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Wasm

Use Wasm programs as a filter.

The Wasm filter lets you modify the incoming records using Wasm technology.

You can extend Fluent Bit capabilities by writing custom filters using built Wasm programs and its runtime. A Wasm-based filter takes the following steps:

  1. (Optional) Compile Ahead Of Time (AOT) objects to optimize the Wasm execution pipeline.

  2. Configure the filter in the main configuration.

  3. Prepare a Wasm program that will be used by the filter.

Configuration parameters

The plugin supports the following configuration parameters:

Key
Description

Wasm_Path

Path to the built Wasm program that will be used. This can be a path relative to the main configuration file.

Event_Format

Define event format to interact with Wasm programs: msgpack or json. Default: json.

Function_Name

Wasm function name that will be triggered to do filtering. It's assumed that the function is built inside the Wasm program specified previously.

Accessible_Paths

Specify the allowlist of paths to be able to access paths from Wasm programs.

Wasm_Heap_Size

Wasm_Stack_Size

Configuration example

Here is a configuration example.

[INPUT]
    Name   dummy
    Tag    dummy.local

[FILTER]
    Name wasm
    Match dummy.*
    Event_Format json # or msgpack
    WASM_Path /path/to/wasm_program.wasm
    Function_Name filter_function_name
    Accessible_Paths .,/path/to/accessible

[OUTPUT]
    Name   stdout
    Match  *

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