WSO2 API Manager periodic error on console

Question

I have installed WSO2 API manager (2.0.0) as 2 instance all-in-one clustered. All working fine except periodically I am seeing following errors on the console:

[2016-10-22 00:57:30,572]  INFO - LogMediator STATUS = Message dispatched to the main sequence. Invalid URL., RESOURCE = /appInstallOrRemove
[2016-10-22 00:57:30,579] ERROR - RelayUtils Error while building Passthrough stream
java.lang.StringIndexOutOfBoundsException: String index out of range: -1
    at java.lang.String.substring(String.java:1967)
    at org.apache.synapse.commons.builders.XFormURLEncodedBuilder.extractParametersFromRequest(XFormURLEncodedBuilder.java:223)
    at org.apache.synapse.commons.builders.XFormURLEncodedBuilder.processDocumentWrapper(XFormURLEncodedBuilder.java:128)
    at org.apache.synapse.commons.builders.XFormURLEncodedBuilder.processDocument(XFormURLEncodedBuilder.java:52)
    at org.apache.synapse.transport.passthru.util.DeferredMessageBuilder.getDocument(DeferredMessageBuilder.java:148)
    at org.apache.synapse.transport.passthru.util.RelayUtils.builldMessage(RelayUtils.java:137)
    at org.apache.synapse.transport.passthru.util.RelayUtils.buildMessage(RelayUtils.java:100)
    at org.apache.synapse.mediators.AbstractListMediator.buildMessage(AbstractListMediator.java:127)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:57)
    at org.apache.synapse.config.xml.AnonymousListMediator.mediate(AnonymousListMediator.java:37)
    at org.apache.synapse.mediators.filters.FilterMediator.mediate(FilterMediator.java:203)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:95)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:57)
    at org.apache.synapse.mediators.filters.InMediator.mediate(InMediator.java:74)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:95)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:57)
    at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
    at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:310)
    at org.apache.synapse.core.axis2.SynapseMessageReceiver.receive(SynapseMessageReceiver.java:75)
    at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
    at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:319)
    at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest(ServerWorker.java:365)
    at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:145)
    at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
[2016-10-22 00:57:30,582] ERROR - AnonymousListMediator Error while building message
org.apache.axis2.AxisFault: Error while building Passthrough stream
    at org.apache.synapse.transport.passthru.util.RelayUtils.handleException(RelayUtils.java:287)
    at org.apache.synapse.transport.passthru.util.RelayUtils.builldMessage(RelayUtils.java:146)
    at org.apache.synapse.transport.passthru.util.RelayUtils.buildMessage(RelayUtils.java:100)
    at org.apache.synapse.mediators.AbstractListMediator.buildMessage(AbstractListMediator.java:127)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:57)
    at org.apache.synapse.config.xml.AnonymousListMediator.mediate(AnonymousListMediator.java:37)
    at org.apache.synapse.mediators.filters.FilterMediator.mediate(FilterMediator.java:203)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:95)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:57)
    at org.apache.synapse.mediators.filters.InMediator.mediate(InMediator.java:74)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:95)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:57)
    at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
    at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:310)
    at org.apache.synapse.core.axis2.SynapseMessageReceiver.receive(SynapseMessageReceiver.java:75)
    at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
    at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:319)
    at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest(ServerWorker.java:365)
    at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:145)
    at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -1
    at java.lang.String.substring(String.java:1967)
    at org.apache.synapse.commons.builders.XFormURLEncodedBuilder.extractParametersFromRequest(XFormURLEncodedBuilder.java:223)
    at org.apache.synapse.commons.builders.XFormURLEncodedBuilder.processDocumentWrapper(XFormURLEncodedBuilder.java:128)
    at org.apache.synapse.commons.builders.XFormURLEncodedBuilder.processDocument(XFormURLEncodedBuilder.java:52)
    at org.apache.synapse.transport.passthru.util.DeferredMessageBuilder.getDocument(DeferredMessageBuilder.java:148)
    at org.apache.synapse.transport.passthru.util.RelayUtils.builldMessage(RelayUtils.java:137)
    ... 22 more
[2016-10-22 00:57:30,583]  INFO - LogMediator STATUS = Executing default 'fault' sequence, ERROR_CODE = 0, ERROR_MESSAGE = Error while building message
[2016-10-22 00:57:30,586] ERROR - ServerWorker Error processing POST reguest for : /appInstallOrRemove. Error detail: org.apache.synapse.SynapseException: Error occured in the mediation of the class mediator. 
java.lang.RuntimeException: org.apache.synapse.SynapseException: Error occured in the mediation of the class mediator
    at org.apache.synapse.FaultHandler.handleFault(FaultHandler.java:108)
    at org.apache.synapse.core.axis2.SynapseMessageReceiver.receive(SynapseMessageReceiver.java:81)
    at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
    at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:319)
    at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest(ServerWorker.java:365)
    at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:145)
    at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.synapse.SynapseException: Error occured in the mediation of the class mediator
    at org.apache.synapse.mediators.ext.ClassMediator.mediate(ClassMediator.java:88)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:95)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:57)
    at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
    at org.apache.synapse.mediators.MediatorFaultHandler.onFault(MediatorFaultHandler.java:93)
    at org.apache.synapse.FaultHandler.handleFault(FaultHandler.java:101)
    ... 9 more
Caused by: java.lang.NullPointerException
    at org.wso2.carbon.apimgt.impl.utils.APIUtil.getAPIProviderFromRESTAPI(APIUtil.java:5217)
    at org.wso2.carbon.apimgt.usage.publisher.APIMgtCommonExecutionPublisher.mediate(APIMgtCommonExecutionPublisher.java:50)
    at org.wso2.carbon.apimgt.usage.publisher.APIMgtFaultHandler.mediate(APIMgtFaultHandler.java:20)
    at org.apache.synapse.mediators.ext.ClassMediator.mediate(ClassMediator.java:84)
    ... 14 more

From my observation, it happens almost every 7 minutes

$ grep 'LogMediator STATUS = Message dispatched' /var/log/wso2am.log
[2016-10-22 00:42:23,445]  INFO - LogMediator STATUS = Message dispatched to the main sequence. Invalid URL., RESOURCE = /appInstallOrRemove
[2016-10-22 00:49:55,114]  INFO - LogMediator STATUS = Message dispatched to the main sequence. Invalid URL., RESOURCE = /appInstallOrRemove
[2016-10-22 00:57:30,572]  INFO - LogMediator STATUS = Message dispatched to the main sequence. Invalid URL., RESOURCE = /appInstallOrRemove
[2016-10-22 00:58:47,528]  INFO - LogMediator STATUS = Message dispatched to the main sequence. Invalid URL., RESOURCE = /appInstallOrRemove
[2016-10-22 01:08:26,239]  INFO - LogMediator STATUS = Message dispatched to the main sequence. Invalid URL., RESOURCE = /appInstallOrRemove

Appreciate any suggestion as why this is happening.

Answer 1

INFO - LogMediator STATUS = Message dispatched to the main sequence. Invalid URL., RESOURCE = /appInstallOrRemove

This error occurs when you send a request to https://localhost:8243/appInstallOrRemove, but there are no APIs deployed with the context appInstallOrRemove.

Update: If you have a look at repository/logs/http_access_<date>.log file, you will see an entry like this.

- xx.xxx.x.xx - - [27/Oct/2016:09:24:26 +0530] "GET /appInstallOrRemove HTTP/1.1" - - "-" "curl/7.36.0"
- xx.xxx.x.xx  - [27/Oct/2016:09:24:26 +0530] "- - " 404 - "-" "-"

Here, xx.xxx.x.xx is the IP of the client.