private NodeCache makeNodeCache(final ServiceInstance<T> instance) {
if (!watchInstances) {
return null;
}
final NodeCache nodeCache =
new NodeCache(client, pathForInstance(instance.getName(), instance.getId()));
try {
nodeCache.start(true);
} catch (Exception e) {
log.error("Could not start node cache for: " + instance, e);
}
NodeCacheListener listener =
new NodeCacheListener() {
@Override
public void nodeChanged() throws Exception {
if (nodeCache.getCurrentData() != null) {
ServiceInstance<T> newInstance =
serializer.deserialize(nodeCache.getCurrentData().getData());
Entry<T> entry = services.get(newInstance.getId());
if (entry != null) {
synchronized (entry) {
entry.service = newInstance;
}
}
} else {
log.warn("Instance data has been deleted for: " + instance);
}
}
};
nodeCache.getListenable().addListener(listener);
return nodeCache;
}
@Override
public void updateService(final ServiceInstance<T> service) throws Exception {
Entry<T> entry = services.get(service.getId());
if (entry == null) {
throw new Exception("Service not registered: " + service);
}
synchronized (entry) {
entry.service = service;
byte[] bytes = serializer.serialize(service);
String path = pathForInstance(service.getName(), service.getId());
client.setData().forPath(path, bytes);
}
}
@VisibleForTesting
protected void internalRegisterService(ServiceInstance<T> service) throws Exception {
byte[] bytes = serializer.serialize(service);
String path = pathForInstance(service.getName(), service.getId());
final int MAX_TRIES = 2;
boolean isDone = false;
for (int i = 0; !isDone && (i < MAX_TRIES); ++i) {
try {
CreateMode mode =
(service.getServiceType() == ServiceType.DYNAMIC)
? CreateMode.EPHEMERAL
: CreateMode.PERSISTENT;
client.create().creatingParentsIfNeeded().withMode(mode).forPath(path, bytes);
isDone = true;
} catch (KeeperException.NodeExistsException e) {
client.delete().forPath(path); // must delete then re-create so that watchers fire
}
}
}
/**
* Register/re-register/update a service instance
*
* @param service service to add
* @throws Exception errors
*/
@Override
public void registerService(ServiceInstance<T> service) throws Exception {
Entry<T> newEntry = new Entry<T>(service);
Entry<T> oldEntry = services.putIfAbsent(service.getId(), newEntry);
Entry<T> useEntry = (oldEntry != null) ? oldEntry : newEntry;
synchronized (useEntry) {
if (useEntry == newEntry) // i.e. is new
{
useEntry.cache = makeNodeCache(service);
}
internalRegisterService(service);
}
}
/**
* @param client the client
* @param basePath base path to store data
* @param serializer serializer for instances (e.g. {@link JsonInstanceSerializer})
* @param thisInstance instance that represents the service that is running. The instance will get
* auto-registered
* @param watchInstances if true, watches for changes to locally registered instances
*/
public ServiceDiscoveryImpl(
CuratorFramework client,
String basePath,
InstanceSerializer<T> serializer,
ServiceInstance<T> thisInstance,
boolean watchInstances) {
this.watchInstances = watchInstances;
this.client = Preconditions.checkNotNull(client, "client cannot be null");
this.basePath = Preconditions.checkNotNull(basePath, "basePath cannot be null");
this.serializer = Preconditions.checkNotNull(serializer, "serializer cannot be null");
if (thisInstance != null) {
Entry<T> entry = new Entry<T>(thisInstance);
entry.cache = makeNodeCache(thisInstance);
services.put(thisInstance.getId(), entry);
}
}
public ExampleServer(CuratorFramework client, String path, String serviceName, String description)
throws Exception {
// in a real application, you'd have a convention of some kind for the
// URI layout
UriSpec uriSpec = new UriSpec("{scheme}://foo.com:{port}");
thisInstance =
ServiceInstance.<InstanceDetails>builder()
.name(serviceName)
.payload(new InstanceDetails(description))
.port((int) (65535 * Math.random())) // in a real application you'd use a common port
.uriSpec(uriSpec)
.build();
// if you mark your payload class with @JsonRootName the provided
// JsonInstanceSerializer will work
JsonInstanceSerializer<InstanceDetails> serializer =
new JsonInstanceSerializer<InstanceDetails>(InstanceDetails.class);
serviceDiscovery =
ServiceDiscoveryBuilder.builder(InstanceDetails.class)
.client(client)
.basePath(path)
.serializer(serializer)
.thisInstance(thisInstance)
.build();
}
/**
* Unregister/remove a service instance
*
* @param service the service
* @throws Exception errors
*/
@Override
public void unregisterService(ServiceInstance<T> service) throws Exception {
Entry<T> entry = services.remove(service.getId());
internalUnregisterService(entry);
}