Using Node.js Agents - Running backend server using SeaLights agent

Owned by Jason Wides
Last updated: Jun 02, 2024 by Marc Amouyal
2 min read

To capture code coverage on your backend server, you need to run it using our Node.js test listener agent.

npx slnodejs run --tokenfile ./path/to/sltoken.txt --buildsessionidfile buildSessionId [--labid <Lab ID>] --workspacepath "." --useinitialcolor true -- /your/backend/server/command

Note the /your/backend/server/command from above refers to "./server/app.js" in the example of command below:

npx slnodejs run --tokenfile ./sltoken.txt --buildsessionidfile buildSessionId --labid "LAB_ID_2" --workspacepath "./server" --useinitialcolor true --useslnode2 -- "./server/app.js"

When the application is up and running and the Sealights Listener agent configured, you can see it properly running as a new entry in the Cockpit -> Live Agents Monitor screen.
You also have the ability to validate the startup parameters in use with your application via the following commands

  • Linux:  ps -ef | grep slnodejs

  • Windows: C:\\Windows\\System32\\wbem\\WMIC.exe process where "name like '%slnodejs%'" get commandline,processid (CMD prompt)

For distributed Test Runner & Test Listener, we recommend using the Lab ID parameter in order to link between the two.
If the lab ID is not provided, the session ID will be used as a Lab ID

Running backend server using SeaLights agent and preload.js

To run your backend service with Sealights without changing the startup command, use the preload.js file and the NODE_OPTIONS environment variable. This is a common practice in docker containers where the ENTRYPOINT cannot be modified.

  • The agent contains a preload.js file under node_modules/slnodejs/lib/preload.js. You use it by setting the environment variable: NODE_OPTIONS="--require ./node_modules/slnodejs/lib/preload.js"

  • In the current working directory, the agent will search for the token in the file sltoken.txt and the build session ID in the file buildSessionId.

  • Other parameters can be passed to the agent using the following syntax: SL_ + {command line flag}. For instance, to pass the lab ID, you can set SL_labId=my_lab_id

Sample docker file:

ENV SL_labId=integ_test_otel ENV NODE_OPTIONS="--require ./node_modules/slnodejs/lib/preload.js" ENTRYPOINT [ "node", "--require", "./tracing.js", "index.js" ]