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Posted to users@tomcat.apache.org by Christopher Schultz <ch...@christopherschultz.net> on 2023/06/29 13:00:04 UTC
[mod_jk] Is it possible to set the value of a specific attribute via HTTP?
All,
I've been using mod_jk forever and have some tools[1][2] to check on the
status of a worker and change its state using the status worker.
One of the samples I check is the "errors" count and if it's above 0
then I report an error to my monitoring system.
The problem is that sometimes we just get a random error here or there,
and my only recourse is to go into the status worker and "reset" the
worker which clears out everything. That may not be a big deal because
honestly I don't care what mod_jk thinks the estimated number of
sessions on a particular node is, but what I'd prefer to do is bleed-off
those errors over time.
For example, we check the service every few minutes. If we have more
than 0 errors, we start checking more frequently. If, every time we
checked, we reduced the error-count by some small number, the count
would eventually reach 0 if the event was temporary but it would
continue to grow as long as there was some kind of persistent error
(like Tomcat-node-is-down).
Is there a way to decrement the "errors" count without resetting all
counters back to zero?
Thanks,
-chris
[1] Hmm... I haven't put my check_mod_jk.py upon GitHub. I should do that.
[2]
https://github.com/ChristopherSchultz/apache-tomcat-stuff/tree/master/bin/mod_jk
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Re: [mod_jk] Is it possible to set the value of a specific attribute via HTTP?
Posted by Christopher Schultz <ch...@christopherschultz.net>.
Jon,
On 6/30/23 17:21, jonmcalexander@wellsfargo.com.INVALID wrote:
> Hi Chris and Rainer,
>
> Just want to add my .02 worth. Having the ability to "Drain" hosts in a Proxy configuration would be an awesome boon so you could gracefully take down a "node" for maintenance, or even just a restart. Then be able to put it back in action afterwards. :-) Of course, only in setups where you are using load-balancing and multiple back-end app servers. :-)
I have a presentation which covers how to do this, including references
to automated tools to drain the servers, how to configure Tomcat to
participate in that draining, etc.
It's this one from ApacheCon 2015:
http://home.apache.org/~schultz/ApacheCon%20NA%202015/Load-balancing%20Tomcat%20with%20mod_jk.pdf
-chris
>> -----Original Message-----
>> From: Christopher Schultz <ch...@christopherschultz.net>
>> Sent: Friday, June 30, 2023 2:19 PM
>> To: users@tomcat.apache.org
>> Subject: Re: [mod_jk] Is it possible to set the value of a specific attribute via
>> HTTP?
>>
>> Rainer,
>>
>> On 6/29/23 17:06, Rainer Jung wrote:
>>> Hi Chris,
>>>
>>> Am 29.06.23 um 15:00 schrieb Christopher Schultz:
>>>> All,
>>>>
>>>> I've been using mod_jk forever and have some tools[1][2] to check on
>>>> the status of a worker and change its state using the status worker.
>>>>
>>>> One of the samples I check is the "errors" count and if it's above 0
>>>> then I report an error to my monitoring system.
>>>>
>>>> The problem is that sometimes we just get a random error here or
>>>> there, and my only recourse is to go into the status worker and
>>>> "reset" the worker which clears out everything. That may not be a big
>>>> deal because honestly I don't care what mod_jk thinks the estimated
>>>> number of sessions on a particular node is, but what I'd prefer to do
>>>> is bleed-off those errors over time.
>>>>
>>>> For example, we check the service every few minutes. If we have more
>>>> than 0 errors, we start checking more frequently. If, every time we
>>>> checked, we reduced the error-count by some small number, the count
>>>> would eventually reach 0 if the event was temporary but it would
>>>> continue to grow as long as there was some kind of persistent error
>>>> (like Tomcat-node-is-down).
>>>>
>>>> Is there a way to decrement the "errors" count without resetting all
>>>> counters back to zero?
>>>>
>>>> Thanks,
>>>> -chris
>>>>
>>>> [1] Hmm... I haven't put my check_mod_jk.py upon GitHub. I should do
>>>> that.
>>>> [2]
>>>>
>> https://urldefense.com/v3/__https://github.com/ChristopherSchultz/apa
>>>> che-tomcat-
>> stuff/tree/master/bin/mod_jk__;!!F9svGWnIaVPGSwU!t6oVjPiPK
>>>>
>> IiI1py49MyQzz_Jewu0_iQqa6xWLqEokHwNpzvlcQ2qAXIfGvhJsWTS34rA8tgC
>> _le50_
>>>> lUkwrMqUjevlf5d9KD$
>>>
>>> no, there is no way to change insdividual runtime counters. As always
>>> it would be possible to code it as an addition to the jk manager. One
>>> would have to think about which counters for which workers (lb,
>>> member, ajp) and whether one should be able to reset to 0, to adjust
>>> by some delta or whatever.
>>>
>>> I have not immediate intention to implement it, at this point just
>>> wanted to mention it is not there but doable.
>>
>> Thank you. I figured you would know best :)
>>
>>> Since I try to push people into mod_proxy, I am hesitant to implement
>>> more and more features which keep people from switching ;)
>>
>> I wouldn't suggest adding this to mod_jk for exactly the same reason.
>> But if the feature DID exist, I would have used it :)
>>
>>> The last feature I added was putting a request id on the log lines
>>> (yet unreleased).
>>
>> Does mod_proxy_balancer have this kind of thing? Does it sound like
>> something worth implementing? mod_jk's support for monitoring and live-
>> adjustments has always been better than mod_proxy_* IMHO but it is
>> catching up. Something like this would be very helpful addition.
>>
>> -chris
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
>> For additional commands, e-mail: users-help@tomcat.apache.org
>
>
> ---------------------------------------------------------------------
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RE: [mod_jk] Is it possible to set the value of a specific attribute via HTTP?
Posted by jo...@wellsfargo.com.INVALID.
Hi Chris and Rainer,
Just want to add my .02 worth. Having the ability to "Drain" hosts in a Proxy configuration would be an awesome boon so you could gracefully take down a "node" for maintenance, or even just a restart. Then be able to put it back in action afterwards. :-) Of course, only in setups where you are using load-balancing and multiple back-end app servers. :-)
Thanks and have a great Weekend!
Dream * Excel * Explore * Inspire
Jon McAlexander
Senior Infrastructure Engineer
Asst. Vice President
He/His
Middleware Product Engineering
Enterprise CIO | EAS | Middleware | Infrastructure Solutions
8080 Cobblestone Rd | Urbandale, IA 50322
MAC: F4469-010
Tel 515-988-2508 | Cell 515-988-2508
jonmcalexander@wellsfargo.com
This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation.
> -----Original Message-----
> From: Christopher Schultz <ch...@christopherschultz.net>
> Sent: Friday, June 30, 2023 2:19 PM
> To: users@tomcat.apache.org
> Subject: Re: [mod_jk] Is it possible to set the value of a specific attribute via
> HTTP?
>
> Rainer,
>
> On 6/29/23 17:06, Rainer Jung wrote:
> > Hi Chris,
> >
> > Am 29.06.23 um 15:00 schrieb Christopher Schultz:
> >> All,
> >>
> >> I've been using mod_jk forever and have some tools[1][2] to check on
> >> the status of a worker and change its state using the status worker.
> >>
> >> One of the samples I check is the "errors" count and if it's above 0
> >> then I report an error to my monitoring system.
> >>
> >> The problem is that sometimes we just get a random error here or
> >> there, and my only recourse is to go into the status worker and
> >> "reset" the worker which clears out everything. That may not be a big
> >> deal because honestly I don't care what mod_jk thinks the estimated
> >> number of sessions on a particular node is, but what I'd prefer to do
> >> is bleed-off those errors over time.
> >>
> >> For example, we check the service every few minutes. If we have more
> >> than 0 errors, we start checking more frequently. If, every time we
> >> checked, we reduced the error-count by some small number, the count
> >> would eventually reach 0 if the event was temporary but it would
> >> continue to grow as long as there was some kind of persistent error
> >> (like Tomcat-node-is-down).
> >>
> >> Is there a way to decrement the "errors" count without resetting all
> >> counters back to zero?
> >>
> >> Thanks,
> >> -chris
> >>
> >> [1] Hmm... I haven't put my check_mod_jk.py upon GitHub. I should do
> >> that.
> >> [2]
> >>
> https://urldefense.com/v3/__https://github.com/ChristopherSchultz/apa
> >> che-tomcat-
> stuff/tree/master/bin/mod_jk__;!!F9svGWnIaVPGSwU!t6oVjPiPK
> >>
> IiI1py49MyQzz_Jewu0_iQqa6xWLqEokHwNpzvlcQ2qAXIfGvhJsWTS34rA8tgC
> _le50_
> >> lUkwrMqUjevlf5d9KD$
> >
> > no, there is no way to change insdividual runtime counters. As always
> > it would be possible to code it as an addition to the jk manager. One
> > would have to think about which counters for which workers (lb,
> > member, ajp) and whether one should be able to reset to 0, to adjust
> > by some delta or whatever.
> >
> > I have not immediate intention to implement it, at this point just
> > wanted to mention it is not there but doable.
>
> Thank you. I figured you would know best :)
>
> > Since I try to push people into mod_proxy, I am hesitant to implement
> > more and more features which keep people from switching ;)
>
> I wouldn't suggest adding this to mod_jk for exactly the same reason.
> But if the feature DID exist, I would have used it :)
>
> > The last feature I added was putting a request id on the log lines
> > (yet unreleased).
>
> Does mod_proxy_balancer have this kind of thing? Does it sound like
> something worth implementing? mod_jk's support for monitoring and live-
> adjustments has always been better than mod_proxy_* IMHO but it is
> catching up. Something like this would be very helpful addition.
>
> -chris
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: users-help@tomcat.apache.org
Re: [mod_jk] Is it possible to set the value of a specific attribute via HTTP?
Posted by Christopher Schultz <ch...@christopherschultz.net>.
Martin,
On 7/3/23 04:47, Martin Knoblauch wrote:
> On 6/29/23 17:06, Rainer Jung wrote:
>>
>>> Since I try to push people into mod_proxy, I am hesitant to implement
>>> more and more features which keep people from switching ;)
>>
>>
> Hi Rainer,
>
> so, what do you suggest for the mod_jk retirement?
> mod_proxy+mod_proxy_ajp, or just proxy to the HTTPS port?
You should consider whether you actually need a "real" reverse-proxy or
if you can get away with "simple" load-balancing from a network balancer
)i.e. one that doesn't know anything about HTTP).
If you still need one, I would recommend migrating from AJP -> HTTP(S).
I have a whole talk about it:
https://tomcat.apache.org/presentations.html#latest-migrate-ajp-http
> Is there an
> equivalent to jkmanager with mod_proxy?
Yes.
-chris
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Re: [mod_jk] Is it possible to set the value of a specific attribute via HTTP?
Posted by Martin Knoblauch <kn...@knobisoft.de>.
On 6/29/23 17:06, Rainer Jung wrote:
>
> > Since I try to push people into mod_proxy, I am hesitant to implement
> > more and more features which keep people from switching ;)
>
>
Hi Rainer,
so, what do you suggest for the mod_jk retirement?
mod_proxy+mod_proxy_ajp, or just proxy to the HTTPS port? Is there an
equivalent to jkmanager with mod_proxy?
Thanks
Martin
--
------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de
www: http://www.knobisoft.de
Re: [mod_jk] Is it possible to set the value of a specific attribute via HTTP?
Posted by Christopher Schultz <ch...@christopherschultz.net>.
Rainer,
On 6/29/23 17:06, Rainer Jung wrote:
> Hi Chris,
>
> Am 29.06.23 um 15:00 schrieb Christopher Schultz:
>> All,
>>
>> I've been using mod_jk forever and have some tools[1][2] to check on
>> the status of a worker and change its state using the status worker.
>>
>> One of the samples I check is the "errors" count and if it's above 0
>> then I report an error to my monitoring system.
>>
>> The problem is that sometimes we just get a random error here or
>> there, and my only recourse is to go into the status worker and
>> "reset" the worker which clears out everything. That may not be a big
>> deal because honestly I don't care what mod_jk thinks the estimated
>> number of sessions on a particular node is, but what I'd prefer to do
>> is bleed-off those errors over time.
>>
>> For example, we check the service every few minutes. If we have more
>> than 0 errors, we start checking more frequently. If, every time we
>> checked, we reduced the error-count by some small number, the count
>> would eventually reach 0 if the event was temporary but it would
>> continue to grow as long as there was some kind of persistent error
>> (like Tomcat-node-is-down).
>>
>> Is there a way to decrement the "errors" count without resetting all
>> counters back to zero?
>>
>> Thanks,
>> -chris
>>
>> [1] Hmm... I haven't put my check_mod_jk.py upon GitHub. I should do
>> that.
>> [2]
>> https://github.com/ChristopherSchultz/apache-tomcat-stuff/tree/master/bin/mod_jk
>
> no, there is no way to change insdividual runtime counters. As always it
> would be possible to code it as an addition to the jk manager. One would
> have to think about which counters for which workers (lb, member, ajp)
> and whether one should be able to reset to 0, to adjust by some delta or
> whatever.
>
> I have not immediate intention to implement it, at this point just
> wanted to mention it is not there but doable.
Thank you. I figured you would know best :)
> Since I try to push people into mod_proxy, I am hesitant to implement
> more and more features which keep people from switching ;)
I wouldn't suggest adding this to mod_jk for exactly the same reason.
But if the feature DID exist, I would have used it :)
> The last feature I added was putting a request id on the log lines (yet
> unreleased).
Does mod_proxy_balancer have this kind of thing? Does it sound like
something worth implementing? mod_jk's support for monitoring and
live-adjustments has always been better than mod_proxy_* IMHO but it is
catching up. Something like this would be very helpful addition.
-chris
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Re: [mod_jk] Is it possible to set the value of a specific attribute via HTTP?
Posted by Rainer Jung <ra...@kippdata.de>.
Hi Chris,
Am 29.06.23 um 15:00 schrieb Christopher Schultz:
> All,
>
> I've been using mod_jk forever and have some tools[1][2] to check on the
> status of a worker and change its state using the status worker.
>
> One of the samples I check is the "errors" count and if it's above 0
> then I report an error to my monitoring system.
>
> The problem is that sometimes we just get a random error here or there,
> and my only recourse is to go into the status worker and "reset" the
> worker which clears out everything. That may not be a big deal because
> honestly I don't care what mod_jk thinks the estimated number of
> sessions on a particular node is, but what I'd prefer to do is bleed-off
> those errors over time.
>
> For example, we check the service every few minutes. If we have more
> than 0 errors, we start checking more frequently. If, every time we
> checked, we reduced the error-count by some small number, the count
> would eventually reach 0 if the event was temporary but it would
> continue to grow as long as there was some kind of persistent error
> (like Tomcat-node-is-down).
>
> Is there a way to decrement the "errors" count without resetting all
> counters back to zero?
>
> Thanks,
> -chris
>
> [1] Hmm... I haven't put my check_mod_jk.py upon GitHub. I should do that.
> [2]
> https://github.com/ChristopherSchultz/apache-tomcat-stuff/tree/master/bin/mod_jk
no, there is no way to change insdividual runtime counters. As always it
would be possible to code it as an addition to the jk manager. One would
have to think about which counters for which workers (lb, member, ajp)
and whether one should be able to reset to 0, to adjust by some delta or
whatever.
I have not immediate intention to implement it, at this point just
wanted to mention it is not there but doable.
Since I try to push people into mod_proxy, I am hesitant to implement
more and more features which keep people from switching ;)
The last feature I added was putting a request id on the log lines (yet
unreleased).
Regards,
Rainer
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