Java tutorial
/* * Copyright 2015-present Facebook, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. You may obtain * a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations * under the License. */ package com.facebook.buck.slb; import com.facebook.buck.event.BuckEventBus; import com.facebook.buck.log.Logger; import com.facebook.buck.timing.Clock; import com.google.common.annotations.VisibleForTesting; import com.google.common.base.Preconditions; import com.google.common.collect.ImmutableList; import com.google.common.util.concurrent.Futures; import com.google.common.util.concurrent.ListenableFuture; import com.google.common.util.concurrent.SettableFuture; import java.io.IOException; import java.net.URI; import java.util.ArrayList; import java.util.List; import java.util.concurrent.ExecutionException; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.ScheduledFuture; import java.util.concurrent.TimeUnit; import okhttp3.Call; import okhttp3.Callback; import okhttp3.OkHttpClient; import okhttp3.Request; import okhttp3.Response; import okhttp3.ResponseBody; public class ClientSideSlb implements HttpLoadBalancer { private static final Logger LOG = Logger.get(ClientSideSlb.class); private final String pingEndpoint; private final ImmutableList<URI> serverPool; private final OkHttpClient pingClient; private final ServerHealthManager healthManager; private final Clock clock; private final ScheduledExecutorService schedulerService; private final ScheduledFuture<?> backgroundHealthChecker; private final BuckEventBus eventBus; public static boolean isSafeToCreate(ClientSideSlbConfig config) { return config.getPingEndpoint() != null && config.getServerPool() != null && config.getServerPool().size() > 0 && config.getEventBus() != null; } // Use the Builder. public ClientSideSlb(ClientSideSlbConfig config) { this(config, new OkHttpClient.Builder() .connectTimeout(config.getConnectionTimeoutMillis(), TimeUnit.MILLISECONDS) .readTimeout(config.getConnectionTimeoutMillis(), TimeUnit.MILLISECONDS) .writeTimeout(config.getConnectionTimeoutMillis(), TimeUnit.MILLISECONDS).build()); } @VisibleForTesting ClientSideSlb(ClientSideSlbConfig config, OkHttpClient pingClient) { this.clock = config.getClock(); this.pingEndpoint = Preconditions.checkNotNull(config.getPingEndpoint()); this.serverPool = Preconditions.checkNotNull(config.getServerPool()); this.eventBus = Preconditions.checkNotNull(config.getEventBus()); Preconditions.checkArgument(serverPool.size() > 0, "No server URLs passed."); this.healthManager = new ServerHealthManager(this.serverPool, config.getErrorCheckTimeRangeMillis(), config.getMaxErrorPercentage(), config.getLatencyCheckTimeRangeMillis(), config.getMaxAcceptableLatencyMillis(), config.getEventBus()); this.pingClient = pingClient; this.schedulerService = config.getSchedulerService(); backgroundHealthChecker = this.schedulerService.scheduleWithFixedDelay( this::backgroundThreadCallForHealthCheck, 0, config.getHealthCheckIntervalMillis(), TimeUnit.MILLISECONDS); } @Override public URI getBestServer() throws NoHealthyServersException { return healthManager.getBestServer(clock.currentTimeMillis()); } @Override public void reportRequestSuccess(URI server) { healthManager.reportRequestSuccess(server, clock.currentTimeMillis()); } @Override public void reportRequestException(URI server) { healthManager.reportRequestError(server, clock.currentTimeMillis()); } @Override public void close() { backgroundHealthChecker.cancel(true); } // TODO(ruibm): Register for BuildStart events in the EventBus and force a health check then. // TODO(ruibm): Log into timeseries information about each run. // TODO(ruibm): Add cache health information to the SuperConsole. private void backgroundThreadCallForHealthCheck() { LOG.verbose("Starting pings. %s", toString()); List<ListenableFuture<PerServerPingData>> futures = new ArrayList<>(); for (URI serverUri : serverPool) { ServerPing serverPing = new ServerPing(serverUri); futures.add(serverPing.getFuture()); } // Wait for all executions to complete or fail. try { List<PerServerPingData> allServerData = Futures.allAsList(futures).get(); LoadBalancerPingEventData.Builder eventData = LoadBalancerPingEventData.builder(); eventData.addAllPerServerData(allServerData); eventBus.post(new LoadBalancerPingEvent(eventData.build())); LOG.verbose("all pings complete %s", toString()); } catch (InterruptedException ex) { LOG.verbose("pings interrupted"); } catch (ExecutionException ex) { LOG.verbose(ex, "some pings failed"); } } public class ServerPing implements Callback { private final SettableFuture<PerServerPingData> future = SettableFuture.create(); URI serverUri; ServerPing(URI serverUri) { this.serverUri = serverUri; Request request = new Request.Builder().url(serverUri.resolve(pingEndpoint).toString()).get().build(); pingClient.newCall(request).enqueue(this); } public ListenableFuture<PerServerPingData> getFuture() { return future; } /* Process the success result of the ping */ @Override public void onResponse(Call call, Response response) throws IOException { PerServerPingData.Builder perServerData = PerServerPingData.builder().setServer(serverUri); long sentRequestMillis = response.sentRequestAtMillis(); if (response.isSuccessful()) { try (ResponseBody responseBody = response.body()) { String body = responseBody.string(); LOG.verbose("Sent ping to %s. Response: %s", serverUri.toString(), body); } long requestLatencyMillis = response.receivedResponseAtMillis() - sentRequestMillis; perServerData.setPingRequestLatencyMillis(requestLatencyMillis); healthManager.reportPingLatency(serverUri, sentRequestMillis, requestLatencyMillis); healthManager.reportRequestSuccess(serverUri, sentRequestMillis); } else { healthManager.reportRequestError(serverUri, sentRequestMillis); } future.set(perServerData.build()); } /* Process the failure result of the ping */ @Override public void onFailure(Call call, IOException e) { healthManager.reportRequestError(serverUri, clock.currentTimeMillis()); PerServerPingData.Builder perServerData = PerServerPingData.builder().setServer(serverUri); perServerData.setException(e); future.set(perServerData.build()); } } }