envoyproxy/envoy

[Events] Add an file event wakeup method with socketpair

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#14,244 opened on Dec 2, 2020

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Description

Description:

The goal is to create a premitive in source/common/event that wakes up (schedules) an event using a socketpair instead of scheduleCallbackCurrentIteration. The reason for that is that scheduleCallbackCurrentIteration is using event_active(&raw_event_, EV_TIMEOUT, 0); which takes a lock.

See comment in: https://github.com/envoyproxy/envoy/pull/13954#discussion_r533796896

This mechanism could be applied to:

  1. Win32 DirectoryWatcher
  2. Replace the wakeup mechanism in dispatcher_impl.cc -> void DispatcherImpl::post(std::function<void()> callback)

For Win32 it is good to also have #10871 if we are going to build on top of socketpairs

Contributor guide

Research direction
Examine the existing DispatcherImpl::post implementation and the referenced comment in pull request #13954. Understand how socketpair wakeup works and consider applying it to Win32 DirectoryWatcher and post mechanism.
Tech stack
cpp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++event loop concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30