Append a directory to Amazon Lambda Environment Variables $NODE_PATH

Question

Default Env Variable as per the docs:

NODE_PATH:/opt/nodejs/node8/node_modules/:/opt/nodejs/node_modules:$LAMBDA_RUNTIME_DIR/node_modules

I want to append my custom directory to it (NOT to override all)

NODE_PATH:$NODE_PATH:/opt/nodejs/mycustom-directory

I tried the above from lambda console it overrides all. $NODE_PATH is added as a string. It is not parsing $NODE_PATH

Output I got when printing env:

NODE_PATH=$NODE_PATH:/opt/nodejs/mycustom-directory

Similar Question but no Solution still: AWS lambda add PATH variable?

Answer 1

I needed this too, as I am using AWS Lambda Layers, which are placed on the default NODE_PATH, and wanted to also be able to use local roots to avoid long relative paths (such as import bar from foo/bar instead of import bar from ../../../../foo/bar, but I didn't find any way to append to NODE_PATH without losing the default ones - as soon as it's set, the paths to node_modules - including the aws-sdk module, are lost.

The only solutions I can think of are:

1. Explicitly set NODE_PATH to the default value plus your custom one (which adds an ugly dependency to lambda internal environment configuration which you shouldn't have to care about)

2. Put your custom library in a layer. Many times this is a good solution if you can extract sub-modules as separate layers (but it doesn't help for situations like elimination of long relative paths within the application itself like I described above).

3. Append programatically, by having the very first lines of your application do

process.env.NODE_PATH = process.env.NODE_PATH + ":my-custom-path";
require("module").Module._initPaths(); // This re-initalizes the module loader to use the new NODE_PATH.

require('some-custom-module-in-my-custom-path'); // should work
require('aws-sdk') // should also work

This may not be the prettiest hack, but it should do the trick (disclaimer: haven't actually tried this in a AWS Lambda environment but it works locally using Node 12 at least).