Random Connection Refused Responses During Stress Testing with Apache Jmeter - jmeter

Question

I have the Apache J Meter Tool on my pc and i am trying to stress my App being deployed on GKE.
Sending some requests concurrently or sequentially i am noticing a wired performance.
For example if i make 100 requests at one of the endpoints ,while the most of the requests are successful, 3 or 4 requests from 100 may return the following message:
org.apache.http.conn.HttpHostConnectException: Connect to 35.246.108.130:31225 [/35.246.108.130] failed: Connection refused: connect
at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:156)
at org.apache.jmeter.protocol.http.sampler.HTTPHC4Impl$JMeterDefaultHttpClientConnectionOperator.connect(HTTPHC4Impl.java:404)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:376)
at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:393)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:236)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
at org.apache.jmeter.protocol.http.sampler.HTTPHC4Impl.executeRequest(HTTPHC4Impl.java:935)
at org.apache.jmeter.protocol.http.sampler.HTTPHC4Impl.sample(HTTPHC4Impl.java:646)
at org.apache.jmeter.protocol.http.sampler.HTTPSamplerProxy.sample(HTTPSamplerProxy.java:66)
at org.apache.jmeter.protocol.http.sampler.HTTPSamplerBase.sample(HTTPSamplerBase.java:1296)
at org.apache.jmeter.protocol.http.sampler.HTTPSamplerBase.sample(HTTPSamplerBase.java:1285)
at org.apache.jmeter.threads.JMeterThread.doSampling(JMeterThread.java:638)
at org.apache.jmeter.threads.JMeterThread.executeSamplePackage(JMeterThread.java:558)
at org.apache.jmeter.threads.JMeterThread.processSampler(JMeterThread.java:489)
at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:256)
at java.lang.Thread.run(Unknown Source)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at org.apache.http.conn.socket.PlainConnectionSocketFactory.connectSocket(PlainConnectionSocketFactory.java:75)
at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:142)
... 19 more
Also, the number of requests returning errors may be different (smaller or bigger) if the tests are conducted by a different host machine.
Any ideas about what may cause this problem?

Answer 1

Knowing that you are performing a stress test, a possible explanation could be that your application crashed at that particular instance and restarted. Connection Refused error is usually thrown when there is no application listening for incoming requests.
More details on this stackoverflow thread
Please check if any APM softwares are running for application logs. You will get more hints as what happened at that moment.