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syslog-ng Open Source Edition 3.36 - 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 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 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 Glossary

How to process messages from an orphan disk-buffer file using a separate syslog-ng OSE instance

This section describes how to read messages from an orphan disk-buffer file by using a separate syslog-ng Open Source Edition (syslog-ng OSE) process running parallel to the already running syslog-ng OSE instance.

Orphan disk-buffer files

In certain situations (for example, after modifying the disk-buffer configuration or losing the persist information), syslog-ng OSE creates a new disk-buffer file instead of using the already existing one. In these situations, the already existing disk-buffer file becomes a so-called orphan disk-buffer file.

NOTE: The syslog-ng OSE application does not store messages in orphan disk-buffer files or forward the messages stored in the disk-buffer file.

Processing the messages from an orphan disk-buffer file by using a separate syslog-ng OSE instance

When syslog-ng OSE creates orphan disk-buffer files, you can start a separate syslog-ng OSE instance parallel to the syslog-ng OSE instance already running, and use the following resolution process to process the messages in the orphan disk-buffer file.

Caution:

Before starting a separate syslog-ng OSE instance to process the messages from the orphan disk-buffer file, consider the following:

  • During the resolution process, a separate syslog-ng OSE instance will be started with its temporary files beside the syslog-ng OSE instance already running.
  • An incorrect startup command and incorrect configurations may cause issues for the syslog-ng OSE instance already running.
  • The disk-buffer file stores processed log messages in the format in which they would have been sent out to the destination.
  • The disk-buffer file doesn't store information about the destination.

To process the messages from an orphan disk-buffer file using a separate syslog-ng OSE instance,

  1. Identify the orphan disk-buffer files and make a record of them. For more information, see How to get information about disk-buffer files.

    It is important to know the type of the disk-buffer file. Disk-buffer file types can be normal (.qf) or reliable (.rqf).

    In the examples during this process, the /opt/syslog-ng/var/syslog-ng-00005.rqf orphan reliable disk-buffer file is used.

  2. Determine the destination of the logs. The content of the disk-buffer may help you determine the logs' destination. For more information, see How to get information about disk-buffer files.

    In the examples during this process, the destination 10.21.10.20 is used with the standard network() port 514.

  3. Create a directory for the temporary instance. In the examples during this process, the /tmp/qdisk directory is used.

    mkdir /tmp/qdisk

    		 Caution:

    Make sure that there is sufficient disk space in the directory. The minimum recommended disk space in the directory is equal to the size of the orphan disk-buffer file.

    If you want to use a different temporary directory (that is, other than /tmp/qdisk), create a symbolic link between /tmp/qdisk and the temporary directory you want to use with ln -s /path/to/tempdir /tmp/qdisk. This will allow you to use the commands in this resolution process.

    If you will not use a different temporary directory, use the /tmp/qdisk temporary directory in the example commands and file names.

  4. Create the configuration file /tmp/qdisk/qdisk.conf for the temporary instance with the following content.

    Example: creating the /tmp/qdisk/qdisk.conf configuration file for the temporary instance
    @version:7.0
@include "scl.conf"

options {
  keep-hostname(yes);
  keep-timestamp(yes);
};

destination d_destination {
#    ADD YOUR DESTINATION HERE

};

log {
  destination(d_destination);
};

  5. Add your destination statement with disk-buffer() to the configuration file. You can copy the destination statement from your running syslog-ng OSE configuration.

    		 Caution:

    Add the dir() option and set the disk-buffer file's destination directory to the temporary directory (that is, /tmp/qdisk) in your destination statement.

    Example: adding the destination statement with disk-buffer() to the configuration file
    network("10.21.10.20"
    disk-buffer(
        disk-buf-size(1048576)
        reliable(yes)
        dir(/tmp/qdisk/)
);

  6. Start the temporary syslog-ng OSE instance in the foreground.

    syslog-ng -Fe -f /tmp/qdisk/qdisk.conf -R /tmp/qdisk/qdisk.persist -c /tmp/qdisk/qdisk.ctl

    The syslog-ng OSE application will log to the console, so you will see any potential error that may occur during startup.

    The following example output displays that an empty disk-buffer file has been created and the connection to the remote destination has been established.

    Example: output displaying newly created empty disk-buffer file and connection established to remote destination
    Follow-mode file source not found, deferring open; filename='/no_such_file_or.dir'
Reliable disk-buffer state saved; filename='/tmp/qdisk/syslog-ng-00000.rqf', qdisk_length='0'
No server license found, running in client mode;
syslog-ng starting up; version='7.0.20', cfg-fingerprint='eaa03b9efb88b87d7c1b0ce7efd042ed8ac0c013', cfg-nonce-ndx='0', cfg-signature='c0327a7f7e6418ce0399a75089377dfb662bb072'
FIPS information; FIPS-mode='disabled'
Syslog connection established; fd='7', server='AF_INET(10.21.10.20:514)', local='AF_INET(0.0.0.0:0)'

  7. To stop syslog-ng OSE, press CTRL+C.

  8. Overwrite the empty disk-buffer file with the orphan disk-buffer file.

    mv /opt/syslog-ng/var/syslog-ng-00005.rqf /tmp/qdisk/syslog-ng-00000.rqf

  9. Start syslog-ng OSE using the command used in Start the temporary syslog-ng OSE instance in the foreground step.

    syslog-ng -Fe -f /tmp/qdisk/qdisk.conf -R /tmp/qdisk/qdisk.persist -c /tmp/qdisk/qdisk.ctl

  10. Open another terminal and check the progress by using one of the following methods.

    • Checking the number of stored logs in the disk-buffer (that is, the last number from the output).

      /opt/syslog-ng/sbin/syslog-ng-ctl stats -c /tmp/qdisk/qdisk.ctl | grep 'dst.*queued'

    • Checking the status of the disk-buffer file.

      dqtool info /tmp/qdisk/syslog-ng-00000.rqf

      An empty disk-buffer file will look similar to this:

      Example: empty disk-buffer file status message

      When checking the status of the disk-buffer files, the terminal will display a similar status message for an empty disk-buffer file:

      Reliable disk-buffer state loaded; filename='/tmp/qdisk/syslog-ng-00000.rqf', queue_length='0', size='0'

  11. Press CTRL+C to stop syslog-ng OSE.

  12. Check the state of the orphan disk-buffer file. For more information, see How to get information about disk-buffer files.

  13. If you have more than one orphan disk-buffer file, repeat the steps following the syslog-ng OSE stop (that is, the steps beginning from overwriting the empty disk-buffer file with the orphan disk-buffer file) for each orphan disk-buffer file.

  14. Remove the temporary directory.

    Example: command for removing the temporary directory

    The following command removes the /mp/qdisk temporary directory:

    rm -rf /tmp/qdisk

Enabling memory buffering

To enable memory buffering, use the log-fifo-size() parameter in the destination. All destination drivers can use memory buffering. Use memory buffering if you want to send logs to destinations where disk-based buffering is not available. Or if you want the fastest solution, and if syslog-ng OSE crash or network downtime is never expected. In these cases, losing logs is possible. This solution does not use disk-based buffering, logs are stored only in the memory.

Example: Example for using memory buffering
destination d_BSD {
    network("127.0.0.1"
        port(3333)
        log-fifo-size(10000)
    );
};

About disk queue files

Normal and reliable queue files

The key difference between disk queue files that employ the reliable(yes) option and not is the strategy they employ. Reliable disk queues guarantee that all the messages passing through them are written to disk first, and removed from the queue only after the destination has confirmed that the message has been successfully received. This prevents message loss, for example, due to syslog-ng OSE crashes if the client and the destination server communicate using the Advanced Log Transport Protocol (ALTP). Note that the Advanced Log Transport Protocol is available only in syslog-ng Premium Edition version 6 LTS. Of course, using the reliable(yes) option introduces a significant performance penalty as well.

Both reliable and normal disk-buffers employ an in-memory output queue (set in quot-size()) and an in-memory overflow queue (set in mem-buf-size() for reliable disk-buffers, or mem-buf-length() for normal disk-buffers). The difference between reliable and normal disk-buffers is that when the reliable disk-buffer uses one of its in-memory queues, it also stores the message on the disk, whereas the normal disk-buffer stores the message only in memory. The normal disk-buffer only uses the disk if the in-memory output buffer is filled up completely. This approach has better performance (due to fewer disk I/O operations), but also carries the risk of losing a maximum of quot-size() plus mem-buf-length() number of messages in case of an unexpected power failure or application crash.

Size of the queue files

Disk queue files tend to grow. Each may take up to disk-buf-size() bytes on the disk. Due to the nature of reliable queue files, all the messages traversing the queue are written to disk, constantly increasing the size of the queue file.

The disk-buffer file's size should be considered as the configured disk-buf-size() at any point of time, even if it does not have messages in it. Truncating the disk-buffer file can slow down disk I/O operations, so syslog-ng OSE does not always truncate the file when it would be possible (see the truncate-size-ratio() option). If a large disk-buffer file is not desirable, you should set the disk-buf-size() option to a smaller value.

 Caution:

One Identity recommends that you do not build upon the current truncating logic of the disk-buffer files, because syslog-ng OSE might pre-allocate the disk-buffer files and never truncate them in the future.

NOTE: The disk-buffer file's size does not strictly correlate to the number of stored messages. If you want to get information about the disk-buffer, use dqtool (for more information, see Getting the status information of disk-buffer files).

NOTE: If a queue file becomes corrupt, syslog-ng OSE starts a new one. This might lead to the queue files consuming more space in total than their maximal configured size and the number of configured queue files multiplied together.

Filters

The following sections describe how to select and filter log messages.

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