How to understand errors (merged) in Google Spanner Monitor?

You can make a toolbar in Stackdriver ( https://app.google.stackdriver.com ) which will break the errors a bit. We are currently working on a resource page for Cloud Spanner that will actually break their error code, but before that you can go to Resources> Metric Explorer and filter by response status:

Sometimes you get error responses using the Cloud Spanner API; FAILED_PRECONDITION is somewhat common if you have many transactions going on at the same time, which invalidates other transactions.