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I have a server with Apache/2.4.6 (CentOS) + OpenSSL/1.0.2k-fips (I know this is an old version of Apache but it cannot be upgraded right now). mpm event is used for multi processing.

When serving HTTP content, everything works as expected :

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The server can handle many requests concurrently without trouble (the test was made with approximately 150 clients, each creating 4 parallel connections = 600 connections). All requests target static content and use keepalive.

with HTTPS/SSL, it's a different story.

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It will quicky use all 400 possible threads (see scoreboard). No async connections will be made. AFAIK it behaves like mpm worker.

At first I thought it was a limitation and that mpm event would work only with HTTP. But this is not what is written in the documentation (under How it Works > Async connections) :

These improvements are valid for both HTTP/HTTPS connections.

EDIT: there is some information in Limitations section of documentation that explain that in some case it might fall back to mpm worker. However it does not seems to apply here.

tigrou
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1 Answers1

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While looking at Apache source code for possible mpm worker fallback conditions, I found the following relevant comment :

If we have an input filter which 'clogs' the input stream, like mod_ssl used to, lets just do the normal read from input filters, like the Worker MPM does.

Since I am using an old version of Apache that could be explain mpm event not working well with SSL.

EDIT: it looks like this has been done in this commit :

core, mod_ssl: Lift the restriction that prevents mod_ssl taking full advantage of the event MPM.

I use Apache 2.4.6 and change has been released later, in 2.4.7.

tigrou
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