description |
---|
A full feature set to access content of your records |
Fluent Bit works internally with structured records and it can be composed of an unlimited number of keys and values. Values can be anything like a number, string, array, or a map.
Having a way to select a specific part of the record is critical for certain core functionalities or plugins, this feature is called Record Accessor.
consider Record Accessor a simple grammar to specify record content and other miscellaneus values.
A record accessor rule starts with the character $
. Using the structured content above as an example the following table describes how to access a record:
{
"log": "some message",
"stream": "stdout",
"labels": {
"color": "blue",
"unset": null,
"project": {
"env": "production"
}
}
}
The following table describe some accessing rules and the expected returned value:
Format | Accessed Value |
---|---|
$log | "some message" |
$labels['color'] | "blue" |
$labels['project']['env'] | "production" |
$labels['unset'] | null |
$labels['undefined'] |
If the accessor key does not exist in the record like the last example $labels['undefined']
, the operation is simply omitted, no exception will occur.
The feature is enabled on a per plugin basis, not all plugins enable this feature. As an example consider a configuration that aims to filter records using grep that only matches where labels have a color blue:
[SERVICE]
flush 1
log_level info
parsers_file parsers.conf
[INPUT]
name tail
path test.log
parser json
[FILTER]
name grep
match *
regex $labels['color'] ^blue$
[OUTPUT]
name stdout
match *
format json_lines
The file content to process in test.log
is the following:
{"log": "message 1", "labels": {"color": "blue"}}
{"log": "message 2", "labels": {"color": "red"}}
{"log": "message 3", "labels": {"color": "green"}}
{"log": "message 4", "labels": {"color": "blue"}}
Running Fluent Bit with the configuration above the output will be:
$ bin/fluent-bit -c fluent-bit.conf
Fluent Bit v1.x.x
* Copyright (C) 2019-2020 The Fluent Bit Authors
* Copyright (C) 2015-2018 Treasure Data
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io
[2020/09/11 16:11:07] [ info] [engine] started (pid=1094177)
[2020/09/11 16:11:07] [ info] [storage] version=1.0.5, initializing...
[2020/09/11 16:11:07] [ info] [storage] in-memory
[2020/09/11 16:11:07] [ info] [storage] normal synchronization mode, checksum disabled, max_chunks_up=128
[2020/09/11 16:11:07] [ info] [sp] stream processor started
[2020/09/11 16:11:07] [ info] inotify_fs_add(): inode=55716713 watch_fd=1 name=test.log
{"date":1599862267.483684,"log":"message 1","labels":{"color":"blue"}}
{"date":1599862267.483692,"log":"message 4","labels":{"color":"blue"}}