Rollback Using Temp Files & Fix Atomic Writes

[aphralG]

Proposed changes

Changes:

• Update Atomic writes to create the temp directory in the location of the NGINX config or a default of "/etc/nginx" if we can't get the config dir. Instead of the file being moved it is now renamed preserving the file permissions etc

• Rollback has changed to before a config apply starts create a copy of the file to a temp directory (need to use copy here to not delete original) at the location of the NGINX config. If a rollback occurs these files are renamed to rollback the files

• File watchers are now enabled by a specific topic sent after we have cleaned up the temp directories, File Watcher now when disabled removes all directories it is watching and then they are added back when it is enabled. This is to prevent an issue where the events that happened while the watcher was disabled were still on the channel when the watcher was enabled causing agent to process those events unnecessarily.

Checklist

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• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13

[sean-breen]

if we can't get the config dir

What does this mean? We will write into the /etc/nginx directory by default? Shouldn't we stop if we can't find the config dir? What happens when we can't find the directory and someone has set it to a non-default location?

[aphralG]

if we can't get the config dir

What does this mean? We will write into the /etc/nginx directory by default? Shouldn't we stop if we can't find the config dir? What happens when we can't find the directory and someone has set it to a non-default location?

I can change it to fail just after discussing with Donal we were just trying to set it to a default in case something happened where it wouldn't be set. But in reality it will probably always bet set as it is sent with the config context.

[sean-breen]

if we can't get the config dir
What does this mean? We will write into the /etc/nginx directory by default? Shouldn't we stop if we can't find the config dir? What happens when we can't find the directory and someone has set it to a non-default location?

I can change it to fail just after discussing with Donal we were just trying to set it to a default in case something happened where it wouldn't be set. But in reality it will probably always bet set as it is sent with the config context.

Fair, I'm more concerned with us writing the intermediary files into the /etc/nginx directory, would it be possible to write the temp files to /etc/nginx-agent or another location that we know will exist and we have access to?

[dhurley]

Think you can remove this from the interface?