omclickhouse: ClickHouse Output Module
Module Name: | omclickhouse |
Author: | Pascal Withopf <pwithopf@adiscon.com> |
Purpose
This module provides native support for logging to ClickHouse. To enable the module use “–enable-clickhouse” while configuring rsyslog. Tests for the testbench can be enabled with “–enable-clickhouse-tests”.
Notable Features
Configuration Parameters
Note
Parameter names are case-insensitive.
Action Parameters
Server
type | default | mandatory |
|
|---|---|---|---|
word | localhost | no | none |
The address of a ClickHouse server.
Port
type | default | mandatory |
|
|---|---|---|---|
integer | 8123 | no | none |
HTTP port to use to connect to ClickHouse.
usehttps
type | default | mandatory |
|
|---|---|---|---|
binary | on | no | none |
Default scheme to use when sending events to ClickHouse if none is specified on a server.
template
type | default | mandatory |
|
|---|---|---|---|
word | StdClickHouseFmt | no | none |
This is the message format that will be sent to ClickHouse. The resulting string needs to be a valid INSERT Query, otherwise ClickHouse will return an error. Defaults to:
"\"INSERT INTO rsyslog.SystemEvents (severity, facility, "
"timestamp, hostname, tag, message) VALUES (%syslogseverity%, %syslogfacility%, "
"'%timereported:::date-unixtimestamp%', '%hostname%', '%syslogtag%', '%msg%')\""
bulkmode
type | default | mandatory |
|
|---|---|---|---|
binary | on | no | none |
The “off” setting means logs are shipped one by one. Each in its own HTTP request. The default “on” will send multiple logs in the same request. This is recommended, because it is many times faster than when bulkmode is turned off. The maximum number of logs sent in a single bulk request depends on your maxbytes and queue settings - usually limited by the dequeue batch size. More information about queues can be found here.
maxbytes
type | default | mandatory |
|
|---|---|---|---|
Size | 104857600/100mb | no | none |
When shipping logs with bulkmode on, maxbytes specifies the maximum size of the request body sent to ClickHouse. Logs are batched until either the buffer reaches maxbytes or the dequeue batch size is reached.
user
type | default | mandatory |
|
|---|---|---|---|
word | default | no | none |
If you have basic HTTP authentication deployed you can specify your user-name here.
pwd
type | default | mandatory |
|
|---|---|---|---|
word | no | none |
Password for basic authentication.
errorFile
type | default | mandatory |
|
|---|---|---|---|
word | none | no | none |
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 clickhouse, a general error is assumed. 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 simply 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 successful.
allowUnsignedCerts
type | default | mandatory |
|
|---|---|---|---|
binary | on | no | none |
The module accepts connections to servers, which have unsigned certificates. If this parameter is disabled, the module will verify whether the certificates are authentic.
skipverifyhost
type | default | mandatory |
|
|---|---|---|---|
boolean | off | no | none |
If “on”, this will set the curl CURLOPT_SSL_VERIFYHOST option to 0. You are strongly discouraged to set this to “on”. It is primarily useful only for debugging or testing.
healthCheckTimeout
type | default | mandatory |
|
|---|---|---|---|
int | 3500 | no | none |
This parameter sets the timeout for checking the availability of ClickHouse. Value is given in milliseconds.
timeout
type | default | mandatory |
|
|---|---|---|---|
int | 0 | no | none |
This parameter sets the timeout for sending data to ClickHouse. Value is given in milliseconds.
Statistic Counter
This plugin maintains global statistics, which accumulate all action instances. The statistic is named “omclickhouse”. Parameters are:
submitted - number of messages submitted for processing (with both success and error result)
fail.httprequests - the number of times a http request failed. Note that a single http request may be used to submit multiple messages, so this number may be (much) lower than failed.http.
failed.http - number of message failures due to connection like-problems (things like remote server down, broken link etc)
fail.clickhouse - number of failures due to clickhouse error reply; Note that this counter does NOT count the number of failed messages but the number of times a failure occurred (a potentially much smaller number). Counting messages would be quite performance-intense and is thus not done.
response.success - number of records successfully sent in bulk index requests - counts the number of successful responses
The fail.httprequests and failed.http counters reflect only failures that omclickhouse detected. Once it detects problems, it (usually, depends on circumstances) tell the rsyslog core that it wants to be suspended until the situation clears (this is a requirement for rsyslog output modules). Once it is suspended, it does NOT receive any further messages. Depending on the user configuration, messages will be lost during this period. Those lost messages will NOT be counted by impstats (as it does not see them).
Examples
Example 1
The following sample does the following:
loads the omclickhouse module
outputs all logs to ClickHouse using the default settings
module(load="omclickhouse")
action(type="omclickhouse")
Example 2
In this example the URL will use http and the specified parameters to create the REST URL.
module(load="omclickhouse")
action(type="omclickhouse" server="127.0.0.1" port="8124" user="user1" pwd="pwd1"
usehttps="off")
Example 3
This example will send messages in batches up to 10MB. If an error occurs it will be written in the error file.
module(load="omclickhouse")
action(type="omclickhouse" maxbytes="10mb" errorfile="clickhouse-error.log")
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
See also
Contributing to Rsyslog:
Source project: rsyslog project README.
Documentation: rsyslog-doc project README
Copyright 2008-2023 Rainer Gerhards (Großrinderfeld), and Others.