syslog-ng Open Source Edition 3.18 - Administration Guide

elasticsearch: Sending messages directly to Elasticsearch version 1.x (DEPRECATED)

Starting with version 3.7 of syslog-ng OSE 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 OSE elasticsearch destination:

• This destination is only supported on the Linux platform.

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

• Sending messages over the HTTP REST API is supported only using the elastic2() destination. Note that in HTTP mode, the elasticsearch2 destination can send log messages to Elasticsearch version 1.x and newer. For details, see elasticsearch2: Sending logs directly to Elasticsearch and Kibana 2.0 or higher.

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

@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 OSE interacts with Elasticsearch.

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

The elasticsearch() driver is actually a reusable configuration snippet configured to receive log messages using the Java language-binding of syslog-ng OSE. For details on using or writing such configuration snippets, see Reusing configuration blocks. You can find the source of the elasticsearch configuration snippet on GitHub. For details on extending syslog-ng OSE in Java, see the Getting started with syslog-ng development guide.

Prerequisites

To send messages from syslog-ng OSE to Elasticsearch, complete the following steps.

How syslog-ng OSE interacts with Elasticsearch

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

• After syslog-ng OSE 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 OSE will repeatedly attempt to connect again after the period set in time-reopen() expires.

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

  • If flush-limit is set to 1: syslog-ng OSE sends the message reliably: it sends a message to Elasticsearch, then waits for a reply from Elasticsearch. In case of failure, syslog-ng OSE repeats sending the message, as set in the retries() parameter. If sending the message fails for retries() times, syslog-ng OSE 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 OSE sends messages in a batch, and receives the response asynchronously. In case of a problem, syslog-ng OSE 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 OSE recognizes the error. In node mode, about 1000 messages can be lost.

  • If concurrent-requests is higher than 1, syslog-ng OSE 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().

Client modes

The syslog-ng OSE application can interact with Elasticsearch in transport mode or node mode.

• Transport mode

  The syslog-ng OSE application uses the transport client API of Elasticsearch, and uses the server(), port(), and cluster() options from the syslog-ng OSE configuration file.

• Node mode

  The syslog-ng OSE application acts as an Elasticsearch node (client no-data), using the node client API of Elasticsearch. Further options for the node can be describe in an Elasticsearch configuration file specified in the resource() option.

  NOTE: In Node mode, it is required to define the home of the elasticsearch installation with the path.home paramter in the .yml file. For example: path.home: /usr/share/elasticsearch.