Assumptions

  • You have a CF deployed
  • You have one proxy app pushed and called appA
  • You have one route mapped to appA called APP_A_ROUTE
  • You have completed the previous stories in this track

Recorded values from previous stories

APP_A_ROUTE=<value>
APP_A_GUID=<value>
DIEGO_CELL_IP=<value>
CONTAINER_APP_PORT=<value>
DIEGO_CELL_APP_PORT=<value>
CONTAINER_ENVOY_PORT=<value>
DIEGO_CELL_ENVOY_PORT=<value>
OVERLAY_IP=<value>

What

In the previous stories you followed the path of a request from a client to an app deployed on Cloud Foundry.

For every successful* response that Gorouter returns to a client it logs an access log. Here successful means “that there was a response from the app with any status code”.

These access logs can be very helpful for debugging. One common situation is that a customer sees via metrics that they are getting lots of 502s. But what apps are returning 502s? Let’s look at the access logs to find out!

How

📝 Look at access logs

  1. Ssh onto the Router VM and become root
  2. Tail the access log 
    tail -f /var/vcap/sys/log/gorouter/access.log

  3. In another terminal curl APP_A_ROUTE.

    You should see something that looks like this:

    APP_A_ROUTE - [2021-02-18T21:22:32.355501523Z] "GET / HTTP/1.1" 200 0 62 "-" "curl/7.54.0" "35.191.2.80:51628" "10.0.1.11:61002" x_forwarded_for:"142.105.202.35, 35.227.211.74, 35.191.2.80" x_forwarded_proto:"http" vcap_request_id:"6cb8b8de-bc85-4479-5f90-1c3a52d88d84" response_time:0.011962 gorouter_time:0.000467 app_id:"cabd9e08-384e-4689-b868-1ba3d5d838bf" app_index:"0" x_cf_routererror:"-" x_b3_traceid:"9d30688835227cf3" x_b3_spanid:"9d30688835227cf3" x_b3_parentspanid:"-" b3:"9d30688835227cf3-9d30688835227cf3"
  • ❓Can you find the status code in the access log?
  • ❓Can you find the x-cf-routererror in the access log?

📚 Read about the X-CF-RouterError

  1. Read about the X-CF-RouterError here and learn how it can be used for debugging.

🤔 Look at the app logs for APP_A.

  1. Use cf logs --recent to look at the app logs for APP_A.
    • ❓Can you find a log line that looks like the access log line?
    • ❓What additional information does the app log contain?

Expected Result

You have found the access log from your curl in the log file on the router VM and in the app logs.

Resources