Focus on Client-side Errors in a Monitoring System

Client-side errors

In a distributed system, clients often access the service via an HTTP request. We can monitor our web and application servers’ logs if a request fails to process. If multiple requests fail, we can observe a spike in internal errors (error 500).

Those errors whose root cause is on the client side are hard to respond to because the service has little to no insight into the client’s system. We might try to look for a dip in the load compared to averages, but such a graph is usually hard. It can have false positives and false negatives due to factors such as unexpectedly variable load or if a small portion of the client population is affected.

There are many factors that can cause failures that can result in clients being unable to reach the server. These include the following:

• Failure in DNS name resolution.
• Any failure in routing along the path from the client to the service provider.
• Any failures with third-party infrastructure, such as middleboxes and content delivery networks (CDNs).