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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: FW: tomcat 8080 thread not reduced
Date Fri, 20 Jan 2017 22:29:10 GMT
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Smith,

On 1/19/17 9:59 PM, smith wrote:
>> "busy" is the same as "active".
> 
> When not use <Executor>, our busy thread always keep under 10
> while the currentThreadCount keeps high (these are get from tomcat
> manager), So we really don't know how many threads are truly free.

Why do you care how many are free? Isn't it more important to know how
many are active? For example, I run my app servers with
maxThreads="150" for the most part. Then, I have Nagios notify me if
the "active count" goes above 135 (that's 90% of my maxThreads).

Nagios, like many monitoring systems, won't scream the first time it
sees something. Instead, it will check again a few times before
complaining. That means that as long as I don't see any significant
duration where the active thread count exceeds 135, I don't get any
alarms going off.

And I don't care how many "free" threads I have. I've decided that I
want "150 and NO MORE". Nothing else matters except the active count.
I don't happen to allow the thread pool to re-size downward (fewer
threads), but if I did, I wouldn't have to change my monitoring at
all. What? The active count is 10 and the total pool size is 20? I
don't care. Wake me up when the active thread count stays high for a
while, indicating to me that we are getting hammered.

> How many are in keepAlivedStatus

Use NIO and forget about it.

Besides, you are using *AJP*. Every thread is *always* in a keepalive
state. So keepalive == idle as far as Tomcat is concerned.

If you were using HTTP, then keepalive would be an issue (and NIO
would be the answer), but you aren't, so it's not.

- -chris

> -----Original Message----- From: Christopher Schultz
> [mailto:chris@christopherschultz.net] Sent: Thursday, January 19,
> 2017 4:38 PM To: Tomcat Users List Subject: Re: FW: tomcat 8080
> thread not reduced
> 
> Smith,
> 
> On 1/18/17 8:25 PM, smith wrote:
>> I don't care if the threads will be reduced, I just want to know
>> why.
> 
> Okay.
> 
>> And we want to use the account to determine when the tomcat
>> capacity is not enough that we need to add max configuration or
>> add new tomcat servers.
> 
> Set your initial and max threads to the same value (pool size = 
> constant) and then monitor the "active count" with a Nagios warning
> at e.g. 80% usage.
> 
>> Since not use the <Executor>, the busy thread account also cannot
>> tell us the correct active threads count.
> 
> "busy" is the same as "active".
> 
>> In another email thread, you said if use <Executor>, it will tell
>> us the right active thread count not just busy count, right?
> 
> I would always use an <Executor> for at least two different
> reasons:
> 
> 1. Thread management (e.g. reducing threads if necessary) 2. Shared
> thread-pools (no need to have port 8080 and 8443 with separate
> pools)
> 
> -chris
> 
>> -----Original Message----- From: Christopher Schultz 
>> [mailto:chris@christopherschultz.net] Sent: Wednesday, January
>> 18, 2017 3:28 PM To: Tomcat Users List Subject: Re: FW: tomcat
>> 8080 thread not reduced
> 
>> Smith,
> 
>> On 1/18/17 12:47 AM, smith wrote:
>>> So the tomcat default executor will not reduce the thread count
>>> until it reach to the max configuration?
> 
>> By default, you get a thread pool that isn't as smart as an
>> executor.
> 
>>> Will it reduce when it reach to max?
> 
>> Not unless you use an <Executor>.
> 
>>> And why the default not reduce the thread?
> 
>> Because it didn't do so in the past, before <Executor> was
>> introduced.
> 
>> I'm curious: if you are willing to have e.g. 200 threads
>> available at any time during the life of the JVM, why does it
>> matter if those threads are reduced during times of inactivity?
> 
>> I think of threads as a resource like memory, where if you are
>> going to allocate X resources, you may as well allocate X
>> resources and be done with it. Growing and shrinking pools of
>> things just adds complexity and reduces performance.
> 
>> Idle threads are "free" other than using a little bit of memory. 
>> So why is it so important for those threads to stop when they
>> don't have any work for a while?
> 
>> -chris
> 
>>> -----Original Message----- From: Christopher Schultz 
>>> [mailto:chris@christopherschultz.net] Sent: Tuesday, January
>>> 17, 2017 7:18 PM To: Tomcat Users List Subject: Re: FW: tomcat
>>> 8080 thread not reduced
> 
>>> Smith,
> 
>>> On 1/16/17 8:22 PM, smith wrote:
>>>> Yes, I think thread count should be reduced when those
>>>> threads are idle
> 
>>>> Is this right? Or it will not reduced?
> 
>>> Id you want Tomcat to reduce the number of idle threads, you'll
>>> need to explicitly configure an <Executor> and use that with
>>> your <Connector> .
> 
>>> -chris
> 
>>>> -----Original Message----- From: Christopher Schultz 
>>>> [mailto:chris@christopherschultz.net] Sent: Monday, January
>>>> 16, 2017 2:20 PM To: Tomcat Users List Subject: Re: FW:
>>>> tomcat 8080 thread not reduced
> 
>>>> Smith,
> 
>>>> There are your only active <Connector>s:
> 
>>>> On 1/14/17 1:30 AM, smith wrote:
>>>>> <Connector port="8080" protocol="HTTP/1.1" maxThreads="300"
>>>>>  connectionTimeout="20000" redirectPort="8443" />
> 
>>>>> [snip]
> 
>>>>> <Connector port="8009" protocol="AJP/1.3"
>>>>> redirectPort="8443" />
> 
>>>> You have not changed any settings from the default. What
>>>> makes you think that your thread count should be reduced when
>>>> those threads are idle?
> 
>>>> -chris
> 
>>>> -------------------------------------------------------------------
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