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This article mainly introduces the relevant knowledge of SpringCloud feign internal code analysis, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe you will gain something after reading this SpringCloud feign internal code analysis article. Let's take a look at it.

1. Overview

Feign is used for inter-service calls, and its internal implementation is a * * JDK-HttpURLConnection (Http) * * call containing Ribbon (load balancer). Although the form of the call is similar to RPC, the actual call is Http, which is why Feign is called a pseudo-RPC call.

two。 Code details

1) initialization of BaseLoadBalancer.java configuration

Key functions: 1. Initialize load balancing strategy 2. Initialize the scheduling strategy of service registration list

Void initWithConfig (IClientConfig clientConfig, IRule rule, IPing ping, LoadBalancerStats stats) {. / / every 30s Ping int pingIntervalTime = Integer.parseInt ("" + clientConfig.getProperty (CommonClientConfigKey.NFLoadBalancerPingInterval, Integer.parseInt ("30") / / up to Ping 2s int maxTotalPingTime = Integer.parseInt ("" + clientConfig.getProperty (CommonClientConfigKey.NFLoadBalancerMaxTotalPingTime, Integer.parseInt ("2")) each time; setPingInterval (pingIntervalTime); setMaxTotalPingTime (maxTotalPingTime) / / cross associate with each other / / i.e. Rule,Ping meet your container LB / / LB, these are your Ping and Rule guys. / / set the load balancing rule setRule (rule); / / initialize the service registration list scheduling policy setPing (ping); setLoadBalancerStats (stats); rule.setLoadBalancer (this);.}

2) initialization of load balancing policy

Key functions: 1. Polling policy is used by default

BaseLoadBalancer.java

Public void setRule (IRule rule) {if (rule! = null) {this.rule = rule;} else {/ * default rule * / / default uses polling policy this.rule = new RoundRobinRule ();} if (this.rule.getLoadBalancer ()! = this) {this.rule.setLoadBalancer (this);}}

RoundRobinRule.java

Private AtomicInteger nextServerCyclicCounter;public Server choose (ILoadBalancer lb, Object key) {if (lb = = null) {log.warn ("no load balancer"); return null;} Server server = null; int count = 0; while (server = = null & & count++

< 10) { List reachableServers = lb.getReachableServers(); List allServers = lb.getAllServers(); int upCount = reachableServers.size(); int serverCount = allServers.size(); if ((upCount == 0) || (serverCount == 0)) { log.warn("No up servers available from load balancer: " + lb); return null; } // 轮询重点算法 int nextServerIndex = incrementAndGetModulo(serverCount); server = allServers.get(nextServerIndex); if (server == null) { /* Transient. */ Thread.yield(); continue; } if (server.isAlive() && (server.isReadyToServe())) { return (server); } // Next. server = null; } if (count >

= 10) {log.warn ("No available alive servers after 10 tries from load balancer:" + lb);} return server;} private int incrementAndGetModulo (int modulo) {for (;;) {int current = nextServerCyclicCounter.get (); int next = (current + 1)% modulo; if (nextServerCyclicCounter.compareAndSet (current, next)) return next;}}

3) initialize the scheduling strategy of fetching service registration list

Key functions: 1. Set the polling interval to 30s once

Note: there is no actual Ping here, just the alive service that gets the cached registration list, in order to improve performance

BaseLoadBalancer.java

Public void setPing (IPing ping) {if (ping! = null) {if (! ping.equals (this.ping)) {this.ping = ping; setupPingTask (); / / since ping data changed}} else {this.ping = null; / / cancel the timer task lbTimer.cancel ();}} void setupPingTask () {if (canSkipPing ()) {return } if (lbTimer! = null) {lbTimer.cancel ();} lbTimer = new ShutdownEnabledTimer ("NFLoadBalancer-PingTimer-" + name, true); / / although the default setting is 10s, during initialization, lbTimer.schedule is set for 30s (new PingTask (), 0, pingIntervalSeconds * 1000); forceQuickPing ();} class Pinger {private final IPingStrategy pingerStrategy Public Pinger (IPingStrategy pingerStrategy) {this.pingerStrategy = pingerStrategy;} public void runPinger () throws Exception {if (! pingInProgress.compareAndSet (false, true)) {return; / / Ping in progress-nothing to do} / / we are "in"-we get to Ping Server [] allServers = null; boolean [] results = null; Lock allLock = null Lock upLock = null; try {/ * * The readLock should be free unless an addServer operation is * going on... * / allLock = allServerLock.readLock (); allLock.lock (); allServers = allServerList.toArray (new Server [allServerList.size ()]); allLock.unlock (); int numCandidates = allServers.length; results = pingerStrategy.pingServers (ping, allServers); final List newUpList = new ArrayList (); final List changedServers = new ArrayList () For (int I = 0; I

< numCandidates; i++) { boolean isAlive = results[i]; Server svr = allServers[i]; boolean oldIsAlive = svr.isAlive(); svr.setAlive(isAlive); if (oldIsAlive != isAlive) { changedServers.add(svr); logger.debug("LoadBalancer [{}]: Server [{}] status changed to {}", name, svr.getId(), (isAlive ? "ALIVE" : "DEAD")); } if (isAlive) { newUpList.add(svr); } } upLock = upServerLock.writeLock(); upLock.lock(); upServerList = newUpList; upLock.unlock(); notifyServerStatusChangeListener(changedServers); } finally { pingInProgress.set(false); } }}private static class SerialPingStrategy implements IPingStrategy { @Override public boolean[] pingServers(IPing ping, Server[] servers) { int numCandidates = servers.length; boolean[] results = new boolean[numCandidates]; logger.debug("LoadBalancer: PingTask executing [{}] servers configured", numCandidates); for (int i = 0; i < numCandidates; i++) { results[i] = false; /* Default answer is DEAD. */ try { // NOTE: IFF we were doing a real ping // assuming we had a large set of servers (say 15) // the logic below will run them serially // hence taking 15 times the amount of time it takes // to ping each server // A better method would be to put this in an executor // pool // But, at the time of this writing, we dont REALLY // use a Real Ping (its mostly in memory eureka call) // hence we can afford to simplify this design and run // this // serially if (ping != null) { results[i] = ping.isAlive(servers[i]); } } catch (Exception e) { logger.error("Exception while pinging Server: '{}'", servers[i], e); } } return results; }} 4) 最后拼接完整URL使用JDK-HttpURLConnection进行调用 SynchronousMethodHandler.java(io.github.openfeign:feign-core:10.10.1/feign.SynchronousMethodHandler.java) Object executeAndDecode(RequestTemplate template, Options options) throws Throwable { Request request = this.targetRequest(template); if (this.logLevel != Level.NONE) { this.logger.logRequest(this.metadata.configKey(), this.logLevel, request); } long start = System.nanoTime(); Response response; try { response = this.client.execute(request, options); response = response.toBuilder().request(request).requestTemplate(template).build(); } catch (IOException var13) { if (this.logLevel != Level.NONE) { this.logger.logIOException(this.metadata.configKey(), this.logLevel, var13, this.elapsedTime(start)); } throw FeignException.errorExecuting(request, var13); } ...} LoadBalancerFeignClient.java @Overridepublic Response execute(Request request, Request.Options options) throws IOException { try { URI asUri = URI.create(request.url()); String clientName = asUri.getHost(); URI uriWithoutHost = cleanUrl(request.url(), clientName); FeignLoadBalancer.RibbonRequest ribbonRequest = new FeignLoadBalancer.RibbonRequest( this.delegate, request, uriWithoutHost); IClientConfig requestConfig = getClientConfig(options, clientName); return lbClient(clientName) .executeWithLoadBalancer(ribbonRequest, requestConfig).toResponse(); } catch (ClientException e) { IOException io = findIOException(e); if (io != null) { throw io; } throw new RuntimeException(e); }} AbstractLoadBalancerAwareClient.java public T executeWithLoadBalancer(final S request, final IClientConfig requestConfig) throws ClientException { LoadBalancerCommand command = buildLoadBalancerCommand(request, requestConfig); try { return command.submit( new ServerOperation() { @Override public Observable call(Server server) { // 获取真实访问URL URI finalUri = reconstructURIWithServer(server, request.getUri()); S requestForServer = (S) request.replaceUri(finalUri); try { return Observable.just(AbstractLoadBalancerAwareClient.this.execute(requestForServer, requestConfig)); } catch (Exception e) { return Observable.error(e); } } }) .toBlocking() .single(); } catch (Exception e) { Throwable t = e.getCause(); if (t instanceof ClientException) { throw (ClientException) t; } else { throw new ClientException(e); } } } FeignLoadBalancer.java @Overridepublic RibbonResponse execute(RibbonRequest request, IClientConfig configOverride) throws IOException { Request.Options options; if (configOverride != null) { RibbonProperties override = RibbonProperties.from(configOverride); options = new Request.Options(override.connectTimeout(this.connectTimeout), override.readTimeout(this.readTimeout)); } else { options = new Request.Options(this.connectTimeout, this.readTimeout); } Response response = request.client().execute(request.toRequest(), options); return new RibbonResponse(request.getUri(), response);} feign.Client.java @Overridepublic Response execute(Request request, Options options) throws IOException { HttpURLConnection connection = convertAndSend(request, options); return convertResponse(connection, request);}Response convertResponse(HttpURLConnection connection, Request request) throws IOException { // 使用HttpURLConnection 真实进行Http调用 int status = connection.getResponseCode(); String reason = connection.getResponseMessage(); if (status < 0) { throw new IOException(format("Invalid status(%s) executing %s %s", status, connection.getRequestMethod(), connection.getURL())); } Map headers = new LinkedHashMap(); for (Map.Entry field : connection.getHeaderFields().entrySet()) { // response message if (field.getKey() != null) { headers.put(field.getKey(), field.getValue()); } } Integer length = connection.getContentLength(); if (length == -1) { length = null; } InputStream stream; if (status >

{stream = connection.getErrorStream ();} else {stream = connection.getInputStream ();} return Response.builder () .status (status) .requests (reason) .headers (headers) .request (request) .body (stream, length) .build ();} this is the end of the article on "SpringCloud feign Internal implementation Code Analysis". Thank you for reading! I believe that everyone has a certain understanding of the knowledge of "SpringCloud feign internal code analysis". If you want to learn more knowledge, you are welcome to follow the industry information channel.

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