Azure AppInsights alert notifications of warnings - azure

Question

I have the following Azure function:
[FunctionName("FunctionSync")]
public async Task Run([TimerTrigger("0 */5 * * * *")]TimerInfo myTimer, ILogger _log) // where ILogger is Microsoft.Extensions.Logging.ILogger
{
try
{
// some code
}
catch (VerizonUnexpectedResponseException ex)
{
log.LogError($"{ex.Message}; response text: '{ex.ResponseText}'");
}
catch(VerizonUnsuccessfulResponseException failed_ex)
{
log.LogWarning($"Unexpected response; Error: '{failed_ex.Response.Error}', Description: '{failed_ex.Response.Description}'");
}
}
So, I wrote to AI some messages as Warning and Error when some conditions are true...
Right now I want to create Alert notifications (to email, for example), I go to Azure App Insights -> Rules -> Create New Rule and I don't understand which Signal Name should I select for it?

Answer 1

Custom log search, where the search could be something like
traces
| where message contains "some recognizable part of your message"
or
exceptions
| where type contains "VerizonUnexpectedResponseException"
or type contains "VerizonUnsuccessfulResponseException"

Answer 2

You should use custom log search.
When create the alert rule, for resources, you should select the connected Application Insights instead of the function app. Then for Condition, select Custom log search.
As per your code, both the messages from log.LogError and log.LogWarning will be flowed into traces table. For messages from log.LogError, the severityLevel property will be set as 3; For messages from log.LogWarning, the severityLevel property will be set as 2. And you can also use cloud_RoleName(here, it should be your function app name) property to identify your function app.
So in Custom log search, the query should look like below:
traces
| where severityLevel in (2,3)
| where cloud_RoleName == "function app name"
Then you can continue configure other settings for this alert rule.