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	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.

parsers.yaml

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

parsers.conf

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
      parser: wasi

  outputs:
    - name: stdout
      match: '*'

fluent-bit.conf