Hi,
I'm using Mulesoft integration tool and invoking Salesforce Apex Rest API (@RestResource(urlMapping = '/matchingtool/*'), it is working since year until couple of weeks or less. for each hour in a 24 hour window the integration may invoke this api for 1000 times, most of the hours it is working completely for those 1000 but for couple of hourls it's failing with this exception. I poste d question in Mulesoft but everyone replying that this might be Salesforce issue so checking here.
Below is Apex code:

@RestResource(urlMapping = '/matchingtool/*')
global class EmpMatchingTool {
    @HttpPost
    global static String getIdByIdentifiers(Identifiers identifiers) {
        ---------
   }
}

Below is complete exception:

org.mule.extension.salesforce.internal.error.exception.service.SalesforceException: Remotely closed
	at org.mule.extension.salesforce.internal.error.exception.service.handlers.IOExceptionHandler.handle(IOExceptionHandler.java:44)
	at org.mule.extension.salesforce.internal.connection.ForceWSCConnection.send(ForceWSCConnection.java:332)
	at org.mule.extension.salesforce.internal.service.apex.rest.ApexRestInvocation.invokeApexRest(ApexRestInvocation.java:392)
	at org.mule.extension.salesforce.internal.service.apex.util.ApexClient.invokeRestMethod(ApexClient.java:188)
	at org.mule.extension.salesforce.internal.service.ApexServiceImpl.lambda$invokeRestMethod$1(ApexServiceImpl.java:66)
	at org.mule.extension.salesforce.internal.connection.ForceWSCConnection.executeOverApexRestClient(ForceWSCConnection.java:239)
	at org.mule.extension.salesforce.internal.service.ForceWSCService.executeOverApexRestClient(ForceWSCService.java:28)
	at org.mule.extension.salesforce.internal.service.ApexServiceImpl.invokeRestMethod(ApexServiceImpl.java:53)
	at org.mule.extension.salesforce.internal.operation.apex.InvokeApexRestMethodOperation.invokeApexRestMethod(InvokeApexRestMethodOperation.java:54)
	at org.mule.extension.salesforce.internal.operation.apex.InvokeApexRestMethodOperation$invokeApexRestMethod$MethodComponentExecutor.execute(Unknown Source)
	at org.mule.runtime.module.extension.internal.runtime.execution.GeneratedMethodComponentExecutor.execute(GeneratedMethodComponentExecutor.java:97)
	at org.mule.runtime.module.extension.internal.runtime.execution.CompletableMethodOperationExecutor.doExecute(CompletableMethodOperationExecutor.java:29)
	at org.mule.runtime.module.extension.internal.runtime.execution.AbstractCompletableMethodOperationExecutor.execute(AbstractCompletableMethodOperationExecutor.java:63)
	at org.mule.runtime.module.extension.internal.runtime.operation.DefaultExecutionMediator.executeCommand(DefaultExecutionMediator.java:211)
	at org.mule.runtime.module.extension.internal.runtime.operation.DefaultExecutionMediator.lambda$executeWithInterceptors$6(DefaultExecutionMediator.java:192)
	at org.mule.runtime.module.extension.internal.runtime.operation.DefaultExecutionMediator.lambda$executeWithRetry$2(DefaultExecutionMediator.java:130)
	at net.jodah.failsafe.Functions.lambda$promiseOfStage$8(Functions.java:193)
	at net.jodah.failsafe.internal.executor.RetryPolicyExecutor$1.call(RetryPolicyExecutor.java:101)
	at net.jodah.failsafe.internal.executor.RetryPolicyExecutor.lambda$supplyAsync$1(RetryPolicyExecutor.java:133)
	at net.jodah.failsafe.Functions.lambda$null$1(Functions.java:69)
	at org.mule.runtime.core.internal.util.rx.ConditionalExecutorServiceDecorator.synchronousSchedule(ConditionalExecutorServiceDecorator.java:181)
	at org.mule.runtime.core.internal.util.rx.ConditionalExecutorServiceDecorator.schedule(ConditionalExecutorServiceDecorator.java:167)
	at net.jodah.failsafe.Functions.lambda$makeAsync$2(Functions.java:79)
	at net.jodah.failsafe.AsyncExecution.executeAsync(AsyncExecution.java:174)
	at net.jodah.failsafe.FailsafeExecutor.callAsync(FailsafeExecutor.java:346)
	at net.jodah.failsafe.FailsafeExecutor.getStageAsync(FailsafeExecutor.java:178)
	at org.mule.runtime.core.internal.retry.policies.SimpleRetryPolicy.applyPolicy(SimpleRetryPolicy.java:90)
	at org.mule.runtime.core.api.retry.policy.RetryPolicyTemplate.applyPolicy(RetryPolicyTemplate.java:144)
	at org.mule.runtime.module.extension.internal.runtime.operation.DefaultExecutionMediator.executeWithRetry(DefaultExecutionMediator.java:128)
	at org.mule.runtime.module.extension.internal.runtime.operation.DefaultExecutionMediator.executeWithInterceptors(DefaultExecutionMediator.java:192)
	at org.mule.runtime.module.extension.internal.runtime.operation.DefaultExecutionMediator.lambda$execute$1(DefaultExecutionMediator.java:113)
	at org.mule.runtime.module.extension.internal.runtime.operation.DefaultExecutionMediator.lambda$new$0(DefaultExecutionMediator.java:61)
	at org.mule.runtime.module.extension.internal.runtime.operation.DefaultExecutionMediator.execute(DefaultExecutionMediator.java:112)
	at org.mule.runtime.module.extension.internal.runtime.operation.ComponentMessageProcessor.executeOperation(ComponentMessageProcessor.java:563)
	at org.mule.runtime.module.extension.internal.runtime.operation.OAuthOperationMessageProcessor.executeOperation(OAuthOperationMessageProcessor.java:58)
	at org.mule.runtime.module.extension.internal.runtime.operation.ComponentMessageProcessor.prepareAndExecuteOperation(ComponentMessageProcessor.java:765)
	at org.mule.runtime.module.extension.internal.runtime.operation.ComponentMessageProcessor.access$100(ComponentMessageProcessor.java:185)
	at org.mule.runtime.module.extension.internal.runtime.operation.ComponentMessageProcessor$4.lambda$innerEventDispatcher$9(ComponentMessageProcessor.java:637)
	at reactor.core.publisher.FluxPeekFuseable$PeekFuseableConditionalSubscriber.tryOnNext(FluxPeekFuseable.java:510)
	at reactor.core.publisher.FluxPeekFuseable$PeekFuseableConditionalSubscriber.tryOnNext(FluxPeekFuseable.java:523)
	at reactor.core.publisher.FluxPublishOn$PublishOnConditionalSubscriber.runAsync(FluxPublishOn.java:866)
	at reactor.core.publisher.FluxPublishOn$PublishOnConditionalSubscriber.run(FluxPublishOn.java:939)
	at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:84)
	at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:37)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at org.mule.service.scheduler.internal.AbstractRunnableFutureDecorator.doRun(AbstractRunnableFutureDecorator.java:111)
	at org.mule.service.scheduler.internal.RunnableFutureDecorator.run(RunnableFutureDecorator.java:54)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)