Traffic policy file blocks events going to Datadog

TL;DR

We want to log events from Ngrok to DataDog. It works as expected with no traffic policy, but any traffic policy blocks the events.

Steps to reproduce

Start sample API

docker network create ngrokTest

docker run --init --platform=linux/amd64 --rm -p 4000:80 --network=ngrokTest --name="api" -e PORT=80 joelatngrok/api-demo

• Create a file named policy.yml with the code below.

on_http_request:
  - actions:
      - type: rate-limit
        config:
          name: 1 request per minute
          algorithm: sliding_window
          capacity: 10
          rate: 1m
          bucket_key:
            - "hasReqHeader('host') ? getReqHeader('host')[0] : 'unknown'"

• Browse to the Domains page in the ngrok dashboard and register a domain
• Replace https://your-domain-in-ngrok in the command below with your domain registered in ngrok
• Replace the authentication token in the command below with your token
• Run the command to publish your api with ngrok

docker run -it --rm --platform=linux/amd64 --network=ngrokTest -v ".:/app" -w "/app" -e NGROK_AUTHTOKEN=your-token ngrok/ngrok:3.22.0-alpine-amd64 http http://api --traffic-policy-file policy.yml --url https://your-domain-in-ngrok

The api should now be accessible at your domain https://your-domain-in-ngrok

The requests will also show up in traffic inspector

Monitor events with Datadog

• Sign up for a Datadog account

• In Step 3 of the Datadog sign-up, click on Docker in the sidebar. Copy and paste the given command into a terminal and run it.

• Once the Datadog site notices your agent is running, click Finish on the page.

• You now no longer need the agent running locally and can remove the Datadog container with the command below.

docker stop dd-agent
docker remove dd-agent
docker image rm gcr.io/datadoghq/agent:7

• Make a note of your Datadog API key, which you can access by clicking your username at the bottom left of the sidebar and clicking API Keys in the menu that opens.

• In the ngrok navigation panel, browse to the Events Stream and add a new subscription.

• In the New Event Subscription sidebar, enter traffic as the Description and then Add a new source. Choose http_request_complete.v0

• Add Datadog as a destination, choose your Datadog site region and API key you noted earlier, and send a test event.
• Open the Datadog site and browse to the Log Explorer page from the navigation panel. You should see that the test event from ngrok will appear.

• In ngrok, click Done and Save to save the event subscription.

Refresh your ngrok API page at https://your-domain-in-ngrok a few times so that new requests are logged in Datadog.

What we expect to see

New events being logged to Datadog

What actually happens

Events only show up in Datadog once the agent is run without specifying the traffic-policy-file flag as below

docker run -it --rm --platform=linux/amd64 --network=ngrokTest -v ".:/app" -w "/app" -e NGROK_AUTHTOKEN=your-token ngrok/ngrok:3.22.0-alpine-amd64 http http://api --url https://your-domain-in-ngrok