Bug 1372439

Summary:	Add ability to swap the default threaded puma web server for thin
Product:	Red Hat CloudForms Management Engine	Reporter:	Joe Rafaniello <jrafanie>
Component:	Appliance	Assignee:	Joe Rafaniello <jrafanie>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Pete Savage <psavage>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	5.7.0	CC:	abellott, cpelland, jhardy, jprause, obarenbo, simaishi
Target Milestone:	GA	Keywords:	TestOnly, ZStream
Target Release:	5.7.0
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	5.7.0.0	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:
Clones:	1372801 (view as bug list)		Environment:
Last Closed:	2017-01-11 20:08:29 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	Feature
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1372801

Description Joe Rafaniello 2016-09-01 17:39:13 UTC

Description of problem:  Puma, by default is a threaded web server, which means each http(s) request will be handled in a new thread.  Since Rails' database connection pool reserves connections to threads, it's possible to exhaust the connection pool with enough web requests spinning up new puma threads.  Thin, by contrast, still processes each request in a single thread by default.  While this is usually slower, you don't have the issues of multiple threads in flight at the same time.

We should make puma the default web server but have an easy option to switch to thin in case there are thread issues with puma.


Version-Release number of selected component (if applicable):  5.6.0+

Comment 1 Joe Rafaniello 2016-09-01 17:40:24 UTC

Upstream pull request: https://github.com/ManageIQ/manageiq/pull/10447

Comment 2 Joe Rafaniello 2016-09-01 17:41:06 UTC

Upstream darga backport: https://github.com/ManageIQ/manageiq/pull/10713

Comment 3 Joe Rafaniello 2016-09-01 17:41:38 UTC

From pull request:

Purpose or Intent

Puma handles each request in a new thread, leading to possible thread issues
with the database connection pool, ActiveSupport::Dependencies interlock and our
locks, or thread unsafe code in our application.

Thin, while it may be run in threads via --threaded, does not use threads by default.
See here

This patch allows for thin 1.7.0+ and gives us an option to use either puma or
thin. Note, earlier versions are not compatible with rack 2.

We still default to puma.

Steps for Testing/QA

Note: Testers/users, the proctitle for UI/Webservice and web socket workers will
look different in ps, top, etc. if you use thin instead of puma. Puma configures
it's own proctitle and we configure the parts that we can. Thin does not, so it
will look like all the other workers.

For example:

thin:
43177 ttys002 0:08.20 MIQ: MiqUiWorker id: 158, uri: http://0.0.0.0:3000

puma:
43871 ttys004 0:00.68 puma 3.3.0 (tcp://0.0.0.0:3000) [MIQ: Web Server Worker]

Comment 4 Joe Rafaniello 2016-09-01 17:44:13 UTC

To change the web server, change puma to thin in the advanced configuration:

:server:
  :rails_server: puma

Comment 6 Satoe Imaishi 2016-09-12 18:53:44 UTC

*** Bug 1375328 has been marked as a duplicate of this bug. ***

Comment 7 Pete Savage 2016-12-12 10:30:08 UTC

Verified in 5.7.0.14