Changing the Source

In this exercise you will make a change in the source code and rebuild/re-deploy the container.

Change the application source code

You can either make a source code change using an editor or you can use the below sed command.

First, make sure you are in the correct source code directory:

cd ~/flask-vote-app

<!-- If you want to use an editor, you could use the nano editor to change the title of the voting definition (e.g. "Linux distribution") and then save the file again:

nano seeds/seed_data.json

Once you have made the change, save the file using CTL-X, then Y and then hit ENTER. -→

Use the following command to substitute some text in the voting definition file for you:

sed -i "s/avourite distribution/avourite Linux Distribution/" seeds/seed_data.json

You have just made a change to the source code. You have changed the word to Distribution. As a developer, you would now want to build and 'test' the application on your 'local workstation' and after you are happy that it works you would commit and push the changes to GitHub.

Check the changes you made with git:

git status

Git should show you that you made a change in the seed_data.json file: modified: seeds/seed_data.json`.

Git can also show you the exact changes you are about to commit:

git diff seeds/seed_data.json

Commit and push the changes

Commit the changes:

git commit -m "Important change" .

After the next command, if you had set up the GitHub webhook in the previous exercise, you should see the source to image build starting automatically. You will see a build pod running in the lower terminal.

Now, push the changes to GitHub:

git push

If you set up a Webhook in the previous exercise, you should see the build automatically starting. Take a look at the lower terminal window and you should see vote-app-2-build 1/1 Running.

Warning: If you DID NOT set up a webhook in the previous exercise, trigger a new build manually with the following command:

oc start-build vote-app

Ensure the build is running before continuing.

Again, follow the build progress:

oc logs bc/vote-app --follow

You should see the python application being built again and a new image being committed/pushed into the internal registry. The application should be re-deployed automatically. Note,this can take a few minutes, especially the Copying blob…​ and the Storing signatures operations can be slow.

Once the new pod is up and running, check the change you just made has been deployed properly.

Verify the application changes

curl -s http://vote-app-%project_namespace%.%cluster_subdomain%/ | grep "<title>"

The output should include your change, for example:

<title>Favourite Linux Distribution</title>

If this does not work, go back and check that the build had finished successfully and that the application has been re-deployed.

Test the application in a browser with the following URL:

That’s the end of this exercise.

You now know how to make changes to your code and test the results. Next you will connect the vote application to a database.