[Koha-devel] Optimizing Starman startup
dcook at prosentient.com.au
dcook at prosentient.com.au
Wed Apr 21 07:23:35 CEST 2021
It looks like newer version of the plugin might have cached spec/schema functionality, but I'm not finding the plugin author very helpful so far. My guess is that maybe... maybe... Mojolicious::Plugin::OpenAPI 3.41+ with JSON::Validator 4.10+ might perform better. But it's just a guess at this point.
David Cook
Software Engineer
Prosentient Systems
Suite 7.03
6a Glen St
Milsons Point NSW 2061
Australia
Office: 02 9212 0899
Online: 02 8005 0595
-----Original Message-----
From: Koha-devel <koha-devel-bounces at lists.koha-community.org> On Behalf Of dcook at prosentient.com.au
Sent: Wednesday, 21 April 2021 1:21 PM
To: 'Ere Maijala' <ere.maijala at helsinki.fi>; koha-devel at lists.koha-community.org
Subject: Re: [Koha-devel] Optimizing Starman startup
Looking at newer versions of Mojolicious::Plugin::OpenAPI and the coding choices are... interesting.
I opened a ticket against JSON::Validator (https://github.com/jhthorsen/json-validator/issues/246), but maybe I should open it against Mojolicious::Plugin::OpenAPI. We'll see how responsive the author is on Github.
Of course, we're using such ancient versions of the Mojolicious modules that even convincing the author to cache validation or skip validation won't really help us in the short- to medium- term.
At the moment, I think that I might just have to resign myself to Koha being slow to start up, as we're beholden to this third-party module.
That said, we could fork Mojolicious::Plugin::OpenAPI.
I suppose I could just do that locally too. Hmmmm.
David Cook
Software Engineer
Prosentient Systems
Suite 7.03
6a Glen St
Milsons Point NSW 2061
Australia
Office: 02 9212 0899
Online: 02 8005 0595
-----Original Message-----
From: Koha-devel <koha-devel-bounces at lists.koha-community.org> On Behalf Of dcook at prosentient.com.au
Sent: Wednesday, 21 April 2021 12:12 PM
To: 'Ere Maijala' <ere.maijala at helsinki.fi>; koha-devel at lists.koha-community.org
Subject: Re: [Koha-devel] Optimizing Starman startup
That was an interesting experience.
When you run koha-plack --start, it spins through a long list of instances quickly, because it returns immediately after starting the Starman master, which doesn't really do much, but fork off worker processes, which then consume a huge amount of resources concurrently.
However, when you preload the app using --preload-app, the resource consumption is in the Starman master, and the command doesn't return until after the Starman master has loaded the app. So you synchronously move through the list 1 by 1.
This has pros and cons.
Pro: You can start 60 Koha instances with very little resource usage, because you're only starting 1 Koha at a time. Yay!
Con: "service koha-common restart" will stop all Plack instances and then start them all. This is suboptimal, as it took me about 3.5 minutes to start 60 Koha instances. That's a lot of downtime for the last Koha instance in that list.
Of course, we could change "koha-common" init service to actually restart instead of stop/start on a "restart" action.
But the other gotcha is Debian package installs/upgrades (hello continuous deployment). According to https://manpages.debian.org/testing/debhelper/dh_installinit.1.en.html, the init script is "stopped" in the prerm and "started" in the postinst. The documentation is not clear if it's at the start or end of postinst...) Based on my review of syslog and /var/log/apt/history.log, it looks like it's actually started at the beginning of postinst, which is before koha-schema-upgrade actually runs. I suppose that makes sense as that should put Koha into maintenance mode until the schema upgrade completes...
Operations is so not fun heh.
Really at the end of the day I guess it comes back to trying to optimize that OpenAPI plugin to reduce the resource consumption and resulting downtime.
David Cook
Software Engineer
Prosentient Systems
Suite 7.03
6a Glen St
Milsons Point NSW 2061
Australia
Office: 02 9212 0899
Online: 02 8005 0595
-----Original Message-----
From: Koha-devel <koha-devel-bounces at lists.koha-community.org> On Behalf Of dcook at prosentient.com.au
Sent: Wednesday, 21 April 2021 10:46 AM
To: 'Ere Maijala' <ere.maijala at helsinki.fi>; koha-devel at lists.koha-community.org
Subject: Re: [Koha-devel] Optimizing Starman startup
Thanks for that optimization. My restart time has gone from 2 minutes 45 seconds to 1 minute 30 seconds. Much better.
Now I'm going to try the preload and see if I can get it down to 45 seconds or better...
David Cook
Software Engineer
Prosentient Systems
Suite 7.03
6a Glen St
Milsons Point NSW 2061
Australia
Office: 02 9212 0899
Online: 02 8005 0595
-----Original Message-----
From: Koha-devel <koha-devel-bounces at lists.koha-community.org> On Behalf Of dcook at prosentient.com.au
Sent: Wednesday, 21 April 2021 10:28 AM
To: 'Ere Maijala' <ere.maijala at helsinki.fi>; koha-devel at lists.koha-community.org
Subject: Re: [Koha-devel] Optimizing Starman startup
Hi Ere,
Thanks for your reply. 24700 looks much better. I'll look at backporting it locally.
Although I'm looking at JSON::Validator::OpenAPI::Mojolicious at https://metacpan.org/pod/release/JHTHORSEN/Mojolicious-Plugin-OpenAPI-2.19/lib/JSON/Validator/OpenAPI/Mojolicious.pm and it says "Do not use this module directly. Use Mojolicious::Plugin::OpenAPI instead." I notice that you're using the "bundle" method. Do we really need that there? Why don't we just load the JSON using the JSON module, merge with the plugin spec files, and then pass it to the OpenAPI plugin? Shouldn't the plugin take care of the $ref replacement?
Hmm... I didn't realize until now that the OpenAPI plugin was doing a validate behind the scenes. That's tricky.
At a glance, we might be able to pre-load the app into the Starman master process pre-fork. There are warnings about doing that with open database connections, so we'd need to review plack.psgi, but a quick glance suggests it might be OK. (Alternatively, I have wondered about running the REST API as a separate process apart from Starman using hypnotoad. According to https://docs.mojolicious.org/Mojolicious/Guides/Cookbook, Mojo::Server::Prefork preloads the application in the manager/master process, and Hypnotoad is based off that, so that would help.)
It does seem like changes to the OpenAPI plugin would be needed for caching.
I'm going to try backporting your change and try pre-loading and see how far that gets me.
David Cook
Software Engineer
Prosentient Systems
Suite 7.03
6a Glen St
Milsons Point NSW 2061
Australia
Office: 02 9212 0899
Online: 02 8005 0595
-----Original Message-----
From: Koha-devel <koha-devel-bounces at lists.koha-community.org> On Behalf Of Ere Maijala
Sent: Tuesday, 20 April 2021 4:48 PM
To: koha-devel at lists.koha-community.org
Subject: Re: [Koha-devel] Optimizing Starman startup
Hi,
I did some work on improving it here:
https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=24700
That shaved a good bit of time from it, but it's still a heavy operation, and it would make sense to
1.) avoid doing it too often
2.) cache the results and avoid doing it if results are cached
If you could address the first one, that'd go a long way. I'm afraid the second one would require changes to the OpenAPI plugin to support caching.
--Ere
dcook at prosentient.com.au kirjoitti 20.4.2021 klo 6.15:
> Hi all,
>
> Do you despair when you see the following periodically in “top” when a
> starman worker is recreated ?
>
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
> COMMAND
>
> 9529 my-koha 20 0 460108 197212 17172 R 100.0 0.4 0:03.41
> /usr/share/koha/api/v1/app.pl
>
> Or the following in top when you install koha-common package or
> restart the koha-common service?
>
> 11101 1-koha 20 0 447232 193320 16076 R 10.6 0.4 0:09.09
> /usr/share/koha/api/v1/app.pl
>
> 11168 1-koha 20 0 447240 193264 16056 R 10.6 0.4 0:08.72
> /usr/share/koha/api/v1/app.pl
>
> 11306 2-koha 20 0 447220 193148 16000 R 10.6 0.4 0:08.07
> /usr/share/koha/api/v1/app.pl
>
> 11543 2-koha 20 0 447232 193036 15828 R 10.6 0.4 0:07.07
> /usr/share/koha/api/v1/app.pl
>
> 11784 3-koha 20 0 441536 189664 16172 R 10.6 0.4 0:06.04
> /usr/share/koha/api/v1/app.pl
>
> 11830 3-koha 20 0 439548 187212 15748 R 10.6 0.4 0:05.82
> /usr/share/koha/api/v1/app.pl
>
> 11831 4-koha 20 0 438620 186344 15748 R 10.6 0.4 0:05.81
> /usr/share/koha/api/v1/app.pl
>
> 11853 4-koha 20 0 437680 185672 16000 R 10.6 0.4 0:05.79
> /usr/share/koha/api/v1/app.pl
>
> Well, I still have a lot of investigation left to do, but I notice 1
> place that a lot of time taken is here (per worker):
>
> my $validator = JSON::Validator::OpenAPI::Mojolicious->new;
>
> $validator->load_and_validate_schema(
>
> $self->home->rel_file("api/v1/swagger/swagger.json"),
>
> {
>
> allow_invalid_ref => 1,
>
> }
>
> );
>
> push @{$self->routes->namespaces}, 'Koha::Plugin';
>
> my $spec = $validator->schema->data;
>
> $self->plugin(
>
> 'Koha::REST::Plugin::PluginRoutes' => {
>
> spec => $spec,
>
> validator => $validator
>
> }
>
> );
>
> $self->plugin(
>
> OpenAPI => {
>
> spec => $spec,
>
> route =>
> $self->routes->under('/api/v1')->to('Auth#under'),
>
> allow_invalid_ref =>
>
> 1, # required by our spec because $ref directly
> under
>
> # Paths-, Parameters-, Definitions- & Info-object
>
> # is not allowed by the OpenAPI specification.
>
> }
>
> );
>
> Anyone have ideas for improving this? Do we have to validate the
> schema every time? Can we move the schema validation into a different
> module and preload it into Starman using the -M flag so that it’s done
> 1 time per Starman master instance rather than 1 time per Starman worker instance?
>
> I find “/usr/share/koha/api/v1/app.pl” to be the bane of deployments,
> as it puts a massive load on a server, when you have multiple Koha
> instances on the server.
>
> David Cook
>
> Software Engineer
>
> Prosentient Systems
>
> Suite 7.03
>
> 6a Glen St
>
> Milsons Point NSW 2061
>
> Australia
>
> Office: 02 9212 0899
>
> Online: 02 8005 0595
>
>
> _______________________________________________
> Koha-devel mailing list
> Koha-devel at lists.koha-community.org
> https://lists.koha-community.org/cgi-bin/mailman/listinfo/koha-devel
> website : https://www.koha-community.org/ git :
> https://git.koha-community.org/ bugs :
> https://bugs.koha-community.org/
>
--
Ere Maijala
Kansalliskirjasto / The National Library of Finland _______________________________________________
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