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eureka server定时任务去判断lease是否过期，然后设置lease对应的instance的状态，然后更新到ResponseCache，供客户端来获取刷新，这里讲下client端的刷新过程中是如何剔除实例的。
client更新task
eureka-client-1.4.12-sources.jar!/com/netflix/discovery/DiscoveryClient.java
if (clientConfig.shouldFetchRegistry()) {
// registry cache refresh timer
int registryFetchIntervalSeconds = clientConfig.getRegistryFetchIntervalSeconds();
int expBackOffBound = clientConfig.getCacheRefreshExecutorExponentialBackOffBound();
scheduler.schedule(
new TimedSupervisorTask(
"cacheRefresh",
scheduler,
cacheRefreshExecutor,
registryFetchIntervalSeconds,
TimeUnit.SECONDS,
expBackOffBound,
new CacheRefreshThread()
),
registryFetchIntervalSeconds, TimeUnit.SECONDS);
}CacheRefreshThread
/**
* The task that fetches the registry information at specified intervals.
*
*/
class CacheRefreshThread implements Runnable {
public void run() {
refreshRegistry();
}
}refreshRegistry
@VisibleForTesting
void refreshRegistry() {
try {
boolean isFetchingRemoteRegionRegistries = isFetchingRemoteRegionRegistries();
boolean remoteRegionsModified = false;
// This makes sure that a dynamic change to remote regions to fetch is honored.
String latestRemoteRegions = clientConfig.fetchRegistryForRemoteRegions();
if (null != latestRemoteRegions) {
String currentRemoteRegions = remoteRegionsToFetch.get();
if (!latestRemoteRegions.equals(currentRemoteRegions)) {
// Both remoteRegionsToFetch and AzToRegionMapper.regionsToFetch need to be in sync
synchronized (instanceRegionChecker.getAzToRegionMapper()) {
if (remoteRegionsToFetch.compareAndSet(currentRemoteRegions, latestRemoteRegions)) {
String[] remoteRegions = latestRemoteRegions.split(",");
remoteRegionsRef.set(remoteRegions);
instanceRegionChecker.getAzToRegionMapper().setRegionsToFetch(remoteRegions);
remoteRegionsModified = true;
} else {
logger.info("Remote regions to fetch modified concurrently," +
" ignoring change from {} to {}", currentRemoteRegions, latestRemoteRegions);
}
}
} else {
// Just refresh mapping to reflect any DNS/Property change
instanceRegionChecker.getAzToRegionMapper().refreshMapping();
}
}
boolean success = fetchRegistry(remoteRegionsModified);
if (success) {
registrySize = localRegionApps.get().size();
lastSuccessfulRegistryFetchTimestamp = System.currentTimeMillis();
}
if (logger.isDebugEnabled()) {
StringBuilder allAppsHashCodes = new StringBuilder();
allAppsHashCodes.append("Local region apps hashcode: ");
allAppsHashCodes.append(localRegionApps.get().getAppsHashCode());
allAppsHashCodes.append(", is fetching remote regions? ");
allAppsHashCodes.append(isFetchingRemoteRegionRegistries);
for (Map.Entry entry : remoteRegionVsApps.entrySet()) {
allAppsHashCodes.append(", Remote region: ");
allAppsHashCodes.append(entry.getKey());
allAppsHashCodes.append(" , apps hashcode: ");
allAppsHashCodes.append(entry.getValue().getAppsHashCode());
}
logger.debug("Completed cache refresh task for discovery. All Apps hash code is {} ",
allAppsHashCodes.toString());
}
} catch (Throwable e) {
logger.error("Cannot fetch registry from server", e);
}
} fetchRegistry
/**
* Fetches the registry information.
*
*
* This method tries to get only deltas after the first fetch unless there
* is an issue in reconciling eureka server and client registry information.
*
*
* @param forceFullRegistryFetch Forces a full registry fetch.
*
* @return true if the registry was fetched
*/
private boolean fetchRegistry(boolean forceFullRegistryFetch) {
Stopwatch tracer = FETCH_REGISTRY_TIMER.start();
try {
// If the delta is disabled or if it is the first time, get all
// applications
Applications applications = getApplications();
if (clientConfig.shouldDisableDelta()
|| (!Strings.isNullOrEmpty(clientConfig.getRegistryRefreshSingleVipAddress()))
|| forceFullRegistryFetch
|| (applications == null)
|| (applications.getRegisteredApplications().size() == 0)
|| (applications.getVersion() == -1)) //Client application does not have latest library supporting delta
{
logger.info("Disable delta property : {}", clientConfig.shouldDisableDelta());
logger.info("Single vip registry refresh property : {}", clientConfig.getRegistryRefreshSingleVipAddress());
logger.info("Force full registry fetch : {}", forceFullRegistryFetch);
logger.info("Application is null : {}", (applications == null));
logger.info("Registered Applications size is zero : {}",
(applications.getRegisteredApplications().size() == 0));
logger.info("Application version is -1: {}", (applications.getVersion() == -1));
getAndStoreFullRegistry();
} else {
getAndUpdateDelta(applications);
}
applications.setAppsHashCode(applications.getReconcileHashCode());
logTotalInstances();
} catch (Throwable e) {
logger.error(PREFIX + appPathIdentifier + " - was unable to refresh its cache! status = " + e.getMessage(), e);
return false;
} finally {
if (tracer != null) {
tracer.stop();
}
}
// Notify about cache refresh before updating the instance remote status
onCacheRefreshed();
// Update remote status based on refreshed data held in the cache
updateInstanceRemoteStatus();
// registry was fetched successfully, so return true
return true;
}getAndUpdateDelta
/**
* Get the delta registry information from the eureka server and update it locally.
* When applying the delta, the following flow is observed:
*
* if (update generation have not advanced (due to another thread))
* atomically try to: update application with the delta and get reconcileHashCode
* abort entire processing otherwise
* do reconciliation if reconcileHashCode clash
* fi
*
* @return the client response
* @throws Throwable on error
*/
private void getAndUpdateDelta(Applications applications) throws Throwable {
long currentUpdateGeneration = fetchRegistryGeneration.get();
Applications delta = null;
EurekaHttpResponse httpResponse = eurekaTransport.queryClient.getDelta(remoteRegionsRef.get());
if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) {
delta = httpResponse.getEntity();
}
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.");
getAndStoreFullRegistry();
} else if (fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1)) {
logger.debug("Got delta update with apps hashcode {}", delta.getAppsHashCode());
String reconcileHashCode = "";
if (fetchRegistryUpdateLock.tryLock()) {
try {
updateDelta(delta);
reconcileHashCode = getReconcileHashCode(applications);
} finally {
fetchRegistryUpdateLock.unlock();
}
} else {
logger.warn("Cannot acquire update lock, aborting getAndUpdateDelta");
}
// There is a diff in number of instances for some reason
if (!reconcileHashCode.equals(delta.getAppsHashCode()) || clientConfig.shouldLogDeltaDiff()) {
reconcileAndLogDifference(delta, reconcileHashCode); // this makes a remoteCall
}
} else {
logger.warn("Not updating application delta as another thread is updating it already");
logger.debug("Ignoring delta update with apps hashcode {}, as another thread is updating it already", delta.getAppsHashCode());
}
} updateDelta
/**
* Updates the delta information fetches from the eureka server into the
* local cache.
*
* @param delta
* the delta information received from eureka server in the last
* poll cycle.
*/
private void updateDelta(Applications delta) {
int deltaCount = 0;
for (Application app : delta.getRegisteredApplications()) {
for (InstanceInfo instance : app.getInstances()) {
Applications applications = getApplications();
String instanceRegion = instanceRegionChecker.getInstanceRegion(instance);
if (!instanceRegionChecker.isLocalRegion(instanceRegion)) {
Applications remoteApps = remoteRegionVsApps.get(instanceRegion);
if (null == remoteApps) {
remoteApps = new Applications();
remoteRegionVsApps.put(instanceRegion, remoteApps);
}
applications = remoteApps;
}
++deltaCount;
if (ActionType.ADDED.equals(instance.getActionType())) {
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Added instance {} to the existing apps in region {}", instance.getId(), instanceRegion);
applications.getRegisteredApplications(instance.getAppName()).addInstance(instance);
} else if (ActionType.MODIFIED.equals(instance.getActionType())) {
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Modified instance {} to the existing apps ", instance.getId());
applications.getRegisteredApplications(instance.getAppName()).addInstance(instance);
} else if (ActionType.DELETED.equals(instance.getActionType())) {
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Deleted instance {} to the existing apps ", instance.getId());
applications.getRegisteredApplications(instance.getAppName()).removeInstance(instance);
}
}
}
logger.debug("The total number of instances fetched by the delta processor : {}", deltaCount);
getApplications().setVersion(delta.getVersion());
getApplications().shuffleInstances(clientConfig.shouldFilterOnlyUpInstances());
for (Applications applications : remoteRegionVsApps.values()) {
applications.setVersion(delta.getVersion());
applications.shuffleInstances(clientConfig.shouldFilterOnlyUpInstances());
}
}获取application信息，判断是否删除，如果是则删除实例
if (ActionType.DELETED.equals(instance.getActionType())) {
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Deleted instance {} to the existing apps ", instance.getId());
applications.getRegisteredApplications(instance.getAppName()).removeInstance(instance);
}doc
微服务Eureka Server原理