Preview: MicroProfile Fault Tolerance in Payara Micro

• To run the Uber JAR, run
  java -jar target/fault-tolerance-1.0-SNAPSHOT-microbundle.jar

• To run the WAR file on a different Payara Micro instance, run
  java -jar /path/to/payara-micro.jar -deploy target/fault-tolerance-1.0-SNAPSHOT.war

Watch the output of Payara Micro to see the URLs created, and visit the endpoints to trigger an example of fault tolerance. Watch the logs to see how Payara Micro behaves.

The example is a simple JAX-RS class with two @GET methods, getEmployeeById and getAllEmployees. There is a list of 4 people which can be returned.

There are 2 methods to introduce simple problematic behaviour, one isDown() which simply returns a boolean based on Math.random() and isSlow() which will sleep for a second based on Math.random()

@GET
    @Path("{id}")
    @Retry(maxRetries = 4, retryOn = {RuntimeException.class})
    public String getEmployeeById(@PathParam("id") int id) {
        System.out.println("Called getEmployeeById a total of " + ++retryCounter + " times");
        if (id >= employees.size()) return "No such employee. Try a number lower than " + employees.size();
        if (isDown()) throw new RuntimeException();
        return employees.get(id);
    }

    private boolean isDown() {
        // approx 80% chance
        return Math.random() > 0.2;
    }

---> invoke <---
 
Called getEmployeeById a total of 1 times
 
 ---> invoke <---
 
Called getEmployeeById a total of 2 times
[2018-01-10T09:25:19.063+0000] [] [INFO] [] [fish.payara.microprofile.faulttolerance.interceptors.RetryInterceptor] [tid: _ThreadID=20 _ThreadName=http-thread-pool::http-listener(1)] [timeMillis: 1515576319063] [levelValue: 800] Retrying as long as maxDuration isnt breached, and no more than {0} times
 
Called getEmployeeById a total of 3 times
Called getEmployeeById a total of 4 times
Called getEmployeeById a total of 5 times
 
 ---> invoke <---
 
Called getEmployeeById a total of 6 times
[2018-01-10T09:25:37.861+0000] [] [INFO] [] [fish.payara.microprofile.faulttolerance.interceptors.RetryInterceptor] [tid: _ThreadID=25 _ThreadName=http-thread-pool::http-listener(6)] [timeMillis: 1515576337861] [levelValue: 800] Retrying as long as maxDuration isnt breached, and no more than {0} times
 
Called getEmployeeById a total of 7 times
Called getEmployeeById a total of 8 times
Called getEmployeeById a total of 9 times
Called getEmployeeById a total of 10 times
[2018-01-10T09:25:38.147+0000] [] [WARNING] [] [javax.enterprise.web] [tid: _ThreadID=25 _ThreadName=http-thread-pool::http-listener(6)] [timeMillis: 1515576338147] [levelValue: 900] [[
  StandardWrapperValve[RestApplication]: Servlet.service() for servlet RestApplication threw exception
java.lang.RuntimeException
        at EmployeeResource.getEmployeeById(EmployeeResource.java:36)
        at org.jboss.weld.proxies.EmployeeResource$Proxy$_$_WeldSubclass.getEmployeeById$super(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.jboss.weld.interceptor.proxy.TerminalAroundInvokeInvocationContext.proceedInternal(TerminalAroundInvokeInvocationContext.java:51)

Timeout and Fallback

private final long TIMEOUT = 500;
    private final long SLEEPTIME = 1000;

    @GET
    @Fallback(fallbackMethod = "getAllEmployeesFallback")
    @Timeout(TIMEOUT)
    public String getAllEmployees() throws InterruptedException {
        if (isSlow()) return employees.toString();
        return employees.toString();
    }

    public String getAllEmployeesFallback() {
        return "It took longer than expected to get all employees. Try again later!";
    }

    private boolean isSlow() throws InterruptedException {
        if (Math.random() > 0.4) {
            // approx 60% chance
            Thread.sleep(SLEEPTIME);
            return true;
        }
        return false;
    }

There are minimal configuration options for Fault Tolerance through asadmin commands. The only configurable aspect relates to the @Asynchronous annotation, which will ensure that the execution of the client request will be on a separate thread. There are two asadmin commands which allow you to get and set the ManagedExecutorService name or ManagedScheduledExecutorService name as follows:

        Usage: asadmin [asadmin-utility-options] set-fault-tolerance-configuration
                [--managedexecutorservicename <managedexecutorservicename>]
                [--managedscheduledexecutorservicename <managedscheduledexecutorservicename>]
                [--target <target(default:server-config)>]
                [-?|--help[=<help(default:false)>]] 

Fault Tolerance is just one of several MicroProfile 1.2 specs that are already implemented, with more on the way.

Stay tuned for more updates on using MicroProfile in Payara Server/Micro!