[PR] Post k8s-events properly from multiple threads (thread-safe)

[kopf-archiver]

A pull request by nolar at 2019-07-14 17:55:36+00:00
Original URL: zalando-incubator/kopf#148
Merged by nolar at 2019-07-16 10:09:40+00:00

Part of an effort to make Kopf-based operators more stable and resilient.

Issue : #142 #136
Related: #128

Description

When k8s-event-posting was moved to a background task (#125), some asyncio-related tasks were made way to complicated (multiple dynamically created loggers) and implemented improperly (non-thread-safe put_nowait() when used across threads).

The non-thread-safeness made some k8s-events not posted as soon as it was possible, but waiting for few seconds until something happens on an asyncio event-loop (because put_nowait() does not wake up the event-loop). And it was failing of debug mode was used.

This has become important since #128 — as not only Kopf's internal routines, but also the sync-handlers (which run in a thread-pool) could log INFO+ messages, which should be posted to k8s.

This PR simplifies the solution to one and only one logger (and therefore one and only one handler), and by posting all k8s-events synchronously but instantly via one and only one function (enqueue()).

In that function (enqueue()), one of the thread-safe methods is used to put an event to a queue: either the same-threaded method (thread-safe by definition), or cross-threaded method (explicitly thread-safe).

Types of Changes

• Refactor/improvements