15. Hystrix Timeouts And Ribbon Clients

When using Hystrix commands that wrap Ribbon clients you want to make sure your Hystrix timeout is configured to be longer than the configured Ribbon timeout, including any potential retries that might be made. For example, if your Ribbon connection timeout is one second and the Ribbon client might retry the request three times, than your Hystrix timeout should be slightly more than three seconds.

15.1 How to Include Hystrix Dashboard

To include the Hystrix Dashboard in your project use the starter with group org.springframework.cloud and artifact id spring-cloud-starter-hystrix-netflix-dashboard. See the Spring Cloud Project page for details on setting up your build system with the current Spring Cloud Release Train.

To run the Hystrix Dashboard annotate your Spring Boot main class with @EnableHystrixDashboard. You then visit /hystrix and point the dashboard to an individual instances /hystrix.stream endpoint in a Hystrix client application.

[Note]Note

When connecting to a /hystrix.stream endpoint which uses HTTPS the certificate used by the server must be trusted by the JVM. If the certificate is not trusted you must import the certificate into the JVM in order for the Hystrix Dashboard to make a successful connection to the stream endpoint.

15.2 Turbine

Looking at an individual instances Hystrix data is not very useful in terms of the overall health of the system. Turbine is an application that aggregates all of the relevant /hystrix.stream endpoints into a combined /turbine.stream for use in the Hystrix Dashboard. Individual instances are located via Eureka. Running Turbine is as simple as annotating your main class with the @EnableTurbine annotation (e.g. using spring-cloud-starter-netflix-turbine to set up the classpath). All of the documented configuration properties from the Turbine 1 wiki apply. The only difference is that the turbine.instanceUrlSuffix does not need the port prepended as this is handled automatically unless turbine.instanceInsertPort=false.

[Note]Note

By default, Turbine looks for the /hystrix.stream endpoint on a registered instance by looking up its hostName and port entries in Eureka, then appending /hystrix.stream to it. If the instance’s metadata contains management.port, it will be used instead of the port value for the /hystrix.stream endpoint. By default, metadata entry management.port is equal to the management.port configuration property, it can be overridden though with following configuration:

eureka:
  instance:
    metadata-map:
      management.port: ${management.port:8081}

The configuration key turbine.appConfig is a list of eureka serviceIds that turbine will use to lookup instances. The turbine stream is then used in the Hystrix dashboard using a url that looks like: http://my.turbine.sever:8080/turbine.stream?cluster=CLUSTERNAME (the cluster parameter can be omitted if the name is "default"). The cluster parameter must match an entry in turbine.aggregator.clusterConfig. Values returned from eureka are uppercase, thus we expect this example to work if there is an app registered with Eureka called "customers":

turbine:
  aggregator:
    clusterConfig: CUSTOMERS
  appConfig: customers

If you need to customize which cluster names should be used by Turbine (you don’t want to store cluster names in turbine.aggregator.clusterConfig configuration) provide a bean of type TurbineClustersProvider.

The clusterName can be customized by a SPEL expression in turbine.clusterNameExpression with root an instance of InstanceInfo. The default value is appName, which means that the Eureka serviceId ends up as the cluster key (i.e. the InstanceInfo for customers has an appName of "CUSTOMERS"). A different example would be turbine.clusterNameExpression=aSGName, which would get the cluster name from the AWS ASG name. Another example:

turbine:
  aggregator:
    clusterConfig: SYSTEM,USER
  appConfig: customers,stores,ui,admin
  clusterNameExpression: metadata['cluster']

In this case, the cluster name from 4 services is pulled from their metadata map, and is expected to have values that include "SYSTEM" and "USER".

To use the "default" cluster for all apps you need a string literal expression (with single quotes, and escaped with double quotes if it is in YAML as well):

turbine:
  appConfig: customers,stores
  clusterNameExpression: "'default'"

Spring Cloud provides a spring-cloud-starter-netflix-turbine that has all the dependencies you need to get a Turbine server running. Just create a Spring Boot application and annotate it with @EnableTurbine.

[Note]Note

by default Spring Cloud allows Turbine to use the host and port to allow multiple processes per host, per cluster. If you want the native Netflix behaviour built into Turbine that does not allow multiple processes per host, per cluster (the key to the instance id is the hostname), then set the property turbine.combineHostPort=false.

15.3 Turbine Stream

In some environments (e.g. in a PaaS setting), the classic Turbine model of pulling metrics from all the distributed Hystrix commands doesn’t work. In that case you might want to have your Hystrix commands push metrics to Turbine, and Spring Cloud enables that with messaging. All you need to do on the client is add a dependency to spring-cloud-netflix-hystrix-stream and the spring-cloud-starter-stream-* of your choice (see Spring Cloud Stream documentation for details on the brokers, and how to configure the client credentials, but it should work out of the box for a local broker).

On the server side Just create a Spring Boot application and annotate it with @EnableTurbineStream and by default it will come up on port 8989 (point your Hystrix dashboard to that port, any path). You can customize the port using either server.port or turbine.stream.port. If you have spring-boot-starter-web and spring-boot-starter-actuator on the classpath as well, then you can open up the Actuator endpoints on a separate port (with Tomcat by default) by providing a management.port which is different.

You can then point the Hystrix Dashboard to the Turbine Stream Server instead of individual Hystrix streams. If Turbine Stream is running on port 8989 on myhost, then put http://myhost:8989 in the stream input field in the Hystrix Dashboard. Circuits will be prefixed by their respective serviceId, followed by a dot, then the circuit name.

Spring Cloud provides a spring-cloud-starter-netflix-turbine-stream that has all the dependencies you need to get a Turbine Stream server running - just add the Stream binder of your choice, e.g. spring-cloud-starter-stream-rabbit. You need Java 8 to run the app because it is Netty-based.