Host Health Monitor

The Host Health Monitor feature of the Functions Runtime monitors various VM sandbox imposed performance counters. The goal is to temporarily stop the host from doing more work when thresholds for any of the counters are about to be exceeded. Examples of the performance counters monitored include Connections, Threads, Processes, NamedPipes, and Sections. When one or more counters are nearing their thresholds, the host will be stopped until the counter values return to normal. If the Function App is scaled out to multiple instances, other instances will continue to run and pick up the workload. Once the counter values return to normal, the host will start processing work again automatically.

The feature is currently only active on Consumption plan, where sandbox limits exist. The feature is enabled by default, but can be disabled/configured via the "healthMonitor" section of host.json.