Preventing accepting queries while custom QueryComponent starts up?

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Preventing accepting queries while custom QueryComponent starts up?

Aaron Daubman
Greetings,

I have several custom QueryComponents that have high one-time startup costs
(hashing things in the index, caching things from a RDBMS, etc...)

Is there a way to prevent solr from accepting connections before all
QueryComponents are "ready"?

Especially, since many of our instance are load-balanced (and
added-in/removed automatically based on admin/ping responses) preventing
ping from answering prior to all custom QueryComponents being ready would
be ideal...

Thanks,
     Aaron
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Re: Preventing accepting queries while custom QueryComponent starts up?

Amit Nithian
I think Solr does this by default and are you executing warming queries in
the firstSearcher so that these actions are done before Solr is ready to
accept real queries?


On Thu, Nov 8, 2012 at 11:54 AM, Aaron Daubman <[hidden email]> wrote:

> Greetings,
>
> I have several custom QueryComponents that have high one-time startup costs
> (hashing things in the index, caching things from a RDBMS, etc...)
>
> Is there a way to prevent solr from accepting connections before all
> QueryComponents are "ready"?
>
> Especially, since many of our instance are load-balanced (and
> added-in/removed automatically based on admin/ping responses) preventing
> ping from answering prior to all custom QueryComponents being ready would
> be ideal...
>
> Thanks,
>      Aaron
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Aaron Daubman
Amit,

I am using warming /firstSearcher queries to ensure this happens before any
external queries are received, however, unless I am misinterpreting the
logs, solr starts responding to admin/ping requests before firstSearcher
completes, and, the LB then puts the solr instance back in the pool, and it
starts accepting connections...


On Thu, Nov 8, 2012 at 4:24 PM, Amit Nithian <[hidden email]> wrote:

> I think Solr does this by default and are you executing warming queries in
> the firstSearcher so that these actions are done before Solr is ready to
> accept real queries?
>
>
> On Thu, Nov 8, 2012 at 11:54 AM, Aaron Daubman <[hidden email]> wrote:
>
> > Greetings,
> >
> > I have several custom QueryComponents that have high one-time startup
> costs
> > (hashing things in the index, caching things from a RDBMS, etc...)
> >
> > Is there a way to prevent solr from accepting connections before all
> > QueryComponents are "ready"?
> >
> > Especially, since many of our instance are load-balanced (and
> > added-in/removed automatically based on admin/ping responses) preventing
> > ping from answering prior to all custom QueryComponents being ready would
> > be ideal...
> >
> > Thanks,
> >      Aaron
> >
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Amit Nithian
Sorry I misunderstood. I am having difficulty finding this but it's never
clear the exact load order. It seems odd that you'd be getting requests
when the filter (DispatchFilter) hasn't 100% loaded yet.

I didn't think that the admin handler would allow requests while the
dispatch filter is still init'ing but sounds like it is? I'll have to play
with this to see.. curious what the problem is for we have a similar setup
but not as bad of an init problem (plus when I deploy, my deploy script
runs some actual simple test queries to ensure they return before enabling
the ping handler to return 200s) to avoid this problem.

Cheers
Amit


On Thu, Nov 8, 2012 at 1:33 PM, Aaron Daubman <[hidden email]> wrote:

> Amit,
>
> I am using warming /firstSearcher queries to ensure this happens before any
> external queries are received, however, unless I am misinterpreting the
> logs, solr starts responding to admin/ping requests before firstSearcher
> completes, and, the LB then puts the solr instance back in the pool, and it
> starts accepting connections...
>
>
> On Thu, Nov 8, 2012 at 4:24 PM, Amit Nithian <[hidden email]> wrote:
>
> > I think Solr does this by default and are you executing warming queries
> in
> > the firstSearcher so that these actions are done before Solr is ready to
> > accept real queries?
> >
> >
> > On Thu, Nov 8, 2012 at 11:54 AM, Aaron Daubman <[hidden email]>
> wrote:
> >
> > > Greetings,
> > >
> > > I have several custom QueryComponents that have high one-time startup
> > costs
> > > (hashing things in the index, caching things from a RDBMS, etc...)
> > >
> > > Is there a way to prevent solr from accepting connections before all
> > > QueryComponents are "ready"?
> > >
> > > Especially, since many of our instance are load-balanced (and
> > > added-in/removed automatically based on admin/ping responses)
> preventing
> > > ping from answering prior to all custom QueryComponents being ready
> would
> > > be ideal...
> > >
> > > Thanks,
> > >      Aaron
> > >
> >
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Aaron Daubman
>  (plus when I deploy, my deploy script
> runs some actual simple test queries to ensure they return before enabling
> the ping handler to return 200s) to avoid this problem.
>

What are you doing to programmatically disable/enable the ping handler?
This sounds like exactly what I should be doing as well...
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Re: Preventing accepting queries while custom QueryComponent starts up?

Amit Nithian
Hi Aaron,

Check out
http://lucene.apache.org/solr/api-4_0_0-BETA/org/apache/solr/handler/PingRequestHandler.html
You'll see the ?action=enable/disable. I have our load balancers remove the
server out of rotation when the response code != 200 for some number of
times in a row which I suspect you are doing too. If I am rolling releasing
our search code to production, it gets disabled, sleep for some known
number of seconds for the LB to yank the search server out of rotation,
push the code, execute some queries using CURL to ensure a response (the
warming process should block the request until done) and then enable.

HTH!
Amit


On Thu, Nov 8, 2012 at 2:01 PM, Aaron Daubman <[hidden email]> wrote:

> >  (plus when I deploy, my deploy script
> > runs some actual simple test queries to ensure they return before
> enabling
> > the ping handler to return 200s) to avoid this problem.
> >
>
> What are you doing to programmatically disable/enable the ping handler?
> This sounds like exactly what I should be doing as well...
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Erick Erickson
In reply to this post by Aaron Daubman
Why does it matter? The whole idea of firstSearcher queries is to warm up
your system as fast as possible. The theory is that upon restarting the
server, let's bet this stuff going immediately... They were never intended
(as far as I know) to complete before any queries were handled. As an
aside, I'm not quite sure I understand why pings during the warmup are a
problem.

But anyway. firstSearcher is particularly relevant because the
autowarmCount settings on your caches are irrelevant when starting the
server, there's no history to autowarm....

But, there's no good reason _not_ to let queries through while
firstSearcher is doing it's tricks, they just get into the queue and are
served as quickly as they may. That might be some time since, as you say,
they may not get serviced until the expensive parts get filled. But I don't
think having them be serviced is doing any harm.

Now, newSearcher and autowarming of the caches is a completely different
beast since having the old searchers continue serving requests until the
warmups _does_ directly impact the user, they don't see random slowness
because a searcher is being opened.

So I guess my real question is whether you're seeing a measurable problem
or if this is a red herring....

FWIW,
Erick


On Thu, Nov 8, 2012 at 2:54 PM, Aaron Daubman <[hidden email]> wrote:

> Greetings,
>
> I have several custom QueryComponents that have high one-time startup costs
> (hashing things in the index, caching things from a RDBMS, etc...)
>
> Is there a way to prevent solr from accepting connections before all
> QueryComponents are "ready"?
>
> Especially, since many of our instance are load-balanced (and
> added-in/removed automatically based on admin/ping responses) preventing
> ping from answering prior to all custom QueryComponents being ready would
> be ideal...
>
> Thanks,
>      Aaron
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Amit Nithian
Yes but the problem is that if user facing queries are hitting a server
that is warming up and isn't being serviced quickly, then you could
potentially bring down your site if all the front end threads are blocked
on Solr queries b/c those queries are waiting (presumably at the container
level since the filter hasn't finished its init() sequence) for the warming
to complete (this is especially notorious when your front end is rails).
This is why your ping to enable/disable a server from the load balancer has
to be accurate with regards to whether or not a server is truly ready and
warm.

I think what I am gathering from this discussion is that the server is
warming up, the ping is going through and tells the load balancer this
server is ready, user queries are hitting this server and are queued
waiting for the firstSearcher to finish (say these initial user queries are
to respond in 500-1000ms) that's terrible for performance.

Alternatively, if you have a bunch of servers behind a load balancer, you
want this one server (or block of servers depending on your deployment) to
be reasonably sure that user queries will return in a decent time (whatever
you define decent to be) hence why this matters.

Let me know if I am missing anything.

Thanks
Amit


On Sat, Nov 10, 2012 at 10:03 AM, Erick Erickson <[hidden email]>wrote:

> Why does it matter? The whole idea of firstSearcher queries is to warm up
> your system as fast as possible. The theory is that upon restarting the
> server, let's bet this stuff going immediately... They were never intended
> (as far as I know) to complete before any queries were handled. As an
> aside, I'm not quite sure I understand why pings during the warmup are a
> problem.
>
> But anyway. firstSearcher is particularly relevant because the
> autowarmCount settings on your caches are irrelevant when starting the
> server, there's no history to autowarm....
>
> But, there's no good reason _not_ to let queries through while
> firstSearcher is doing it's tricks, they just get into the queue and are
> served as quickly as they may. That might be some time since, as you say,
> they may not get serviced until the expensive parts get filled. But I don't
> think having them be serviced is doing any harm.
>
> Now, newSearcher and autowarming of the caches is a completely different
> beast since having the old searchers continue serving requests until the
> warmups _does_ directly impact the user, they don't see random slowness
> because a searcher is being opened.
>
> So I guess my real question is whether you're seeing a measurable problem
> or if this is a red herring....
>
> FWIW,
> Erick
>
>
> On Thu, Nov 8, 2012 at 2:54 PM, Aaron Daubman <[hidden email]> wrote:
>
> > Greetings,
> >
> > I have several custom QueryComponents that have high one-time startup
> costs
> > (hashing things in the index, caching things from a RDBMS, etc...)
> >
> > Is there a way to prevent solr from accepting connections before all
> > QueryComponents are "ready"?
> >
> > Especially, since many of our instance are load-balanced (and
> > added-in/removed automatically based on admin/ping responses) preventing
> > ping from answering prior to all custom QueryComponents being ready would
> > be ideal...
> >
> > Thanks,
> >      Aaron
> >
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Erick Erickson
Hmmm, rather than hit the ping query, why not just send in a real query and
only let the queued ones through after the response?

Just a random thought
Erick


On Sat, Nov 10, 2012 at 2:53 PM, Amit Nithian <[hidden email]> wrote:

> Yes but the problem is that if user facing queries are hitting a server
> that is warming up and isn't being serviced quickly, then you could
> potentially bring down your site if all the front end threads are blocked
> on Solr queries b/c those queries are waiting (presumably at the container
> level since the filter hasn't finished its init() sequence) for the warming
> to complete (this is especially notorious when your front end is rails).
> This is why your ping to enable/disable a server from the load balancer has
> to be accurate with regards to whether or not a server is truly ready and
> warm.
>
> I think what I am gathering from this discussion is that the server is
> warming up, the ping is going through and tells the load balancer this
> server is ready, user queries are hitting this server and are queued
> waiting for the firstSearcher to finish (say these initial user queries are
> to respond in 500-1000ms) that's terrible for performance.
>
> Alternatively, if you have a bunch of servers behind a load balancer, you
> want this one server (or block of servers depending on your deployment) to
> be reasonably sure that user queries will return in a decent time (whatever
> you define decent to be) hence why this matters.
>
> Let me know if I am missing anything.
>
> Thanks
> Amit
>
>
> On Sat, Nov 10, 2012 at 10:03 AM, Erick Erickson <[hidden email]
> >wrote:
>
> > Why does it matter? The whole idea of firstSearcher queries is to warm up
> > your system as fast as possible. The theory is that upon restarting the
> > server, let's bet this stuff going immediately... They were never
> intended
> > (as far as I know) to complete before any queries were handled. As an
> > aside, I'm not quite sure I understand why pings during the warmup are a
> > problem.
> >
> > But anyway. firstSearcher is particularly relevant because the
> > autowarmCount settings on your caches are irrelevant when starting the
> > server, there's no history to autowarm....
> >
> > But, there's no good reason _not_ to let queries through while
> > firstSearcher is doing it's tricks, they just get into the queue and are
> > served as quickly as they may. That might be some time since, as you say,
> > they may not get serviced until the expensive parts get filled. But I
> don't
> > think having them be serviced is doing any harm.
> >
> > Now, newSearcher and autowarming of the caches is a completely different
> > beast since having the old searchers continue serving requests until the
> > warmups _does_ directly impact the user, they don't see random slowness
> > because a searcher is being opened.
> >
> > So I guess my real question is whether you're seeing a measurable problem
> > or if this is a red herring....
> >
> > FWIW,
> > Erick
> >
> >
> > On Thu, Nov 8, 2012 at 2:54 PM, Aaron Daubman <[hidden email]> wrote:
> >
> > > Greetings,
> > >
> > > I have several custom QueryComponents that have high one-time startup
> > costs
> > > (hashing things in the index, caching things from a RDBMS, etc...)
> > >
> > > Is there a way to prevent solr from accepting connections before all
> > > QueryComponents are "ready"?
> > >
> > > Especially, since many of our instance are load-balanced (and
> > > added-in/removed automatically based on admin/ping responses)
> preventing
> > > ping from answering prior to all custom QueryComponents being ready
> would
> > > be ideal...
> > >
> > > Thanks,
> > >      Aaron
> > >
> >
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Amit Nithian
Yeah that's what I was suggesting in my response too. I don't think your
load balancer should be doing this but whatever script does the release
(restarting the container) should do this so that when the ping is enabled
the warming has finished.


On Sat, Nov 10, 2012 at 3:33 PM, Erick Erickson <[hidden email]>wrote:

> Hmmm, rather than hit the ping query, why not just send in a real query and
> only let the queued ones through after the response?
>
> Just a random thought
> Erick
>
>
> On Sat, Nov 10, 2012 at 2:53 PM, Amit Nithian <[hidden email]> wrote:
>
> > Yes but the problem is that if user facing queries are hitting a server
> > that is warming up and isn't being serviced quickly, then you could
> > potentially bring down your site if all the front end threads are blocked
> > on Solr queries b/c those queries are waiting (presumably at the
> container
> > level since the filter hasn't finished its init() sequence) for the
> warming
> > to complete (this is especially notorious when your front end is rails).
> > This is why your ping to enable/disable a server from the load balancer
> has
> > to be accurate with regards to whether or not a server is truly ready and
> > warm.
> >
> > I think what I am gathering from this discussion is that the server is
> > warming up, the ping is going through and tells the load balancer this
> > server is ready, user queries are hitting this server and are queued
> > waiting for the firstSearcher to finish (say these initial user queries
> are
> > to respond in 500-1000ms) that's terrible for performance.
> >
> > Alternatively, if you have a bunch of servers behind a load balancer, you
> > want this one server (or block of servers depending on your deployment)
> to
> > be reasonably sure that user queries will return in a decent time
> (whatever
> > you define decent to be) hence why this matters.
> >
> > Let me know if I am missing anything.
> >
> > Thanks
> > Amit
> >
> >
> > On Sat, Nov 10, 2012 at 10:03 AM, Erick Erickson <
> [hidden email]
> > >wrote:
> >
> > > Why does it matter? The whole idea of firstSearcher queries is to warm
> up
> > > your system as fast as possible. The theory is that upon restarting the
> > > server, let's bet this stuff going immediately... They were never
> > intended
> > > (as far as I know) to complete before any queries were handled. As an
> > > aside, I'm not quite sure I understand why pings during the warmup are
> a
> > > problem.
> > >
> > > But anyway. firstSearcher is particularly relevant because the
> > > autowarmCount settings on your caches are irrelevant when starting the
> > > server, there's no history to autowarm....
> > >
> > > But, there's no good reason _not_ to let queries through while
> > > firstSearcher is doing it's tricks, they just get into the queue and
> are
> > > served as quickly as they may. That might be some time since, as you
> say,
> > > they may not get serviced until the expensive parts get filled. But I
> > don't
> > > think having them be serviced is doing any harm.
> > >
> > > Now, newSearcher and autowarming of the caches is a completely
> different
> > > beast since having the old searchers continue serving requests until
> the
> > > warmups _does_ directly impact the user, they don't see random slowness
> > > because a searcher is being opened.
> > >
> > > So I guess my real question is whether you're seeing a measurable
> problem
> > > or if this is a red herring....
> > >
> > > FWIW,
> > > Erick
> > >
> > >
> > > On Thu, Nov 8, 2012 at 2:54 PM, Aaron Daubman <[hidden email]>
> wrote:
> > >
> > > > Greetings,
> > > >
> > > > I have several custom QueryComponents that have high one-time startup
> > > costs
> > > > (hashing things in the index, caching things from a RDBMS, etc...)
> > > >
> > > > Is there a way to prevent solr from accepting connections before all
> > > > QueryComponents are "ready"?
> > > >
> > > > Especially, since many of our instance are load-balanced (and
> > > > added-in/removed automatically based on admin/ping responses)
> > preventing
> > > > ping from answering prior to all custom QueryComponents being ready
> > would
> > > > be ideal...
> > > >
> > > > Thanks,
> > > >      Aaron
> > > >
> > >
> >
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Jack Krupansky-2
Is the issue here that the Solr node is continuously "live" with the load
balancer so that the moment during startup that Solr can respond to
anything, the load balancer will be sending it traffic and that this can
occur while Solr is still warming up?

First, shouldn't we be encouraging people to have an app layer between Solr
and the outside world? If so, the app layer should simply not respond to
traffic until the app layer can verified that Solr has stabilized. If not,
then maybe we do need to suggest a change to Solr so that the developer can
control exactly when Solr becomes "live" and responsive to incoming traffic.

At a minimum, we should document when that moment is today in terms of an
explicit contract. It sounds like the problem is that the contract is either
nonexistent, vague, ambiguous, non-deterministic, or whatever.

-- Jack Krupansky

-----Original Message-----
From: Amit Nithian
Sent: Saturday, November 10, 2012 4:24 PM
To: [hidden email]
Subject: Re: Preventing accepting queries while custom QueryComponent starts
up?

Yeah that's what I was suggesting in my response too. I don't think your
load balancer should be doing this but whatever script does the release
(restarting the container) should do this so that when the ping is enabled
the warming has finished.


On Sat, Nov 10, 2012 at 3:33 PM, Erick Erickson
<[hidden email]>wrote:

> Hmmm, rather than hit the ping query, why not just send in a real query
> and
> only let the queued ones through after the response?
>
> Just a random thought
> Erick
>
>
> On Sat, Nov 10, 2012 at 2:53 PM, Amit Nithian <[hidden email]> wrote:
>
> > Yes but the problem is that if user facing queries are hitting a server
> > that is warming up and isn't being serviced quickly, then you could
> > potentially bring down your site if all the front end threads are
> > blocked
> > on Solr queries b/c those queries are waiting (presumably at the
> container
> > level since the filter hasn't finished its init() sequence) for the
> warming
> > to complete (this is especially notorious when your front end is rails).
> > This is why your ping to enable/disable a server from the load balancer
> has
> > to be accurate with regards to whether or not a server is truly ready
> > and
> > warm.
> >
> > I think what I am gathering from this discussion is that the server is
> > warming up, the ping is going through and tells the load balancer this
> > server is ready, user queries are hitting this server and are queued
> > waiting for the firstSearcher to finish (say these initial user queries
> are
> > to respond in 500-1000ms) that's terrible for performance.
> >
> > Alternatively, if you have a bunch of servers behind a load balancer,
> > you
> > want this one server (or block of servers depending on your deployment)
> to
> > be reasonably sure that user queries will return in a decent time
> (whatever
> > you define decent to be) hence why this matters.
> >
> > Let me know if I am missing anything.
> >
> > Thanks
> > Amit
> >
> >
> > On Sat, Nov 10, 2012 at 10:03 AM, Erick Erickson <
> [hidden email]
> > >wrote:
> >
> > > Why does it matter? The whole idea of firstSearcher queries is to warm
> up
> > > your system as fast as possible. The theory is that upon restarting
> > > the
> > > server, let's bet this stuff going immediately... They were never
> > intended
> > > (as far as I know) to complete before any queries were handled. As an
> > > aside, I'm not quite sure I understand why pings during the warmup are
> a
> > > problem.
> > >
> > > But anyway. firstSearcher is particularly relevant because the
> > > autowarmCount settings on your caches are irrelevant when starting the
> > > server, there's no history to autowarm....
> > >
> > > But, there's no good reason _not_ to let queries through while
> > > firstSearcher is doing it's tricks, they just get into the queue and
> are
> > > served as quickly as they may. That might be some time since, as you
> say,
> > > they may not get serviced until the expensive parts get filled. But I
> > don't
> > > think having them be serviced is doing any harm.
> > >
> > > Now, newSearcher and autowarming of the caches is a completely
> different
> > > beast since having the old searchers continue serving requests until
> the
> > > warmups _does_ directly impact the user, they don't see random
> > > slowness
> > > because a searcher is being opened.
> > >
> > > So I guess my real question is whether you're seeing a measurable
> problem
> > > or if this is a red herring....
> > >
> > > FWIW,
> > > Erick
> > >
> > >
> > > On Thu, Nov 8, 2012 at 2:54 PM, Aaron Daubman <[hidden email]>
> wrote:
> > >
> > > > Greetings,
> > > >
> > > > I have several custom QueryComponents that have high one-time
> > > > startup
> > > costs
> > > > (hashing things in the index, caching things from a RDBMS, etc...)
> > > >
> > > > Is there a way to prevent solr from accepting connections before all
> > > > QueryComponents are "ready"?
> > > >
> > > > Especially, since many of our instance are load-balanced (and
> > > > added-in/removed automatically based on admin/ping responses)
> > preventing
> > > > ping from answering prior to all custom QueryComponents being ready
> > would
> > > > be ideal...
> > > >
> > > > Thanks,
> > > >      Aaron
> > > >
> > >
> >
>

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Re: Preventing accepting queries while custom QueryComponent starts up?

Amit Nithian
Jack,

I think the issue is that the ping which is used to determine whether or
not the server is live returns a seemingly false positive back to the load
balancer (and indirectly the client) that this server is ready to go when
in fact it's not. Reading this page (
http://wiki.apache.org/solr/SolrConfigXml), it does seem to be documented
to do this but it may not be fully stressed to hide your Solr behind a load
balancer.  I am more than happy to write up a post that, in my opinion at
least, stresses some best practices on the use of Solr based on my
experience if others find this useful.

What seems odd here is that the ping is a query so maybe the ping query in
the solrconfig (for Aaron and others having this) should be configured to
hit the handler that is used by the front end app so that while that
handler is warming up the ping query will be blocked.

Of course using the load balancer means that the app layer knows nothing
about servers in and out of rotation.

Cheers!
Amit


On Sun, Nov 11, 2012 at 8:05 AM, Jack Krupansky <[hidden email]>wrote:

> Is the issue here that the Solr node is continuously "live" with the load
> balancer so that the moment during startup that Solr can respond to
> anything, the load balancer will be sending it traffic and that this can
> occur while Solr is still warming up?
>
> First, shouldn't we be encouraging people to have an app layer between
> Solr and the outside world? If so, the app layer should simply not respond
> to traffic until the app layer can verified that Solr has stabilized. If
> not, then maybe we do need to suggest a change to Solr so that the
> developer can control exactly when Solr becomes "live" and responsive to
> incoming traffic.
>
> At a minimum, we should document when that moment is today in terms of an
> explicit contract. It sounds like the problem is that the contract is
> either nonexistent, vague, ambiguous, non-deterministic, or whatever.
>
> -- Jack Krupansky
>
> -----Original Message----- From: Amit Nithian
> Sent: Saturday, November 10, 2012 4:24 PM
> To: [hidden email]
> Subject: Re: Preventing accepting queries while custom QueryComponent
> starts up?
>
>
> Yeah that's what I was suggesting in my response too. I don't think your
> load balancer should be doing this but whatever script does the release
> (restarting the container) should do this so that when the ping is enabled
> the warming has finished.
>
>
> On Sat, Nov 10, 2012 at 3:33 PM, Erick Erickson <[hidden email]>*
> *wrote:
>
>  Hmmm, rather than hit the ping query, why not just send in a real query
>> and
>> only let the queued ones through after the response?
>>
>> Just a random thought
>> Erick
>>
>>
>> On Sat, Nov 10, 2012 at 2:53 PM, Amit Nithian <[hidden email]> wrote:
>>
>> > Yes but the problem is that if user facing queries are hitting a server
>> > that is warming up and isn't being serviced quickly, then you could
>> > potentially bring down your site if all the front end threads are >
>> blocked
>> > on Solr queries b/c those queries are waiting (presumably at the
>> container
>> > level since the filter hasn't finished its init() sequence) for the
>> warming
>> > to complete (this is especially notorious when your front end is rails).
>> > This is why your ping to enable/disable a server from the load balancer
>> has
>> > to be accurate with regards to whether or not a server is truly ready >
>> and
>> > warm.
>> >
>> > I think what I am gathering from this discussion is that the server is
>> > warming up, the ping is going through and tells the load balancer this
>> > server is ready, user queries are hitting this server and are queued
>> > waiting for the firstSearcher to finish (say these initial user queries
>> are
>> > to respond in 500-1000ms) that's terrible for performance.
>> >
>> > Alternatively, if you have a bunch of servers behind a load balancer, >
>> you
>> > want this one server (or block of servers depending on your deployment)
>> to
>> > be reasonably sure that user queries will return in a decent time
>> (whatever
>> > you define decent to be) hence why this matters.
>> >
>> > Let me know if I am missing anything.
>> >
>> > Thanks
>> > Amit
>> >
>> >
>> > On Sat, Nov 10, 2012 at 10:03 AM, Erick Erickson <
>> [hidden email]
>> > >wrote:
>> >
>> > > Why does it matter? The whole idea of firstSearcher queries is to warm
>> up
>> > > your system as fast as possible. The theory is that upon restarting >
>> > the
>> > > server, let's bet this stuff going immediately... They were never
>> > intended
>> > > (as far as I know) to complete before any queries were handled. As an
>> > > aside, I'm not quite sure I understand why pings during the warmup are
>> a
>> > > problem.
>> > >
>> > > But anyway. firstSearcher is particularly relevant because the
>> > > autowarmCount settings on your caches are irrelevant when starting the
>> > > server, there's no history to autowarm....
>> > >
>> > > But, there's no good reason _not_ to let queries through while
>> > > firstSearcher is doing it's tricks, they just get into the queue and
>> are
>> > > served as quickly as they may. That might be some time since, as you
>> say,
>> > > they may not get serviced until the expensive parts get filled. But I
>> > don't
>> > > think having them be serviced is doing any harm.
>> > >
>> > > Now, newSearcher and autowarming of the caches is a completely
>> different
>> > > beast since having the old searchers continue serving requests until
>> the
>> > > warmups _does_ directly impact the user, they don't see random > >
>> slowness
>> > > because a searcher is being opened.
>> > >
>> > > So I guess my real question is whether you're seeing a measurable
>> problem
>> > > or if this is a red herring....
>> > >
>> > > FWIW,
>> > > Erick
>> > >
>> > >
>> > > On Thu, Nov 8, 2012 at 2:54 PM, Aaron Daubman <[hidden email]>
>> wrote:
>> > >
>> > > > Greetings,
>> > > >
>> > > > I have several custom QueryComponents that have high one-time > > >
>> startup
>> > > costs
>> > > > (hashing things in the index, caching things from a RDBMS, etc...)
>> > > >
>> > > > Is there a way to prevent solr from accepting connections before all
>> > > > QueryComponents are "ready"?
>> > > >
>> > > > Especially, since many of our instance are load-balanced (and
>> > > > added-in/removed automatically based on admin/ping responses)
>> > preventing
>> > > > ping from answering prior to all custom QueryComponents being ready
>> > would
>> > > > be ideal...
>> > > >
>> > > > Thanks,
>> > > >      Aaron
>> > > >
>> > >
>> >
>>
>>
>
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Re: Preventing accepting queries while custom QueryComponent starts up?

Chris Hostetter-3
In reply to this post by Aaron Daubman

: I have several custom QueryComponents that have high one-time startup costs
: (hashing things in the index, caching things from a RDBMS, etc...)

you need to provide more details about how your custom components work --
in particular: where in teh lifecycle of your components is this
high-startup cost happening?

: Is there a way to prevent solr from accepting connections before all
: QueryComponents are "ready"?

Define "ready" ? ... things that happen in the init() and inform(SolrCore)
methods will completley prevent the SolrCore from being available for
queries.

Likewise: if you are using "firstSearcher" warming queries, then the
"useColdSearcher" option in solrconfig.xml can be used to control wether
or not external requests will "block" until the searcher is available or
not -- however this doesn't prevent the servlet container from "accepting"
the HTTP connection.  but as mentioned, this is where things like the
PingRequestHandler and the enable/disable commands can be used to take
servers in and out of rotation with your load balancer -- assuming that
your load balanver can be configured to monitor the ping URL.  
Alternatively you can just use native features of your load balancer to
control this independent of solr (but the ping handler is a nice way of
letting one set of dev/ops folks own the solr servers and control their
availability even if they don't have the ability to control the load
blaancer itself)


-Hoss