Spring Sleuth

Sleuth is used to trace calls in a microservices environment. It creates a trace-id over the whole interactions and a span-id between each call.  For example, there is a call from a client to a microservice to load information for a customer id.  First is the call to the customer service, then the recent orders and accounts services.  All these calls would share the same trace-id but between each one is a different span-id.  To turn on sleuth just add the following dependencies into the pom.  You'll also need to add an application name.

spring.application.name=My Server

Maven

<dependency>

    <groupId>org.springframework.cloud</groupId>

    <artifactId>spring-cloud-starter-sleuth</artifactId>

    <version>1.2.0.RELEASE</version>

</dependency>

The trace and span ids will now be created and can be seen in the headers.

To log this and make it useful though is one thing but there is a graphical tool which makes this very easy.

Zipkin

Zipkin can be configured so that all Sleuth output is sent there and it allows a view of the interactions so that the times and services called can be seen.  To configure and use zipkin just add another dependency,

<dependency>

    <groupId>org.springframework.cloud</groupId>

    <artifactId>spring-cloud-sleuth-zipkin</artifactId>

    <version>1.2.0.RELEASE</version>
</dependency>

By default everything is logged to localhost:9411 but this can be changed by adding a property

spring.zipkin.baseurl=http://zipkin:9411/

Docker

If you are running with docker you'll need to add a zipkin image into the compose file,

      

  zipkin:

    image: openzipkin/zipkin

    networks:

      - my-network

    hostname: zipkin

    ports:
      - "9411:9411"

Docker crib sheet

Here are a list of commands that are useful for docker, docker-machine and docker-compose

Listings

// See what docker containers are running
> docker ps

// See which images exist
> docker images
> docker image ls

// See which networks exist (usually created as part of docker-compose)
> docker network ls

// See which volumes exist
> docker volume ls

Removing Images and Containers

// List the images and then remove one using the image id
> docker rmi <image_id>

// List the containers and remove one using the container id
> docker rm <container_id>

// Remove a volume
> docker volume rm <volume_id>

// Remove a network
> docker network rm <network_id>

Starting and stopping

// Start a particular image and routing 1234 on localhost to 5678 on the docker image.  For a web application you'll need to expose the application server port such as 8080 eg -p 8080:8080
// After running this it'll show up on a docker ps as a container running this image
> docker run -p 1234:5678 <image_id>

// Start an image in 'detached' mode to keep the output quiet
> docker run -d -p 1234:5678 <image_id>

// View the logs of the docker container running a particular image
> docker logs <container_id>

// Stop a particular container
> docker stop <container_id>

// Attach a shell to a running docker container
> docker exec -it <container_id> "/bin/bash"

// Start with an environment variable
> docker run -d -e MY_ENVIRONMENT_VAR=bob <image_id>

Other useful commands

// See what resources are currently being used
> docker stats

// Grab the logs from a docker machine
> dockers logs <container_id> > output.log

// Copy a file from a docker image to the local machine
> docker cp <container_id>:<container file path> <local path>
> docker cp ab34d4532e78:/tmp/log.txt ./

docker-machine

// Useful where the host machine doesn't support natively such as anything pre windows 10

// Get the ip of the docker-machine, usually 192.168.99.100
> docker-machine ip