The csvserver assignment

The developer team of the csvserver was working hard to get it ready for production. The team decided to go for a trip before the launch, and has been missing since then. You have been given the responsibility to figure out how to get the csvserver running correctly with the help of the following document. You might need to understand why things are failing and try to fix them, and make it ready for a launch¹.

Prerequisites

You don't need to know Docker or Prometheus beforehand to solve this assignment, take a look at the following docs and understand the basics about these tools.

• Read Docker orientation and setup: https://docs.docker.com/get-started/
• Read Docker build and run your image: https://docs.docker.com/get-started/part2/
• Read Get started with Docker Compose: https://docs.docker.com/compose/gettingstarted/
• Read Prometheus getting started: https://prometheus.io/docs/prometheus/latest/getting_started/
• Read Prometheus installation with Docker: https://prometheus.io/docs/prometheus/latest/installation/
• Install Docker and docker-compose on your machine and run following commands,

  docker pull infracloudio/csvserver:latest
  docker pull prom/prometheus:v2.22.0

• Clone this repository to your machine. (Don't fork it).
• Use bash shell for all the operations, other shells like ksh, fish etc might cause unknown issues.
• Create a new private repository on GitHub.
• cd into the solution directory, and perform all the steps from that directory.

NOTE: If you have a Windows machine, you can try to do this assignment on WSL-2 or use https://labs.play-with-docker.com or install GNU/Linux (i.e. Ubuntu) in a virtual machine.

Please note

• Any step from the assignment does not require you to modify the container image, or build your own container image at all.
• Make sure all the files you create have the exact same names as given.
• Don't commit all of your work as a single commit, commit it as you finish each part, so we can see the work as you built it up.
• The solution should work on a different machine, which has docker and docker-compose, without any modifications.
• Reading this document carefully is the key to solve this assignment.
• If you need more time or are stuck at some point, don't hesitate to reach out to us.

Part I

1. Run the container image infracloudio/csvserver:latest in background and check if it's running.
2. If it's failing then try to find the reason, once you find the reason, move to the next step.
3. Write a bash script gencsv.sh to generate a file named inputFile whose content looks like:

   0, 234
   1, 98
   2, 34
   

   These are comma separated values with index and a random number.
   • Running the script with two arguments as ./gencsv.sh 2 8, should generate the file inputFile with 7 such entries in current directory. Where the index of first entry is 2 and the last entry is 8.
4. Run the container again in the background with file generated in (3) available inside the container (remember the reason you found in (2)).
5. Get shell access to the container and find the port on which the application is listening. Once done, stop / delete the running container.
6. Same as (4), run the container and make sure,
   • The application is accessible on the host at http://localhost:9393
   • Set the environment variable CSVSERVER_BORDER to have value Orange.

The application should be accessible at http://localhost:9393, it should have the 7 entries from inputFile and the welcome note should have an orange color border.

NOTE: If you are using play-with-docker.com then you will see the number 9393 highlighted at the top. You can access the application by clicking on that instead of using http://localhost:9393

NOTE: On play-with-docker.com, you can create files in the terminal and edit them with their online editor.

Save the solution

• Create a file called README.md in the solution directory with all the commands you executed as part of this section (Part I).
• Write the docker run command you executed for (6) in a file named part-1-cmd.
• Run one of the following commands which will generate a file with name part-1-output.

  curl -o ./part-1-output http://localhost:9393/raw
  # if the above command fails use,
  wget -O ./part-1-output http://localhost:9393/raw

• Run the following command which will generate a file with name part-1-logs.

  docker logs [container_id] >& part-1-logs

• Make sure that the files gencsv.sh, inputFile, part-1-cmd, part-1-output, part-1-logs are present in the solution directory.
• Commit and push the changes to your repository on GitHub.

NOTE: One should be able to follow the instructions from the solution/README.md file and get csvserver running on their machine.

Part II

0. Delete any containers running from the last part.
1. Create a docker-compose.yaml file for the setup from part I.
2. Use an environment variable file named csvserver.env in docker-compose.yaml to pass environment variables used in part I.
3. One should be able to run the application with docker-compose up.

Save the solution

• Copy the docker-compose.yaml to the solution directory.
• Commit and push the changes to your repository on GitHub.

Part III

0. Delete any containers running from the last part.
1. Add Prometheus container (prom/prometheus:v2.22.0) to the docker-compose.yaml form part II.
2. Configure Prometheus to collect data from our application at <application>:<port>/metrics endpoint. (Where the <port> is the port from I.5)
3. Make sure that Prometheus is accessible at http://localhost:9090 on the host.
4. Type csvserver_records in the query box of Prometheus. Click on Execute and then switch to the Graph tab.

The Prometheus instance should be accessible at http://localhost:9090, and it should show a straight line graph with value 7 (consider shrinking the time range to 5m).

Save the solution

• Update the docker-compose.yaml from the solution directory.
• Add any other files you may have created to the solution directory.
• Commit and push the changes to your repository on GitHub.

Possible errors / caveats on different host OS

1. SELinux enabled GNU/Linux machine: open /****/****: permission denied

2020/10/29 13:22:56 error while reading the file "/****/****": open /****/****: permission denied

Check the permission of the file inputFile on host. If SELinux is enabled on the host then the argument to -v should be something like ****/inputFile:/****/****:z (the extra :z at the end). Same thing needs to be in the docker-compose.yaml.

Submitting the solution

Once you have pushed your progress,

• Add anju-infracloud as collaborators to the repository.
• Reply to the email with link to your repository / send an email to anju [at] infracloud [dot] io.

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1: This scenario is inspired by the Tying This Together: Reverse Engineering a Production Service section of chapter 28 from the Site Reliability Engineering book by Google.