boolean expression - Page 85

How to unit test synchronized code

- by gillJ

Hi, I am new to Java and junit. I have the following peice of code that I want to test. Would appreciate if you could send your ideas about what's the best way to go about testing it. Basically, the following code is about electing a leader form a Cluster. The leader holds a lock on the shared cache and services of the leader get resumed and disposed if it somehow looses the lock on the cache. How can i make sure that a leader/thread still holds the lock on the cache and that another thread cannot get its services resumed while the first is in execution? public interface ContinuousService { public void resume(); public void pause(); } public abstract class ClusterServiceManager { private volatile boolean leader = false; private volatile boolean electable = true; private List<ContinuousService> services; protected synchronized void onElected() { if (!leader) { for (ContinuousService service : services) { service.resume(); } leader = true; } } protected synchronized void onDeposed() { if (leader) { for (ContinuousService service : services) { service.pause(); } leader = false; } } public void setServices(List<ContinuousService> services) { this.services = services; } @ManagedAttribute public boolean isElectable() { return electable; } @ManagedAttribute public boolean isLeader() { return leader; } public class TangosolLeaderElector extends ClusterServiceManager implements Runnable { private static final Logger log = LoggerFactory.getLogger(TangosolLeaderElector.class); private String election; private long electionWaitTime= 5000L; private NamedCache cache; public void start() { log.info("Starting LeaderElector ({})",election); Thread t = new Thread(this, "LeaderElector ("+election+")"); t.setDaemon(true); t.start(); } public void run() { // Give the connection a chance to start itself up try { Thread.sleep(1000); } catch (InterruptedException e) {} boolean wasElectable = !isElectable(); while (true) { if (isElectable()) { if (!wasElectable) { log.info("Leadership requested on election: {}",election); wasElectable = isElectable(); } boolean elected = false; try { // Try and get the lock on the LeaderElectorCache for the current election if (!cache.lock(election, electionWaitTime)) { // We didn't get the lock. cycle round again. // This code to ensure we check the electable flag every now & then continue; } elected = true; log.info("Leadership taken on election: {}",election); onElected(); // Wait here until the services fail in some way. while (true) { try { Thread.sleep(electionWaitTime); } catch (InterruptedException e) {} if (!cache.lock(election, 0)) { log.warn("Cache lock no longer held for election: {}", election); break; } else if (!isElectable()) { log.warn("Node is no longer electable for election: {}", election); break; } // We're fine - loop round and go back to sleep. } } catch (Exception e) { if (log.isErrorEnabled()) { log.error("Leadership election " + election + " failed (try bfmq logs for details)", e); } } finally { if (elected) { cache.unlock(election); log.info("Leadership resigned on election: {}",election); onDeposed(); } // On deposition, do not try and get re-elected for at least the standard wait time. try { Thread.sleep(electionWaitTime); } catch (InterruptedException e) {} } } else { // Not electable - wait a bit and check again. if (wasElectable) { log.info("Leadership NOT requested on election ({}) - node not electable",election); wasElectable = isElectable(); } try { Thread.sleep(electionWaitTime); } catch (InterruptedException e) {} } } } public void setElection(String election) { this.election = election; } @ManagedAttribute public String getElection() { return election; } public void setNamedCache(NamedCache nc) { this.cache = nc; }

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