@Configuration
class EurekaServerInitializerConfiguration implements ServletContextAware
@Override
public void start() {
new Thread(new Runnable() {
@Override
public void run() {
try {
eurekaServerBootstrap.contextInitialized(EurekaServerInitializerConfiguration.this.servletContext);
publish(new EurekaRegistryAvailableEvent(getEurekaServerConfig()));
EurekaServerInitializerConfiguration.this.running = true;
publish(new EurekaServerStartedEvent(getEurekaServerConfig()));
}
catch (Exception ex) {
}
}
}).start();
}
public void contextInitialized(ServletContext context) {
try {
initEurekaEnvironment();
initEurekaServerContext();
context.setAttribute(EurekaServerContext.class.getName(), this.serverContext);
}
catch (Throwable e) {
log.error("Cannot bootstrap eureka server :", e);
throw new RuntimeException("Cannot bootstrap eureka server :", e);
}
}
int registryCount = this.registry.syncUp();
如果存在已启动的server,会复制已启动server的注册信息。
Applications apps = eurekaClient.getApplications();
for (Application app : apps.getRegisteredApplications()) {
for (InstanceInfo instance : app.getInstances()) {
try {
if (isRegisterable(instance)) {
register(instance, instance.getLeaseInfo().getDurationInSecs(), true);
count++;
}
} catch (Throwable t) {
logger.error("During DS init copy", t);
}
}
}
private final ConcurrentHashMap<String, Map<String, Lease<InstanceInfo>>> registry = new ConcurrentHashMap<String, Map<String, Lease<InstanceInfo>>>();
gMap = registry.putIfAbsent(registrant.getAppName(), gNewMap);
if (this.expectedNumberOfRenewsPerMin > 0) {
// Since the client wants to cancel it, reduce the threshold
// (1
// for 30 seconds, 2 for a minute)
this.expectedNumberOfRenewsPerMin = this.expectedNumberOfRenewsPerMin + 2;
this.numberOfRenewsPerMinThreshold =
(int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
}
这里是Eureka的自我保护机制,每注册上一个实例,重新算一下。
默认是每30秒一个client心跳一次,一分钟就是两次,这里加一个实例,就是加2次,硬编码了,所以都说尽量不要改心跳时间配置。
@POST
@Consumes({"application/json", "application/xml"})
public Response addInstance(InstanceInfo info,
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
...
registry.register(info, "true".equals(isReplication));
return Response.status(204).build(); // 204 to be backwards compatible
}
ApplicationResource类似于Controller,通过Jersey实现RESTful。
@Override
public void register(final InstanceInfo info, final boolean isReplication) {
handleRegistration(info, resolveInstanceLeaseDuration(info), isReplication);
super.register(info, isReplication);
}
第一步发布事件publishEvent,第二部进入主要register实现
@Override
public void register(final InstanceInfo info, final boolean isReplication) {
..
super.register(info, leaseDuration, isReplication);
replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
}
@PUT
public Response renewLease(
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,
@QueryParam("overriddenstatus") String overriddenStatus,
@QueryParam("status") String status,
@QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {
boolean isFromReplicaNode = "true".equals(isReplication);
boolean isSuccess = registry.renew(app.getName(), id, isFromReplicaNode);
...
}
由InstanceRegistry -> AbstractInstanceRegistry -> PeerAwareInstanceRegistryImpl
最后标记为renewed,默认续60s
public void renew() {
lastUpdateTimestamp = System.currentTimeMillis() + duration;
}
duration默认为90
服务取消cancel流程类似。
入口ApplicationsResource.getContainers
主要方法
response = Response.ok(responseCache.get(cacheKey)).build();
从缓存中取信息,默认缓存时间为30s,设置在ResponseCacheImpl的构造器中。
Eureka Server定期清理服务的定时器在AbstractInstanceRegistry的内部类EvictionTask执行的,使用的java.util.TimerTask定时器。
@Override
public void run() {
try {
long compensationTimeMs = getCompensationTimeMs();
logger.info("Running the evict task with compensationTime {}ms", compensationTimeMs);
evict(compensationTimeMs);
} catch (Throwable e) {
logger.error("Could not run the evict task", e);
}
}
默认的evictionIntervalTimerInMs是60秒,每60s执行一次清理任务。
public void evict(long additionalLeaseMs) {
// We collect first all expired items, to evict them in random order. For large eviction sets,
// if we do not that, we might wipe out whole apps before self preservation kicks in. By randomizing it,
// the impact should be evenly distributed across all applications.
List<Lease<InstanceInfo>> expiredLeases = new ArrayList<>();
for (Entry<String, Map<String, Lease<InstanceInfo>>> groupEntry : registry.entrySet()) {
Map<String, Lease<InstanceInfo>> leaseMap = groupEntry.getValue();
if (leaseMap != null) {
for (Entry<String, Lease<InstanceInfo>> leaseEntry : leaseMap.entrySet()) {
Lease<InstanceInfo> lease = leaseEntry.getValue();
if (lease.isExpired(additionalLeaseMs) && lease.getHolder() != null) {
expiredLeases.add(lease);
}
}
}
}
// To compensate for GC pauses or drifting local time, we need to use current registry size as a base for
// triggering self-preservation. Without that we would wipe out full registry.
int registrySize = (int) getLocalRegistrySize();
int registrySizeThreshold = (int) (registrySize * serverConfig.getRenewalPercentThreshold());
int evictionLimit = registrySize - registrySizeThreshold;
int toEvict = Math.min(expiredLeases.size(), evictionLimit);
if (toEvict > 0) {
logger.info("Evicting {} items (expired={}, evictionLimit={})", toEvict, expiredLeases.size(), evictionLimit);
Random random = new Random(System.currentTimeMillis());
for (int i = 0; i < toEvict; i++) {
// Pick a random item (Knuth shuffle algorithm)
int next = i + random.nextInt(expiredLeases.size() - i);
Collections.swap(expiredLeases, i, next);
Lease<InstanceInfo> lease = expiredLeases.get(i);
String appName = lease.getHolder().getAppName();
String id = lease.getHolder().getId();
EXPIRED.increment();
logger.warn("DS: Registry: expired lease for {}/{}", appName, id);
internalCancel(appName, id, false);
}
}
}
大致步骤是,先循环服务找出过期的服务,判断原则是:
public boolean isExpired(long additionalLeaseMs) {
return (evictionTimestamp > 0 || System.currentTimeMillis() > (lastUpdateTimestamp + duration + additionalLeaseMs));
}
duration租长默认是90s,也就是服务90s内没发送心跳就要去除(心跳默认时间是30s,eureka.Instance.lease-renewal-interval-in-seconds)。
去除的方法是internalCancel(appName, id, false),进行cancel操作。
public class DefaultEurekaServerContext implements EurekaServerContext
@PostConstruct
@Override
public void initialize() throws Exception {
logger.info("Initializing ...");
peerEurekaNodes.start();
registry.init(peerEurekaNodes);
logger.info("Initialized");
}
public void start() {
taskExecutor = Executors.newSingleThreadScheduledExecutor(
new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
Thread thread = new Thread(r, "Eureka-PeerNodesUpdater");
thread.setDaemon(true);
return thread;
}
}
);
try {
updatePeerEurekaNodes(resolvePeerUrls());
Runnable peersUpdateTask = new Runnable() {
@Override
public void run() {
try {
updatePeerEurekaNodes(resolvePeerUrls());
} catch (Throwable e) {
logger.error("Cannot update the replica Nodes", e);
}
}
};
taskExecutor.scheduleWithFixedDelay(
peersUpdateTask,
serverConfig.getPeerEurekaNodesUpdateIntervalMs(),
serverConfig.getPeerEurekaNodesUpdateIntervalMs(),
TimeUnit.MILLISECONDS
);
} catch (Exception e) {
throw new IllegalStateException(e);
}
for (PeerEurekaNode node : peerEurekaNodes) {
logger.info("Replica node URL: " + node.getServiceUrl());
}
}
实现在updatePeerEurekaNodes()中,通过比对serviceUrl和discoveryServiceUrls
定时时间默认是10分钟