mosquitto-users team mailing list archive

["andypiperuk@xxxxxxxxx" <andypiperuk@xxxxxxxxx>]

You know that the Eclipse Paho project has a Lua client due to hit Git
within days, right?

On Wednesday, December 12, 2012, Bart Van Der Meerssche wrote:

> Hello list,
>
> I'm currently writing Lua bindings for libmosquitto [1]. Since Lua does
> not support preemptive multithreading, using mosquitto_loop_start is not an
> option. As suggested in the libmosquitto documentation, I'm integrating
> mosquitto_loop_read/write/misc into a Lua event loop instead. The basic
> functionality works ok. However, when a network error occurs or the broker
> shuts down, the event loop starts busy looping. strace output:
>
> poll([{fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 2, -1) = 1 ([{fd=6,
> revents=POLLIN}])
> read(6, "", 1)                          = 0
> poll([{fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 2, -1) = 1 ([{fd=6,
> revents=POLLIN}])
> read(6, "", 1)                          = 0
>
> ...
>
> stracing the libmosquitto event loop:
> [pid 12721] select(4, [3], [], NULL, {1, 0}) = 1 (in [3], left {0, 332713})
> [pid 12721] read(3, "", 1)              = 0
> [pid 12721] close(3)                    = 0
>
> Looking at the mosquitto_loop code shows that if a read or write error
> occurs, the socket is closed with the private _mosquitto_socket_close
> function, which updates the internal mosq state as well. This means that
> the current libmosquitto API doesn't allow a proper implementation in an
> external event loop. Making _mosquitto_socket_close public would be a
> start. Integrating the rc handling of:
> * rc = mosquitto_loop_read(mosq, max_packets)
> * rc = mosquitto_loop_write(mosq, max_packets)
> inside these public functions could be an even cleaner approach.
>
> Would such a code change be an option?
>
> [1] https://github.com/flukso/**flm02/tree/rfm12/openwrt/**
> package/lua-mosquitto/src<https://github.com/flukso/flm02/tree/rfm12/openwrt/package/lua-mosquitto/src>
>
>
> Cheers
> /Bart
>
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