Provide metrics

[aaugustin]

I'm thinking of something along the lines of:

websocket.get_metrics()

{
    "lifetime": 23.780,
    "latency": 0.423,
    "frames": {
        "rcvd": {
            "text": 93,
            "pong": 17,
        },
        "rcvd": {
            "text": 1,
            "ping": 17,
        },
    },
}

I'm not sure what would be must useful to track.

Idea sparked in #919.

[adriansev]

maybe avg_{rcvd,txd}_{compressed,uncompressed}_frame_size ? latency would be the ping/pong one i imagine, so maybe an tuple of min/avg/max/mdev ?

[aaugustin]

Nice suggestions!

[aaugustin]

Latency is now available via a dedicated API. See #1195.

One year later, I'm not sure about implementing the rest:

• Buffer sizes: I don't know how to get the TCP buffers at the OS level, which are the largest buffers in the system for the most common WebSocket use cases (small messages).
• Compression: it's not just about the size, it's also about CPU usage, so benchmarks compression is best done offline with scripts similar to experimentation/compression/broadcast.py
• Messages sent or received: this is easy to implement outside of websockets — just count what you send or receive; I don't really want to add overhead for everyone when it isn't a common feature request.

[aaugustin]

Also I looked for prior art in other WebSocket frameworks and couldn't find anything resembling this. Typical metrics are things like "number of connections to the server".