private boolean fetchAndStoreDelta()

in eureka-core/src/main/java/com/netflix/eureka/registry/RemoteRegionRegistry.java [263:303]
36 lines of code
6 McCabe index (conditional complexity)

    private boolean fetchAndStoreDelta() throws Throwable {
        long currGeneration = fetchRegistryGeneration.get();
        Applications delta = fetchRemoteRegistry(true);

        if (delta == null) {
            logger.error("The delta is null for some reason. Not storing this information");
        } else if (fetchRegistryGeneration.compareAndSet(currGeneration, currGeneration + 1)) {
            this.applicationsDelta.set(delta);
        } else {
            delta = null;  // set the delta to null so we don't use it
            logger.warn("Not updating delta as another thread is updating it already");
        }

        if (delta == null) {
            logger.warn("The server does not allow the delta revision to be applied because it is not "
                    + "safe. Hence got the full registry.");
            return storeFullRegistry();
        } else {
            String reconcileHashCode = "";
            if (fetchRegistryUpdateLock.tryLock()) {
                try {
                    updateDelta(delta);
                    reconcileHashCode = getApplications().getReconcileHashCode();
                } finally {
                    fetchRegistryUpdateLock.unlock();
                }
            } else {
                logger.warn("Cannot acquire update lock, aborting updateDelta operation of fetchAndStoreDelta");
            }

            // There is a diff in number of instances for some reason
            if (!reconcileHashCode.equals(delta.getAppsHashCode())) {
                deltaMismatches++;
                return reconcileAndLogDifference(delta, reconcileHashCode);
            } else {
                deltaSuccesses++;
            }
        }

        return delta != null;
    }