configFile: directly write changes to configFile

[clwluvw]

In some situations, the config.json is volumed from somewhere else and the file is busy, move can't be performed on this file and configFile.Save() will be failed because it's trying to move another file to this file. This will write changes directly to the file.

Signed-off-by: Seena Fallah seenafallah@gmail.com

- What I did
Write config file changes directly to the file.

- How to verify it
Volume docker config in a slave mode and try to change it with docker login inside the container

- Description for the changelog
Perform config file changes even if the file is busy

- A picture of a cute animal (not mandatory but encouraged)

[codecov-io]

Codecov Report

Merging #2902 (5e71de4) into master (2291f61) will decrease coverage by 0.00%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master    #2902      +/-   ##
==========================================
- Coverage   57.05%   57.05%   -0.01%     
==========================================
  Files         297      296       -1     
  Lines       18653    18631      -22     
==========================================
- Hits        10643    10630      -13     
+ Misses       7151     7146       -5     
+ Partials      859      855       -4     

[thaJeztah]

Hmmm... not sure about this change. The temp-file was added for a reason, and to make sure that writes would be preformed atomically (see #1359). Removing this would mean we introduce that problem again.

What other process is using the file in your case that prevents it from being accessed?

[clwluvw]

What other process is using the file in your case that prevents it from being accessed?

@thaJeztah The file is volumed to a container and It can't be removed so moving another file to this file will be failed. For example, mount ~/.docker/config.json from your host to the container and then run docker login inside the container and it will be failed!

[clwluvw]

Hmmm... not sure about this change. The temp-file was added for a reason, and to make sure that writes would be preformed atomically (see #1359). Removing this would mean we introduce that problem again.

@thaJeztah I used flock to handle concurrent writes to the config file. What's your idea?