thread Local Cached Connection - websocket

Question

I was using JMeter properties for storing the threadLocalCachedConnection object. I made sure to use unique property names as properties.
In thread group 1, I had a JSR223 PostProcessor to scrape session per thread(VU), and then store it in a property called sessionID.
And I added another JSR223 PostProcessor as a child of the last sampler in the Thread Group1.
def connection = sampler.threadLocalCachedConnection
props.put("presenterConnection" + ctx.getThreadNum(), connection.get())
In Thread Group 2, I added a JSR223 PreProcessor as a child of the first sampler.
def presenterConnection = props.get('presenterConnection' + ctx.getThreadNum())
sampler.threadLocalCachedConnection.set(presenterConnection)
String sendCommand = "SEND\n" +
"content-type:application/json;charset=UTF-8\n" +
"destination:/v1/session/${__property(sessionId)}/command\n" +
"id:perftest01-presenter-${__property(sessionId)}\n" +
"\n" +
"{\"type\": \"go-to-slide\", \"data\": {\"index\": 0}}\n" +
'\0' // note: NULL char at end
;
vars.put("wsStompSendCommand", sendCommand);
I tested with 2 threads (VUs). Why both threads were using the last sessionId instead of using one sessionId per thread??

Answer 1

As per JMeter Documentation:
Properties are not the same as variables. Variables are local to a thread; properties are common to all threads
so your line
props.put('sessionId', vars.get('sessionUUID'))
creates a global sessionId propety which is:
common for all Threads no matter in which Thread Group they are
exists until you shut down JMeter/JVM
You need to play the same trick as with the presenterConnection to wit:
props.put('sessionId_'+ ctx.getThreadNum(), vars.get('sessionUUID'))
and then read it where required:
def sessionId = props.get('sessionId_'+ ctx.getThreadNum())
More information: Apache Groovy: What Is Groovy Used For?