syslog-ng Premium Edition 7.0.12 - Administration Guide

Sending and storing log messages — destinations and destination drivers

A destination is where a log message is sent if the filtering rules match. Similarly to sources, destinations consist of one or more drivers, each defining where and how messages are sent.

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

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

destination d_demo_tcp {
    network("10.1.2.3" port(1999));
};

destination d_tcp {
    network("target_host" port(1999));
};

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

elasticsearch: Sending messages directly to Elasticsearch version 1.x

Starting with version 5.6 of syslog-ng PE can directly send log messages to Elasticsearch, allowing you to search and analyze your data in real time, and visualize it with Kibana.

Note the following limitations when using the syslog-ng PE elasticsearch destination:

• This destination is only supported on the Linux platforms that use the linux glibc2.11 installer, including: Debian 7 (wheezy), Red Hat ES 7, Ubuntu 12.04 (Precise Pangolin), Ubuntu 14.04 (Trusty Tahr).

• Since syslog-ng PE uses the official Java Elasticsearch libraries, the elasticsearch destination has significant memory usage.

• The log messages of the underlying client libraries are available in the internal() source of syslog-ng PE.

@module mod-java
@include "scl.conf"

elasticsearch(
    index("syslog-ng_${YEAR}.${MONTH}.${DAY}")
    type("test")
    cluster("syslog-ng")
);

@module mod-java
@include "scl.conf"

destination d_elastic {
    elasticsearch(
        index("syslog-ng_${YEAR}.${MONTH}.${DAY}")
        type("test")
    );
};

@module mod-java
@include "scl.conf"

options {
    threaded(yes);
    use-uniqid(yes);
};

source s_syslog {
    syslog();
};

destination d_elastic {
    elasticsearch(
        index("syslog-ng_${YEAR}.${MONTH}.${DAY}")
        type("test")
        cluster("syslog-ng")
        client-mode("transport")
        custom-id("${UNIQID}")
        flush-limit("10000")
    );
};

log {
    source(s_syslog);
    destination(d_elastic);
    flags(flow-control);
};

• To install the software required for the elasticsearch destination, see Prerequisites.

• For details on how the elasticsearch destination works, see How syslog-ng PE interacts with Elasticsearch.

• For the list of options, see Elasticsearch destination options.

Prerequisites

The following describes how to send messages from syslog-ng PE to Elasticsearch.

How syslog-ng PE interacts with Elasticsearch

The syslog-ng PE application sends the log messages to the official Elasticsearch client library, which forwards the data to the Elasticsearch nodes. The way how syslog-ng PE interacts with Elasticsearch is described in the following steps.

• After syslog-ng PE is started and the first message arrives to the elasticsearch destination, the elasticsearch destination tries to connect to the Elasticsearch server or cluster. If the connection fails, syslog-ng PE will repeatedly attempt to connect again after the period set in time-reopen() expires.

• If the connection is established, syslog-ng PE sends JSON-formatted messages to Elasticsearch.

  • If flush-limit is set to 1: syslog-ng PE sends the message reliably: it sends a message to Elasticsearch, then waits for a reply from Elasticsearch. In case of failure, syslog-ng PE repeats sending the message, as set in the retries() parameter. If sending the message fails for retries() times, syslog-ng PE drops the message.

    This method ensures reliable message transfer, but is slow (about 1000 messages/second).

  • If flush-limit is higher than 1: syslog-ng PE sends messages in a batch, and receives the response asynchronously. In case of a problem, syslog-ng PE cannot resend the messages.

    This method is relatively fast (depending on the size of flush-limit, about 8000 messages/second), but the transfer is not reliable. In transport mode, over 5000-30000 messages can be lost before syslog-ng PE recognizes the error. In node mode, about 1000 messages can be lost.

  • If concurrent-requests is higher than 1, syslog-ng PE can send multiple batches simultaneously, increasing performance (and also the number of messages that can be lost in case of an error). For details, see concurrent-requests().