Gelf Log Listener in Python

gelf_to_file.py

#!/usr/bin/env python

import gzip
import socket
import sys
import zlib
from pathlib import Path


def persist(event: dict):
    print("persist", event)
    path = Path("events.log")
    path = path.open("a")
    path.write(f"{event}\n")
    path.close()


def decode(event: bytes) -> str:
    print("decode event")
    event = event.decode()
    return event


def decompress_zlib(data: bytes) -> bytes | None:
    try:
        print("decompress zlib event")
        event = zlib.decompress(data)
        return event
    except Exception as e:
        print("zlib decompress failed", e)


def decompress_gzip(data: bytes) -> bytes | None:
    try:
        print("decompress gzip event")
        event = gzip.decompress(data)
        return event
    except Exception as e:
        print("gzip decompress failed.", e)


if __name__ == "__main__":
    HOST = "127.0.0.1"  # use, 0.0.0.0 symbolic name meaning all available interfaces
    PORT = 12201  # default port for GELF UDP

    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  # this creates UDP socket
    print("socket created")
    try:
        s.bind((HOST, PORT))
    except socket.error as e:
        print("bind failed. Error Code : " + str(e[0]) + " Message " + e[1])
        sys.exit()
    print("socket bind complete")

    print("reading stream now")
    while True:
        # 8192 is the largest size that a udp packet can handle
        data, addr = s.recvfrom(1024)  # buffer size is 1024 bytes

        print("ingested event from", addr)

        event = decompress_gzip(data) or decompress_zlib(data)
        if event:
            event = decode(event)
        else:
            print("uncompressed event")
            event = decode(data)

        persist(event)

Example producer:

docker run \
      --log-driver gelf --log-opt gelf-address=udp://127.0.0.1:12201 --log-opt gelf-compression-type=gzip \
      alpine /bin/sh -c "while true; do echo hello world; sleep 1; done;"

Configuration options here https://docs.docker.com/config/containers/logging/gelf/