Adding diagnostic events documentation

Author: soninaren

articles/azure-functions/TOC.yml

@@ -750,6 +750,14 @@
             href: errors-diagnostics/sdk-rules/azf0001.md
           - name: AZF0002
             href: errors-diagnostics/sdk-rules/azf0002.md
+        - name: Diagnostic events
+          items:
+          - name: AZFD0001
+            href: errors-diagnostics/diagnostic-events/azfd0001.md
+          - name: AZFD0002
+            href: errors-diagnostics/diagnostic-events/azfd0002.md
+          - name: AZFD0003
+            href: errors-diagnostics/diagnostic-events/azfd0003.md
     - name: host.json 2.x reference
       href: functions-host-json.md
     - name: host.json 1.x reference

articles/azure-functions/errors-diagnostics/diagnostic-events/azfd0001.md

@@ -0,0 +1,32 @@
+---
+title: "AZFD0001: AzureWebJobsStorage app setting is not present."
+titleSuffix: "Azure Functions"
+description: "AZFD0001: AzureWebJobsStorage app setting is not present"
+author: soninaren
+ms.author: nasoni
+ms.topic: troubleshooting
+ms.date: 09/03/2022
+---
+
+# AZFD0001: AzureWebJobsStorage app setting is not present.
+
+This event is triggered when the function app does not have AzureWebJobsStorage app setting configured for the function app.
+
+| | Value |
+|-|-|
+| **Event ID** |AZFD0001|
+| **Category** |[Usage]|
+| **Severity** |Error|
+
+## Event description
+`AzureWebJobsStorage` app setting is used to store the connection string of the Azure Storage account associated with the function app. The Azure Functions runtime uses this connection for core behaviors such as coordinating singleton execution of timer triggers, default app key storage and storing diagnostic events.
+
+Refer to this article for more information on `AzureWebJobsStorage` information: https://docs.microsoft.com/en-us/azure/azure-functions/functions-app-settings#azurewebjobsstorage
+
+## How to resolve the event
+
+To resolve this event you need create a new app setting on your function app with name "AzureWebJobsStorage" with a valid Azure Storage account connection string as the value.
+
+## When to suppress the event
+
+This rule should not be suppressed.

articles/azure-functions/errors-diagnostics/diagnostic-events/azfd0002.md

@@ -0,0 +1,30 @@
+---
+title: "AZFD0002: Value of AzureWebJobsStorage app setting is invalid."
+titleSuffix: "Azure Functions"
+description: "AZFD0002: Value of AzureWebJobsStorage app setting is invalid."
+author: soninaren
+ms.author: nasoni
+ms.topic: troubleshooting
+ms.date: 09/03/2022
+---
+
+# AZFD0002: Value of AzureWebJobsStorage app setting is invalid.
+
+This event is triggered when the value of `AzureWebJobsStorage` is not a valid Azure Storage connection string or it is a Keyvault reference.
+
+| | Value |
+|-|-|
+| **Event ID** |AZFD0002|
+| **Category** |[Usage]|
+| **Severity** |Error|
+
+## Event description
+`AzureWebJobsStorage` app setting is used to store the connection string of the Azure Storage associated with the function app. The Azure Functions runtime uses this connection for core behaviors such as coordinating singleton execution of timer triggers, default app key storage and storing diagnostic events. This app setting needs to have a valid Azure Storage connection string.
+
+Refer to this article for more information on `AzureWebJobsStorage` information: https://docs.microsoft.com/en-us/azure/azure-functions/functions-app-settings#azurewebjobsstorage
+
+## How to resolve the event
+To resolve this event you need update the value of `AzureWebJobsStorage` app setting on your function app with a valid Azure Storage account connection string.
+
+## When to suppress the event
+This event should suppressed if your function app needs to use Azure Key Vault reference for storing the value of `AzureWebjobsStorage` app setting.

articles/azure-functions/errors-diagnostics/diagnostic-events/azfd0003.md

@@ -0,0 +1,32 @@
+---
+title: "AZFD0003: Encountered a StorageException while trying to fetch the diagnostic events."
+titleSuffix: "Azure Functions"
+description: "AZFD0003: Encountered a StorageException while trying to fetch the diagnostic events."
+author: soninaren
+ms.author: nasoni
+ms.topic: troubleshooting
+ms.date: 09/03/2022
+---
+
+# AZFD0003: Encountered a StorageException while trying to fetch the diagnostic events.
+
+This event is triggered when the Azure Storage connection string stored within the `AzureWebJobsStorage` does not have permissions to access table storage or causes the storage exceptions when trying to connect to Azure Storage.
+
+| | Value |
+|-|-|
+| **Event ID** |AZFD0003|
+| **Category** |[Usage]|
+| **Severity** |Error|
+
+## Event description
+`AzureWebJobsStorage` app setting is used to store the connection string of the Azure Storage associated with the function app. The Azure Functions runtime uses this connection for core behaviors such as coordinating singleton execution of timer triggers, default app key storage and storing diagnostic events. 
+
+This `AzureWebJobsStorage` needs to have permissions (read, write, delete, add and create) to table storage to be able store and fetch diagnostic events.
+
+Refer to this article for more information on `AzureWebJobsStorage` information: https://docs.microsoft.com/en-us/azure/azure-functions/functions-app-settings#azurewebjobsstorage
+
+## How to resolve the event
+To resolve this event the connection string stored in `AzureWebJobsStorage` app setting needs to have read, write, delete, add and create permissions to Azure Table storage. Additionally Azure Storage clients should be able to Azure Storage with this connection string without incurring Storage exceptions.
+
+## When to suppress the event
+This event should not be suppressed.