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syslog-ng Open Source Edition 3.33 - 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 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 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 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 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

Glob patterns without regular expression support

There are no supported flags() options for glob patterns without regular expression support.

Optimizing regular expressions

The host(), match(), and program() filter functions and some other syslog-ng objects accept regular expressions as parameters. But evaluating general regular expressions puts a high load on the CPU, which can cause problems when the message traffic is very high. Often the regular expression can be replaced with simple filter functions and logical operators. Using simple filters and logical operators, the same effect can be achieved at a much lower CPU load.

Example: Optimizing regular expressions in filters

Suppose you need a filter that matches the following error message logged by the xntpd NTP daemon:

xntpd[1567]: time error -1159.777379 is too large (set clock manually);

The following filter uses regular expressions and matches every instance and variant of this message.

filter f_demo_regexp {
    program("demo_program") and
    match("time error .* is too large .* set clock manually");
};

Segmenting the match() part of this filter into separate match() functions greatly improves the performance of the filter.

filter f_demo_optimized_regexp {
    program("demo_program") and
    match("time error") and
    match("is too large") and
    match("set clock manually");
};

parser: Parse and segment structured messages

The filters and default macros of syslog-ng work well on the headers and metainformation of the log messages, but are rather limited when processing the content of the messages. Parsers can segment the content of the messages into name-value pairs, and these names can be used as user-defined macros. Subsequent filtering or other type of processing of the message can use these custom macros to refer to parts of the message. Parsers are global objects most often used together with filters and rewrite rules.

The syslog-ng OSE application provides the following possibilities to parse the messages, or parts of the messages:

The syslog-ng OSE application provides built-in parsers for the following application logs:

Parsing syslog messages

By default, syslog-ng OSE parses every message using the syslog-parser as a syslog message, and fills the macros with values of the message. The syslog-parser does not discard messages: the message cannot be parsed as a syslog message, the entire message (including its header) is stored in the $MSG macro. If you do not want to parse the message as a syslog message, use the flags(no-parse) option of the source.

You can also use the syslog-parser to explicitly parse a message, or a part of a message as a syslog message (for example, after rewriting the beginning of a message that does not comply with the syslog standards).

Example: Using junctions

For example, suppose that you have a single network source that receives log messages from different devices, and some devices send messages that are not RFC-compliant (some routers are notorious for that). To solve this problem in earlier versions of syslog-ng OSE, you had to create two different network sources using different IP addresses or ports: one that received the RFC-compliant messages, and one that received the improperly formatted messages (for example, using the flags(no-parse) option). Using junctions this becomes much more simple: you can use a single network source to receive every message, then use a junction and two channels. The first channel processes the RFC-compliant messages, the second everything else. At the end, every message is stored in a single file. The filters used in the example can be host() filters (if you have a list of the IP addresses of the devices sending non-compliant messages), but that depends on your environment.

log {
    source {
        syslog(
            ip(10.1.2.3)
            transport("tcp")
            flags(no-parse)
        );
    };
    junction {
        channel {
            filter(f_compliant_hosts);
            parser {
                syslog-parser();
            };
        };
        channel {
            filter(f_noncompliant_hosts);
        };
    };
    destination {
        file("/var/log/messages");
    };
};

Since every channel receives every message that reaches the junction, use the flags(final) option in the channels to avoid the unnecessary processing the messages multiple times:

log {
    source {
        syslog(
            ip(10.1.2.3)
            transport("tcp")
            flags(no-parse)
        );
    };
    junction {
        channel {
            filter(f_compliant_hosts);
            parser {
                syslog-parser();
            };
            flags(final);
        };
        channel {
            filter(f_noncompliant_hosts);
            flags(final);
        };
    };
    destination {
        file("/var/log/messages");
    };
};

Note that syslog-ng OSE has several parsers that you can use to parse non-compliant messages. You can even write a custom syslog-ng parser in Python. For details, see parser: Parse and segment structured messages.

Note that by default, the syslog-parser attempts to parse the message as an RFC3164-formatted (BSD-syslog) message. To parse the message as an RFC5424-formatted message, use the flags(syslog-protocol) option in the parser.

syslog-parser(flags(syslog-protocol));
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