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syslog-ng Premium Edition 7.0.18 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng 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 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) 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 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 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 hdfs: Storing messages on the Hadoop Distributed File System (HDFS) http: Posting messages over HTTP kafka: Publishing messages to Apache Kafka 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 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

Python code in external files

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

Instead of writing Python code into your syslog-ng PE 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 PE 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 PE 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 PE 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 PE 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 PE. (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 PE. For details, see Logging from your Python code.

Logging from your Python code

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

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

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

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

Logging to the internal() source is available in syslog-ng PE version 7.0.14 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 PE 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); };
    

Collecting log messages — sources and source drivers

How sources work

A source is where syslog-ng receives log messages. Sources consist of one or more drivers, each defining where and how messages are received.

To define a source, add a source statement to the syslog-ng configuration file using the following syntax:

source <identifier> {
    source-driver(params);
    source-driver(params);
    ...
};

Example: A simple source statement

The following source statement receives messages on the TCP port 1999 of the interface having the 10.1.2.3 IP address.

source s_demo_tcp {
    network(
        ip(10.1.2.3)
        port(1999)
    );
};
Example: A source statement using two source drivers

The following source statement receives messages on the 1999 TCP port and the 1999 UDP port of the interface having the 10.1.2.3 IP address.

source s_demo_two_drivers {
    network(
        ip(10.1.2.3)
        port(1999)
    );
    network(
        ip(10.1.2.3)
        port(1999)
        transport("udp")
    );
};
Example: Setting default priority and facility

If the message received by the source does not have a proper syslog header, you can use the default-facility() and default-priority() options to set the facility and priority of the messages. Note that these values are applied only to messages that do not set these parameters in their header.

source headerless_messages {
    network(
        default-facility(syslog)
        default-priority(emerg)
    );
};

Define a source only once. The same source can be used in several log paths. Duplicating sources causes syslog-ng to open the source (TCP/IP port, file, and so on) more than once, which might cause problems. For example, include the /dev/log file source only in one source statement, and use this statement in more than one log path if needed.

Caution:

Sources and destinations are initialized only when they are used in a log statement. For example, syslog-ng PE starts listening on a port or starts polling a file only if the source is used in a log statement. For details on creating log statements, see Routing messages: log paths, flags, and filters.

To collect log messages on a specific platform, it is important to know how the native syslogd communicates on that platform. The following table summarizes the operation methods of syslogd on some of the tested platforms:

Table 8: Communication methods used between the applications and syslogd
Platform Method
Linux A SOCK_DGRAM unix socket named /dev/log. Newer distributions that use systemd collect log messages into a journal file.
BSD flavors A SOCK_DGRAM unix socket named /var/run/log.
Solaris (2.5 or below) An SVR4 style STREAMS device named /dev/log.
Solaris (2.6 or above) In addition to the STREAMS device used in earlier versions, 2.6 uses a new multithreaded IPC method called door. By default the door used by syslogd is /etc/.syslog_door.
HP-UX 11 or later HP-UX uses a named pipe called /dev/log that is padded to 2048 bytes, for example, source s_hp-ux {pipe ("/dev/log" pad-size(2048)}.
AIX 5.2 and 5.3 A SOCK_STREAM or SOCK_DGRAM unix socket called /dev/log.

Each possible communication mechanism has a corresponding source driver in syslog-ng. For example, to open a unix socket with SOCK_DGRAM style communication use the driver unix-dgram. The same socket using the SOCK_STREAM style — as used under Linux — is called unix-stream.

Example: Source statement on a Linux based operating system

The following source statement collects the following log messages:

  • internal(): Messages generated by syslog-ng.

  • network(transport("udp")): Messages arriving to the 514/UDP port of any interface of the host.

  • unix-dgram("/dev/log");: Messages arriving to the /dev/log socket.

source s_demo {
    internal();
    network(transport("udp"));
    unix-dgram("/dev/log");
};

The following table lists the source drivers available in syslog-ng.

Table 9: Source drivers available in syslog-ng
Name Description
file() Opens the specified file and reads messages.
internal() Messages generated internally in syslog-ng.
linux-audit() Reads the logfiles of the auditd application.
network() Receives messages from remote hosts using the BSD-syslog protocol over IPv4 and IPv6. Supports the TCP, UDP, ALTP, and TLS network protocols.
pipe() Opens the specified named pipe and reads messages.
program() Opens the specified application and reads messages from its standard output.
python() and python-fetcher() Receive or fetch messages using a custom source written in Python.
sun-stream(), sun-streams() Opens the specified STREAMS device on Solaris systems and reads incoming messages.
syslog() Listens for incoming messages using the new IETF-standard syslog protocol.
system() Automatically detects which platform syslog-ng PE is running on, and collects the native log messages of that platform.
systemd-journal() Collects messages directly from the journal of platforms that use systemd.
systemd-syslog() Collects messages from the journal using a socket on platforms that use systemd.
unix-dgram() Opens the specified unix socket in SOCK_DGRAM mode and listens for incoming messages.
unix-stream() Opens the specified unix socket in SOCK_STREAM mode and listens for incoming messages.
windowsevent() Reads messages from the Windows Event Collector tool.
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