syslog-ng Open Source Edition 3.21 - 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) 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 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

Using pattern databases

To classify messages using a pattern database, include a db-parser() statement in your syslog-ng configuration file using the following syntax:

Declaration:
parser <identifier> {
    db-parser(file("<database_filename>"));
};

Note that using the parser in a log statement only performs the classification, but does not automatically do anything with the results of the classification.

Example: Defining pattern databases

The following statement uses the database located at /opt/syslog-ng/var/db/patterndb.xml.

parser pattern_db {
    db-parser(
        file("/opt/syslog-ng/var/db/patterndb.xml")
    );
};

To apply the patterns on the incoming messages, include the parser in a log statement:

log {
    source(s_all);
    parser(pattern_db);
    destination( di_messages_class);
};

By default, syslog-ng tries to apply the patterns to the body of the incoming messages, that is, to the value of the $MESSAGE macro. If you want to apply patterns to a specific field, or to an expression created from the log message (for example, using template functions or other parsers), use the message-template() option. For example:

parser pattern_db {
    db-parser(
        file("/opt/syslog-ng/var/db/patterndb.xml")
        message-template("${MY-CUSTOM-FIELD-TO-PROCESS}")
    );
};

By default, syslog-ng uses the name of the application (content of the ${PROGRAM} macro) to select which rules to apply to the message. If the content of the ${PROGRAM} macro is not the proper name of the application, you can use the program-template() option to specify it. For example:

parser pattern_db {
    db-parser(
        file("/opt/syslog-ng/var/db/patterndb.xml")
        program-template("${MY-CUSTOM-FIELD-TO-SELECT-RULES}")
    );
};

Note that the program-template() option is available in syslog-ng OSE version 3.21 and later.

NOTE:

The default location of the pattern database file is /opt/syslog-ng/var/run/patterndb.xml. The file option of the db-parser() statement can be used to specify a different file, thus different db-parser statements can use different pattern databases.

Example: Using classification results

The following destination separates the log messages into different files based on the class assigned to the pattern that matches the message (for example Violation and Security type messages are stored in a separate file), and also adds the ID of the matching rule to the message:

destination di_messages_class {
    file(
        "/var/log/messages-${.classifier.class}"
        template("${.classifier.rule_id};${S_UNIXTIME};${SOURCEIP};${HOST};${PROGRAM};${PID};${MESSAGE}\n")
        template-escape(no)
    );
};

Note that if you chain pattern databases, that is, use multiple databases in the same log path, the class assigned to the message (the value of ${.classifier.class}) will be the one assigned by the last pattern database. As a result, a message might be classified as unknown even if a previous parser successfully classified it. For example, consider the following configuration:

log {
    ...
    parser(db_parser1);
    parser(db_parser2);
    ...
};

Even if db_parser1 matches the message, db_parser2 might set ${.classifier.class} to unknown. To avoid this problem, you can use an 'if' statement to apply the second parser only if the first parser could not classify the message:

log {
    ...
    parser{ db-parser(file("db_parser1.xml")); };
    if (match("^unknown$" value(".classifier.class"))) {
        parser { db-parser(file("db_parser2.xml")); };
    };
    ...
};

For details on how to create your own pattern databases see The syslog-ng pattern database format.

Drop unmatched messages

If you want to automatically drop unmatched messages (that is, discard every message that does not match a pattern in the pattern database), use the drop-unmatched() option in the definition of the pattern database:

parser pattern_db {
    db-parser(
        file("/opt/syslog-ng/var/db/patterndb.xml")
        drop-unmatched(yes)
    );
};

Note that the drop-unmatched() option is available in syslog-ng OSE version 3.11 and later.


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