Exec Wasi

The Exec Wasi input plugin lets you execute Wasm programs that are WASI targets like external programs and collect event logs from there.

Configuration parameters

The plugin supports the following configuration parameters:

Key	Description
WASI_Path	The location of a Wasm program file.
Parser	Specify the name of a parser to interpret the entry as a structured message.
Accessible_Paths	Specify the allowed list of paths to be able to access paths from WASM programs.
Interval_Sec	Polling interval (seconds).
Interval_NSec	Polling interval (nanosecond).
Wasm_Heap_Size	Size of the heap size of Wasm execution. Review unit sizes for allowed values.
Wasm_Stack_Size	Size of the stack size of Wasm execution. Review unit sizes for allowed values.
Buf_Size	Size of the buffer See unit sizes for allowed values.
Oneshot	Only run once at startup. This allows collection of data precedent to the Fluent Bit startup (Boolean, default: false).
Threaded	Indicates whether to run this input in its own thread. Default: false.

Configuration examples

Here is a configuration example.

in_exec_wasi can handle parsers. To retrieve from structured data from a WASM program, you must create a parser.conf:

The Time_Format should be aligned for the format of your using timestamp.

This example assumes the WASM program writes JSON style strings to stdout.

parsers.yaml

parsers:
    - name: wasi
      format: json
      time_key: time
      time_format: '%Y-%m-%dT%H:%M:%S.%L %z'

parsers.conf

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

Then, you can specify the parsers.conf in the main Fluent Bit configuration:

fluent-bit.yaml

service:
    flush: 1
    daemon: off
    parsers_file: parsers.yaml
    log_level: info
    http_server: off
    http_listen: 0.0.0.0
    http_port: 2020
    
pipeline:
    inputs:
      - name: exec_wasi
        tag: exec.wasi.local
        wasi_path: /path/to/wasi/program.wasm
        # Note: run from the 'wasi_path' location.
        accessible_paths: /path/to/accessible
        
    outputs:
        - name: stdout
          match: '*'

fluent-bit.conf

[SERVICE]
    Flush        1
    Daemon       Off
    Parsers_File parsers.conf
    Log_Level    info
    HTTP_Server  Off
    HTTP_Listen  0.0.0.0
    HTTP_Port    2020

[INPUT]
    Name exec_wasi
    Tag  exec.wasi.local
    WASI_Path /path/to/wasi/program.wasm
    Accessible_Paths .,/path/to/accessible
    Parser wasi

[OUTPUT]
    Name  stdout
    Match *