switch to relative path

[rouille]

Purpose

Use relative path in place of absolute path when creating a symbolic link to a base profile in the temporary folder of a scenario. That way, the link won'th break if we change the root of the file system (e.g. /home/EGM/v2 is renamed /home/BES) or when we move a scenario to a backup disk.

What is the code doing?

There is no code.

Where to look

In the _create_link_to_base_profile method of the Simulation Input class. I use the cd command to move into the temporary folder of the scenario and then create a symbolic link to the base profile using a relative path.

Time estimate

2min. This can be tested on creating, running, extracting a dummy scenario and then moving it to RE-Storage.

[jenhagg]

Just checking, we don't have any code that assumes the current directory (so cd won't break anything)? If not, then this looks good.

[danielolsen]

Just checking, we don't have any code that assumes the current directory (so cd won't break anything)? If not, then this looks good.

Could we end the command with cd - to go back to wherever we were before?

[jenhagg]

Could we end the command with cd - to go back to wherever we were before?

@danielolsen nice, I didn't know that one.

[rouille]

When you execute a command on the server using paramiko, the command will always be interpreted from the user's home folder as shown below:

>>> from powersimdata.utility.transfer_data import setup_server_connection
>>> client = setup_server_connection()
>>> stdin, stdout, stderr = client.exec_command("cd /home/EGM/; ls -l")
>>> stdout.readlines()
['total 12\n', '-rw-rw-r--  1 kmueller regroup  654 Apr 15 13:26 gurobi.lic\n', 'drwxrwsr-x 10 brdo     regroup 4096 Jul 10 11:11 v2\n', '-rwxrwxr--  1 brdo     regroup  600 Jun  8 22:19 zeus2heracles.sh\n']
>>>
>>> stdin, stdout, stderr = client.exec_command("ls -l")
>>> stdout.readlines()
['total 100\n', '-rw-rw-r-- 1 brdo brdo        0 Jun 19  2019 200\n', 'drwxr-xr-x 2 brdo brdo     4096 May 14  2019 Desktop\n', 'drwxr-xr-x 3 brdo brdo     4096 May 15  2019 Documents\n', 'drwxr-xr-x 2 brdo brdo     4096 May 14  2019 Downloads\n', '-rw-rw-r-- 1 brdo brdo      654 Apr 15 13:30 gurobi.lic\n', 'drwxrwsr-x 2 brdo regroup 53248 Feb 20 11:34 input\n', 'drwxr-xr-x 2 brdo brdo     4096 Jul  4 11:24 Music\n', 'drwxr-xr-x 2 brdo brdo     4096 May 14  2019 Pictures\n', 'drwxrwxr-x 4 brdo brdo     4096 Apr 29 15:02 PowerSimData\n', 'drwxrwxr-x 4 brdo brdo     4096 Apr 29 17:05 PreREISE\n', 'drwxr-xr-x 2 brdo brdo     4096 May 14  2019 Public\n', 'drwxr-xr-x 2 brdo brdo     4096 May 14  2019 Templates\n', 'drwxr-xr-x 2 brdo brdo     4096 May 14  2019 Videos\n', '-rwxrwxr-- 1 brdo brdo      603 Jun  7 20:30 zeus2heracles.sh\n']

In the first command, I change directory and list it. In the second command I list the current directory, which happen to be my home.

[danielolsen]

Why do we cd instead of doing posixpath.join(self.TMP_DIR, target)?

[rouille]

I am not sure how we could get a link with a relative path if we don't first move into self.TMP_DIR and pointing to the source from there. Maybe I don't understand the question.

[danielolsen]

My understanding of relative path symlinks is that they are like a string, and are only resolved when they are accessed (i.e. after they are created). So we should be able to write that string to the target folder no matter where we call ln from.

[rouille]

done