RSyslog Documentation

omhiredis: Redis Output Module

Module Name:omhiredis
Author:Brian Knox <bknox@digitalocean.com>

Purpose

This module provides native support for writing to Redis, using the hiredis client library.

Configuration Parameters

Note

Parameter names are case-insensitive.

Action Parameters

Server

typedefaultmandatoryobsolete legacy directive
wordnonenonone

Name or address of the Redis server

ServerPort

typedefaultmandatoryobsolete legacy directive
integer6379nonone

Port of the Redis server if the server is not listening on the default port.

ServerPassword

typedefaultmandatoryobsolete legacy directive
wordnonenonone

Password to support authenticated redis database server to push messages across networks and datacenters. Parameter is optional if not provided AUTH command wont be sent to the server.

Mode

typedefaultmandatoryobsolete legacy directive
wordtemplatenonone

Mode to run the output action in: “queue”, “publish” or “set”. If not supplied, the original “template” mode is used.

Note

Due to a config parsing bug in 8.13, explicitly setting this to “template” mode will result in a config parsing error.

If mode is “set”, omhiredis will send SET commands. If “expiration” parameter is provided (see parameter below), omhiredis will send SETEX commands.

Template

typedefaultmandatoryobsolete legacy directive
wordRSYSLOG_ForwardFormatnonone

Template is required if using “template” mode.

Key

typedefaultmandatoryobsolete legacy directive
wordnonenonone

Key is required if using “publish”, “queue” or “set” modes.

Dynakey

typedefaultmandatoryobsolete legacy directive
binaryoffnonone

If set to “on”, the key value will be considered a template by Rsyslog. Useful when dynamic key generation is desired.

Userpush

typedefaultmandatoryobsolete legacy directive
binaryoffnonone

If set to on, use RPUSH instead of LPUSH, if not set or off, use LPUSH.

Expiration

typedefaultmandatoryobsolete legacy directive
number0nonone

Only applicable with mode “set”. Specifies an expiration for the keys set by omhiredis. If this parameter is not specified, the value will be 0 so keys will last forever, otherwise they will last for X seconds.

Examples

Example 1: Template mode

In “template” mode, the string constructed by the template is sent to Redis as a command.

Note

This mode has problems with strings with spaces in them - full message won’t work correctly. In this mode, the template argument is required, and the key argument is meaningless.

module(load="omhiredis")

template(
  name="program_count_tmpl"
  type="string"
  string="HINCRBY progcount %programname% 1")

action(
  name="count_programs"
  server="my-redis-server.example.com"
  serverport="6379"
  type="omhiredis"
  mode="template"
  template="program_count_tmpl")

Results

Here’s an example redis-cli session where we HGETALL the counts:

> redis-cli
127.0.0.1:6379> HGETALL progcount
1) "rsyslogd"
2) "35"
3) "rsyslogd-pstats"
4) "4302"

Example 2: Queue mode

In “queue” mode, the syslog message is pushed into a Redis list at “key”, using the LPUSH command. If a template is not supplied, the plugin will default to the RSYSLOG_ForwardFormat template.

module(load="omhiredis")

action(
  name="push_redis"
  server="my-redis-server.example.com"
  serverport="6379"
  type="omhiredis"
  mode="queue"
  key="my_queue")

Results

Here’s an example redis-cli session where we RPOP from the queue:

> redis-cli
127.0.0.1:6379> RPOP my_queue

"<46>2015-09-17T10:54:50.080252-04:00 myhost rsyslogd: [origin software=\"rsyslogd\" swVersion=\"8.13.0.master\" x-pid=\"6452\" x-info=\"http://www.rsyslog.com\"] start"

127.0.0.1:6379>

Example 3: Publish mode

In “publish” mode, the syslog message is published to a Redis topic set by “key”. If a template is not supplied, the plugin will default to the RSYSLOG_ForwardFormat template.

module(load="omhiredis")

action(
  name="publish_redis"
  server="my-redis-server.example.com"
  serverport="6379"
  type="omhiredis"
  mode="publish"
  key="my_channel")

Results

Here’s an example redis-cli session where we SUBSCRIBE to the topic:

> redis-cli

127.0.0.1:6379> subscribe my_channel

Reading messages... (press Ctrl-C to quit)

1) "subscribe"

2) "my_channel"

3) (integer) 1

1) "message"

2) "my_channel"

3) "<46>2015-09-17T10:55:44.486416-04:00 myhost rsyslogd-pstats: {\"name\":\"imuxsock\",\"origin\":\"imuxsock\",\"submitted\":0,\"ratelimit.discarded\":0,\"ratelimit.numratelimiters\":0}"

Example 4: Set mode

In “set” mode, the syslog message is set as a Redis key at “key”. If a template is not supplied, the plugin will default to the RSYSLOG_ForwardFormat template.

module(load="omhiredis")

action(
  name="set_redis"
  server="my-redis-server.example.com"
  serverport="6379"
  type="omhiredis"
  mode="set"
  key="my_key")

Results

Here’s an example redis-cli session where we get the key:

> redis-cli

127.0.0.1:6379> get my_key

"<46>2019-12-17T20:16:54.781239+00:00 localhost rsyslogd-pstats: { \"name\": \"main Q\", \"origin\": \"core.queue\",
\"size\": 3, \"enqueued\": 7, \"full\": 0, \"discarded.full\": 0, \"discarded.nf\": 0, \"maxqsize\": 3 }"

127.0.0.1:6379> ttl my_key

(integer) -1

Example 5: Set mode with expiration

In “set” mode when “expiration” is set to a positive integer, the syslog message is set as a Redis key at “key”, with expiration “expiration”. If a template is not supplied, the plugin will default to the RSYSLOG_ForwardFormat template.

module(load="omhiredis")

action(
  name="set_redis"
  server="my-redis-server.example.com"
  serverport="6379"
  type="omhiredis"
  mode="set"
  key="my_key"
  expiration="10")

Results

Here’s an example redis-cli session where we get the key and test the expiration:

> redis-cli

127.0.0.1:6379> get my_key

"<46>2019-12-17T20:16:54.781239+00:00 localhost rsyslogd-pstats: { \"name\": \"main Q\", \"origin\": \"core.queue\",
\"size\": 3, \"enqueued\": 7, \"full\": 0, \"discarded.full\": 0, \"discarded.nf\": 0, \"maxqsize\": 3 }"

127.0.0.1:6379> ttl my_key

(integer) 10

127.0.0.1:6379> ttl my_key

(integer) 3

127.0.0.1:6379> ttl my_key

(integer) -2

127.0.0.1:6379> get my_key

(nil)

Example 6: Set mode with dynamic key

In any mode with “key” defined and “dynakey” as “on”, the key used during operation will be dynamically generated by Rsyslog using templating.

module(load="omhiredis")

template(name="example-template" type="string" string="%hostname%")

action(
  name="set_redis"
  server="my-redis-server.example.com"
  serverport="6379"
  type="omhiredis"
  mode="set"
  key="example-template"
  dynakey="on")

Results

Here’s an example redis-cli session where we get the dynamic key:

> redis-cli

127.0.0.1:6379> keys *

(empty list or set)

127.0.0.1:6379> keys *

1) "localhost"

See also

Help with configuring/using Rsyslog:

  • Mailing list - best route for general questions
  • GitHub: rsyslog source project - detailed questions, reporting issues that are believed to be bugs with Rsyslog
  • Stack Exchange (View, Ask) - experimental support from rsyslog community

See also

Contributing to Rsyslog:

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