Dear Tomcat Users/Mark, I was finally able to retrieve the thread name from the workerThreadName attribute in RequestProcessor.tomcatExecutor for a request. In order to observe this, the request had to be long-running, which allowed JMX to capture the thread’s active state before it completed. However, I’ve observed that the keepAliveCount remains zero in this setup as well. Additionally, the connectionCount appears to reflect the number of incoming requests at that moment, but resets to 1 once the request has completed processing. Given this behavior, I’m curious to know whether the formula: (connectionCount – keepAliveCount) is still considered a reliable way to determine the number of virtual threads that are created or active at any point in time when using useVirtualThreads="true". I would appreciate any insights or clarifications on this. Thanks, Rose Mary
From: Mark Thomas <ma...@apache.org> Date: Wednesday, 9 April 2025 at 4:12 PM To: users@tomcat.apache.org <users@tomcat.apache.org> Subject: [EXTERNAL] Re: Monitoring Virtual Threads via JMX / MBeans in Tomcat On 03/04/2025 13:05, Rose Mary P T wrote: > HI Mark, > > Thanks for your response. > > I would like to seek your guidance regarding an issue I am encountering > with my current Tomcat setup. Specifically, your recent suggestions > appear to contradict my existing configuration. Could you kindly confirm > whether the following executor and connector setup in Tomcat 10.1.36 is > correct? > > <Executor name="tomcatExecutor" namePrefix ="test" > className="org.apache.catalina.core.StandardVirtualThreadExecutor"/> > > <Connector port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol" > > connectionTimeout="18000" redirectPort="8443" > > executor="tomcatExecutor" > > useVirtualThreads="true"/> That should work. Although I do wonder on why you have configured an executor here. There isn't really any point with virtual threads. > In my setup, I am using *Http11NioProtocol* exclusively. However, I am > noticing the following: > > * *keepAliveCount* remains zero. > * *connectionCount* is consistently reported as 1. That suggests that the Tomcat instance isn't processing any requests. > * There is no visible value for |RequestProcessor#workerThreadName|. > Please see the screenshot : Screenshots don't work on the mailing list. Post it somewhere we can look at it. Mark > * > > I would greatly appreciate your insight into this matter, especially if > the configuration provided requires any adjustments or if there are > specific conditions I need to be aware of for the virtual threads to > function as expected. > > To clarify your previous question on the deployed application in > tomcat : This is a simple spring boot application which prints current > date in a loop of 100 > > Thank you for your time and assistance. I look forward to your response. > > Regards, > > Rose Mary > > *From: *Mark Thomas <ma...@apache.org> > *Date: *Thursday, 3 April 2025 at 2:49 PM > *To: *users@tomcat.apache.org <users@tomcat.apache.org> > *Subject: *[EXTERNAL] Re: Monitoring Virtual Threads via JMX / MBeans in > Tomcat > > On 28/03/2025 09:08, Rose Mary P T wrote: >> Hi Mark, >> Thank you for the confirmation. >> As per your suggestion, I have modified the deployed application so that it >> no longer spawns any threads but instead executes a few calls. > > Please clarify what you mean by "executes a few calls". > >> Additionally, I kept the previous executor and connection configurations for >> Tomcat. However, I still do not see any noticeable changes in the >> keepAliveCount attribute. The connectionCount currently shows a value of 1. >> At this point, I'm unsure of the next troubleshooting steps or what specific >> aspects to investigate further. Any guidance on what to focus on next would >> be greatly appreciated. >> Additionally, could you suggest if there is any MBean attribute that can >> help identify whether the threads being used are virtual threads or platform >> threads? > > For Tomcat requests, the current thread name includes "virt" if it is a > virtual thread. Look at RequestProcessor#workerThreadName for one place > to see the thread names used for requests > > With NIO2, keepAliveCount will always be -1 as it isn't tracked. > Switching to NIO would make keepAliveCount available. > > connectionCount will always be 1 more than the current connections. i.e. > a value of 1 means there are no current requests. > > Mark > > >> Thank you for your continued support. >> >> Best Regards, >> Rose Mary >> >> >> From: Mark Thomas <ma...@apache.org> >> Date: Thursday, 27 March 2025 at 9:25 PM >> To: users@tomcat.apache.org <users@tomcat.apache.org> >> Subject: [EXTERNAL] Re: Monitoring Virtual Threads via JMX / MBeans in Tomcat >> On 26/03/2025 10:38, Rose Mary P T wrote: >>> Dear Tomcat Users, >>> I hope this message finds you well. >>> As per your previous email, we attempted to fetch the virtual thread count >>> from the keepAliveCount attribute in the Catalina.ThreadPool MBean. >>> For context, here is the setup we used: >>> >>> * We created a sample Spring Boot application that continuously >>> creates virtual threads in a loop. >> >> If the application is creating the threads then this won't work. The >> (connectionCount - keepAliveCount) approach only works for virtual >> threads created by Tomcat for processing requests. >> >> If the application is creating the virtual threads then I'd suggest >> adding tracking for the current number of virtual threads to the >> application. >> >> Mark >> >>> * The application was deployed in the TOMCAT_LOCATION/webapps >>> directory and started on localhost. >>> In Apache Tomcat 10.1.36, we added the following configuration to the >>> server.xml file to enable virtual threads: >>> <Executor name="tomcatExecutor" >>> className="org.apache.catalina.core.StandardVirtualThreadExecutor"/> >>> <Connector port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol" >>> connectionTimeout="18000" redirectPort="8443" >>> executor="tomcatExecutor" >>> useVirtualThreads="true"/> >>> >>> Its observed in the logs that virtual threads were being created as >>> expected. However, we noticed that the keepAliveCount attribute in the >>> Catalina.ThreadPool MBean is showing a value of 0, even though virtual >>> threads are being spawned. >>> It seems that the keepAliveCount attribute does not provide a valid value >>> for counting the virtual threads. We were wondering if this is expected >>> behavior, or if there is a different way to monitor the virtual threads >>> created in Tomcat. >>> We would also like to know if there's a way to differentiate between >>> platform threads and virtual threads using any MBean attribute in the >>> Catalina service or elsewhere in Tomcat's MBean architecture. >>> We would greatly appreciate any guidance or insights you can provide >>> regarding this issue. >>> Best Regards, >>> Rose Mary >>> >>> >>> >>> From: Joash Jose <joash.j...@ibm.com> >>> Date: Wednesday, 26 March 2025 at 12:48 PM >>> To: Rose Mary P T <rose.mary...@ibm.com> >>> Subject: <no subject> >>> >>> >>> >>> Begin forwarded message: >>> >>> From: Mark Thomas <ma...@apache.org> >>> Subject: [EXTERNAL] Re: Monitoring Virtual Threads via JMX / MBeans in >>> Tomcat >>> Date: 6 March 2025 at 2:08:43 PM IST >>> To: <users@tomcat.apache.org> >>> Reply-To: "Tomcat Users List" <users@tomcat.apache.org> >>> >>> On 06/03/2025 06:29, Joash Jose wrote: >>> >>> Dear Apache Tomcat Support Team, >>> I hope this message finds you well. >>> I am writing to inquire whether Apache Tomcat (tomacat version is 10.1.33 >>> running on Java 21) exposes virtual thread metrics through JMX / MBeans. >>> Specifically: >>> Virtual Thread Visibility: >>> Does Tomcat provide MBeans (e.g., under Catalina:type=Executor) to monitor >>> virtual thread usage, such as active virtual thread counts, creation rate, >>> or parking states? >>> >>> No with a few caveats - see below). >>> >>> >>> If not, are there plans to add such metrics in future releases? >>> >>> No. >>> >>> >>> Or any alternate ways with which we can monitor this from tomcat side.? >>> >>> (connectionCount - keepAliveCount) should be a reasonable estimate of the >>> virtual threads currently being used. >>> >>> If the requests are synchronous (and there is little point using virtual >>> threads with async requests) then the creation rate is derivable from the >>> requestCount in the GlobalRequestProcessor. >>> >>> There is no information on parking states. >>> >>> >>> Configuration Clarification: >>> We have configured Tomcat 10.1.33 with, >>> <Executor name="tomcatThreadPool" >>> className="org.apache.catalina.core.StandardVirtualThreadExecutor"/> >>> <Connector port="8080" >>> protocol="org.apache.coyote.http11.Http11Nio2Protocol" >>> connectionTimeout="18000" socket.soTimeout="18000" redirectPort="8443" >>> enableLookups="false" URIEncoding="UTF-8" compression="on" >>> useVirtualThreads="true" server="ARandomServer"/> >>> >>> The <Executor .../> element isn't being used. Why configure it? >>> >>> >>> While this works, the existing ThreadPool MBeans show currentThreadsBusy=-1 >>> and maxThreads=200 (incorrect in case of virtual threads). Is this expected >>> behavior? >>> >>> Yes. >>> >>> >>> JVM vs. Tomcat Metrics: >>> We observe that the JVM’s java.lang.management.ThreadMXBean includes >>> virtual threads, but this aggregates data across all applications on the >>> JVM. Does Tomcat offer a way to isolate virtual thread metrics specific to >>> Tomcat? >>> >>> No, because the JVM doesn't provide a mechanism to have multiple >>> pools/groups/anything of virtual threads. >>> >>> Mark >>> >>> >>> --------------------------------------------------------------------- >>> To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org >>> For additional commands, e-mail: users-h...@tomcat.apache.org >>> Begin forwarded message: >>> >>> From: Joash Jose <joash.j...@ibm.com> >>> Subject: Monitoring Virtual Threads via JMX / MBeans in Tomcat >>> Date: 6 March 2025 at 11:59:29 AM IST >>> To: <d...@tomcat.apache.org>, <users@tomcat.apache.org> >>> >>> Dear Apache Tomcat Support Team, >>> >>> I hope this message finds you well. >>> >>> I am writing to inquire whether Apache Tomcat (tomacat version is 10.1.33 >>> running on Java 21) exposes virtual thread metrics through JMX / MBeans. >>> Specifically: >>> >>> Virtual Thread Visibility: >>> >>> Does Tomcat provide MBeans (e.g., under Catalina:type=Executor) to monitor >>> virtual thread usage, such as active virtual thread counts, creation rate, >>> or parking states? >>> If not, are there plans to add such metrics in future releases? >>> Or any alternate ways with which we can monitor this from tomcat side.? >>> >>> Configuration Clarification: >>> We have configured Tomcat 10.1.33 with, >>> <Executor name="tomcatThreadPool" >>> className="org.apache.catalina.core.StandardVirtualThreadExecutor"/> >>> <Connector port="8080" >>> protocol="org.apache.coyote.http11.Http11Nio2Protocol" >>> connectionTimeout="18000" socket.soTimeout="18000" redirectPort="8443" >>> enableLookups="false" URIEncoding="UTF-8" compression="on" >>> useVirtualThreads="true" server="ARandomServer"/> >>> While this works, the existing ThreadPool MBeans show currentThreadsBusy=-1 >>> and maxThreads=200 (incorrect in case of virtual threads). Is this expected >>> behavior? >>> >>> JVM vs. Tomcat Metrics: >>> We observe that the JVM’s java.lang.management.ThreadMXBean includes >>> virtual threads, but this aggregates data across all applications on the >>> JVM. Does Tomcat offer a way to isolate virtual thread metrics specific to >>> Tomcat? >>> >>> Regards, >>> Joash >>> Begin forwarded message: >>> >>> From: Joash Jose <joash.j...@ibm.com.INVALID> >>> Subject: [EXTERNAL] Monitoring Virtual Threads via JMX / MBeans in Tomcat >>> Date: 6 March 2025 at 11:59:40 AM IST >>> To: "d...@tomcat.apache.org" <d...@tomcat.apache.org>, >>> "users@tomcat.apache.org" <users@tomcat.apache.org> >>> Reply-To: "Tomcat Users List" <users@tomcat.apache.org> >>> >>> Dear Apache Tomcat Support Team, >>> >>> I hope this message finds you well. >>> >>> I am writing to inquire whether Apache Tomcat (tomacat version is 10.1.33 >>> running on Java 21) exposes virtual thread metrics through JMX / MBeans. >>> Specifically: >>> >>> Virtual Thread Visibility: >>> >>> Does Tomcat provide MBeans (e.g., under Catalina:type=Executor) to monitor >>> virtual thread usage, such as active virtual thread counts, creation rate, >>> or parking states? >>> If not, are there plans to add such metrics in future releases? >>> Or any alternate ways with which we can monitor this from tomcat side.? >>> >>> Configuration Clarification: >>> We have configured Tomcat 10.1.33 with, >>> <Executor name="tomcatThreadPool" >>> className="org.apache.catalina.core.StandardVirtualThreadExecutor"/> >>> <Connector port="8080" >>> protocol="org.apache.coyote.http11.Http11Nio2Protocol" >>> connectionTimeout="18000" socket.soTimeout="18000" redirectPort="8443" >>> enableLookups="false" URIEncoding="UTF-8" compression="on" >>> useVirtualThreads="true" server="ARandomServer"/> >>> While this works, the existing ThreadPool MBeans show currentThreadsBusy=-1 >>> and maxThreads=200 (incorrect in case of virtual threads). Is this expected >>> behavior? >>> >>> JVM vs. Tomcat Metrics: >>> We observe that the JVM’s java.lang.management.ThreadMXBean includes >>> virtual threads, but this aggregates data across all applications on the >>> JVM. Does Tomcat offer a way to isolate virtual thread metrics specific to >>> Tomcat? >>> >>> Regards, >>> Joash >>> --------------------------------------------------------------------- >>> To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org >>> For additional commands, e-mail: users-h...@tomcat.apache.org >>> >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org >> For additional commands, e-mail: users-h...@tomcat.apache.org > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
