Try out a Lambda function locally before you upload it to the cloud.

Trylam runs as a small NodeJS library. It can be installed as a development dependency, so that it adds nothing to the production runtime.

A typical setup involves doing the following:

1. Add a development dependency to the Lambda NodeJS project:

   npm install trylam --save-dev
   

2. Once installed, start up Trylam as follows:

   node ./node_modules/trylam/trylam.js index.handler
   

   Where index.handler is the Lambda file name and function name respectively.

   NOTE: Two additional optional parameters can be specified:

   • Argument 2: The path to the Lambda entrypoint. This can be useful if the function is not in the root directory of the project. Do not include leading or trailing slashes (/)
   • Arrgument 3: The file extension. By default .js is used. To set to blank, pass the string "NONE".

   A full invocation may look like the following:

   node ./node_modules/trylam/trylam.js index.handler src/lambdas .ts
   

3. To invoke Trylam, make an HTTP call on port 9000 (the default port). For example:

   curl --request POST --url http://localhost:9000/ --data '{ "key1": "value1", "key2": [ "item21","item22"]}'
   

   NOTE: The --data will be used as the event parameter to the Lambda function.

   After running, you should see the results of the invocation on the console. Example:

   {"statusCode":200,"body":"\"Hello from Lambda!\""}
   

4. To Use Visual Studio Code to debug the function: Add a launch configuration:

   {
       "version": "0.2.0",
       "configurations": [
           {
               "type": "node",
               "request": "launch",
               "name": "Launch Program",
               "skipFiles": [
                   "<node_internals>/**"
               ],
               "program": "${workspaceFolder}/node_modules/trylam/trylam.js",
               "args": ["index.handler"]
           }
       ]
   }
   

   NOTE:: The above configuration assumes the Lambda entry point is named handler() and the name of the Lambda file is index.js.

   Set a breakpoint in the Lambda handler, and invoke the function via a curl call:

   curl --request POST --url http://localhost:9000/2015-03-31/functions/function/invocations --data '{ "key1": "value1", "key2": [ "item21","item22"]}'
   

From the root directory:

1. Bump the version number in package.json
2. Run npm pack
3. Run npm publish --registry http://localhost:4873

I'm not sure, but I'll say this. The next step is NOT to add infrastructure deployment code to this library. Use your normal CI/CD process to build, deploy, and verify things. Geez Louise, what's wrong w/ that stuff - it worked for decades... why are you trying to ditch it? Did it start wearing Dad Jeans or something?

It's probably obvious, but you can call Cloud services by simply setting AWS credentials in your environment before starting trylam. There are numerous ways to do this, but the simplest is probably just setting the three environment variables in the terminal. (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN)

That's it. At least for now.

No and then.