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Exec WASI

{% hint style="info" %} Supported event types: logs {% endhint %}

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 Default
accessible_paths Specify the allowed list of paths to be able to access paths from Wasm programs. .
buf_size Size of the buffer. Review unit sizes for allowed values. 4096
interval_nsec Polling interval (nanosecond). 0
interval_sec Polling interval (seconds). 1
oneshot Execute the command only once at startup. false
parser Specify the name of a parser to interpret the entry as a structured message.
threaded Indicates whether to run this input in its own thread. false
wasi_path The location of a Wasm program file.
wasm_heap_size Size of the heap size of Wasm execution. Review unit sizes for allowed values. 8192
wasm_stack_size Size of the stack size of Wasm execution. Review unit sizes for allowed values. 8192

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 your using for timestamps.

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

{% tabs %} {% tab title="parsers.yaml" %}

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

{% endtab %} {% tab title="parsers.conf" %}

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

{% endtab %} {% endtabs %}

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

{% tabs %} {% tab title="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
      parser: wasi

  outputs:
    - name: stdout
      match: '*'

{% endtab %} {% tab title="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 *

{% endtab %} {% endtabs %}