Monitoring Config

Azure Application insight has sampling feature (default enable) that will randomly ignore some of logs when it exceeds a specified threshold (unknown the threshold).
The Azure function monitoring tracking could tell you the failure or success by inspecting the log. The sampling feature would cause the problem of not telling you the result of function execution. source
Adding following config at Azure function host.json to disable it:

{
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": false,
        "maxTelemetryItemsPerSecond" : 20,
        "excludedTypes": "Request;Exception"
      }
    }
  }
}

Azure Function

Shared

Because many functions (may not only yours) share computing resources, there are some limitations:

• Multiple functions within a Azure function application may clash
• There are many Azure defined limitations such as Threads, processes, connections, sockets, etc. source

webapp

• So far so good, need pay higher fees. Didn't see values comparing with VMs.