SpringCloud源码剖析-Eureka Server服务注册表拉取

/**返回所有的应用* Get information about all {@link com.netflix.discovery.shared.Applications}.*/@GETpublicResponsegetContainers(@PathParam("version") Stringversion,
@HeaderParam(HEADER_ACCEPT) StringacceptHeader,
@HeaderParam(HEADER_ACCEPT_ENCODING) StringacceptEncoding,
@HeaderParam(EurekaAccept.HTTP_X_EUREKA_ACCEPT) StringeurekaAccept,
@ContextUriInfouriInfo,
@Nullable@QueryParam("regions") StringregionsStr) {
booleanisRemoteRegionRequested=null!=regionsStr&&!regionsStr.isEmpty();
String[] regions=null;
if (!isRemoteRegionRequested) {
//注册表全量拉取统计计数增加EurekaMonitors.GET_ALL.increment();
    } else {
regions=regionsStr.toLowerCase().split(",");
Arrays.sort(regions); // So we don't have different caches for same regions queried in different order.EurekaMonitors.GET_ALL_WITH_REMOTE_REGIONS.increment();
    }
// Check if the server allows the access to the registry. The server can// restrict access if it is not// ready to serve traffic depending on various reasons.//检查服务端时候准备好可以被访问if (!registry.shouldAllowAccess(isRemoteRegionRequested)) {
returnResponse.status(Status.FORBIDDEN).build();
    }
CurrentRequestVersion.set(Version.toEnum(version));
//处理返回的数据类型默认JSONKeyTypekeyType=Key.KeyType.JSON;
StringreturnMediaType=MediaType.APPLICATION_JSON;
if (acceptHeader==null||!acceptHeader.contains(HEADER_JSON_VALUE)) {
//请求头么有指定格式，返回XML格式keyType=Key.KeyType.XML;
returnMediaType=MediaType.APPLICATION_XML;
    }
//创建缓存keyKeycacheKey=newKey(Key.EntityType.Application,
ResponseCacheImpl.ALL_APPS,  //通过ALL_APPS构建key keyType, CurrentRequestVersion.get(), EurekaAccept.fromString(eurekaAccept), regions                          );
Responseresponse;
//这里判断是否是GZIP格式，返回结果的编码类型不一样，获取方式是一致的if (acceptEncoding!=null&&acceptEncoding.contains(HEADER_GZIP_VALUE)) {
//如果格式是gzip，调用responseCache.getGZIP(cacheKey)获取//底层会从一个ConcurrentMap<Key, Value> readOnlyCacheMap 只读缓存中去获取全量注册表response=Response.ok(responseCache.getGZIP(cacheKey))
            .header(HEADER_CONTENT_ENCODING, HEADER_GZIP_VALUE)
            .header(HEADER_CONTENT_TYPE, returnMediaType)
            .build();
    } else {
//普通获取responseCache.get(cacheKey)//底层会从一个ConcurrentMap<Key, Value> readOnlyCacheMap 只读缓存中去获取全量注册表response=Response.ok(responseCache.get(cacheKey))
            .build();
    }
returnresponse;
}

/*** Get the payload in both compressed and uncompressed form.*/@VisibleForTestingValuegetValue(finalKeykey, booleanuseReadOnlyCache) {
Valuepayload=null;
try {
if (useReadOnlyCache) {
//从只读缓存中获取finalValuecurrentPayload=readOnlyCacheMap.get(key);
if (currentPayload!=null) {
payload=currentPayload;
            } else {
//如果只读缓存中获取不到，从读写缓存中获取payload=readWriteCacheMap.get(key);
readOnlyCacheMap.put(key, payload);
            }
        } else {
payload=readWriteCacheMap.get(key);
        }
    } catch (Throwablet) {
logger.error("Cannot get value for key : {}", key, t);
    }
returnpayload;
}

/**获取Applications服务注册表中有改变的服务，注册，取消，状态更改和过期都会造成服务的改变* Get information about all delta changes in {@link com.netflix.discovery.shared.Applications}.** <p>* The delta changes represent the registry information change for a period* as configured by* {@link EurekaServerConfig#getRetentionTimeInMSInDeltaQueue()}. The* changes that can happen in a registry include* <em>Registrations,Cancels,Status Changes and Expirations</em>. Normally* the changes to the registry are infrequent and hence getting just the* delta will be much more efficient than getting the complete registry.* </p>** <p>* Since the delta information is cached over a period of time, the requests* may return the same data multiple times within the window configured by* {@link EurekaServerConfig#getRetentionTimeInMSInDeltaQueue()}.The clients* are expected to handle this duplicate information.* <p>** @param version the version of the request.* @param acceptHeader the accept header to indicate whether to serve  JSON or XML data.* @param acceptEncoding the accept header to indicate whether to serve compressed or uncompressed data.* @param eurekaAccept an eureka accept extension, see {@link com.netflix.appinfo.EurekaAccept}* @param uriInfo  the {@link java.net.URI} information of the request made.* @return response containing the delta information of the*         {@link AbstractInstanceRegistry}.*/@Path("delta")
@GETpublicResponsegetContainerDifferential(
@PathParam("version") Stringversion,
@HeaderParam(HEADER_ACCEPT) StringacceptHeader,
@HeaderParam(HEADER_ACCEPT_ENCODING) StringacceptEncoding,
@HeaderParam(EurekaAccept.HTTP_X_EUREKA_ACCEPT) StringeurekaAccept,
@ContextUriInfouriInfo, @Nullable@QueryParam("regions") StringregionsStr) {
booleanisRemoteRegionRequested=null!=regionsStr&&!regionsStr.isEmpty();
// If the delta flag is disabled in discovery or if the lease expiration// has been disabled, redirect clients to get all instances//如果禁用了Delta注册表差异化拉取，或者服务不可访问，返回拒绝if ((serverConfig.shouldDisableDelta()) || (!registry.shouldAllowAccess(isRemoteRegionRequested))) {
returnResponse.status(Status.FORBIDDEN).build();
    }
String[] regions=null;
if (!isRemoteRegionRequested) {
EurekaMonitors.GET_ALL_DELTA.increment();
    } else {
regions=regionsStr.toLowerCase().split(",");
Arrays.sort(regions); // So we don't have different caches for same regions queried in different order.EurekaMonitors.GET_ALL_DELTA_WITH_REMOTE_REGIONS.increment();
    }
CurrentRequestVersion.set(Version.toEnum(version));
//处理反会的数据格式JSON默认KeyTypekeyType=Key.KeyType.JSON;
StringreturnMediaType=MediaType.APPLICATION_JSON;
if (acceptHeader==null||!acceptHeader.contains(HEADER_JSON_VALUE)) {
keyType=Key.KeyType.XML;
returnMediaType=MediaType.APPLICATION_XML;
    }
//构建缓存keyKeycacheKey=newKey(Key.EntityType.Application,
ResponseCacheImpl.ALL_APPS_DELTA,    //通过ALL_APPS_DELTA构建key keyType, CurrentRequestVersion.get(), EurekaAccept.fromString(eurekaAccept), regions                          );
if (acceptEncoding!=null&&acceptEncoding.contains(HEADER_GZIP_VALUE)) {
//从responseCache获取内容returnResponse.ok(responseCache.getGZIP(cacheKey))
            .header(HEADER_CONTENT_ENCODING, HEADER_GZIP_VALUE)
            .header(HEADER_CONTENT_TYPE, returnMediaType)
            .build();
    } else {
returnResponse.ok(responseCache.get(cacheKey))
            .build();
    }
}