How to hot deploy with mod_fcgid? about s2i-perl-container HOT 17 CLOSED

I could help with it.

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@yselkowitz Can you please provide us more information about hot-deploy? Any documentation? How it should work in a container? The issue is related only to RHEL7 images, right? And even, how can we set up and test it?

Thank you

CC: @michal-josef-spacek @pkubatrh @hhorak

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/cc @phracek

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The links above show the enablement of hot config and the application being tested. In short, it is relying on setting PERL_APACHE2_RELOAD to control this, which means it's relying on Apache2::Reload with mod_perl. UBI 8 uses mod_fcgid, so that won't do anything. I think the solution might be plackup -r but does that require changing the s2i glue to conditionally pass -r to plackup based on a new environment variable? Or is there a better way to handle this?

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The links above show the enablement of hot config and the application being tested. In short, it is relying on setting PERL_APACHE2_RELOAD to control this, which means it's relying on Apache2::Reload with mod_perl. UBI 8 uses mod_fcgid, so that won't do anything. I think the solution might be plackup -r but does that require changing the s2i glue to conditionally pass -r to plackup based on a new environment variable? Or is there a better way to handle this?

@michal-josef-spacek Does it help you @yselkowitz comment to implement it and test it?

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@phracek @yselkowitz
plackup -r -R __DIRS_WHICH_MONITOR__ is working, preparing PR for it.

Some questions which i am trying to understand:

• This plackup -r working only to specified directories and check across inotify all changes in them. Is it expected usage? This not affect e.g. installed rpms.
• How is this Apache2::Reload working? When i changed file or included file, reload was done without this Apache2::Reload usage too.

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1. Yes, see https://metacpan.org/dist/Plack/view/script/plackup#-r,-reload
2. Apache2::Reload is only included in the mod_perl-based rhel7 builder image, not the mod_fcgid-based ubi8 ones. It is triggered in the run script.

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@yselkowitz I know this answers. My questions are more deeply in both scenes. ok, i will prepare PR and will discuss more after.

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I have filed a Bugzilla for this issue. https://bugzilla.redhat.com/show_bug.cgi?id=2023278

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@yselkowitz First thing:

• When we have application for hot plug "https://github.com/openshift/origin/tree/master/test/extended/testdata/image_ecosystem/perl-hotdeploy"
• This mean, that moving from container based on mod_perl to container based on mod_fcgi means that application changes from mod_perl app to classic cgi app. This mean that each request call full application again.
• This mean that we need deliver new application. Possibilities are:
  • PSGI application (configuration is present by $PSGI_FILE env variable)
  • FCGI application (configuration is present for each *.fcgi script)

For me the best example application is counter application, which stores state of counter. This is nice example to test if application is loaded again and again or running.

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PSGI application for hot-deploy PR: openshift/origin#26607

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btw: On old containers this PSGI application hasn't possiblity of this kind of reload.

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Support for this in s2i-perl container: #221

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@yselkowitz @phracek I added tests for PSGI_RELOAD functionality

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Rebase PR again: #236

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This is fixed by #236

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@yselkowitz If you need some other help from me, ping me, please.

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