Add documentation about running METviewer through Docker.

[JohnHalleyGotway]

Describe the Task

Add documentation about running METviewer through Docker. When applying the METviewer Docker image to the NOAA/SWPC project, Jonathan learned a lot about running METviewer through Docker. Recommend that we add a chapter or section to the METviewer User's Guide about doing so.

In particular, we ran into permissions issues that looked like this:

musial6:SWPC johnhg$ docker-compose up -d
Creating mysql_mv ... done
Creating metviewer_1 ... error

ERROR: for metviewer_1  Cannot start service metviewer: Cannot link to a non running container: /mysql_mv AS /metviewer_1/mysql_mv

ERROR: for metviewer  Cannot start service metviewer: Cannot link to a non running container: /mysql_mv AS /metviewer_1/mysql_mv
ERROR: Encountered errors while bringing up the project.

Running docker logs reveals:

musial6:SWPC johnhg$ docker logs 41674fa11eb1
2021-02-10 22:36:24+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.7.33-1debian10 started.
2021-02-10 22:36:24+00:00 [Note] [Entrypoint]: Initializing database files
mysqld: Can't create/write to file '/var/lib/mysql/is_writable' (Errcode: 1 - Operation not permitted)
2021-02-10T22:36:24.707591Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2021-02-10T22:36:24.713566Z 0 [ERROR] --initialize specified but the data directory exists and is not writable. Aborting.
2021-02-10T22:36:24.713608Z 0 [ERROR] Aborting

The reason for this error is as follows:

• $MYSQL_DIR points to a directory (mysql) on my local machine.
• But the permissions on my local mysql directory are set too restrictive.
• The docker-compose.yml file launches MySQL as the mysql user in the mysql group and mounts my local $MYSQL_DIR to /var/lib/mysql inside the container.
• But the test to see if the mysql user can write to /var/lib/mysql/is_writable fails because the permissions on my local machine are too restrictive.

So in this case, we should advise users to open up the permissions on their local machine... or solve this permissions issue in some other way.

Recommend that this be one of the several lessons learned in the METviewer chapter about Docker.

Time Estimate

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Issues should represent approximately 1 to 3 days of work.

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Define Related Issue(s)

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• METplus, MET, METdatadb, METviewer, METexpress, METcalcpy, METplotpy

Task Checklist

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• Complete the issue definition above, including the Time Estimate and Funding Source.
• Fork this repository or create a branch of develop.
  Branch name: feature_<Issue Number>_<Description>
• Complete the development and test your changes.
• Add/update log messages for easier debugging.
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