The filter plugins allows to alter the incoming data generated by the input plugins. As of this version the following filter plugins are available:

In order to let a Filter be applied over some data, the Match rule must exists and it must match the Tag for the incoming data.

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

aaa
aab
bbb
ccc
ddd
eee
fff
ggg

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

[INPUT]
    Name   tail
    Path   lines.txt

[FILTER]
    Name   grep
    Match  *
    Regex  log aa

[OUTPUT]
    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 kubernetes.labels.app), you could use combination of nest and grep filters. Here is an example that will exclude records that match kubernetes.labels.app: myapp:

[FILTER]
    Name         nest
    Match        *
    Operation    lift
    Nested_under kubernetes

[FILTER]
    Name         nest
    Match        *
    Operation    lift
    Nested_under labels

[FILTER]
    Name    grep
    Match   *
    Exclude app myapp

Fluent Bit Kubernetes Filter allows to enrich your log files with Kubernetes metadata.

When Fluent Bit is deployed in Kubernetes as a DaemonSet and configured to read the log files from the containers (using tail or systemd input plugins), this filter aims to perform the following operations:

• Analyze the Tag and extract the following metadata:

  • Pod Name

  • Namespace

  • Container Name

  • Container ID

• Query Kubernetes API Server to obtain extra metadata for the POD in question:

  • Pod ID

  • Labels

  • Annotations

The data is cached locally in memory and appended to each record.

Configuration Parameters

The plugin supports the following configuration parameters:

Processing the 'log' value

Kubernetes Filter aims to provide several ways to process the data contained in the log key. The following explanation of the workflow assumes that your original Docker parser defined in parsers.conf is as follows:

[PARSER]
    Name         docker
    Format       json
    Time_Key     time
    Time_Format  %Y-%m-%dT%H:%M:%S.%L
    Time_Keep    On

Since Fluent Bit v1.2 we are not suggesting the use of decoders (Decode_Field_As) if you are using Elasticsearch database in the output to avoid data type conflicts.

To perform processing of the log key, it's mandatory to enable the Merge_Log configuration property in this filter, then the following processing order will be done:

• If a Pod suggest a parser, the filter will use that parser to process the content of log.

• If the option Merge_Parser was set and the Pod did not suggest a parser, process the log content using the suggested parser in the configuration.

• If no Pod was suggested and no Merge_Parser is set, try to handle the content as JSON.

If log value processing fails, the value is untouched. The order above is not chained, meaning it's exclusive and the filter will try only one of the options above, not all of them.

Kubernetes Annotations

A flexible feature of Fluent Bit Kubernetes filter is that allow Kubernetes Pods to suggest certain behaviors for the log processor pipeline when processing the records. At the moment it support:

• Suggest a pre-defined parser

• Request to exclude logs

The following annotations are available:

Annotation Examples in Pod definition

Suggest a parser

The following Pod definition runs a Pod that emits Apache logs to the standard output, in the Annotations it suggest that the data should be processed using the pre-defined parser called apache:

apiVersion: v1
kind: Pod
metadata:
  name: apache-logs
  labels:
    app: apache-logs
  annotations:
    fluentbit.io/parser: apache
spec:
  containers:
  - name: apache
    image: edsiper/apache_logs

Request to exclude logs

There are certain situations where the user would like to request that the log processor simply skip the logs from the Pod in question:

apiVersion: v1
kind: Pod
metadata:
  name: apache-logs
  labels:
    app: apache-logs
  annotations:
    fluentbit.io/exclude: "true"
spec:
  containers:
  - name: apache
    image: edsiper/apache_logs

Note that the annotation value is boolean which can take a true or false and must be quoted.

Workflow of Tail + Kubernetes Filter

Kubernetes Filter depends on either Tail or Systemd input plugins to process and enrich records with Kubernetes metadata. Here we will explain the workflow of Tail and how it configuration is correlated with Kubernetes filter. Consider the following configuration example (just for demo purposes, not production):

[INPUT]
    Name    tail
    Tag     kube.*
    Path    /var/log/containers/*.log
    Parser  docker

[FILTER]
    Name             kubernetes
    Match            kube.*
    Kube_URL         https://kubernetes.default.svc:443
    Kube_CA_File     /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
    Kube_Token_File  /var/run/secrets/kubernetes.io/serviceaccount/token
    Kube_Tag_Prefix  kube.var.log.containers.
    Merge_Log        On
    Merge_Log_Key    log_processed

In the input section, the Tail plugin will monitor all files ending in .log in path /var/log/containers/. For every file it will read every line and apply the docker parser. Then the records are emitted to the next step with an expanded tag.

Tail support Tags expansion, which means that if a tag have a star character (*), it will replace the value with the absolute path of the monitored file, so if you file name and path is:

/var/log/container/apache-logs-annotated_default_apache-aeeccc7a9f00f6e4e066aeff0434cf80621215071f1b20a51e8340aa7c35eac6.log

then the Tag for every record of that file becomes:

kube.var.log.containers.apache-logs-annotated_default_apache-aeeccc7a9f00f6e4e066aeff0434cf80621215071f1b20a51e8340aa7c35eac6.log

note that slashes are replaced with dots.

When Kubernetes Filter runs, it will try to match all records that starts with kube. (note the ending dot), so records from the file mentioned above will hit the matching rule and the filter will try to enrich the records

Kubernetes Filter do not care from where the logs comes from, but it cares about the absolute name of the monitored file, because that information contains the pod name and namespace name that are used to retrieve associated metadata to the running Pod from the Kubernetes Master/API Server.

If the configuration property Kube_Tag_Prefix was configured (available on Fluent Bit >= 1.1.x), it will use that value to remove the prefix that was appended to the Tag in the previous Input section. Note that the configuration property defaults to _kube._var.logs.containers. , so the previous Tag content will be transformed from:

kube.var.log.containers.apache-logs-annotated_default_apache-aeeccc7a9f00f6e4e066aeff0434cf80621215071f1b20a51e8340aa7c35eac6.log

to:

apache-logs-annotated_default_apache-aeeccc7a9f00f6e4e066aeff0434cf80621215071f1b20a51e8340aa7c35eac6.log

the transformation above do not modify the original Tag, just creates a new representation for the filter to perform metadata lookup.

that new value is used by the filter to lookup the pod name and namespace, for that purpose it uses an internal Regular expression:

(?<pod_name>[a-z0-9](?:[-a-z0-9]*[a-z0-9])?(?:\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*)_(?<namespace_name>[^_]+)_(?<container_name>.+)-(?<docker_id>[a-z0-9]{64})\.log$

If you want to know more details, check the source code of that definition here.

You can see on Rublar.com web site how this operation is performed, check the following demo link:

• https://rubular.com/r/HZz3tYAahj6JCd

Custom Regex

Under certain and not common conditions, a user would want to alter that hard-coded regular expression, for that purpose the option Regex_Parser can be used (documented on top).

Final Comments

So at this point the filter is able to gather the values of pod_name and namespace, with that information it will check in the local cache (internal hash table) if some metadata for that key pair exists, if so, it will enrich the record with the metadata value, otherwise it will connect to the Kubernetes Master/API Server and retrieve that information.

The Parser Filter plugin allows to parse field in event records.

Configuration Parameters

The plugin supports the following configuration parameters:

Getting Started

Configuration File

This is an example to parser a record {"data":"100 0.5 true This is example"}.

The plugin needs parser file which defines how to parse field.

[PARSER]
    Name dummy_test
    Format regex
    Regex ^(?<INT>[^ ]+) (?<FLOAT>[^ ]+) (?<BOOL>[^ ]+) (?<STRING>.+)$

The path of parser file should be written in configuration file at [SERVICE] section.

[SERVICE]
    Parsers_File /path/to/parsers.conf

[INPUT]
    Name dummy
    Tag  dummy.data
    Dummy {"data":"100 0.5 true This is example"}

[FILTER]
    Name parser
    Match dummy.*
    Key_Name data
    Parser dummy_test

[OUTPUT]
    Name stdout
    Match *

The output is

$ fluent-bit -c dummy.conf
Fluent-Bit v0.12.0
Copyright (C) Treasure Data

[2017/07/06 22:33:12] [ info] [engine] started
[0] dummy.data: [1499347993.001371317, {"INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}]
[1] dummy.data: [1499347994.001303118, {"INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}]
[2] dummy.data: [1499347995.001296133, {"INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}]
[3] dummy.data: [1499347996.001320284, {"INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}]

You can see the record {"data":"100 0.5 true This is example"} are parsed.

Preserve original fields

By default, the parser plugin only keeps the parsed fields in its output.

If you enable Reserve_Data, all other fields are preserved:

[PARSER]
    Name dummy_test
    Format regex
    Regex ^(?<INT>[^ ]+) (?<FLOAT>[^ ]+) (?<BOOL>[^ ]+) (?<STRING>.+)$

[SERVICE]
    Parsers_File /path/to/parsers.conf

[INPUT]
    Name dummy
    Tag  dummy.data
    Dummy {"data":"100 0.5 true This is example", "key1":"value1", "key2":"value2"}

[FILTER]
    Name parser
    Match dummy.*
    Key_Name data
    Parser dummy_test
    Reserve_Data On

This will produce the output:

$ fluent-bit -c dummy.conf
Fluent-Bit v0.12.0
Copyright (C) Treasure Data

[2017/07/06 22:33:12] [ info] [engine] started
[0] dummy.data: [1499347993.001371317, {"INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}, "key1":"value1", "key2":"value2"]
[1] dummy.data: [1499347994.001303118, {"INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}, "key1":"value1", "key2":"value2"]
[2] dummy.data: [1499347995.001296133, {"INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}, "key1":"value1", "key2":"value2"]
[3] dummy.data: [1499347996.001320284, {"INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}, "key1":"value1", "key2":"value2"]

If you enable Reserved_Data and Preserve_Key, the original key field will be preserved as well:

[PARSER]
    Name dummy_test
    Format regex
    Regex ^(?<INT>[^ ]+) (?<FLOAT>[^ ]+) (?<BOOL>[^ ]+) (?<STRING>.+)$

[SERVICE]
    Parsers_File /path/to/parsers.conf

[INPUT]
    Name dummy
    Tag  dummy.data
    Dummy {"data":"100 0.5 true This is example", "key1":"value1", "key2":"value2"}

[FILTER]
    Name parser
    Match dummy.*
    Key_Name data
    Parser dummy_test
    Reserve_Data On
    Preserve_Key On

This will produce the output:

$ fluent-bit -c dummy.conf
Fluent-Bit v0.12.0
Copyright (C) Treasure Data

[2017/07/06 22:33:12] [ info] [engine] started
[0] dummy.data: [1499347993.001371317, {"data":"100 0.5 true This is example", "INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}]
[1] dummy.data: [1499347994.001303118, {"data":"100 0.5 true This is example", "INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}]
[2] dummy.data: [1499347995.001296133, {"data":"100 0.5 true This is example", "INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}]
[3] dummy.data: [1499347996.001320284, {"data":"100 0.5 true This is example", "INT"=>"100", "FLOAT"=>"0.5", "BOOL"=>"true", "STRING"=>"This is example"}]

The Record Modifier Filter plugin allows to append fields or to exclude specific fields.

Configuration Parameters

The plugin supports the following configuration parameters: Remove_key and Whitelist_key are exclusive.

Getting Started

In order to start filtering records, you can run the filter from the command line or through the configuration file.

This is a sample in_mem record to filter.

Append fields

The following configuration file is to append product name and hostname (via environment variable) to record.

You can also run the filter from command line.

The output will be

Remove fields with Remove_key

The following configuration file is to remove 'Swap.*' fields.

You can also run the filter from command line.

The output will be

Remove fields with Whitelist_key

The following configuration file is to remain 'Mem.*' fields.

You can also run the filter from command line.

The output will be

The Throttle Filter plugin sets the average Rate of messages per Interval, based on leaky bucket and sliding window algorithm. In case of overflood, it will leak within certain rate.

Configuration Parameters

The plugin supports the following configuration parameters:

Functional description

Lets imagine we have configured:

we received 1 message first second, 3 messages 2nd, and 5 3rd. As you can see, disregard that Window is actually 5, we use "slow" start to prevent overflooding during the startup.

But as soon as we reached Window size * Interval, we will have true sliding window with aggregation over complete window.

When we have average over window is more than Rate, we will start dropping messages, so that

will become:

As you can see, last pane of the window was overwritten and 1 message was dropped.

Interval vs Window size

You might noticed possibility to configure Interval of the Window shift. It is counter intuitive, but there is a difference between two examples above:

and

Even though both examples will allow maximum Rate of 60 messages per minute, first example may get all 60 messages within first second, and will drop all the rest for the entire minute:

While the second example will not allow more than 1 message per second every second, making output rate more smooth:

It may drop some data if the rate is ragged. I would recommend to use bigger interval and rate for streams of rare but important events, while keep Window bigger and Interval small for constantly intensive inputs.

Command Line

Note: 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 throttle filter will apply a rate limit and only pass the records which are read below the certain rate:

Configuration File

The example above will pass 1000 messages per second in average over 300 seconds.

Lua Filter allows you to modify the incoming records using custom Scripts.

Due to the necessity to have a flexible filtering mechanism, now is possible to extend Fluent Bit capabilities writing simple filters using Lua programming language. A Lua based filter takes two steps:

• Configure the Filter in the main configuration

• Prepare a Lua script that will be used by the Filter

Content:

Configuration Parameters

The plugin supports the following configuration parameters:

Getting Started

In order to test the filter, you can run the plugin from the command line or through the configuration file. The following examples uses the input plugin for data ingestion, invoke Lua filter using the script and calls the function which only print the same information to the standard output:

Command Line

From the command line you can use the following options:

Configuration File

In your main configuration file append the following Input, Filter & Output sections:

Lua Script Filter API

The life cycle of a filter have the following steps:

• Upon Tag matching by filter_lua, it may process or bypass the record.

• If filter_lua accepts the record, it will invoke the function defined in the call property which basically is the name of a function defined in the Lua script.

• Invoke Lua function passing each record in JSON format.

• Upon return, validate return value and take some action (described above)

Callback Prototype

The Lua script can have one or multiple callbacks that can be used by filter_lua, it prototype is as follows:

Function Arguments

Return Values

Each callback must return three values:

Code Examples

For functional examples of this interface, please refer to the code samples provided in the source code of the project located here:

Number Type

In Lua, Fluent Bit treats number as double. It means an integer field (e.g. IDs, log levels) will be converted double. To avoid type conversion, Type_int_key property is available.

The Nest Filter plugin allows you to operate on or with nested data. Its modes of operation are

• nest - Take a set of records and place them in a map

• lift - Take a map by key and lift its records up

Example usage (nest)

As an example using JSON notation, to nest keys matching the Wildcard value Key* under a new key NestKey the transformation becomes,

Example (input)

Example (output)

Example usage (lift)

As an example using JSON notation, to lift keys nested under the Nested_under value NestKey* the transformation becomes,

Example (input)

Example (output)

Configuration Parameters

The plugin supports the following configuration parameters:

Getting Started

Example #1 - nest

Command Line

Note: Using the command line mode requires quotes parse the wildcard properly. The use of a configuration file is recommended.

The following command will load the mem plugin. Then the nest filter will match the wildcard rule to the keys and nest the keys matching Mem.* under the new key NEST.

Configuration File

Result

The output of both the command line and configuration invocations should be identical and result in the following output.

Example #1 - nest and lift undo

This example nests all Mem.* and Swap,* items under the Stats key and then reverses these actions with a lift operation. The output appears unchanged.

Configuration File

Result

Example #2 - nest 3 levels deep

This example takes the keys starting with Mem.* and nests them under LAYER1, which itself is then nested under LAYER2, which is nested under LAYER3.

Configuration File

Result

Example #3 - multiple nest and lift filters with prefix

This example starts with the 3-level deep nesting of Example 2 and applies the lift filter three times to reverse the operations. The end result is that all records are at the top level, without nesting, again. One prefix is added for each level that is lifted.

Configuration file

Result

The Standard Output Filter plugin allows to print to the standard output the data received through the input plugin.

Configuration Parameters

There are no parameters.

Getting Started

In order to start filtering records, you can run the filter from the command line or through the configuration file.

Command Line

Configuration File

In your main configuration file append the following FILTER sections:

The Modify Filter plugin allows you to change records using rules and conditions.

Example usage

As an example using JSON notation to,

• Rename Key2 to RenamedKey

• Add a key OtherKey with value Value3 if OtherKey does not yet exist

Example (input)

Example (output)

Configuration Parameters

Rules

The plugin supports the following rules:

• Rules are case insensitive, parameters are not

• Any number of rules can be set in a filter instance.

• Rules are applied in the order they appear, with each rule operating on the result of the previous rule.

Conditions

The plugin supports the following conditions:

• Conditions are case insensitive, parameters are not

• Any number of conditions can be set.

• Conditions apply to the whole filter instance and all its rules. Not to individual rules.

• All conditions have to be true for the rules to be applied.

Example #1 - Add and Rename

Using command Line

Note: Using the command line mode requires quotes parse the wildcard properly. The use of a configuration file is recommended.

Configuration File

Result

The output of both the command line and configuration invocations should be identical and result in the following output.

Example #2 - Conditionally Add and Remove

Configuration File

Result

Example #3 - Emoji

Configuration File

Result