bind/doc/dev/libuv.md

Libuv Notes

This document describes various notes related to the using of the libuv library.

Queueing Events onto the uv_loop_t

The upstream documentation on the I/O loop describes the order in which are the various handles processed. However, it does not describe the order in which the loop processes the events in the same buckets, and because it is counterintuitive, it is described here.

When scheduling the events of the same class (f.e. uv_*_start() or uv_close()), the events are executed in the LIFO order (e.g. it's a stack, not a queue). The reasoning for the upstream design choice is described in the upstream issue.

What does this means in practice? F.e. when closing the handles:

uv_close(&handle1, callback1);
uv_close(&handle2, callback2);

The callback2() will be called before the callback1(), so if they are using the same resource, the resource can be freed in the callback1() and not in the callback2().

Same applies f.e. to the uv_idle_t, if you want the action1() to execute before action2(), the valid code would be:

uv_idle_start(&idle2, action2);
uv_idle_start(&idle1, action1);

which is really counterintuitive.