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本文主要研究一下eureka instance的lastDirtyTimestamp

server端

• lastDirtyTimestamp last timestamp when this instance information was updated.

即该instance在client端最后被修改的时间戳

instance的接口，除了更新meta以及cancelLease操作外，其他修改的操作都要带上lastDirtyTimestamp，比如 eureka-core-1.8.8-sources.jar!/com/netflix/eureka/resources/InstanceResource.java

@PUT    public Response renewLease(            @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,            @QueryParam("overriddenstatus") String overriddenStatus,            @QueryParam("status") String status,            @QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {        //......    }    @PUT    @Path("status")    public Response statusUpdate(            @QueryParam("value") String newStatus,            @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,            @QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {        //......    }    @DELETE    @Path("status")    public Response deleteStatusUpdate(            @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,            @QueryParam("value") String newStatusValue,            @QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {        //......    }

除renewLease外，其他两个的lastDirtyTimestamp仅仅是用来做传递用。

renewLease

@PUT    public Response renewLease(            @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,            @QueryParam("overriddenstatus") String overriddenStatus,            @QueryParam("status") String status,            @QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {        boolean isFromReplicaNode = "true".equals(isReplication);        boolean isSuccess = registry.renew(app.getName(), id, isFromReplicaNode);        // Not found in the registry, immediately ask for a register        if (!isSuccess) {            logger.warn("Not Found (Renew): {} - {}", app.getName(), id);            return Response.status(Status.NOT_FOUND).build();        }        // Check if we need to sync based on dirty time stamp, the client        // instance might have changed some value        Response response = null;        if (lastDirtyTimestamp != null && serverConfig.shouldSyncWhenTimestampDiffers()) {            response = this.validateDirtyTimestamp(Long.valueOf(lastDirtyTimestamp), isFromReplicaNode);            // Store the overridden status since the validation found out the node that replicates wins            if (response.getStatus() == Response.Status.NOT_FOUND.getStatusCode()                    && (overriddenStatus != null)                    && !(InstanceStatus.UNKNOWN.name().equals(overriddenStatus))                    && isFromReplicaNode) {                registry.storeOverriddenStatusIfRequired(app.getAppName(), id, InstanceStatus.valueOf(overriddenStatus));            }        } else {            response = Response.ok().build();        }        logger.debug("Found (Renew): {} - {}; reply status={}", app.getName(), id, response.getStatus());        return response;    }

如果renew不成功，则返回404，client端则会执行register逻辑 如果renew成功，且lastDirtyTimestamp不为null，则判断是否需要SyncWhenTimestampDiffers，默认true

validateDirtyTimestamp

private Response validateDirtyTimestamp(Long lastDirtyTimestamp,                                            boolean isReplication) {        InstanceInfo appInfo = registry.getInstanceByAppAndId(app.getName(), id, false);        if (appInfo != null) {            if ((lastDirtyTimestamp != null) && (!lastDirtyTimestamp.equals(appInfo.getLastDirtyTimestamp()))) {                Object[] args = {id, appInfo.getLastDirtyTimestamp(), lastDirtyTimestamp, isReplication};                if (lastDirtyTimestamp > appInfo.getLastDirtyTimestamp()) {                    logger.debug(                            "Time to sync, since the last dirty timestamp differs -"                                    + " ReplicationInstance id : {},Registry : {} Incoming: {} Replication: {}",                            args);                    return Response.status(Status.NOT_FOUND).build();                } else if (appInfo.getLastDirtyTimestamp() > lastDirtyTimestamp) {                    // In the case of replication, send the current instance info in the registry for the                    // replicating node to sync itself with this one.                    if (isReplication) {                        logger.debug(                                "Time to sync, since the last dirty timestamp differs -"                                        + " ReplicationInstance id : {},Registry : {} Incoming: {} Replication: {}",                                args);                        return Response.status(Status.CONFLICT).entity(appInfo).build();                    } else {                        return Response.ok().build();                    }                }            }        }        return Response.ok().build();    }

如果lastDirtyTimestamp参数大于server本地instance的lastDirtyTimestamp值，则response返回404； 如果是server本地大于lastDirtyTimestamp参数，不是replication模式则返回200，replication模式，则返回409 Conflict，让调用方同步自己的数据。

PeerEurekaNode

eureka-core-1.8.8-sources.jar!/com/netflix/eureka/cluster/PeerEurekaNode.java

/**     * Send the heartbeat information of an instance to the node represented by     * this class. If the instance does not exist the node, the instance     * registration information is sent again to the peer node.     *     * @param appName     *            the application name of the instance.     * @param id     *            the unique identifier of the instance.     * @param info     *            the instance info {@link InstanceInfo} of the instance.     * @param overriddenStatus     *            the overridden status information if any of the instance.     * @throws Throwable     */    public void heartbeat(final String appName, final String id,                          final InstanceInfo info, final InstanceStatus overriddenStatus,                          boolean primeConnection) throws Throwable {        if (primeConnection) {            // We do not care about the result for priming request.            replicationClient.sendHeartBeat(appName, id, info, overriddenStatus);            return;        }        ReplicationTask replicationTask = new InstanceReplicationTask(targetHost, Action.Heartbeat, info, overriddenStatus, false) {            @Override            public EurekaHttpResponse
    
      execute() throws Throwable {                return replicationClient.sendHeartBeat(appName, id, info, overriddenStatus);            }            @Override            public void handleFailure(int statusCode, Object responseEntity) throws Throwable {                super.handleFailure(statusCode, responseEntity);                if (statusCode == 404) {                    logger.warn("{}: missing entry.", getTaskName());                    if (info != null) {                        logger.warn("{}: cannot find instance id {} and hence replicating the instance with status {}",                                getTaskName(), info.getId(), info.getStatus());                        register(info);                    }                } else if (config.shouldSyncWhenTimestampDiffers()) {                    InstanceInfo peerInstanceInfo = (InstanceInfo) responseEntity;                    if (peerInstanceInfo != null) {                        syncInstancesIfTimestampDiffers(appName, id, info, peerInstanceInfo);                    }                }            }        };        long expiryTime = System.currentTimeMillis() + getLeaseRenewalOf(info);        batchingDispatcher.process(taskId("heartbeat", info), replicationTask, expiryTime);    }
    

这里的handleFailure，对于404的处理就是重新register；其他的就是诸如409的情况，先判断是否开启shouldSyncWhenTimestampDiffers配置，这个默认是true，然后将peer返回的最新info信息覆盖到本地

syncInstancesIfTimestampDiffers

/**     * Synchronize {@link InstanceInfo} information if the timestamp between     * this node and the peer eureka nodes vary.     */    private void syncInstancesIfTimestampDiffers(String appName, String id, InstanceInfo info, InstanceInfo infoFromPeer) {        try {            if (infoFromPeer != null) {                logger.warn("Peer wants us to take the instance information from it, since the timestamp differs,"                        + "Id : {} My Timestamp : {}, Peer's timestamp: {}", id, info.getLastDirtyTimestamp(), infoFromPeer.getLastDirtyTimestamp());                if (infoFromPeer.getOverriddenStatus() != null && !InstanceStatus.UNKNOWN.equals(infoFromPeer.getOverriddenStatus())) {                    logger.warn("Overridden Status info -id {}, mine {}, peer's {}", id, info.getOverriddenStatus(), infoFromPeer.getOverriddenStatus());                    registry.storeOverriddenStatusIfRequired(appName, id, infoFromPeer.getOverriddenStatus());                }                registry.register(infoFromPeer, true);            }        } catch (Throwable e) {            logger.warn("Exception when trying to set information from peer :", e);        }    }

这一段就是peerNode在replicate中遇到409的时候，根据返回的InstanceInfo覆盖本地的过程。

client端

eureka-client-1.8.8-sources.jar!/com/netflix/appinfo/InstanceInfo.java

/**     * Sets the dirty flag so that the instance information can be carried to     * the discovery server on the next heartbeat.     */    public synchronized void setIsDirty() {        isInstanceInfoDirty = true;        lastDirtyTimestamp = System.currentTimeMillis();    }

这个是更改lastDirtyTimestamp的基本方法，调用这个方法的其他方法如下：

@Deprecated    public void setSID(String sid) {        this.sid = sid;        setIsDirty();    }    /**     * Set the status for this instance.     *     * @param status status for this instance.     * @return the prev status if a different status from the current was set, null otherwise     */    public synchronized InstanceStatus setStatus(InstanceStatus status) {        if (this.status != status) {            InstanceStatus prev = this.status;            this.status = status;            setIsDirty();            return prev;        }        return null;    }    /**     * @param isDirty true if dirty, false otherwise.     * @deprecated use {@link #setIsDirty()} and {@link #unsetIsDirty(long)} to set and unset     * 
     * Sets the dirty flag so that the instance information can be carried to     * the discovery server on the next heartbeat.     */    @Deprecated    public synchronized void setIsDirty(boolean isDirty) {        if (isDirty) {            setIsDirty();        } else {            isInstanceInfoDirty = false;            // else don't update lastDirtyTimestamp as we are setting isDirty to false        }    }    /**     * Set the dirty flag, and also return the timestamp of the isDirty event     *     * @return the timestamp when the isDirty flag is set     */    public synchronized long setIsDirtyWithTime() {        setIsDirty();        return lastDirtyTimestamp;    }    /**     * Register application specific metadata to be sent to the discovery     * server.     *     * @param runtimeMetadata     *            Map containing key/value pairs.     */    synchronized void registerRuntimeMetadata(            Map
     
       runtimeMetadata) {        metadata.putAll(runtimeMetadata);        setIsDirty();    }
     

isInstanceInfoDirty

@JsonIgnore    public boolean isDirty() {        return isInstanceInfoDirty;    }    /**     * @return the lastDirtyTimestamp if is dirty, null otherwise.     */    public synchronized Long isDirtyWithTime() {        if (isInstanceInfoDirty) {            return lastDirtyTimestamp;        } else {            return null;        }    }    /**     * Unset the dirty flag iff the unsetDirtyTimestamp matches the lastDirtyTimestamp. No-op if     * lastDirtyTimestamp > unsetDirtyTimestamp     *     * @param unsetDirtyTimestamp the expected lastDirtyTimestamp to unset.     */    public synchronized void unsetIsDirty(long unsetDirtyTimestamp) {        if (lastDirtyTimestamp <= unsetDirtyTimestamp) {            isInstanceInfoDirty = false;        } else {        }    }

这个方法，如果lastDirtyTimestamp <= unsetDirtyTimestamp，则标识isInstanceInfoDirty为false

InstanceInfoReplicator

eureka-client-1.8.8-sources.jar!/com/netflix/discovery/InstanceInfoReplicator.java

public void run() {        try {            discoveryClient.refreshInstanceInfo();            Long dirtyTimestamp = instanceInfo.isDirtyWithTime();            if (dirtyTimestamp != null) {                discoveryClient.register();                instanceInfo.unsetIsDirty(dirtyTimestamp);            }        } catch (Throwable t) {            logger.warn("There was a problem with the instance info replicator", t);        } finally {            Future next = scheduler.schedule(this, replicationIntervalSeconds, TimeUnit.SECONDS);            scheduledPeriodicRef.set(next);        }    }

这里首先refreshInstanceInfo，之后判断如果是isInstanceInfoDirty则会执行register操作

refreshInstanceInfo

/**     * Refresh the current local instanceInfo. Note that after a valid refresh where changes are observed, the     * isDirty flag on the instanceInfo is set to true     */    void refreshInstanceInfo() {        applicationInfoManager.refreshDataCenterInfoIfRequired();        applicationInfoManager.refreshLeaseInfoIfRequired();        InstanceStatus status;        try {            status = getHealthCheckHandler().getStatus(instanceInfo.getStatus());        } catch (Exception e) {            logger.warn("Exception from healthcheckHandler.getStatus, setting status to DOWN", e);            status = InstanceStatus.DOWN;        }        if (null != status) {            applicationInfoManager.setInstanceStatus(status);        }    }

refreshDataCenterInfoIfRequired

eureka-client-1.8.8-sources.jar!/com/netflix/appinfo/ApplicationInfoManager.java

/**     * Refetches the hostname to check if it has changed. If it has, the entire     * DataCenterInfo is refetched and passed on to the eureka     * server on next heartbeat.     *     * see {@link InstanceInfo#getHostName()} for explanation on why the hostname is used as the default address     */    public void refreshDataCenterInfoIfRequired() {        String existingAddress = instanceInfo.getHostName();        String newAddress;        if (config instanceof RefreshableInstanceConfig) {            // Refresh data center info, and return up to date address            newAddress = ((RefreshableInstanceConfig) config).resolveDefaultAddress(true);        } else {            newAddress = config.getHostName(true);        }        String newIp = config.getIpAddress();        if (newAddress != null && !newAddress.equals(existingAddress)) {            logger.warn("The address changed from : {} => {}", existingAddress, newAddress);            // :( in the legacy code here the builder is acting as a mutator.            // This is hard to fix as this same instanceInfo instance is referenced elsewhere.            // We will most likely re-write the client at sometime so not fixing for now.            InstanceInfo.Builder builder = new InstanceInfo.Builder(instanceInfo);            builder.setHostName(newAddress).setIPAddr(newIp).setDataCenterInfo(config.getDataCenterInfo());            instanceInfo.setIsDirty();        }    }    public void refreshLeaseInfoIfRequired() {        LeaseInfo leaseInfo = instanceInfo.getLeaseInfo();        if (leaseInfo == null) {            return;        }        int currentLeaseDuration = config.getLeaseExpirationDurationInSeconds();        int currentLeaseRenewal = config.getLeaseRenewalIntervalInSeconds();        if (leaseInfo.getDurationInSecs() != currentLeaseDuration || leaseInfo.getRenewalIntervalInSecs() != currentLeaseRenewal) {            LeaseInfo newLeaseInfo = LeaseInfo.Builder.newBuilder()                    .setRenewalIntervalInSecs(currentLeaseRenewal)                    .setDurationInSecs(currentLeaseDuration)                    .build();            instanceInfo.setLeaseInfo(newLeaseInfo);            instanceInfo.setIsDirty();        }    }

从新刷新配置，如果有变更则instanceInfo.setIsDirty()

小结

在server端，处理renewLease的时候，对lastDirtyTimestamp参数进行判断，如果大于server本地instance的lastDirtyTimestamp值，则response返回404；如果是server本地大于lastDirtyTimestamp参数，不是replication模式则返回200，replication模式，则返回409 Conflict，让调用方同步自己的数据。

在client端，有两个属性，一个是lastDirtyTimestamp，一个是isInstanceInfoDirty。在更新instance的status的时候，会调用setIsDirty，即更新lastDirtyTimestamp以及设置isInstanceInfoDirty为true；然后client端还有个InstanceInfoReplicator定时任务，会定时读取配置文件，如果有变更则调用setIsDirty，之后是调用instanceInfo.isDirtyWithTime()，如果是dirty则会重新register并重置isInstanceInfoDirty，更新lastDirtyTimestamp。

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