Talk about eureka server’s instance Registration and Metadata Change Interface

  springcloud

Order

This article mainly studies the instance registration and metadata change interface of eureka server.

ApplicationResource.addInstance

eureka-core-1.8.8-sources.jar! /com/netflix/eureka/resources/ApplicationResource.java

    @POST
    @Consumes({"application/json", "application/xml"})
    public Response addInstance(InstanceInfo info,
                                @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
        logger.debug("Registering instance {} (replication={})", info.getId(), isReplication);
        // validate that the instanceinfo contains all the necessary required fields
        if (isBlank(info.getId())) {
            return Response.status(400).entity("Missing instanceId").build();
        } else if (isBlank(info.getHostName())) {
            return Response.status(400).entity("Missing hostname").build();
        } else if (isBlank(info.getIPAddr())) {
            return Response.status(400).entity("Missing ip address").build();
        } else if (isBlank(info.getAppName())) {
            return Response.status(400).entity("Missing appName").build();
        } else if (!appName.equals(info.getAppName())) {
            return Response.status(400).entity("Mismatched appName, expecting " + appName + " but was " + info.getAppName()).build();
        } else if (info.getDataCenterInfo() == null) {
            return Response.status(400).entity("Missing dataCenterInfo").build();
        } else if (info.getDataCenterInfo().getName() == null) {
            return Response.status(400).entity("Missing dataCenterInfo Name").build();
        }

        // handle cases where clients may be registering with bad DataCenterInfo with missing data
        DataCenterInfo dataCenterInfo = info.getDataCenterInfo();
        if (dataCenterInfo instanceof UniqueIdentifier) {
            String dataCenterInfoId = ((UniqueIdentifier) dataCenterInfo).getId();
            if (isBlank(dataCenterInfoId)) {
                boolean experimental = "true".equalsIgnoreCase(serverConfig.getExperimental("registration.validation.dataCenterInfoId"));
                if (experimental) {
                    String entity = "DataCenterInfo of type " + dataCenterInfo.getClass() + " must contain a valid id";
                    return Response.status(400).entity(entity).build();
                } else if (dataCenterInfo instanceof AmazonInfo) {
                    AmazonInfo amazonInfo = (AmazonInfo) dataCenterInfo;
                    String effectiveId = amazonInfo.get(AmazonInfo.MetaDataKey.instanceId);
                    if (effectiveId == null) {
                        amazonInfo.getMetadata().put(AmazonInfo.MetaDataKey.instanceId.getName(), info.getId());
                    }
                } else {
                    logger.warn("Registering DataCenterInfo of type {} without an appropriate id", dataCenterInfo.getClass());
                }
            }
        }

        registry.register(info, "true".equals(isReplication));
        return Response.status(204).build();  // 204 to be backwards compatible
    }

This is the server-side processing logic for registering application instances

Example

curl -i -H "Content-Type: application/json"  -H "Accept-Encoding: gzip" -X POST -d '{
  "instance": {
    "instanceId": "test1",
    "app": "test-service",
    "appGroupName": null,
    "ipAddr": "127.0.0.1",
    "sid": "na",
    "homePageUrl": null,
    "statusPageUrl": null,
    "healthCheckUrl": null,
    "secureHealthCheckUrl": null,
    "vipAddress": "test-service",
    "secureVipAddress": "test-service",
    "countryId": 1,
    "dataCenterInfo": {
      "@class": "com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo",
      "name": "MyOwn"
    },
    "hostName": "127.0.0.1",
    "status": "UP",
    "leaseInfo": null,
    "isCoordinatingDiscoveryServer": false,
    "lastUpdatedTimestamp": 1525661162147,
    "lastDirtyTimestamp": 1525661162147,
    "actionType": null,
    "asgName": null,
    "overridden_status": "UNKNOWN",
    "port": {
      "$": 9090,
      "@enabled": "true"
    },
    "securePort": {
      "$": 7002,
      "@enabled": "false"
    },
    "metadata": {
      "@class": "java.util.Collections$EmptyMap"
    }
  }
}' http://localhost:8761/eureka/apps/test-service

Return

HTTP/1.1 204
Content-Type: application/xml
Date: Mon, 07 May 2018 03:01:23 GMT

InstanceResource.updateMetadata

eureka-core-1.8.8-sources.jar! /com/netflix/eureka/resources/InstanceResource.java

    @PUT
    @Path("metadata")
    public Response updateMetadata(@Context UriInfo uriInfo) {
        try {
            InstanceInfo instanceInfo = registry.getInstanceByAppAndId(app.getName(), id);
            // ReplicationInstance information is not found, generate an error
            if (instanceInfo == null) {
                logger.error("Cannot find instance while updating metadata for instance {}", id);
                return Response.serverError().build();
            }
            MultivaluedMap<String, String> queryParams = uriInfo.getQueryParameters();
            Set<Entry<String, List<String>>> entrySet = queryParams.entrySet();
            Map<String, String> metadataMap = instanceInfo.getMetadata();
            // Metadata map is empty - create a new map
            if (Collections.emptyMap().getClass().equals(metadataMap.getClass())) {
                metadataMap = new ConcurrentHashMap<String, String>();
                InstanceInfo.Builder builder = new InstanceInfo.Builder(instanceInfo);
                builder.setMetadata(metadataMap);
                instanceInfo = builder.build();
            }
            // Add all the user supplied entries to the map
            for (Entry<String, List<String>> entry : entrySet) {
                metadataMap.put(entry.getKey(), entry.getValue().get(0));
            }
            registry.register(instanceInfo, false);
            return Response.ok().build();
        } catch (Throwable e) {
            logger.error("Error updating metadata for instance {}", id, e);
            return Response.serverError().build();
        }

    }

This is the server-side processing logic to change meta

Example

curl -i -X PUT http://localhost:8761/eureka/apps/test-service/test1/metadata?env=prod

Return

HTTP/1.1 200
Content-Type: application/xml
Content-Length: 0
Date: Mon, 07 May 2018 03:03:37 GMT

Summary

  • POST /eureka/apps/{appId}

Instance information can be registered/updated

  • PUT /eureka/apps/{appId}/{instanceId}/metadata? metaKey1=metaValue1

Can be used to update meta information

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