一 Eureka
1. 需要掌握的一些基礎知識
“Applications”：注冊在Eureka Server上的應用集合。-- 對應多個**Application**
“Application”：具體的一個應用（eureka-provider）。-- 對應多個"InstanceInfo"(localhost:8070,
localhost:8071, localhost:8072)
"InstanceInfo"：應用實例。 IP + Port
源代碼：
Applications.java
1 // 2 // Source code recreated from a .class file by IntelliJ IDEA 3 // (powered by Fernflower decompiler) 4 // 5 6 package com.netflix.discovery.shared; 7 8 import com.fasterxml.jackson.annotation.JsonCreator; 9 import com.fasterxml.jackson.annotation.JsonIgnore; 10 import com.fasterxml.jackson.annotation.JsonProperty; 11 import com.fasterxml.jackson.annotation.JsonRootName; 12 import com.netflix.appinfo.InstanceInfo; 13 import com.netflix.appinfo.InstanceInfo.ActionType; 14 import com.netflix.appinfo.InstanceInfo.InstanceStatus; 15 import com.netflix.discovery.EurekaClientConfig; 16 import com.netflix.discovery.InstanceRegionChecker; 17 import com.netflix.discovery.provider.Serializer; 18 import com.thoughtworks.xstream.annotations.XStreamAlias; 19 import com.thoughtworks.xstream.annotations.XStreamImplicit; 20 import java.util.AbstractQueue; 21 import java.util.ArrayList; 22 import java.util.Collections; 23 import java.util.HashSet; 24 import java.util.Iterator; 25 import java.util.List; 26 import java.util.Locale; 27 import java.util.Map; 28 import java.util.Set; 29 import java.util.TreeMap; 30 import java.util.Map.Entry; 31 import java.util.concurrent.ConcurrentHashMap; 32 import java.util.concurrent.ConcurrentLinkedQueue; 33 import java.util.concurrent.atomic.AtomicInteger; 34 import java.util.concurrent.atomic.AtomicLong; 35 import java.util.concurrent.atomic.AtomicReference; 36 import javax.annotation.Nullable; 37 import org.slf4j.Logger; 38 import org.slf4j.LoggerFactory; 39 40 @Serializer("com.netflix.discovery.converters.EntityBodyConverter") 41 @XStreamAlias("applications") 42 @JsonRootName("applications") 43 public class Applications { 44 private static final String APP_INSTANCEID_DELIMITER = "$$"; 45 private static final Logger logger = LoggerFactory.getLogger(Applications.class); 46 private static final String STATUS_DELIMITER = "_"; 47 private Long versionDelta = -1L; 48 @XStreamImplicit 49 private AbstractQueue<Application> applications = new ConcurrentLinkedQueue(); 50 private Map<String, Application> appNameApplicationMap = new ConcurrentHashMap(); 51 private Map<String, AbstractQueue<InstanceInfo>> virtualHostNameAppMap = new ConcurrentHashMap(); 52 private Map<String, AbstractQueue<InstanceInfo>> secureVirtualHostNameAppMap = new ConcurrentHashMap(); 53 private Map<String, AtomicLong> virtualHostNameIndexMap = new ConcurrentHashMap(); 54 private Map<String, AtomicLong> secureVirtualHostNameIndexMap = new ConcurrentHashMap(); 55 private Map<String, AtomicReference<List<InstanceInfo>>> shuffleVirtualHostNameMap = new ConcurrentHashMap(); 56 private Map<String, AtomicReference<List<InstanceInfo>>> shuffledSecureVirtualHostNameMap = new ConcurrentHashMap(); 57 private String appsHashCode; 58 59 public Applications() { 60 } 61 62 @JsonCreator 63 public Applications(@JsonProperty("appsHashCode") String appsHashCode, @JsonProperty("versionDelta") Long versionDelta, @JsonProperty("application") List<Application> registeredApplications) { 64 Iterator var4 = registeredApplications.iterator(); 65 66 while(var4.hasNext()) { 67 Application app = (Application)var4.next(); 68 this.addApplication(app); 69 } 70 71 this.appsHashCode = appsHashCode; 72 this.versionDelta = versionDelta; 73 } 74 75 public Applications(List<Application> apps) { 76 this.applications.addAll(apps); 77 } 78 79 public void addApplication(Application app) { 80 this.appNameApplicationMap.put(app.getName().toUpperCase(Locale.ROOT), app); 81 this.addInstancesToVIPMaps(app); 82 this.applications.add(app); 83 } 84 85 @JsonProperty("application") 86 public List<Application> getRegisteredApplications() { 87 List<Application> list = new ArrayList(); 88 list.addAll(this.applications); 89 return list; 90 } 91 92 public Application getRegisteredApplications(String appName) { 93 return (Application)this.appNameApplicationMap.get(appName.toUpperCase(Locale.ROOT)); 94 } 95 96 public List<InstanceInfo> getInstancesByVirtualHostName(String virtualHostName) { 97 AtomicReference<List<InstanceInfo>> ref = (AtomicReference)this.shuffleVirtualHostNameMap.get(virtualHostName.toUpperCase(Locale.ROOT)); 98 return (List)(ref != null && ref.get() != null ? (List)ref.get() : new ArrayList()); 99 } 100 101 public List<InstanceInfo> getInstancesBySecureVirtualHostName(String secureVirtualHostName) { 102 AtomicReference<List<InstanceInfo>> ref = (AtomicReference)this.shuffledSecureVirtualHostNameMap.get(secureVirtualHostName.toUpperCase(Locale.ROOT)); 103 return (List)(ref != null && ref.get() != null ? (List)ref.get() : new ArrayList()); 104 } 105 106 public int size() { 107 int result = 0; 108 109 Application application; 110 for(Iterator var2 = this.applications.iterator(); var2.hasNext(); result += application.size()) { 111 application = (Application)var2.next(); 112 } 113 114 return result; 115 } 116 117 /** @deprecated */ 118 @Deprecated 119 public void setVersion(Long version) { 120 this.versionDelta = version; 121 } 122 123 /** @deprecated */ 124 @Deprecated 125 @JsonIgnore 126 public Long getVersion() { 127 return this.versionDelta; 128 } 129 130 public void setAppsHashCode(String hashCode) { 131 this.appsHashCode = hashCode; 132 } 133 134 @JsonIgnore 135 public String getAppsHashCode() { 136 return this.appsHashCode; 137 } 138 139 @JsonIgnore 140 public String getReconcileHashCode() { 141 TreeMap<String, AtomicInteger> instanceCountMap = new TreeMap(); 142 this.populateInstanceCountMap(instanceCountMap); 143 return getReconcileHashCode(instanceCountMap); 144 } 145 146 public void populateInstanceCountMap(TreeMap<String, AtomicInteger> instanceCountMap) { 147 Iterator var2 = this.getRegisteredApplications().iterator(); 148 149 while(var2.hasNext()) { 150 Application app = (Application)var2.next(); 151 152 AtomicInteger instanceCount; 153 for(Iterator var4 = app.getInstancesAsIsFromEureka().iterator(); var4.hasNext(); instanceCount.incrementAndGet()) { 154 InstanceInfo info = (InstanceInfo)var4.next(); 155 instanceCount = (AtomicInteger)instanceCountMap.get(info.getStatus().name()); 156 if (instanceCount == null) { 157 instanceCount = new AtomicInteger(0); 158 instanceCountMap.put(info.getStatus().name(), instanceCount); 159 } 160 } 161 } 162 163 } 164 165 public static String getReconcileHashCode(TreeMap<String, AtomicInteger> instanceCountMap) { 166 String reconcileHashCode = ""; 167 168 Entry mapEntry; 169 for(Iterator var2 = instanceCountMap.entrySet().iterator(); var2.hasNext(); reconcileHashCode = reconcileHashCode + (String)mapEntry.getKey() + "_" + ((AtomicInteger)mapEntry.getValue()).get() + "_") { 170 mapEntry = (Entry)var2.next(); 171 } 172 173 return reconcileHashCode; 174 } 175 176 public Map<String, List<String>> getReconcileMapDiff(Applications apps) { 177 Map<String, List<String>> diffMap = new TreeMap(); 178 Set<Applications.Pair> allInstanceAppInstanceIds = new HashSet(); 179 Iterator var4 = apps.getRegisteredApplications().iterator(); 180 181 while(true) { 182 Application thisApp; 183 while(var4.hasNext()) { 184 Application otherApp = (Application)var4.next(); 185 thisApp = this.getRegisteredApplications(otherApp.getName()); 186 if (thisApp == null) { 187 logger.warn("Application not found in local cache : {}", otherApp.getName()); 188 } else { 189 Iterator var7 = thisApp.getInstancesAsIsFromEureka().iterator(); 190 191 InstanceInfo otherInstanceInfo; 192 while(var7.hasNext()) { 193 otherInstanceInfo = (InstanceInfo)var7.next(); 194 allInstanceAppInstanceIds.add(new Applications.Pair(thisApp.getName(), otherInstanceInfo.getId())); 195 } 196 197 for(var7 = otherApp.getInstancesAsIsFromEureka().iterator(); var7.hasNext(); allInstanceAppInstanceIds.remove(new Applications.Pair(otherApp.getName(), otherInstanceInfo.getId()))) { 198 otherInstanceInfo = (InstanceInfo)var7.next(); 199 InstanceInfo thisInstanceInfo = thisApp.getByInstanceId(otherInstanceInfo.getId()); 200 Object diffList; 201 if (thisInstanceInfo == null) { 202 diffList = (List)diffMap.get(ActionType.DELETED.name()); 203 if (diffList == null) { 204 diffList = new ArrayList(); 205 diffMap.put(ActionType.DELETED.name(), diffList); 206 } 207 208 ((List)diffList).add(otherInstanceInfo.getId()); 209 } else if (!thisInstanceInfo.getStatus().name().equalsIgnoreCase(otherInstanceInfo.getStatus().name())) { 210 diffList = (List)diffMap.get(ActionType.MODIFIED.name()); 211 if (diffList == null) { 212 diffList = new ArrayList(); 213 diffMap.put(ActionType.MODIFIED.name(), diffList); 214 } 215 216 ((List)diffList).add(thisInstanceInfo.getId() + "$$" + thisInstanceInfo.getStatus().name() + "$$" + otherInstanceInfo.getStatus().name()); 217 } 218 } 219 } 220 } 221 222 var4 = allInstanceAppInstanceIds.iterator(); 223 224 while(var4.hasNext()) { 225 Applications.Pair pair = (Applications.Pair)var4.next(); 226 thisApp = new Application(pair.getItem1()); 227 InstanceInfo thisInstanceInfo = thisApp.getByInstanceId(pair.getItem2()); 228 if (thisInstanceInfo != null) { 229 List<String> diffList = (List)diffMap.get(ActionType.ADDED.name()); 230 if (diffList == null) { 231 diffList = new ArrayList(); 232 diffMap.put(ActionType.ADDED.name(), diffList); 233 } 234 235 ((List)diffList).add(thisInstanceInfo.getId()); 236 } 237 } 238 239 return diffMap; 240 } 241 } 242 243 public void shuffleInstances(boolean filterUpInstances) { 244 this.shuffleInstances(filterUpInstances, false, (Map)null, (EurekaClientConfig)null, (InstanceRegionChecker)null); 245 } 246 247 public void shuffleAndIndexInstances(Map<String, Applications> remoteRegionsRegistry, EurekaClientConfig clientConfig, InstanceRegionChecker instanceRegionChecker) { 248 this.shuffleInstances(clientConfig.shouldFilterOnlyUpInstances(), true, remoteRegionsRegistry, clientConfig, instanceRegionChecker); 249 } 250 251 private void shuffleInstances(boolean filterUpInstances, boolean indexByRemoteRegions, @Nullable Map<String, Applications> remoteRegionsRegistry, @Nullable EurekaClientConfig clientConfig, @Nullable InstanceRegionChecker instanceRegionChecker) { 252 this.virtualHostNameAppMap.clear(); 253 this.secureVirtualHostNameAppMap.clear(); 254 255 Application application; 256 for(Iterator var6 = this.appNameApplicationMap.values().iterator(); var6.hasNext(); this.addInstancesToVIPMaps(application)) { 257 application = (Application)var6.next(); 258 if (indexByRemoteRegions) { 259 application.shuffleAndStoreInstances(remoteRegionsRegistry, clientConfig, instanceRegionChecker); 260 } else { 261 application.shuffleAndStoreInstances(filterUpInstances); 262 } 263 } 264 265 this.shuffleAndFilterInstances(this.virtualHostNameAppMap, this.shuffleVirtualHostNameMap, this.virtualHostNameIndexMap, filterUpInstances); 266 this.shuffleAndFilterInstances(this.secureVirtualHostNameAppMap, this.shuffledSecureVirtualHostNameMap, this.secureVirtualHostNameIndexMap, filterUpInstances); 267 } 268 269 public AtomicLong getNextIndex(String virtualHostname, boolean secure) { 270 return secure ? (AtomicLong)this.secureVirtualHostNameIndexMap.get(virtualHostname) : (AtomicLong)this.virtualHostNameIndexMap.get(virtualHostname); 271 } 272 273 private void shuffleAndFilterInstances(Map<String, AbstractQueue<InstanceInfo>> srcMap, Map<String, AtomicReference<List<InstanceInfo>>> destMap, Map<String, AtomicLong> vipIndexMap, boolean filterUpInstances) { 274 Iterator var5 = srcMap.entrySet().iterator(); 275 276 while(var5.hasNext()) { 277 Entry<String, AbstractQueue<InstanceInfo>> entries = (Entry)var5.next(); 278 AbstractQueue<InstanceInfo> instanceInfoQueue = (AbstractQueue)entries.getValue(); 279 List<InstanceInfo> l = new ArrayList(instanceInfoQueue); 280 if (filterUpInstances) { 281 Iterator it = l.iterator(); 282 283 while(it.hasNext()) { 284 InstanceInfo instanceInfo = (InstanceInfo)it.next(); 285 if (!InstanceStatus.UP.equals(instanceInfo.getStatus())) { 286 it.remove(); 287 } 288 } 289 } 290 291 Collections.shuffle(l); 292 AtomicReference<List<InstanceInfo>> instanceInfoList = (AtomicReference)destMap.get(entries.getKey()); 293 if (instanceInfoList == null) { 294 instanceInfoList = new AtomicReference(l); 295 destMap.put(entries.getKey(), instanceInfoList); 296 } 297 298 instanceInfoList.set(l); 299 vipIndexMap.put(entries.getKey(), new AtomicLong(0L)); 300 } 301 302 Set<String> srcVips = srcMap.keySet(); 303 Set<String> destVips = destMap.keySet(); 304 destVips.retainAll(srcVips); 305 } 306 307 private void addInstanceToMap(InstanceInfo info, String vipAddresses, Map<String, AbstractQueue<InstanceInfo>> vipMap) { 308 if (vipAddresses != null) { 309 String[] vipAddressArray = vipAddresses.split(","); 310 String[] var5 = vipAddressArray; 311 int var6 = vipAddressArray.length; 312 313 for(int var7 = 0; var7 < var6; ++var7) { 314 String vipAddress = var5[var7]; 315 String vipName = vipAddress.toUpperCase(Locale.ROOT); 316 AbstractQueue<InstanceInfo> instanceInfoList = (AbstractQueue)vipMap.get(vipName); 317 if (instanceInfoList == null) { 318 instanceInfoList = new ConcurrentLinkedQueue(); 319 vipMap.put(vipName, instanceInfoList); 320 } 321 322 ((AbstractQueue)instanceInfoList).add(info); 323 } 324 } 325 326 } 327 328 private void addInstancesToVIPMaps(Application app) { 329 Iterator var2 = app.getInstances().iterator(); 330 331 while(true) { 332 InstanceInfo info; 333 String vipAddresses; 334 String secureVipAddresses; 335 do { 336 if (!var2.hasNext()) { 337 return; 338 } 339 340 info = (InstanceInfo)var2.next(); 341 vipAddresses = info.getVIPAddress(); 342 secureVipAddresses = info.getSecureVipAddress(); 343 } while(vipAddresses == null && secureVipAddresses == null); 344 345 this.addInstanceToMap(info, vipAddresses, this.virtualHostNameAppMap); 346 this.addInstanceToMap(info, secureVipAddresses, this.secureVirtualHostNameAppMap); 347 } 348 } 349 350 private static final class Pair { 351 private final String item1; 352 private final String item2; 353 354 public Pair(String item1, String item2) { 355 this.item1 = item1; 356 this.item2 = item2; 357 } 358 359 public int hashCode() { 360 int prime = true; 361 int result = 1; 362 int result = 31 * result + (this.item1 == null ? 0 : this.item1.hashCode()); 363 result = 31 * result + (this.item2 == null ? 0 : this.item2.hashCode()); 364 return result; 365 } 366 367 public boolean equals(Object obj) { 368 if (this == obj) { 369 return true; 370 } else if (obj == null) { 371 return false; 372 } else if (this.getClass() != obj.getClass()) { 373 return false; 374 } else { 375 Applications.Pair other = (Applications.Pair)obj; 376 if (this.item1 == null) { 377 if (other.item1 != null) { 378 return false; 379 } 380 } else if (!this.item1.equals(other.item1)) { 381 return false; 382 } 383 384 if (this.item2 == null) { 385 if (other.item2 != null) { 386 return false; 387 } 388 } else if (!this.item2.equals(other.item2)) { 389 return false; 390 } 391 392 return true; 393 } 394 } 395 396 public String getItem1() { 397 return this.item1; 398 } 399 400 public String getItem2() { 401 return this.item2; 402 } 403 } 404 }
源代碼49行為Applications的主要數據結構，可見其數據結構為一個Queue，Queue中的是
Application。
Application.java：
1 // 2 // Source code recreated from a .class file by IntelliJ IDEA 3 // (powered by Fernflower decompiler) 4 // 5 6 package com.netflix.discovery.shared; 7 8 import com.fasterxml.jackson.annotation.JsonCreator; 9 import com.fasterxml.jackson.annotation.JsonIgnore; 10 import com.fasterxml.jackson.annotation.JsonProperty; 11 import com.fasterxml.jackson.annotation.JsonRootName; 12 import com.netflix.appinfo.InstanceInfo; 13 import com.netflix.appinfo.InstanceInfo.InstanceStatus; 14 import com.netflix.discovery.EurekaClientConfig; 15 import com.netflix.discovery.InstanceRegionChecker; 16 import com.netflix.discovery.provider.Serializer; 17 import com.netflix.discovery.util.StringCache; 18 import com.thoughtworks.xstream.annotations.XStreamAlias; 19 import com.thoughtworks.xstream.annotations.XStreamImplicit; 20 import com.thoughtworks.xstream.annotations.XStreamOmitField; 21 import java.util.ArrayList; 22 import java.util.Collections; 23 import java.util.Iterator; 24 import java.util.LinkedHashSet; 25 import java.util.List; 26 import java.util.Map; 27 import java.util.Set; 28 import java.util.concurrent.ConcurrentHashMap; 29 import java.util.concurrent.atomic.AtomicReference; 30 import javax.annotation.Nullable; 31 32 @Serializer("com.netflix.discovery.converters.EntityBodyConverter") 33 @XStreamAlias("application") 34 @JsonRootName("application") 35 public class Application { 36 private String name; 37 @XStreamOmitField 38 private volatile boolean isDirty; 39 @XStreamImplicit 40 private final Set<InstanceInfo> instances; 41 private AtomicReference<List<InstanceInfo>> shuffledInstances; 42 private Map<String, InstanceInfo> instancesMap; 43 44 public String toString() { 45 return "Application [name=" + this.name + ", isDirty=" + this.isDirty + ", instances=" + this.instances + ", shuffledInstances=" + this.shuffledInstances + ", instancesMap=" + this.instancesMap + "]"; 46 } 47 48 public Application() { 49 this.isDirty = false; 50 this.shuffledInstances = new AtomicReference(); 51 this.instances = new LinkedHashSet(); 52 this.instancesMap = new ConcurrentHashMap(); 53 } 54 55 public Application(String name) { 56 this.isDirty = false; 57 this.shuffledInstances = new AtomicReference(); 58 this.name = StringCache.intern(name); 59 this.instancesMap = new ConcurrentHashMap(); 60 this.instances = new LinkedHashSet(); 61 } 62 63 @JsonCreator 64 public Application(@JsonProperty("name") String name, @JsonProperty("instance") List<InstanceInfo> instances) { 65 this(name); 66 Iterator var3 = instances.iterator(); 67 68 while(var3.hasNext()) { 69 InstanceInfo instanceInfo = (InstanceInfo)var3.next(); 70 this.addInstance(instanceInfo); 71 } 72 73 } 74 75 public void addInstance(InstanceInfo i) { 76 this.instancesMap.put(i.getId(), i); 77 Set var2 = this.instances; 78 synchronized(this.instances) { 79 this.instances.remove(i); 80 this.instances.add(i); 81 this.isDirty = true; 82 } 83 } 84 85 public void removeInstance(InstanceInfo i) { 86 this.removeInstance(i, true); 87 } 88 89 @JsonProperty("instance") 90 public List<InstanceInfo> getInstances() { 91 return this.shuffledInstances.get() == null ? this.getInstancesAsIsFromEureka() : (List)this.shuffledInstances.get(); 92 } 93 94 @JsonIgnore 95 public List<InstanceInfo> getInstancesAsIsFromEureka() { 96 Set var1 = this.instances; 97 synchronized(this.instances) { 98 return new ArrayList(this.instances); 99 } 100 } 101 102 public InstanceInfo getByInstanceId(String id) { 103 return (InstanceInfo)this.instancesMap.get(id); 104 } 105 106 public String getName() { 107 return this.name; 108 } 109 110 public void setName(String name) { 111 this.name = StringCache.intern(name); 112 } 113 114 public int size() { 115 return this.instances.size(); 116 } 117 118 public void shuffleAndStoreInstances(boolean filterUpInstances) { 119 this._shuffleAndStoreInstances(filterUpInstances, false, (Map)null, (EurekaClientConfig)null, (InstanceRegionChecker)null); 120 } 121 122 public void shuffleAndStoreInstances(Map<String, Applications> remoteRegionsRegistry, EurekaClientConfig clientConfig, InstanceRegionChecker instanceRegionChecker) { 123 this._shuffleAndStoreInstances(clientConfig.shouldFilterOnlyUpInstances(), true, remoteRegionsRegistry, clientConfig, instanceRegionChecker); 124 } 125 126 private void _shuffleAndStoreInstances(boolean filterUpInstances, boolean indexByRemoteRegions, @Nullable Map<String, Applications> remoteRegionsRegistry, @Nullable EurekaClientConfig clientConfig, @Nullable InstanceRegionChecker instanceRegionChecker) { 127 Set var7 = this.instances; 128 ArrayList instanceInfoList; 129 synchronized(this.instances) { 130 instanceInfoList = new ArrayList(this.instances); 131 } 132 133 if (indexByRemoteRegions || filterUpInstances) { 134 Iterator it = instanceInfoList.iterator(); 135 136 label50: 137 while(true) { 138 while(true) { 139 if (!it.hasNext()) { 140 break label50; 141 } 142 143 InstanceInfo instanceInfo = (InstanceInfo)it.next(); 144 if (filterUpInstances && !InstanceStatus.UP.equals(instanceInfo.getStatus())) { 145 it.remove(); 146 } else if (indexByRemoteRegions && null != instanceRegionChecker && null != clientConfig && null != remoteRegionsRegistry) { 147 String instanceRegion = instanceRegionChecker.getInstanceRegion(instanceInfo); 148 if (!instanceRegionChecker.isLocalRegion(instanceRegion)) { 149 Applications appsForRemoteRegion = (Applications)remoteRegionsRegistry.get(instanceRegion); 150 if (null == appsForRemoteRegion) { 151 appsForRemoteRegion = new Applications(); 152 remoteRegionsRegistry.put(instanceRegion, appsForRemoteRegion); 153 } 154 155 Application remoteApp = appsForRemoteRegion.getRegisteredApplications(instanceInfo.getAppName()); 156 if (null == remoteApp) { 157 remoteApp = new Application(instanceInfo.getAppName()); 158 appsForRemoteRegion.addApplication(remoteApp); 159 } 160 161 remoteApp.addInstance(instanceInfo); 162 this.removeInstance(instanceInfo, false); 163 it.remove(); 164 } 165 } 166 } 167 } 168 } 169 170 Collections.shuffle(instanceInfoList); 171 this.shuffledInstances.set(instanceInfoList); 172 } 173 174 private void removeInstance(InstanceInfo i, boolean markAsDirty) { 175 this.instancesMap.remove(i.getId()); 176 Set var3 = this.instances; 177 synchronized(this.instances) { 178 this.instances.remove(i); 179 if (markAsDirty) { 180 this.isDirty = true; 181 } 182 183 } 184 } 185 }
源代碼第40行，是Application的主要數據結構，其定義的是一個Set，Set中是是
InstanceInfo
2. 源碼解析
（1）任務的初始化
任務的初始化是由DiscoveryClient.java的構造方法
DiscoveryClient(ApplicationInfoManager applicationInfoManager,
EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args,
Provider<BackupRegistry> backupRegistryProvider) 創建並執行一些線程容器
完成的（scheduler線程池）。該定時任務用於從注冊中心獲取服務列表、心跳、
向注冊中心注冊自己。創建容器代碼片段
this.scheduler = Executors.newScheduledThreadPool(2, (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-%d").setDaemon(true).build()); this.heartbeatExecutor = new ThreadPoolExecutor(1, this.clientConfig.getHeartbeatExecutorThreadPoolSize(), 0L, TimeUnit.SECONDS, new SynchronousQueue(), (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-HeartbeatExecutor-%d").setDaemon(true).build()); this.cacheRefreshExecutor = new ThreadPoolExecutor(1, this.clientConfig.getCacheRefreshExecutorThreadPoolSize(), 0L, TimeUnit.SECONDS, new SynchronousQueue(), (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-CacheRefreshExecutor-%d").setDaemon(true).build());
執行定時任務代碼片段（構造方法調用initScheduledTasks()方法完成的）
1 1、一個從注冊中心獲取服務列表的任務，頻率：registryFetchIntervalSeconds（默認30s） 2 if (clientConfig.shouldFetchRegistry()) { 3 // registry cache refresh timer 4 int registryFetchIntervalSeconds = clientConfig.getRegistryFetchIntervalSeconds(); 5 int expBackOffBound = clientConfig.getCacheRefreshExecutorExponentialBackOffBound(); 6 scheduler.schedule( 7 new TimedSupervisorTask( 8 "cacheRefresh", 9 scheduler, 10 cacheRefreshExecutor, 11 registryFetchIntervalSeconds, 12 TimeUnit.SECONDS, 13 expBackOffBound, 14 new CacheRefreshThread() 15 ), 16 registryFetchIntervalSeconds, TimeUnit.SECONDS); 17 } 18 ``` 19 20 21 22 2、客戶端啟動一個心跳線程，向注冊中心發送心跳，頻率：renewalIntervalInSecs（默認30s） 23 // Heartbeat timer 24 scheduler.schedule( 25 new TimedSupervisorTask( 26 "heartbeat", 27 scheduler, 28 heartbeatExecutor, 29 renewalIntervalInSecs, 30 TimeUnit.SECONDS, 31 expBackOffBound, 32 new HeartbeatThread() 33 ), 34 renewalIntervalInSecs, TimeUnit.SECONDS); 35 ``` 36 37 38 39 40 3、客戶端向注冊中心注冊自己，頻率：InstanceInfoReplicationIntervalSeconds（默認30s）定時的上報自己的信息 。
注冊是為了定時的向注冊中心上報自己的信息，所以他需要不停的注冊，而不是注冊一次 41 instanceInfoReplicator = new InstanceInfoReplicator( 42 this, 43 instanceInfo, 44 clientConfig.getInstanceInfoReplicationIntervalSeconds(), 45 2); // burstSize 46 ```
（2）向服務端獲取服務列表
思路：（a）客戶端先從緩存中獲取服務列表
（b）根據緩存的情況進行增量或是全量更新服務列表
（c）發送http請求到服務端
（d）服務端先去讀緩存中獲取服務列表如果沒有則去寫緩存中獲取服務列表並將寫緩存中
服務列表緩存到讀緩存中
（e）服務端返回結果給客戶端
（f）客戶端將結果緩存到自己的緩存中
引入一個問題：
客戶端A（A1、A2、A3）調用客戶端C（C1、C2、C3），當A1調用C1的時候，C1宕機，那么
這時候調用失敗，這個時候需要加入降級來保證可用性
（2）向服務端注冊
（1）客戶端通過http請求將 “服務名稱”+“ip”+"端口號"（instance）發送給服務端（post請求，參數
為InstanceInfo）
（2）服務端存儲信息並將這些信息同步給其它Eureka服務器
注：注冊傳的是instanceInfo。
-- 服務端根據appName、instanceInfo獲取Instance
-- 對比同一instanceInfo節點下的的的節點（服務端存儲的和客戶端新傳過去的）的時間戳誰
的比較新，將較新節點的存儲到緩存中（gMap）。
注意：客戶端創建的節點是臨時節點。
（3）對比時間戳，得到一個真正的instanceinfo
服務端處理Instance源碼：
AbstractInstanceRegistry.java
1 public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) { 2 try { 3 this.read.lock(); 4 Map<String, Lease<InstanceInfo>> gMap = (Map)this.registry.get(registrant.getAppName()); 5 EurekaMonitors.REGISTER.increment(isReplication); 6 if (gMap == null) { 7 ConcurrentHashMap<String, Lease<InstanceInfo>> gNewMap = new ConcurrentHashMap(); 8 gMap = (Map)this.registry.putIfAbsent(registrant.getAppName(), gNewMap); 9 if (gMap == null) { 10 gMap = gNewMap; 11 } 12 } 13 14 Lease<InstanceInfo> existingLease = (Lease)((Map)gMap).get(registrant.getId()); 15 if (existingLease != null && existingLease.getHolder() != null) { 16 Long existingLastDirtyTimestamp = ((InstanceInfo)existingLease.getHolder()).getLastDirtyTimestamp(); 17 Long registrationLastDirtyTimestamp = registrant.getLastDirtyTimestamp(); 18 logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp); 19 if (existingLastDirtyTimestamp > registrationLastDirtyTimestamp) { 20 logger.warn("There is an existing lease and the existing lease's dirty timestamp {} is greater than the one that is being registered {}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp); 21 logger.warn("Using the existing instanceInfo instead of the new instanceInfo as the registrant"); 22 registrant = (InstanceInfo)existingLease.getHolder(); 23 } 24 } else { 25 Object var6 = this.lock; 26 synchronized(this.lock) { 27 if (this.expectedNumberOfRenewsPerMin > 0) { 28 this.expectedNumberOfRenewsPerMin += 2; 29 this.numberOfRenewsPerMinThreshold = (int)((double)this.expectedNumberOfRenewsPerMin * this.serverConfig.getRenewalPercentThreshold()); 30 } 31 } 32 33 logger.debug("No previous lease information found; it is new registration"); 34 } 35 36 Lease<InstanceInfo> lease = new Lease(registrant, leaseDuration); 37 if (existingLease != null) { 38 lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp()); 39 } 40 41 ((Map)gMap).put(registrant.getId(), lease); 42 AbstractInstanceRegistry.CircularQueue var20 = this.recentRegisteredQueue; 43 synchronized(this.recentRegisteredQueue) { 44 this.recentRegisteredQueue.add(new Pair(System.currentTimeMillis(), registrant.getAppName() + "(" + registrant.getId() + ")")); 45 } 46 47 if (!InstanceStatus.UNKNOWN.equals(registrant.getOverriddenStatus())) { 48 logger.debug("Found overridden status {} for instance {}. Checking to see if needs to be add to the overrides", registrant.getOverriddenStatus(), registrant.getId()); 49 if (!this.overriddenInstanceStatusMap.containsKey(registrant.getId())) { 50 logger.info("Not found overridden id {} and hence adding it", registrant.getId()); 51 this.overriddenInstanceStatusMap.put(registrant.getId(), registrant.getOverriddenStatus()); 52 } 53 } 54 55 InstanceStatus overriddenStatusFromMap = (InstanceStatus)this.overriddenInstanceStatusMap.get(registrant.getId()); 56 if (overriddenStatusFromMap != null) { 57 logger.info("Storing overridden status {} from map", overriddenStatusFromMap); 58 registrant.setOverriddenStatus(overriddenStatusFromMap); 59 } 60 61 InstanceStatus overriddenInstanceStatus = this.getOverriddenInstanceStatus(registrant, existingLease, isReplication); 62 registrant.setStatusWithoutDirty(overriddenInstanceStatus); 63 if (InstanceStatus.UP.equals(registrant.getStatus())) { 64 lease.serviceUp(); 65 } 66 67 registrant.setActionType(ActionType.ADDED); 68 this.recentlyChangedQueue.add(new AbstractInstanceRegistry.RecentlyChangedItem(lease)); 69 registrant.setLastUpdatedTimestamp(); 70 this.invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress()); 71 logger.info("Registered instance {}/{} with status {} (replication={})", new Object[]{registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication}); 72 } finally { 73 this.read.unlock(); 74 } 75 76 }
（3）心跳
（a）客戶端向服務端發送http請求（參數包括appName，instanceInfo）
源代碼：
AbstractJerseyEurekaHttpClient.java
public EurekaHttpResponse<InstanceInfo> sendHeartBeat(String appName, String id, InstanceInfo info, InstanceStatus overriddenStatus) { String urlPath = "apps/" + appName + '/' + id; ClientResponse response = null; EurekaHttpResponse var10; try { WebResource webResource = this.jerseyClient.resource(this.serviceUrl).path(urlPath).queryParam("status", info.getStatus().toString()).queryParam("lastDirtyTimestamp", info.getLastDirtyTimestamp().toString()); if (overriddenStatus != null) { webResource = webResource.queryParam("overriddenstatus", overriddenStatus.name()); } Builder requestBuilder = webResource.getRequestBuilder(); this.addExtraHeaders(requestBuilder); response = (ClientResponse)requestBuilder.put(ClientResponse.class); EurekaHttpResponseBuilder<InstanceInfo> eurekaResponseBuilder = EurekaHttpResponse.anEurekaHttpResponse(response.getStatus(), InstanceInfo.class).headers(headersOf(response)); if (response.hasEntity()) { eurekaResponseBuilder.entity(response.getEntity(InstanceInfo.class)); } var10 = eurekaResponseBuilder.build(); } finally { if (logger.isDebugEnabled()) { logger.debug("Jersey HTTP PUT {}/{}; statusCode={}", new Object[]{this.serviceUrl, urlPath, response == null ? "N/A" : response.getStatus()}); } if (response != null) { response.close(); } } return var10; }
（b）服務端接收到請求，進行續約並同步給其它Eureka
-- 判斷實例是否存在，如果存在就進行續約，如果不存在續約失敗
-- 續約（更新時間戳lastUpdateTimestamp）
（c）更新時間戳完成續約
續約源代碼：Lease.java
public void renew() { this.lastUpdateTimestamp = System.currentTimeMillis() + this.duration; }
（4）服務下線
（a）客戶端停掉初始化時創建的定時任務
（b）向服務端發送http請求
（c）服務端執行下線並復制給其它的Eureka
下線其實就是把gMap中需要移除的實例設置一個被移除的時間戳。
下線源代碼：Lease.java
public void cancel() { if (this.evictionTimestamp <= 0L) { this.evictionTimestamp = System.currentTimeMillis(); } }
（d）通過租約超時來判斷超時，代碼
public boolean isExpired(long additionalLeaseMs) { return this.evictionTimestamp > 0L || System.currentTimeMillis() > this.lastUpdateTimestamp + this.duration + additionalLeaseMs; }
二 Ribbon
1. 一些分析
增加@LoadBalance注解其實是為RestTemplate添加了一個LoadBalancerInterceptor攔
截器。
注：是在原來的攔截器基礎上在增加一個一個攔截器。
其思路是將原來：http://eureka-provider/order/...請求改成實際：
http://localhost:8081/order/...的請求
（1）通過查找LoadBalanced在哪里用過，找到類LoadBalancerAutoConfiguration.java
關鍵代碼在LoadBalancerAutoConfiguration.java的內之類
LoadBalancerInterceptorConfig中，關鍵代碼如下：
3 static class LoadBalancerInterceptorConfig { 4 LoadBalancerInterceptorConfig() { 5 } 6 7 @Bean 8 public LoadBalancerInterceptor ribbonInterceptor(LoadBalancerClient loadBalancerClient, LoadBalancerRequestFactory requestFactory) { 9 return new LoadBalancerInterceptor(loadBalancerClient, requestFactory); 10 } 11 12 @Bean 13 @ConditionalOnMissingBean 14 public RestTemplateCustomizer restTemplateCustomizer(final LoadBalancerInterceptor loadBalancerInterceptor) { 15 return new RestTemplateCustomizer() { 16 public void customize(RestTemplate restTemplate) { 17 List<ClientHttpRequestInterceptor> list = new ArrayList(restTemplate.getInterceptors());
//在原來的攔截器基礎上在增加一個loadBalancerInterceptor
18 list.add(loadBalancerInterceptor); 19 restTemplate.setInterceptors(list); 20 } 21 }; 22 } 23 }
可見，它拿到原來的Interceptors加入原來的Interceptors中。
（2）而LoadBalancerInterceptor 實際上是 ClientHttpRequestInterceptor的實現類，源
代碼，LoadBalancerInterceptor .java：
1 // 2 // Source code recreated from a .class file by IntelliJ IDEA 3 // (powered by Fernflower decompiler) 4 // 5 6 package org.springframework.cloud.client.loadbalancer; 7 8 import java.io.IOException; 9 import java.net.URI; 10 import org.springframework.http.HttpRequest; 11 import org.springframework.http.client.ClientHttpRequestExecution; 12 import org.springframework.http.client.ClientHttpRequestInterceptor; 13 import org.springframework.http.client.ClientHttpResponse; 14 import org.springframework.util.Assert; 15 16 public class LoadBalancerInterceptor implements ClientHttpRequestInterceptor { 17 private LoadBalancerClient loadBalancer; 18 private LoadBalancerRequestFactory requestFactory; 19 20 public LoadBalancerInterceptor(LoadBalancerClient loadBalancer, LoadBalancerRequestFactory requestFactory) { 21 this.loadBalancer = loadBalancer; 22 this.requestFactory = requestFactory; 23 } 24 25 public LoadBalancerInterceptor(LoadBalancerClient loadBalancer) { 26 this(loadBalancer, new LoadBalancerRequestFactory(loadBalancer)); 27 } 28 29 public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException { 30 URI originalUri = request.getURI(); 31 String serviceName = originalUri.getHost(); 32 Assert.state(serviceName != null, "Request URI does not contain a valid hostname: " + originalUri); 33 return (ClientHttpResponse)this.loadBalancer.execute(serviceName, this.requestFactory.createRequest(request, body, execution)); 34 } 35 }
標紅的方法為關鍵方法，它是攔截器的和心類。
下面我們需要關注一下：LoadBalancerInterceptor.java是如何處理服務調用的
（3）debug跟入queryForObject()；發現真正執行代碼為：
1 public ClientHttpResponse execute(HttpRequest request, final byte[] body) throws IOException { 2 if (this.iterator.hasNext()) { 3 ClientHttpRequestInterceptor nextInterceptor = (ClientHttpRequestInterceptor)this.iterator.next();
4 return nextInterceptor.intercept(request, body, this); 5 } else { 6 ClientHttpRequest delegate = InterceptingClientHttpRequest.this.requestFactory.createRequest(request.getURI(), request.getMethod()); 7 Iterator var4 = request.getHeaders().entrySet().iterator(); 8 9 while(var4.hasNext()) { 10 Entry<String, List<String>> entry = (Entry)var4.next(); 11 List<String> values = (List)entry.getValue(); 12 Iterator var7 = values.iterator(); 13 14 while(var7.hasNext()) { 15 String value = (String)var7.next(); 16 delegate.getHeaders().add((String)entry.getKey(), value); 17 } 18 } 19 20 if (body.length > 0) { 21 if (delegate instanceof StreamingHttpOutputMessage) { 22 StreamingHttpOutputMessage streamingOutputMessage = (StreamingHttpOutputMessage)delegate; 23 streamingOutputMessage.setBody(new Body() { 24 public void writeTo(OutputStream outputStream) throws IOException { 25 StreamUtils.copy(body, outputStream); 26 } 27 }); 28 } else { 29 StreamUtils.copy(body, delegate.getBody()); 30 } 31 } 32 33 return delegate.execute(); 34 } 35 }
其中標紅的代碼為關鍵代碼。通過debug發現，nextInterceptor真正的實現是一個
LoadBalancerInterceptor，所以nextInterceptor.intercept實際執行代碼是
LoadBalancerInterceptor.java中的public ClientHttpResponse intercept(
HttpRequest request, byte[] body,ClientHttpRequestExecution execution) throws
IOException方法（該方法很熟悉吧，在上面的筆記中出現過）
1 public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException { 2 URI originalUri = request.getURI(); 3 String serviceName = originalUri.getHost(); 4 Assert.state(serviceName != null, "Request URI does not contain a valid hostname: " + originalUri); 5 return (ClientHttpResponse)this.loadBalancer.execute(serviceName, this.requestFactory.createRequest(request, body, execution)); 6 }
loadBalancer的實現類是RibbonLoadBalancerClient，RibbonLoadBalancerClient才
是真正客戶端負載均衡的實現類
（4）進入execute方法（真正的boss）：
1 public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
//拿到可用的服務列表 2 ILoadBalancer loadBalancer = this.getLoadBalancer(serviceId);
//通過一定算法得到一個服務 3 Server server = this.getServer(loadBalancer); 4 if (server == null) { 5 throw new IllegalStateException("No instances available for " + serviceId); 6 } else { 7 RibbonLoadBalancerClient.RibbonServer ribbonServer = new RibbonLoadBalancerClient.RibbonServer(serviceId, server, this.isSecure(server, serviceId), this.serverIntrospector(serviceId).getMetadata(server)); 8 return this.execute(serviceId, ribbonServer, request); 9 } 10 }
通過debug觀察，發現serviceId是“eureka-provider”，debug進入this.getLoadBalancer，
多進幾層，發現最終執行代碼：
1 public <C> C getInstance(String name, Class<C> type) { 2 C instance = super.getInstance(name, type); 3 if (instance != null) { 4 return instance; 5 } else { 6 IClientConfig config = (IClientConfig)this.getInstance(name, IClientConfig.class); 7 return instantiateWithConfig(this.getContext(name), type, config); 8 } 9 }
name的值是服務名稱，這里是eureka-provider，其實這一步說白了就是根據服務
名稱獲取例如http://ip+端口的形式
this.getLoadBalancedIntercept的返回值
DynamicServerListLoadBalancer:{ NFLoadBalancer: name = eureka - provider, current list of Servers = [localhost: 8072, localhost: 8071], Load balancer stats = Zone stats: { unknown = [Zone: unknown;Instance count: 2;Active connections count: 0;Circuit breaker tripped count: 0;Active connections per server: 0.0;] }, Server stats: [ [Server: localhost: 8072;Zone: UNKNOWN;Total Requests: 0;Successive connection failure: 0;Total blackout seconds: 0;Last connection made: Thu Jan 01 08: 00: 00 CST 1970;First connection made: Thu Jan 01 08: 00: 00 CST 1970;Active Connections: 0;total failure count in last(1000) msecs: 0;average resp time: 0.0;90 percentile resp time: 0.0;95 percentile resp time: 0.0;min resp time: 0.0;max resp time: 0.0;stddev resp time: 0.0], [Server: localhost: 8071;Zone: UNKNOWN;Total Requests: 0;Successive connection failure: 0;Total blackout seconds: 0;Last connection made: Thu Jan 01 08: 00: 00 CST 1970;First connection made: Thu Jan 01 08: 00: 00 CST 1970;Active Connections: 0;total failure count in last(1000) msecs: 0;average resp time: 0.0;90 percentile resp time: 0.0;95 percentile resp time: 0.0;min resp time: 0.0;max resp time: 0.0;stddev resp time: 0.0] ] }ServerList:com.netflix.loadbalancer.ConfigurationBasedServerList@5353dd09
進入（4）中的 public <T> T execute(String serviceId,
LoadBalancerRequest<T> request) throws IOException方法，其執行
的方法為：
1 protected Server getServer(ILoadBalancer loadBalancer) { 2 return loadBalancer == null ? null : loadBalancer.chooseServer("default"); 3 }
debug進入loadBalancer.chooseServer("default");發現執行的方法為：
1 public Server chooseServer(Object key) { 2 if (this.counter == null) { 3 this.counter = this.createCounter(); 4 } 5 6 this.counter.increment(); 7 if (this.rule == null) { 8 return null; 9 } else { 10 try { 11 return this.rule.choose(key); 12 } catch (Exception var3) { 13 logger.warn("LoadBalancer [{}]: Error choosing server for key {}", new Object[]{this.name, key, var3}); 14 return null; 15 } 16 } 17 }
rule就是負載均衡的策略，rule的裝載代碼：
1 @Bean 2 @ConditionalOnMissingBean 3 public IRule ribbonRule(IClientConfig config) { 4 if (this.propertiesFactory.isSet(IRule.class, this.name)) { 5 return (IRule)this.propertiesFactory.get(IRule.class, config, this.name); 6 } else { 7 ZoneAvoidanceRule rule = new ZoneAvoidanceRule(); 8 rule.initWithNiwsConfig(config); 9 return rule; 10 } 11
@ConditionalOnMissingBean，如果不存在就走方法中的代碼，也就是說當自己
實例化一個rule的時候就不會裝載默認的rule了
執行流程：
（1）根據serviceId（服務名）獲取LoadBalancer，LoadBalancer中包含了機器的IP、端口
號等信息機器的IP、端口號信息（json）：
```properties DynamicServerListLoadBalancer:{ NFLoadBalancer: name = eureka - provider, current list of Servers = [localhost: 8072, localhost: 8071], Load balancer stats = Zone stats: { unknown = [Zone: unknown;Instance count: 2;Active connections count: 0;Circuit breaker tripped count: 0;Active connections per server: 0.0;] }, Server stats: [ [Server: localhost: 8072;Zone: UNKNOWN;Total Requests: 0;Successive connection failure: 0;Total blackout seconds: 0;Last connection made: Thu Jan 01 08: 00: 00 CST 1970;First connection made: Thu Jan 01 08: 00: 00 CST 1970;Active Connections: 0;total failure count in last(1000) msecs: 0;average resp time: 0.0;90 percentile resp time: 0.0;95 percentile resp time: 0.0;min resp time: 0.0;max resp time: 0.0;stddev resp time: 0.0], [Server: localhost: 8071;Zone: UNKNOWN;Total Requests: 0;Successive connection failure: 0;Total blackout seconds: 0;Last connection made: Thu Jan 01 08: 00: 00 CST 1970;First connection made: Thu Jan 01 08: 00: 00 CST 1970;Active Connections: 0;total failure count in last(1000) msecs: 0;average resp time: 0.0;90 percentile resp time: 0.0;95 percentile resp time: 0.0;min resp time: 0.0;max resp time: 0.0;stddev resp time: 0.0] ] }ServerList:com.netflix.loadbalancer.ConfigurationBasedServerList@5353dd09
（2）根據LoadBalance獲取一個Server（負載均衡），在這里調用了rule，如果沒有rule，
則使用默認的，調用
源代碼，RibbonLoadBalancerClient.java
public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException { ILoadBalancer loadBalancer = this.getLoadBalancer(serviceId); Server server = this.getServer(loadBalancer); if (server == null) { throw new IllegalStateException("No instances available for " + serviceId); } else { RibbonLoadBalancerClient.RibbonServer ribbonServer = new RibbonLoadBalancerClient.RibbonServer(serviceId, server, this.isSecure(server, serviceId), this.serverIntrospector(serviceId).getMetadata(server)); return this.execute(serviceId, ribbonServer, request); } }
調用rule的源代碼，BaseLoadBalancer.java
public Server chooseServer(Object key) { if (this.counter == null) { this.counter = this.createCounter(); } this.counter.increment(); if (this.rule == null) { return null; } else { try { return this.rule.choose(key); } catch (Exception var3) { logger.warn("LoadBalancer [{}]: Error choosing server for key {}", new Object[]{this.name, key, var3}); return null; } } }
服務降級式應該考慮業務是否能夠降級，有的業務流量不能降級有的業務流程是可以降級的
//在原來的攔截器基礎上在增加一個loadBalancerInterceptor