Setting qgis-server environment variables

Question

I need to know how to set qgis-server environment variables, because I can't find a good explanation of how this works here on the SE or in the documentation. The specific environment variable I am trying to set is QGIS_SERVER_PARALLEL_RENDERING.

I have searched within many directories that contain the miscellaneous workings of qgis-server and Apache 2, but it doesn't seem to be located within any .cfg/.ini files I have found.

I don't think it matters much, but I'm running Ubuntu Desktop 21.04, qgis and qgis-server 3.2, and Lizmap 3.4.4.

pic 1 shows the variables, but not how to set them
qgis server documentation page

pic 2 explains what happens without explaining what happens confusion #2

Answer 1

Considering, you deployed QGIS Server with Apache FCGI (If other approaches, recipe/answer would change)

You can set the environment variable within Apache configuration file with

FcgidInitialEnv QGIS_SERVER_PARALLEL_RENDERING "1"

You can inspect this sample code for an example in context

Two ways to find out the answer:

Simple one:

• Go to https://github.com and do a search using keyword QGIS_SERVER_PARALLEL_RENDERING like this url https://github.com/search?q=QGIS_SERVER_PARALLEL_RENDERING

• Then, on the left, click on "Code" to get an url like https://github.com/search?p=2&q=QGIS_SERVER_PARALLEL_RENDERING&type=Code

• Then, inspect results to try to find relevant samples

Complex one:

If already familiar with Apache, looking at https://docs.qgis.org/3.16/en/docs/server_manual/plugins.html#http-server-configuration that mentioned below

FcgidInitialEnv QGIS_PLUGINPATH "/var/www/qgis-server/plugins"

and see that QGIS_PLUGINPATH was mentioned in https://docs.qgis.org/3.16/en/docs/server_manual/config.html#environment-variables to guess how to use QGIS_SERVER_PARALLEL_RENDERING. Must admit this way is not easy.