exceeded unchecked error limit (Broken pipe)

[Mehgugs]

I think this is a problem on my end just wanted to know what this error actually means.

/usr/local/share/lua/5.3/cqueues/socket.lua:578: exceeded unchecked error limit (Broken pipe)

Lua 5.3.5  Copyright (C) 1994-2018 Lua.org, PUC-Rio
> require"cqueues".VERSION
20171014

I believe this error occurs when calling

function send(state, op, d, identify)
    state.shard_mutex:lock()
    local success, err
    if identify or state.session_id then
        if state.connected then
            success, err = state.socket:send(encode {op = op, d = d}, 0x1)
        else
            success, err = false, 'Not connected to gateway'
        end
    else
        success, err = false, 'Invalid session'
    end
    state.shard_mutex:unlockAfter(GATEWAY_DELAY)
    return state, success, err
end

state.socket is a lua-http websocket client.

Only thing possibly worth noting is that I have interposed wrap to provide some debug logging.

[Mehgugs]

Okay so after reading up in the manual, I appear to be getting too many EPIPEs. I dont think this is my fault, since I'm only calling send here (in the case that caused the error) in response to a heartbeat message from socket so I should be connected, (my logs show no close message was sent to the websocket so in theory I should be able to send fine)

In the manual it mentions clearing errors, but I'm not sure exactly what it means by this. Should I just be handling EPIPE then calling clearerr ?

[daurnimator]

If you log any errors returned by socket functions, what does EPIPE come from?

[Mehgugs]

I'm not sure exactly because there's some indirection (i need to put an xpcall inside wrap to get the inner stack of the function which received the thrown error) but i believe it's state.socket:send which is returning EPIPE. This is likely a case of me not handling these correctly (I dont know how to clear the errors so the count will only increase over time) and the read direction works correctly since I still receive events from the server.

[pspacek]

FYI we have seen this on HTTP server built on lua-http:

[pspacek]

[worker.background] error: /usr/share/lua/5.1/cqueues/socket.lua:578: exceeded unchecked error limit (Broken pipe) stack traceback:
        [C]: in function 'send'
        /usr/share/lua/5.1/cqueues/socket.lua:578: in function 'xwrite'
        /usr/share/lua/5.1/http/h2_connection.lua:425: in function 'write_http2_frame'
        /usr/share/lua/5.1/http/h2_stream.lua:718: in function 'rst_stream'
        /usr/share/lua/5.1/http/h2_stream.lua:1199: in function 'shutdown'
        /usr/share/lua/5.1/http/server.lua:197: in function </usr/share/lua/5.1/http/server.lua:195>

[pspacek]

My guess is that EPIPE can happen if HTTP client terminates connection ungracefully or something like that.