How to pass environmental variable for Node.js in Docker instance

Ed_P · April 12, 2022, 11:55pm

Hello.
I’m struggling with installation of the OpenCV into the Docker-compose instance of n8n.

As far as I understood I need to install openCV first inside the Linux using apk and then install a Nodes.js module via npm. So far my dockerfile looks like this:

ARG tag=latest
FROM n8nio/n8n:$tag
RUN apk --update add curl curl-dev libcurl linux-headers opencv
RUN npm install -g opencv

The problem with this setup comes from here:

github.com

peterbraden/node-opencv/blob/f0a03a4be7064ca4d75ff2f16f8cf206fe982456/utils/find-opencv.js#L18$L23

      
        
              '--libs' : '--libs'
            }
            var flag = flags[process.argv[2]] || '--exists'
            
            

            

            
// Normally |pkg-config opencv ...| could report either OpenCV 2.x or OpenCV 3.y
            // depending on what is installed.  To enable both 2.x and 3.y to co-exist on
            // the same machine, the opencv.pc for 3.y can be installed as opencv3.pc and
            // then selected by |export PKG_CONFIG_OPENCV3=1| before building node-opencv.
            var opencv = process.env.PKG_CONFIG_OPENCV3 === "1" ? "opencv3" : ' "opencv >= 2.3.1"';
            opencv = process.env.PKG_CONFIG_OPENCV4 === "1" ? "opencv4" : opencv;
            
            
function main(){
                //Try using pkg-config, but if it fails and it is on Windows, try the fallback
                exec("pkg-config " + opencv + " " + flag, function(error, stdout, stderr){
                    if(error){
                        if(process.platform === "win32"){
                            fallback();
                        }
                        else{

There is a version check for opencv. I have ver. 4 and need to pass PKG_CONFIG_OPENCV4=1 into npm (not Docker). Can I just change something in RUN npm install command?

I found that there is a .npmrc file or a preinstall script. But I have very little idea where to put them since the whole stuff is in Docker. Do I need to RUN some other commands before RUN npm install?

Thanks a lot in advance.

jon · April 13, 2022, 8:15am

Hey @Ed_P,

I am not sure this is really a question for us as it doesn’t appear to be related to n8n directly. The comment above what you have seems to suggest it is just a case of using RUN export PKG_CONFIG_OPENCV3=1 | npm install -g opencv.