtt() source.

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Limitations to using the mqtt() destination

Using the mqtt() source of syslog-ng OSE has the following limitations:

  • You can only use the mqtt() source with syslog-ng OSE version 3.35 or higher.

  • You cannot use the mqtt() source without installing the the eclipse-paho-mqtt-c library.

  • For more information about how you can download and install the eclipse-paho-mqtt-c library, see Eclipse Paho on the Eclipse Foundation website.

  • The current implementation of the mqtt() source supports versions 3.1 and 3.1.1 of the MQTT protocol

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Options of the mqtt() source

The mqtt() source has the following options.

Required options: address(), fallback-topic(), and topic().

Type: string
Default: tcp://localhost:1883
Required: yes

Description: Specifies the hostname or IP address, and the port number of the MQTT broker to which syslog-ng OSE will send the log messages.

Syntax: <protocol type>://<host>:<port>

Type: string
Default: syslog-ng-source-{topic option}
Required: no

Description: The client-id() is used to identify the client to the MQTT server, which stores session data for each client. The session data can contains information regarding which message has been sent, received. It is not possible to set the client-id() to an empty string. To always start a new session see the cleansession() option.

Type: yes | no
Default: no

Description: This option instruments the MQTT broker to clean the session data when connecting. The session data contains information about which message was processed.

Type: URL
Default: N/A

Description: Specifies HTTP/HTTPS proxy for WebSocket connections.

Type: positive integer number (in seconds)
Default: 60

Description: Specifies the number of seconds that syslog-ng OSE keeps the connection between the broker and clients open in case there is no message traffic. When keep-alive() number of seconds pass, the connection is terminated, and you have to reconnect.

On the MQTT side, the keep alive function provides a workaround method to access connections that are still open.

Type: string
Default: N/A

Description: The password used to authenticate on the MQTT broker.

Type: string


Description:If you receive the following error message during syslog-ng OSE startup, set the persist-name() option of the duplicate drivers:

Error checking the uniqueness of the persist names, please override it with persist-name option. Shutting down.

This error happens if you use identical drivers in multiple sources, for example, if you configure two file sources to read from the same file. In this case, set the persist-name() of the drivers to a custom string, for example, persist-name("example-persist-name1").

Type: number
Default: 0

Possible values:

0 - at most once (the fastest option)

1 - at least once (a much slower option than 0)

2 - exactly once (the slowest option)

Description: The Quality of Service (QoS) level in MQTT messaging is an agreement between sender and receiver on the guarantee of delivering a message.

Type: tls options
Default: n/a

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

The following options are relevant for the mqtt() tls() block: ca-dir(), ca-file(), cert-file(), cipher-suite(), key-file(), peer-verify(), ssl-version(), use-system-cert-store().

Type: string or template
Default: N/A

Description: Required option. Specifies the MQTT topic.

NOTE: The current implementation of the mqtt() destination does not support using the following characters for topic names:

  • $

  • +

  • #

Type: string
Default: N/A

Description: The username used to authenticate on the MQTT broker.

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