Hazelcast Client Hangs

[Anay Kamat]

Hi,

We are using hazelcast in our project. In its current setup, hazelcast
runs on two nodes while clients are deployed on three other nodes.
However, we keep getting "There is no response for Call <abc>
operation=CONCURRENT_MAP_LOCK in X seconds" messages. In worst case,
the operation appears to get no response even till 30 seconds.

It would be of great help if you have any idea regarding why we are
facing this issue.

Some more details related to our setup:

1) Hazelcast servers are started using TestApp provided in hazelcast
package.
2) Hazelcast version is 1.9.3.1
3) Every client has a single instance of HazelcastClient which is
shared by Tomcat threads.

We even performed a small load test over similar setup. We observed
that for a sinlge HazelcastClient serving many concurrent requests,
every request has to wait for previous request (even
CONCURRENT_MAP_GET) to get over. Is there some sort of locking inside
HazelcastClient for every operation?

It's a concern for us as in some cases, application has to wait for as
much as 30 seconds to get data from cache which affects the
performance of our system.

[Fuad Malikov]

Hi,

no we don't have any locking inside the client. You should be able to concurrently do operations unless yourself is doing any lock. And this message is only printed for the operations started from the client and not finished yet. I think that your code was doing a lock operation and probably it was locked by someone else and the call didn't return until the lock is unlocked by the first owner. So are you sure that you don't use the lock?

Fuad

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[Maria Vereschak]

Fuad,
Is it ok to start Hazelcast server using TestApp which comes in
hazelcast package ?

[Fuad Malikov]

Yes that's fine it by TestApp we mean com.hazelcast.examples.TestApp but not the test.sh.
The TestApp is a command line application. You can use com.hazelcast.examples.StartServer too; Which is nothing but

package com.hazelcast.examples;

import com.hazelcast.core.Hazelcast;

public class StartServer {
    public static void main(String[] args) {
        Hazelcast.getCluster();