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Posted to users@tomcat.apache.org by Jo...@wellsfargo.com.INVALID on 2024/03/11 21:47:18 UTC
When does Tomcat add and remove threads?
I am using Tomcat 9.x.
When does Tomcat add and remove threads from its internal thread pool? I'm talking about the threads with names like http-nio-8080-exec-1. It appears the thread pool is Tomcat's own ThreadPoolExecutor but I don't see the exact behavior documented. I'm familiar with how java.util.concurrent does it, but it looks like Tomcat's version is a little different.
Thanks
RE: When does Tomcat add and remove threads?
Posted by Harri Pesonen <ha...@sinch.com>.
Yes the standard JDK ThreadPoolExecutor behavior is bad.
Here is a good thread describing how to fix ThreadPoolExecutor to behave how it should be.
https://stackoverflow.com/questions/19528304/how-to-get-the-threadpoolexecutor-to-increase-threads-to-max-before-queueing
Obviously Tomcat had to do similar thing.
I wish that JDK would add some kind of easy option to ThreadPoolExecutor to add more threads instead of adding to queue, when all existing threads are busy, because the current behavior does not make sense.
-Harri
-----Original Message-----
From: John.E.Gregg@wellsfargo.com.INVALID <Jo...@wellsfargo.com.INVALID>
Sent: tiistai 12. maaliskuuta 2024 18.54
To: users@tomcat.apache.org
Subject: RE: When does Tomcat add and remove threads?
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All,
> -----Original Message-----
> From: Christopher Schultz <ch...@christopherschultz.net>
> Sent: Tuesday, March 12, 2024 8:31 AM
> To: users@tomcat.apache.org
> Subject: Re: When does Tomcat add and remove threads?
>
> John,
>
> On 3/11/24 18:14, John.E.Gregg@wellsfargo.com.INVALID wrote:
> > From: Christopher Schultz <ch...@christopherschultz.net>
> > Sent: Monday, March 11, 2024 5:09 PM
> >
> >> On 3/11/24 17:47, John.E.Gregg@wellsfargo.com.INVALID wrote:
> >>> I am using Tomcat 9.x.
> >>>
> >>> When does Tomcat add and remove threads from its internal thread
> >>> pool? I'm talking about the threads with names like
> >>> http-nio-8080-exec-1. It appears the thread pool is Tomcat's own
> >>> ThreadPoolExecutor but I don't see the exact behavior documented.
> >>> I'm familiar with how java.util.concurrent does it, but it looks
> >>> like Tomcat's version is a little different.
> >>
> >> Are you looking for a technical explanation with code references,
> >> or a plain-English description of when threads are created and
> >> added? >
> > Mostly plain English like the j.u.c. ThreadPoolExecutor Java doc has.
> > What happens when all core threads are in use? When do tasks go on
> > the queue? When does core thread + 1 get added? When do threads
> > get removed?
> Tomcat will create thread pools under two separate circumstances. They
> are related, but behave somewhat differently.
>
> First, if you declare an <Executor> in your server.xml, then a thread
> pool will be created. You can control the number of threads and their
> retention policy such as "keep X spare threads around" and "retire
> threads after N seconds without being used."
>
> Second, if you declare a <Connector> without specifying an "executor",
> a thread pool will be configured for you but you don't really have
> control over it because all those nice configuration options for an
> <Executor> are not available on the <Connector>. If you want to
> control those settings, use a <Connector> linked with an <Executor>.
> To be clear, if you declare a <Connector> without an "executor"
> attribute, your thread pool will be of a fixed size and threads will
> never be released. (I think the thread pool starts small and grows but
> will never shrink.)
>
> An <Executor> is implemented in the StandardThreadExecutor and
> ThreadPoolExecutor classes, which I believe were adaptations of
> classes from java.util.concurrent introduced into Tomcat before
> java.util.concurrent was actually available -- which is why it wasn't
> used directly in Tomcat. (NB: The ThreadPoolExecutor class in Tomcat
> contains an "@author Doug Lea" tag. The Tomcat source is licensed
> under AL2, the JDK source is licensed under GPL2, but the original was
> released by Doug Lea into the public domain under a CC0
> 1.0 Deed license.)
>
> The re-sizing occurs in the ThreadPoolExecutor class if you'd like to
> read it. It is not entirely straightforward. You could start by
> reading the code for the runWorker(Worker w) method where, at the end, processWorkerExit is called.
>
> But since Tomcat's ThreadPoolExecutor is basically Java's
> ThreadPoolExecutor, they work the same.
>
> -chris
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: users-help@tomcat.apache.org
I took matters in to my own hands and wrote a test to see what was happening.
Unlike java.util.concurrent.ThreadPoolExecutor, Tomcat's TPE adds threads when all core threads are busy. It only adds tasks to the queue when max threads are busy. I prefer this behavior to the JDK behavior.
Threads are removed when idle for 60 seconds. This appears to be hard-coded in AbstreactEndpoint.createExecutor().
Thanks
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Re: When does Tomcat add and remove threads?
Posted by Rémy Maucherat <re...@apache.org>.
On Tue, Mar 12, 2024 at 5:55 PM <Jo...@wellsfargo.com.invalid> wrote:
>
> All,
>
>
> > -----Original Message-----
> > From: Christopher Schultz <ch...@christopherschultz.net>
> > Sent: Tuesday, March 12, 2024 8:31 AM
> > To: users@tomcat.apache.org
> > Subject: Re: When does Tomcat add and remove threads?
> >
> > John,
> >
> > On 3/11/24 18:14, John.E.Gregg@wellsfargo.com.INVALID wrote:
> > > From: Christopher Schultz <ch...@christopherschultz.net>
> > > Sent: Monday, March 11, 2024 5:09 PM
> > >
> > >> On 3/11/24 17:47, John.E.Gregg@wellsfargo.com.INVALID wrote:
> > >>> I am using Tomcat 9.x.
> > >>>
> > >>> When does Tomcat add and remove threads from its internal thread
> > >>> pool? I'm talking about the threads with names like
> > >>> http-nio-8080-exec-1. It appears the thread pool is Tomcat's own
> > >>> ThreadPoolExecutor but I don't see the exact behavior documented.
> > >>> I'm familiar with how java.util.concurrent does it, but it looks
> > >>> like Tomcat's version is a little different.
> > >>
> > >> Are you looking for a technical explanation with code references, or
> > >> a plain-English description of when threads are created and added? >
> > > Mostly plain English like the j.u.c. ThreadPoolExecutor Java doc has.
> > > What happens when all core threads are in use? When do tasks go on
> > > the queue? When does core thread + 1 get added? When do threads get
> > > removed?
> > Tomcat will create thread pools under two separate circumstances. They are
> > related, but behave somewhat differently.
> >
> > First, if you declare an <Executor> in your server.xml, then a thread pool will be
> > created. You can control the number of threads and their retention policy such
> > as "keep X spare threads around" and "retire threads after N seconds without
> > being used."
> >
> > Second, if you declare a <Connector> without specifying an "executor", a
> > thread pool will be configured for you but you don't really have control over it
> > because all those nice configuration options for an <Executor> are not available
> > on the <Connector>. If you want to control those settings, use a <Connector>
> > linked with an <Executor>. To be clear, if you declare a <Connector> without an
> > "executor" attribute, your thread pool will be of a fixed size and threads will
> > never be released. (I think the thread pool starts small and grows but will
> > never shrink.)
> >
> > An <Executor> is implemented in the StandardThreadExecutor and
> > ThreadPoolExecutor classes, which I believe were adaptations of classes from
> > java.util.concurrent introduced into Tomcat before java.util.concurrent was
> > actually available -- which is why it wasn't used directly in Tomcat. (NB: The
> > ThreadPoolExecutor class in Tomcat contains an "@author Doug Lea" tag. The
> > Tomcat source is licensed under AL2, the JDK source is licensed under GPL2,
> > but the original was released by Doug Lea into the public domain under a CC0
> > 1.0 Deed license.)
> >
> > The re-sizing occurs in the ThreadPoolExecutor class if you'd like to read it. It is
> > not entirely straightforward. You could start by reading the code for the
> > runWorker(Worker w) method where, at the end, processWorkerExit is called.
> >
> > But since Tomcat's ThreadPoolExecutor is basically Java's ThreadPoolExecutor,
> > they work the same.
> >
> > -chris
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> > For additional commands, e-mail: users-help@tomcat.apache.org
>
> I took matters in to my own hands and wrote a test to see what was happening.
>
> Unlike java.util.concurrent.ThreadPoolExecutor, Tomcat's TPE adds threads when all core threads are busy. It only adds tasks to the queue when max threads are busy. I prefer this behavior to the JDK behavior.
>
> Threads are removed when idle for 60 seconds. This appears to be hard-coded in AbstreactEndpoint.createExecutor().
I have added configuration for that, since this was not right.
Rémy
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RE: When does Tomcat add and remove threads?
Posted by Jo...@wellsfargo.com.INVALID.
All,
> -----Original Message-----
> From: Christopher Schultz <ch...@christopherschultz.net>
> Sent: Tuesday, March 12, 2024 8:31 AM
> To: users@tomcat.apache.org
> Subject: Re: When does Tomcat add and remove threads?
>
> John,
>
> On 3/11/24 18:14, John.E.Gregg@wellsfargo.com.INVALID wrote:
> > From: Christopher Schultz <ch...@christopherschultz.net>
> > Sent: Monday, March 11, 2024 5:09 PM
> >
> >> On 3/11/24 17:47, John.E.Gregg@wellsfargo.com.INVALID wrote:
> >>> I am using Tomcat 9.x.
> >>>
> >>> When does Tomcat add and remove threads from its internal thread
> >>> pool? I'm talking about the threads with names like
> >>> http-nio-8080-exec-1. It appears the thread pool is Tomcat's own
> >>> ThreadPoolExecutor but I don't see the exact behavior documented.
> >>> I'm familiar with how java.util.concurrent does it, but it looks
> >>> like Tomcat's version is a little different.
> >>
> >> Are you looking for a technical explanation with code references, or
> >> a plain-English description of when threads are created and added? >
> > Mostly plain English like the j.u.c. ThreadPoolExecutor Java doc has.
> > What happens when all core threads are in use? When do tasks go on
> > the queue? When does core thread + 1 get added? When do threads get
> > removed?
> Tomcat will create thread pools under two separate circumstances. They are
> related, but behave somewhat differently.
>
> First, if you declare an <Executor> in your server.xml, then a thread pool will be
> created. You can control the number of threads and their retention policy such
> as "keep X spare threads around" and "retire threads after N seconds without
> being used."
>
> Second, if you declare a <Connector> without specifying an "executor", a
> thread pool will be configured for you but you don't really have control over it
> because all those nice configuration options for an <Executor> are not available
> on the <Connector>. If you want to control those settings, use a <Connector>
> linked with an <Executor>. To be clear, if you declare a <Connector> without an
> "executor" attribute, your thread pool will be of a fixed size and threads will
> never be released. (I think the thread pool starts small and grows but will
> never shrink.)
>
> An <Executor> is implemented in the StandardThreadExecutor and
> ThreadPoolExecutor classes, which I believe were adaptations of classes from
> java.util.concurrent introduced into Tomcat before java.util.concurrent was
> actually available -- which is why it wasn't used directly in Tomcat. (NB: The
> ThreadPoolExecutor class in Tomcat contains an "@author Doug Lea" tag. The
> Tomcat source is licensed under AL2, the JDK source is licensed under GPL2,
> but the original was released by Doug Lea into the public domain under a CC0
> 1.0 Deed license.)
>
> The re-sizing occurs in the ThreadPoolExecutor class if you'd like to read it. It is
> not entirely straightforward. You could start by reading the code for the
> runWorker(Worker w) method where, at the end, processWorkerExit is called.
>
> But since Tomcat's ThreadPoolExecutor is basically Java's ThreadPoolExecutor,
> they work the same.
>
> -chris
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: users-help@tomcat.apache.org
I took matters in to my own hands and wrote a test to see what was happening.
Unlike java.util.concurrent.ThreadPoolExecutor, Tomcat's TPE adds threads when all core threads are busy. It only adds tasks to the queue when max threads are busy. I prefer this behavior to the JDK behavior.
Threads are removed when idle for 60 seconds. This appears to be hard-coded in AbstreactEndpoint.createExecutor().
Thanks
Re: When does Tomcat add and remove threads?
Posted by Christopher Schultz <ch...@christopherschultz.net>.
John,
On 3/11/24 18:14, John.E.Gregg@wellsfargo.com.INVALID wrote:
> From: Christopher Schultz <ch...@christopherschultz.net>
> Sent: Monday, March 11, 2024 5:09 PM
>
>> On 3/11/24 17:47, John.E.Gregg@wellsfargo.com.INVALID wrote:
>>> I am using Tomcat 9.x.
>>>
>>> When does Tomcat add and remove threads from its internal thread
>>> pool? I'm talking about the threads with names like
>>> http-nio-8080-exec-1. It appears the thread pool is Tomcat's own
>>> ThreadPoolExecutor but I don't see the exact behavior documented.
>>> I'm familiar with how java.util.concurrent does it, but it looks like
>>> Tomcat's version is a little different.
>>
>> Are you looking for a technical explanation with code references,
>> or a plain-English description of when threads are created and
>> added? >
> Mostly plain English like the j.u.c. ThreadPoolExecutor Java doc
> has. What happens when all core threads are in use? When do tasks go
> on the queue? When does core thread + 1 get added? When do threads
> get removed?
Tomcat will create thread pools under two separate circumstances. They
are related, but behave somewhat differently.
First, if you declare an <Executor> in your server.xml, then a thread
pool will be created. You can control the number of threads and their
retention policy such as "keep X spare threads around" and "retire
threads after N seconds without being used."
Second, if you declare a <Connector> without specifying an "executor", a
thread pool will be configured for you but you don't really have control
over it because all those nice configuration options for an <Executor>
are not available on the <Connector>. If you want to control those
settings, use a <Connector> linked with an <Executor>. To be clear, if
you declare a <Connector> without an "executor" attribute, your thread
pool will be of a fixed size and threads will never be released. (I
think the thread pool starts small and grows but will never shrink.)
An <Executor> is implemented in the StandardThreadExecutor and
ThreadPoolExecutor classes, which I believe were adaptations of classes
from java.util.concurrent introduced into Tomcat before
java.util.concurrent was actually available -- which is why it wasn't
used directly in Tomcat. (NB: The ThreadPoolExecutor class in Tomcat
contains an "@author Doug Lea" tag. The Tomcat source is licensed under
AL2, the JDK source is licensed under GPL2, but the original was
released by Doug Lea into the public domain under a CC0 1.0 Deed license.)
The re-sizing occurs in the ThreadPoolExecutor class if you'd like to
read it. It is not entirely straightforward. You could start by reading
the code for the runWorker(Worker w) method where, at the end,
processWorkerExit is called.
But since Tomcat's ThreadPoolExecutor is basically Java's
ThreadPoolExecutor, they work the same.
-chris
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
For additional commands, e-mail: users-help@tomcat.apache.org
Re: When does Tomcat add and remove threads?
Posted by Jo...@wellsfargo.com.INVALID.
Chris,
________________________________
From: Christopher Schultz <ch...@christopherschultz.net>
Sent: Monday, March 11, 2024 5:09 PM
To: users@tomcat.apache.org <us...@tomcat.apache.org>
Subject: Re: When does Tomcat add and remove threads?
John,
On 3/11/24 17:47, John.E.Gregg@wellsfargo.com.INVALID wrote:
> I am using Tomcat 9.x.
>
> When does Tomcat add and remove threads from its internal thread
> pool? I'm talking about the threads with names like
> http-nio-8080-exec-1. It appears the thread pool is Tomcat's own
> ThreadPoolExecutor but I don't see the exact behavior documented.
> I'm familiar with how java.util.concurrent does it, but it looks like
> Tomcat's version is a little different.
Are you looking for a technical explanation with code references, or a
plain-English description of when threads are created and added?
-chris
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
For additional commands, e-mail: users-help@tomcat.apache.org
Mostly plain English like the j.u.c. ThreadPoolExecutor Java doc has. What happens when all core threads are in use? When do tasks go on the queue? When does core thread + 1 get added? When do threads get removed?
Thanks
Re: When does Tomcat add and remove threads?
Posted by Christopher Schultz <ch...@christopherschultz.net>.
John,
On 3/11/24 17:47, John.E.Gregg@wellsfargo.com.INVALID wrote:
> I am using Tomcat 9.x.
>
> When does Tomcat add and remove threads from its internal thread
> pool? I'm talking about the threads with names like
> http-nio-8080-exec-1. It appears the thread pool is Tomcat's own
> ThreadPoolExecutor but I don't see the exact behavior documented.
> I'm familiar with how java.util.concurrent does it, but it looks like
> Tomcat's version is a little different.
Are you looking for a technical explanation with code references, or a
plain-English description of when threads are created and added?
-chris
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
For additional commands, e-mail: users-help@tomcat.apache.org