About systemd notify in solr

[Taisuke Miyazaki <mi...@lifull.com>]

Hi,
I am currently managing Solr with systemd.
However, systemd's Type=simple considers the process successful as soon as
it starts, so in order to ensure the success of the process after startup,
I am waiting until it is ready to accept http requests after startup.
The wait process is just a simple script that makes a request to
http://localhost:8983/solr until 200 OK is returned.

I am not particularly troubled by this specification, but I believe that
systemd has a type Type=notify, which can be used to make solr active when
it is ready. (I don't know how useful this would be, but if everyone is
implementing wait processing, it might be a little useful)

Are there any plans to support Type=notify in the future?
Or is it possible to hook the startup completion event from the plugin? If
possible, we are considering making this as a prototype and providing
feedback.

Thanks,

Taisuke

Re: About systemd notify in solr

[Taisuke Miyazaki <mi...@lifull.com>]

Sorry, I omitted a bit about the wait script, it waits until it can make an
http connection and then makes a request to the health check handler.

Indeed, it seems to be difficult because each environment seems to have
different timing for when to notify.

I think it is important to have a health check for startup integration, but
it seems inadequate when only considering notify.

Either way, it will be after systemd integration is implemented.
Thank you.

Taisuke

2022年3月8日(火) 11:53 Shawn Heisey <ap...@elyograg.org>:

> On 3/6/2022 11:23 PM, Taisuke Miyazaki wrote:
> > I am currently managing Solr with systemd.
> > However, systemd's Type=simple considers the process successful as soon
> as
> > it starts, so in order to ensure the success of the process after
> startup,
> > I am waiting until it is ready to accept http requests after startup.
> > The wait process is just a simple script that makes a request to
> > http://localhost:8983/solr  until 200 OK is returned.
> >
> > I am not particularly troubled by this specification, but I believe that
> > systemd has a type Type=notify, which can be used to make solr active
> when
> > it is ready. (I don't know how useful this would be, but if everyone is
> > implementing wait processing, it might be a little useful)
> >
> > Are there any plans to support Type=notify in the future?
> > Or is it possible to hook the startup completion event from the plugin?
> If
> > possible, we are considering making this as a prototype and providing
> > feedback.
>
> At this time, the project does not have any kind of official systemd
> integration, so you must be using something unofficial, or something you
> wrote yourself.  To find out what is supported by a Solr systemd
> integration, you would have to talk to whoever wrote it, because it did
> not come from the Solr project.
>
> I am not aware of any kind of existing reliable test that you can do
> which indicates Solr is fully operational.  The URL that you are
> visiting for your test gets redirected to the admin UI.  I could be
> wrong about this, but I believe that the admin UI can be reached before
> the rest of Solr has fully started.  The admin UI is html and
> javascript, and mostly runs in the browser, not on the server.
>
> We are looking to support systemd, it just hasn't happened yet.
>
> https://issues.apache.org/jira/browse/SOLR-14410
>
> I believe that a central health check URL path for the service as a
> whole will be a prerequisite for any startup integration beyond what's
> already available from the project, which is for sysvinit. For
> individual indexes, Solr does already have a health-check mechanism, via
> the ping handler.  But that is for an individual index, not the whole
> program.
>
> Thanks,
> Shawn
>
>

Re: About systemd notify in solr

[Shawn Heisey <ap...@elyograg.org>]

On 3/6/2022 11:23 PM, Taisuke Miyazaki wrote:
> I am currently managing Solr with systemd.
> However, systemd's Type=simple considers the process successful as soon as
> it starts, so in order to ensure the success of the process after startup,
> I am waiting until it is ready to accept http requests after startup.
> The wait process is just a simple script that makes a request to
> http://localhost:8983/solr  until 200 OK is returned.
>
> I am not particularly troubled by this specification, but I believe that
> systemd has a type Type=notify, which can be used to make solr active when
> it is ready. (I don't know how useful this would be, but if everyone is
> implementing wait processing, it might be a little useful)
>
> Are there any plans to support Type=notify in the future?
> Or is it possible to hook the startup completion event from the plugin? If
> possible, we are considering making this as a prototype and providing
> feedback.

At this time, the project does not have any kind of official systemd 
integration, so you must be using something unofficial, or something you 
wrote yourself.  To find out what is supported by a Solr systemd 
integration, you would have to talk to whoever wrote it, because it did 
not come from the Solr project.

I am not aware of any kind of existing reliable test that you can do 
which indicates Solr is fully operational.  The URL that you are 
visiting for your test gets redirected to the admin UI.  I could be 
wrong about this, but I believe that the admin UI can be reached before 
the rest of Solr has fully started.  The admin UI is html and 
javascript, and mostly runs in the browser, not on the server.

We are looking to support systemd, it just hasn't happened yet.

https://issues.apache.org/jira/browse/SOLR-14410

I believe that a central health check URL path for the service as a 
whole will be a prerequisite for any startup integration beyond what's 
already available from the project, which is for sysvinit. For 
individual indexes, Solr does already have a health-check mechanism, via 
the ping handler.  But that is for an individual index, not the whole 
program.

Thanks,
Shawn