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syslog-ng Open Source Edition 3.22 - 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 linux-audit: Collecting messages from Linux audit logs network: Collecting messages using the RFC3164 protocol (network() driver) nodejs: Receiving JSON messages from nodejs applications mbox: Converting local e-mail 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 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: Publishing messages to Apache Kafka (C implementation, using the librdkafka client) loggly: Using Loggly logmatic: Using Logmatic.io mongodb: Storing messages in a MongoDB database 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 (e-mail) from logs snmp: Sending SNMP traps Splunk: Sending log messages to Splunk sql: Storing messages in an SQL database stomp: Publishing messages using STOMP syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng: Forwarding messages and tags 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 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

Generating configuration blocks from a script

Purpose:

The syslog-ng OSE application can automatically execute scripts when it is started, and can include the output of such script in the configuration file. To create and use a script that generates a part of the syslog-ng OSE configuration file (actually, a configuration block), complete the following steps. The steps include examples for collecting Apache access log files (access.log) from subdirectories, but you can create any script that creates a valid syslog-ng OSE configuration snippet.

Steps:
  1. Navigate to the directory where you have installed syslog-ng OSE (for example, /opt/syslog-ng/share/include/scl/), and create a new directory, for example, apache-access-logs. The name of the directory will be used in the syslog-ng OSE configuration file as well, so use a descriptive name.

  2. Create a file called plugin.conf in this new directory.

  3. Edit the plugin.conf file and add the following line:

    @module confgen context(source) name(<directory-name>) exec("`scl-root`/<directory-name>/<my-script>")

    Replace <directory-name> with the name of the directory (for example, apache-access-logs), and <my-script> with the filename of your script (for example, apache-access-logs.sh). You can reference the script in your syslog-ng OSE configuration file as a configuration block using the value name option.

    The context option determines the type of the configuration snippet that the script generates, and must be one of the following: destination, filter, log, parser, rewrite, root, source. The root blocks can be used in the "root" context of the configuration file, that is, outside any other statements. In the example, context(source) means that the output of the script will be used within a source statement.

  4. Write a script that generates the output you need, and formats it to a configuration snippet that syslog-ng OSE can use. The filename of the script must match with the filename used in plugin.conf, for example, apache-access-logs.sh.

    The following example checks the /var/log/apache2/ directory and its subdirectories, and creates a source driver for every directory that contains an access.log file.

    #!/bin/bash
    for i in `find /var/log/apache2/ -type d`; do
        echo "file(\"$i/access.log\" flags(no-parse) program-override(\"apache2\"));";
    done;

    The script generates an output similar to this one, where service* is the actual name of a subdirectory:

    file("/var/log/apache2/service1/access.log" flags(no-parse) program-override("apache2"));
    file("/var/log/apache2/service2/access.log" flags(no-parse) program-override("apache2"));
    
  5. Include the plugin.conf file in the syslog-ng.conf file — or a file already included into syslog-ng.conf. Version 3.7 and newer automatically includes the *.conf files from the <directory-where-syslog-ng-is-installed>/scl/*/ directories. For details on including configuration files, see Including configuration files.

  6. Add the block you defined in the plugin.conf file to your syslog-ng OSE configuration file. You can reference the block using the value of the name option from the plugin.conf file, followed by parentheses, for example, apache-access-logs(). Make sure to use the block in the appropriate context of the configuration file, for example, within a source statement if the value of the context option in the plugin.conf file is source.

    @include "scl.conf"
    ...
    source s_apache {
        file("/var/log/apache2/access.log" flags(no-parse) program-override("apache2"));
        file("/var/log/apache2/error.log" flags(no-parse) program-override("apache2"));
        file("/var/log/apache2/ssl.log" flags(no-parse) program-override("apache2"));
        apache-access-logs();
    };
    
    log {
        source(s_apache); destination(d_central);
    };
    ...
  7. Check if your modified syslog-ng OSE configuration file is syntactically correct using the syslog-ng --syntax-only command.

  8. If your modified configuration is syntactically correct, load the new configuration file using the syslog-ng-ctl reload command.

Python code in external files

You can extend and customize syslog-ng OSE easily by writing destinations, parsers, template functions, and sources in Python.

Instead of writing Python code into your syslog-ng OSE configuration file, you can store the Python code for your Python object in an external file. That way, it is easier to write, maintain, and debug the code. You can store the Python code in any directory in your system, but make sure to include it in your Python path.

When referencing a Python class from an external file in the class() option of a Python block in the syslog-ng OSE configuration file, the class name must include the name of the Python file containing the class, without the path and the .py extension. For example, if the MyDestination class is available in the /etc/syslog-ng/etc/pythonexample.py file, use class("pythonexample.MyDestination"):

destination d_python_to_file {
    python(
        class("pythonexample.MyDestination")
    );
};
log {
    source(src);
    destination(d_python_to_file);
};

If you store the Python code in a separate Python file and only include it in the syslog-ng OSE configuration file, make sure that the PYTHON_PATH environment variable includes the path to the Python file, and export the PYTHON_PATH environment variable. For example, if you start syslog-ng OSE manually from a terminal and you store your Python files in the /opt/syslog-ng/etc directory, use the following command: export PYTHONPATH=/opt/syslog-ng/etc

In production, when syslog-ng OSE starts on boot, you must configure your startup script to include the Python path. The exact method depends on your operating system. For recent Red Hat Enterprise Linux, Fedora, and CentOS distributions that use systemd, the systemctl command sources the /etc/sysconfig/syslog-ng file before starting syslog-ng OSE. (On openSUSE and SLES, /etc/sysconfig/syslog file.) Append the following line to the end of this file: PYTHONPATH="<path-to-your-python-file>", for example, PYTHONPATH="/opt/syslog-ng/etc"

To help debugging and troubleshooting your Python code, you can send log messages to the internal() source of syslog-ng OSE. For details, see Logging from your Python code.

Logging from your Python code

You can extend and customize syslog-ng OSE easily by writing destinations, parsers, template functions, and sources in Python.

To debug and troubleshoot your Python code, syslog-ng OSE allows you to use the logger() method to send log messages to the internal() source of syslog-ng OSE. That way the diagnostic messages of your Python code are treated the same way as other such log messages of syslog-ng OSE. This has the following benefits:

  • The logger() method respects the log level settings of syslog-ng OSE. You can write error, warning, info, debug, and trace level messages.

  • You can follow what your Python code is doing even if syslog-ng OSE is running as a daemon in the background.

Logging to the internal() source is available in syslog-ng OSE version 3.20 and later.

To send log messages to the internal() source from Python

  1. Add the following import to your Python code:

    import syslogng
  2. Create a logger object:

    logger = syslogng.Logger()
  3. Use the logger object in your Python code, for example:

    logger.info("This is a sample log message send from the Python code.")

    You can use the following log levels: logger.error, logger.warning, logger.info, logger.debug, logger.trace

  4. Make sure that your syslog-ng OSE configuration includes the internal() source, for example:

    source s_internal { internal(); };
    destination d_internal { file("/var/log/internal.txt"); };
    log {source(s_internal); destination(d_internal); };
    

source: Read, receive, and collect log messages

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