Let us examine the error docker error failed to compute the cache key, the reasons, and the most effective troubleshooting steps to avoid the error with the support of our Docker hosting support services at Bobcares.

Troubleshoot- Docker failed to Compute Cache Key Not Found Error

The Docker failed to compute cache key problem occurs when the docker buildcommand is called in a directory that does not contain the Dockefile.

Error

parent-directory
- test-file-1.py
- child-directory (child directory with Dockerfile)
-DockerFile
- test-file-2.py

The Dockerfile can be found in the child directory of the directory structure shown above.

Wrong Execution of the Docker Build

Considering the directory layout above, the first error was that we were on the parent directory and expecting to run docker-build successfully, but the Dockerfile was located in the child directory.

Here is the incorrect directory:

$ pwd
/home/rwagh/my-project/parent-directory

The following is the error that we will receive after running the docker-build command –

failed to compute cache key: "/parent-directory/child-directory/test-file-2.py" not found: not found.

Fix Error: Failed to Compute Cache Key

We now understand the issue and problem linked to the way the docker-build command is being executed. So our goal is to run the Dockerfile located in the child directory. Follow the troubleshooting steps given below:

1. Firstly we have to navigate and switch to the parent directory –

   cd /home/rwagh/my-project/parent-directory
2. Following that, we must run the following docker-build command, specifying the Docker file in the child directory:

   docker build -f child-directoryDockerfile

So the command above will assist us in resolving the docker error that failed to compute the cache key. The only thing that was lacking was to indicate the exact path of the Dockerfile that was already in the correct directory.

Note: It is usually suggested to use the explicit docker-file path to avoid issues caused by Visual Studio’s fuzziness.

 look for the missing directory

If the previous procedure does not assist to resolve the issue, carefully examine the logs and go through the errors.

Another error may appear in the logs stating that test-file-2.py is missing.

failed to compute cache key: "/child-directory/test-file-2.py" not found: not found

So the issue that we can see over here is either of these two:

1. Either the entire directory is missing or it is incomplete. – test-file-2.py in /child-directory
2. Or we’re missing something. test-file-2.py is a Python script.

To avoid this problem, we must ensure that the files in the project directory are checked.

Other troubleshooting options :

• Examine the.dockerignore file. It’s possible that it overlooks the required files for the copy operation, resulting in the failure to compute the cache key error.
• If we set the Docker environment to Windows while adding Docker support, we can run into the same problem. Even executing it in Visual Studio resulted in issues.

  As Docker runs in the Windows Subsystem for Linux, we can change the environment to Linux in this scenario (WSL). After that move back to the terminal to run the commands. We will be able to remove the error by moving the Solutions or the Root folder.

After that, we can do the docker build like this:

docker build -t containername/tag -f ProjectFolder/Dockerfile.

Then type in the  docker run:

docker run containername/tag

This will remove the error.

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Conclusion

To conclude we have now gone through the docker error failed to compute cache key error along with the possible causes and the Troubleshooting tips to effectively remove the error within a few simple steps with the assistance of our Docker hosting support services.