PurePath for error analysis

Analyzing individual requests is often a useful way of gaining a better understanding of detected errors. In the image below, you can see that requests to Redis started to fail around the 10:45 mark on the timeline. To find the Failure rate tab, go to the service’s details page, and select View (View requests, View dynamic web requests, or View resources).

Select View backtrace to see where these requests came from. We can now see that all of these requests originate in the weather-express service. We also see that nearly all failed Redis calls have the same Exception—an AbortError caused by a closed connection.

We can go one step further, down to the affected Node.js PurePaths. With the weather-express service selected, select the Analyze tab in the bottom right corner of the page and then select View PurePaths on the left column. Below you can see such a Node.js PurePath and its code-level execution tree. Note that the Redis method call leads to an error. You can see where this error occurs in the flow of the Node.js code.

We can also analyze the exception that occurs at this point in the request. Just select the Exceptions tab.

Each PurePath shows a unique set of parameters leading up to the error. With this approach to analysis, the PurePath view can be very useful in helping you understand why certain exceptions occurred.