Re: Tomcat 10 and virtual thread

Hi,

I have never tried doing it through the executor like that.  How I enable virtual threads in server.xml is like this:

 <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443"
               maxParameterCount="1000"
               useVirtualThreads="true" />

You should be using at least JDK21 for that to work.  When you do a thread dump you will see virtual threads in the dump.

Extra info FYI: Running with JVM argument -Djdk.tracePinnedThreads=full prints a complete stack trace when a thread blocks while pinned, with the native frames and frames holding monitors highlighted. Running with -Djdk.tracePinnedThreads=short limits the output to just the problematic frames:

Thread[#41,ForkJoinPool-1-worker-4,5,CarrierThreads]
    com.mysql.cj.jdbc.ConnectionImpl.isValid(ConnectionImpl.java:2516) <== monitors:1
Thread[#39,ForkJoinPool-1-worker-2,5,CarrierThreads]
    com.mysql.cj.jdbc.ConnectionImpl.isValid(ConnectionImpl.java:2516) <== monitors:1
Thread[#41,ForkJoinPool-1-worker-4,5,CarrierThreads]
    com.mysql.cj.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:2005) <== monitors:1
Thread[#43,ForkJoinPool-1-worker-5,5,CarrierThreads]
    com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:893) <== monitors:1
    com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1061) <== monitors:1
    com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1009) <== monitors:1
Thread[#43,ForkJoinPool-1-worker-5,5,CarrierThreads]
    com.mysql.cj.jdbc.ConnectionImpl.commit(ConnectionImpl.java:791) <== monitors:1
Thread[#43,ForkJoinPool-1-worker-5,5,CarrierThreads]
    com.mysql.cj.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:2005) <== monitors:1

Regards,

William Crowell

From: COURTAULT Francois <[email protected]>
Date: Monday, November 3, 2025 at 11:05 AM
To: [email protected] <[email protected]>
Subject: Tomcat 10 and virtual thread

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Hello everyone,

Looking at https://tomcat.apache.org/tomcat-10.1-doc/config/executor.html we can configure Tomcat 10.1.x to use virtual threads
instead of platform threads. Do you confirm ?

The way to do it, as far as I understood, is to:

  *   first, declare an executor in server.xml like below
<Executor name="virtualThread"
                                      className="org.apache.catalina.core.StandardVirtualThreadExecutor" />

  *   second, use a connector which will refer this above Executor thanks to its name attribute.
The way I do it, is to update line 74, in server.xml, from <Connector port="8080" protocol="HTTP/1.1" to
                                                                                                                         <Connector executor="virtualThread" port="8080" protocol="HTTP/1.1"

I started Tomcat and triggered a thread dump.
I was not able to see any tomcat-virt string.
Does it mean that the virtual thread usage is still disabled ?

What's wrong with my configuration ?

Best Regards.






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