The Grep Filter plugin allows to match or exclude specific records based in regular expression patterns.

Configuration Parameters

The plugin supports the following configuration parameters:

Getting Started

In order to start filtering records, you can run the filter from the command line or through the configuration file. The following example assumes that you have a file called lines.txt with the following content


Command Line

Note: using the command line mode need special attention to quote the regular expressions properly. It's suggested to use a configuration file.

The following command will load the tail plugin and read the content of lines.txt file. Then the grep filter will apply a regular expression rule over the log field (created by tail plugin) and only pass the records which field value starts with aa:

$ bin/fluent-bit -i tail -p 'path=lines.txt' -F grep -p 'regex=log aa' -m '*' -o stdout

Configuration File

    Name   tail
    Path   lines.txt

    Name   grep
    Match  *
    Regex  log aa

    Name   stdout
    Match  *

The filter allows to use multiple rules which are applied in order, you can have many Regex and Exclude entries as required.

Nested fields example

Currently nested fields are not supported. If you have records in the following format

    "kubernetes": {
        "pod_name": "myapp-0",
        "namespace_name": "default",
        "pod_id": "216cd7ae-1c7e-11e8-bb40-000c298df552",
        "labels": {
            "app": "myapp"
        "host": "minikube",
        "container_name": "myapp",
        "docker_id": "370face382c7603fdd309d8c6aaaf434fd98b92421ce7c7c8aafe7697d4aa362"

and if you want to exclude records that match given nested field (for example, you could use combination of nest and grep filters. Here is an example that will exclude records that match myapp:

    Name         nest
    Match        *
    Operation    lift
    Nested_under kubernetes

    Name         nest
    Match        *
    Operation    lift
    Nested_under labels

    Name    grep
    Match   *
    Exclude app myapp

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