omelasticsearch: Elasticsearch Output Module¶

Module Name: omelasticsearch

Author:Rainer Gerhards <rgerhards@adiscon.com>

Available since:6.4.0+

Description:

This module provides native support for logging to Elasticsearch.

Action Parameters:

server Host name or IP address of the Elasticsearch server. Defaults to “localhost”
serverport

HTTP port to connect to Elasticsearch. Defaults to 9200
searchIndex Elasticsearch index to send your logs to. Defaults to “system”
dynSearchIndex<on/off> Whether the string provided for searchIndex should be taken as a template. Defaults to “off”, which means the index name will be taken literally. Otherwise, it will look for a template with that name, and the resulting string will be the index name. For example, let’s assume you define a template named “date-days” containing “%timereported:1:10:date-rfc3339%”. Then, with dynSearchIndex=”on”, if you say searchIndex=”date-days”, each log will be sent to and index named after the first 10 characters of the timestamp, like “2013-03-22”.
searchType Elasticsearch type to send your index to. Defaults to “events”
dynSearchType <on/off> Like dynSearchIndex, it allows you to specify a template for searchType, instead of a static string.
asyncrepl<on/off> By default, an indexing operation returns after all replica shards have indexed the document. With asyncrepl=”on” it will return after it was indexed on the primary shard only - thus trading some consistency for speed.
usehttps<on/off> Send events over HTTPS instead of HTTP. Good for when you have Elasticsearch behind Apache or something else that can add HTTPS. Note that if you have a self-signed certificate, you’d need to install it first. This is done by copying the certificate to a trusted path and then running update-ca-certificates. That trusted path is typically /usr/local/share/ca-certificates but check the man page of update-ca-certificates for the default path of your distro
timeout How long Elasticsearch will wait for a primary shard to be available for indexing your log before sending back an error. Defaults to “1m”.
template This is the JSON document that will be indexed in Elasticsearch. The resulting string needs to be a valid JSON, otherwise Elasticsearch will return an error. Defaults to:

$template JSONDefault, "{\"message\":\"%msg:::json%\",\"fromhost\":\"%HOSTNAME:::json%\",\"facility\":\"%syslogfacility-text%\",\"priority\":\"%syslogpriority-text%\",\"timereported\":\"%timereported:::date-rfc3339%\",\"timegenerated\":\"%timegenerated:::date-rfc3339%\"}"

Which will produce this sort of documents (pretty-printed here for readability):

{
    "message": " this is a test message",
    "fromhost": "test-host",
    "facility": "user",
    "priority": "info",
    "timereported": "2013-03-12T18:05:01.344864+02:00",
    "timegenerated": "2013-03-12T18:05:01.344864+02:00"
}

bulkmode<on/off> The default “off” setting means logs are shipped one by one. Each in its own HTTP request, using the Index API. Set it to “on” and it will use Elasticsearch’s Bulk API to send multiple logs in the same request. The maximum number of logs sent in a single bulk request depends on your queue settings - usually limited by the dequeue batch size. More information about queues can be found here.
parent Specifying a string here will index your logs with that string the parent ID of those logs. Please note that you need to define the parent field in your mapping for that to work. By default, logs are indexed without a parent.
dynParent<on/off> Using the same parent for all the logs sent in the same action is quite unlikely. So you’d probably want to turn this “on” and specify a template that will provide meaningful parent IDs for your logs.
uid If you have basic HTTP authentication deployed (eg through the elasticsearch-basic plugin), you can specify your user-name here.
pwd Password for basic authentication.
errorfile <filename> (optional)

If specified, records failed in bulk mode are written to this file, including their error cause. Rsyslog itself does not process the file any more, but the idea behind that mechanism is that the user can create a script to periodically inspect the error file and react appropriately. As the complete request is included, it is possible to simply resubmit messages from that script.

Please note: when rsyslog has problems connecting to elasticsearch, a general error is assumed and the submit is retried. However, if we receive negative responses during batch processing, we assume an error in the data itself (like a mandatory field is not filled in, a format error or something along those lines). Such errors cannot be solved by simpy resubmitting the record. As such, they are written to the error file so that the user (script) can examine them and act appropriately. Note that e.g. after search index reconfiguration (e.g. dropping the mandatory attribute) a resubmit may be succesful.

Samples:

The following sample does the following:

loads the omelasticsearch module
outputs all logs to Elasticsearch using the default settings

module(load="omelasticsearch")
*.*     action(type="omelasticsearch")

The following sample does the following:

loads the omelasticsearch module
defines a template that will make the JSON contain the following properties
- RFC-3339 timestamp when the event was generated
- the message part of the event
- hostname of the system that generated the message
- severity of the event, as a string
- facility, as a string
- the tag of the event
outputs to Elasticsearch with the following settings
- host name of the server is myserver.local
- port is 9200
- JSON docs will look as defined in the template above
- index will be “test-index”
- type will be “test-type”
- activate bulk mode. For that to work effectively, we use an in-memory queue that can hold up to 5000 events. The maximum bulk size will be 300
- retry indefinitely if the HTTP request failed (eg: if the target server is down)

module(load="omelasticsearch")
template(name="testTemplate"
         type="list"
         option.json="on") {
           constant(value="{")
             constant(value="\"timestamp\":\"")      property(name="timereported" dateFormat="rfc3339")
             constant(value="\",\"message\":\"")     property(name="msg")
             constant(value="\",\"host\":\"")        property(name="hostname")
             constant(value="\",\"severity\":\"")    property(name="syslogseverity-text")
             constant(value="\",\"facility\":\"")    property(name="syslogfacility-text")
             constant(value="\",\"syslogtag\":\"")   property(name="syslogtag")
           constant(value="\"}")
         }
action(type="omelasticsearch"
       server="myserver.local"
       serverport="9200"
       template="testTemplate"
       searchIndex="test-index"
       searchType="test-type"
       bulkmode="on"
       queue.type="linkedlist"
       queue.size="5000"
       queue.dequeuebatchsize="300"
       action.resumeretrycount="-1")