Prerequisites
To send messages from syslog-ng OSE to Elasticsearch, complete the following steps.
Steps:
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Download and install the Java Runtime Environment (JRE), 2.x (or newer). The syslog-ng OSE elasticsearch2 destination is tested and supported when using the Oracle implementation of Java. Other implementations are untested and unsupported, they may or may not work as expected.
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NOTE: This step is only required if you use the elasticsearch2 destination in node mode or transport mode.
Download the Elasticsearch libraries (version 2.x or newer from the 2.x line) from https://www.elastic.co/downloads/elasticsearch.
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NOTE: This step is only required if you use the elasticsearch2 destination in node mode or transport mode.
Extract the Elasticsearch libraries into a temporary directory, then collect the various .jar files into a single directory (for example, /opt/elasticsearch/lib/) where syslog-ng OSE can access them. You must specify this directory in the syslog-ng OSE configuration file. The files are located in the lib directory and its subdirectories of the Elasticsearch release package.
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.
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After syslog-ng OSE is started and the first message arrives to the elasticsearch2 destination, the elasticsearch2 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.
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If the connection is established, syslog-ng OSE sends JSON-formatted messages to Elasticsearch.
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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).
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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.
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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).
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Version
Client modes
The syslog-ng OSE application can interact with Elasticsearch in the following modes of operation:
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HTTP mode
The syslog-ng OSE application sends messages over HTTP using the REST API of Elasticsearch, and uses the cluster-url() and cluster() options from the syslog-ng OSE configuration file. In HTTP mode, syslog-ng OSE elasticsearch2 driver can send log messages to every Elasticsearch version, including 1.x-6.x. Note that HTTP mode is available in syslog-ng OSE version
In version
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HTTPS mode
The syslog-ng OSE application sends messages over an encrypted and optionally authenticated HTTPS channel using the REST API of Elasticsearch, and uses the cluster-url() and cluster() options from the syslog-ng OSE configuration file. In HTTPS mode, syslog-ng OSE elasticsearch2 driver can send log messages to every Elasticsearch version, including 1.x-6.x. Note that HTTPS mode is available in syslog-ng OSE version
This mode supports password-based and certificate-based authentication of the client, and can verify the certificate of the server as well.
In version
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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.
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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 parameter in the .yml file. For example: path.home: /usr/share/elasticsearch.
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Search Guard mode
Use the Search Guard Elasticsearch plugin to encrypt and authenticate your connections from syslog-ng OSE to Elasticsearch 2.x. For Elasticsearch versions 5.x and newer, use HTTPS mode. For details on configuring Search Guard mode, see Search Guard and syslog-ng OSE.
Search Guard and syslog-ng OSE
Purpose:
Version
To connect to an Elasticsearch 5.x or newer cluster, use HTTPS mode.
Steps:
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Install the Search Guard plugin on your syslog-ng OSE host. Use the plugin version that matches the version of your Elasticsearch installation.
sudo /usr/share/elasticsearch/bin/plugin install -b com.floragunn/search-guard-ssl/<version-number-of-the-plugin>
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Create a certificate for your syslog-ng OSE host, and add the certificate to the SYSLOG_NG-NODE_NAME-keystore.jks file. You can configure the location of this file in the Elasticsearch resources file under the path.conf parameter. For details, see the Search Guard documentation.
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Configure an Elasticsearch destination in syslog-ng OSE that uses the searchguard client mode. For example:
destination d_elasticsearch { elasticsearch2( client-lib-dir("/usr/share/elasticsearch/plugins/search-guard-ssl/*.jar:/usr/share/elasticsearch/lib") index("syslog-${YEAR}.${MONTH}.${DAY}") type("syslog") time-zone("UTC") client-mode("searchguard") resource("/etc/syslog-ng/elasticsearch.yml") ); }; -
Configure the Elasticsearch resource file (for example, /etc/syslog-ng/elasticsearch.yml) as needed for your environment. Note the searchguard: section.
cluster: name: elasticsearch discovery: zen: ping: unicast: hosts: - <ip-address-of-the-elasticsearch-server> node: name: syslog_ng_secure data; false master: false path: home: /etc/syslog-ng conf: /etc/syslog-ng searchguard: ssl: transport: keystore_filepath: syslog_ng-keystore.jks keystore_password: changeit truststore_filepath: truststore.jks truststore_password: changeit enforce_hostname_verification: true