A very strange behaviors of docker contained wordpress cont

I suspected the problem may come with Azure file through SMB.  So I created a new wordpress container with a local /var/www/html folder (not a volume from Azure file).  The the problem disappeared.

So the problem is the SMB Azure file?

I then use the following command to host a python http server and mount the azure volume to it.

sudo docker run -it --rm --name my-running-script -p 8000:8000 -v vol3:/usr/src/myapp -w /usr/src/myapp python:2 python -m SimpleHTTPServer 8000

There is no problem at all with this python server. 

The only thing I can think is that the apache config in the wordpress container does not work well with SMB volume, especially when a big file is served in fast speed. 

I then mounted the azure file volume to a php container without wordpress

sudo docker run --rm -p 8000:80 --name my-apache-php-app -v vol3:/var/www/html php:7.0-apache

The problem can be reproduced. So there is nothing to do with wordpress.

I then tried the same thing on apache httpd

docker run --rm --name my-apache-app -p 8000:80 -v vol3:/usr/local/apache2/htdocs/ httpd:2.4

I can reproduce the problem. So that the problem is apache, not php.

I run apache with local dir 

sudo docker run --rm --name my-apache-app -p 8000:80 -v "$PWD":/usr/local/apache2/htdocs/ httpd:2.4

It worked well, the problem disappeared; which comes to the summary, docker apache is not working well with Docker Volume Driver. 

The file I used to test is only 3.7M.  Good news is that wordpress can still work well with this problem. I think that wordpress files are small enough to hide this problem.

I then used php CLI as a php web host 

sudo docker run -it --rm --name my-running-script -p 8000:8000 -v vol3:/usr/src/myapp -w /usr/src/myapp php:7.0-cli php -S 0.0.0.0:8000

This time, the problem is gone for directly file access (better than apache). But once I download the file with a download.php file, the problem comes back.

I used readfile function in the download.php file to read a local file

I then changed the local file URL to a HTTP URL, then it worked. This is really dirty, because the php file go through internet to reach it's own server to read a local file as a remote file.

Now comes to the solution.

run a python http server

sudo docker run -it -d --name python_http -p 8001:80 -v vol4:/usr/src/myapp -w /usr/src/myapp python:2 python -m SimpleHTTPServer 80

Add this http server to the same network as wordpress server

docker network connect --alias python_http_host wp-net python_http

Then in the download.php file, use http://python_http/... in the readfile function to read a remote file from another docker container, which is actually a local file.

Problem solved!!! But this requires a new docker container running.

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Feng