private String readOrDefineClusterId()

in src/main/java/org/apache/sling/discovery/oak/cluster/OakClusterViewService.java [445:493]
46 lines of code
10 McCabe index (conditional complexity)

    private String readOrDefineClusterId(ResourceResolver resourceResolver) throws PersistenceException {
        //TODO: if Config gets a specific, public getDiscoveryResourcePath, this can be simplified:
        final String clusterInstancesPath = config.getClusterInstancesPath();
        final String discoveryResourcePath = clusterInstancesPath.substring(0, 
                clusterInstancesPath.lastIndexOf("/", clusterInstancesPath.length()-2));
        final int MAX_RETRIES = 5;
        for(int retryCnt=0; retryCnt<MAX_RETRIES; retryCnt++) {
            Resource varDiscoveryOak = resourceResolver.getResource(discoveryResourcePath);
            if (varDiscoveryOak == null) {
                varDiscoveryOak = ResourceHelper.getOrCreateResource(resourceResolver, discoveryResourcePath);
            }
            if (varDiscoveryOak == null) {
                logger.error("readOrDefinedClusterId: Could not create: "+discoveryResourcePath);
                throw new RuntimeException("could not create " + discoveryResourcePath);
            }
            ModifiableValueMap props = varDiscoveryOak.adaptTo(ModifiableValueMap.class);
            if (props == null) {
                logger.error("readOrDefineClusterId: Could not adaptTo ModifiableValueMap: "+varDiscoveryOak);
                throw new RuntimeException("could not adaptTo ModifiableValueMap: " + varDiscoveryOak);
            }
            Object clusterIdObj = props.get(PROPERTY_CLUSTER_ID);
            String clusterId = (clusterIdObj == null) ? null : String.valueOf(clusterIdObj);
            if (clusterId != null && clusterId.length() > 0) {
                logger.trace("readOrDefineClusterId: read clusterId from repo as {}", clusterId);
                return clusterId;
            }

            // must now define a new clusterId and store it under /var/discovery/oak
            final String newClusterId = UUID.randomUUID().toString();
            props.put(PROPERTY_CLUSTER_ID, newClusterId);
            props.put(PROPERTY_CLUSTER_ID_DEFINED_BY, getSlingId());
            props.put(PROPERTY_CLUSTER_ID_DEFINED_AT, Calendar.getInstance());
            try {
                logger.info("readOrDefineClusterId: storing new clusterId as " + newClusterId);
                resourceResolver.commit();
                return newClusterId;
            } catch (PersistenceException e) {
                logger.warn("readOrDefineClusterId: could not persist clusterId "
                        + "(retrying in 1 sec max " + (MAX_RETRIES - retryCnt - 1) + " more times: " + e, e);
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e1) {
                    logger.warn("readOrDefineClusterId: got interrupted: "+e1, e1);
                }
                logger.info("readOrDefineClusterId: retrying now.");
            }
        }
        throw new RuntimeException("failed to write new clusterId (see log file earlier for more details)");
    }