[APM] Add error rate chart to Errors overview and detail views

[formgeist]

Summary

Related design issue elastic/apm#264

We want to add a new error rate chart to the Errors overview and detail views to improve our overall errors experience in APM and to better inform users of their ratio of errors versus the number of transactions they are recording.

Solution

The error rate chart will sit next to the Error occurrences chart. It will be a line chart of the error rate; number of transactions / number of error occurrences.

As we're dealing with errors, we'll be using the euiColorVis7 for the line chart color.

[elasticmachine]

Pinging @elastic/apm-ui (Team:apm)

[felixbarny]

Just some ideas: What can be quite useful is to see which transactions cause the most errors. Either by showing the top x transactions in the same chart (maybe even stacked so the total error rate is still there) or in a table. The approach with the table overlaps a bit with the table in the transactions overview which would also benefit from an error rate column.

[formgeist]

Just some ideas: What can be quite useful is to see which transactions cause the most errors. Either by showing the top x transactions in the same chart (maybe even stacked so the total error rate is still there) or in a table. The approach with the table overlaps a bit with the table in the transactions overview which would also benefit from an error rate column.

Thanks @felixbarny those are all valid and great suggestions for additional improvements. I think it deserves its own issue. Would you mind creating one in APM?

I think we should definitely consider having the error rate column in the Transactions overview table possibly with the first iteration, but I've created a separate issue to track this.