Facing issue with Function App

Question

I need to check this function App complete logs for 12-August-2026. Because in storage account logs it is showing as Metadata created but in FunctionApp logs its now showing the logs after Validation successful completion for Request no. REQ0000003509 at timestamp like 8/12/2026, 2:45:07.485 AM to 8/12/2026, 2:49:07.488 AM

Answer 1

To check complete Azure Function logs for 12-Aug-2026, use the logs stored in Application Insights / Log Analytics instead of Log Stream. Log Stream is for live output, while historical function logs can be queried from the FunctionAppLogs table.

1. In the Azure portal, open the Function App.
2. Go to Diagnose and solve problems and run Function Configuration Checks.
   • Verify that only one Application Insights setting exists:
     • APPLICATIONINSIGHTS_CONNECTION_STRING or
     • APPINSIGHTS_INSTRUMENTATIONKEY
   • APPLICATIONINSIGHTS_CONNECTION_STRING is the recommended setting.
3. If Application Insights is enabled, query the FunctionAppLogs table for the time window around the missing activity.

Example KQL to review logs around the reported time:

FunctionAppLogs
| where TimeGenerated between (datetime(2026-08-12 02:45:07.485) .. datetime(2026-08-12 02:49:07.488))
| project TimeGenerated, HostInstanceId, Level, Category, Message, FunctionInvocationId, FunctionName, ExceptionType, ExceptionMessage, _ResourceId
| sort by TimeGenerated asc

To focus on warnings and errors:

FunctionAppLogs
| where TimeGenerated between (datetime(2026-08-12 02:45:07.485) .. datetime(2026-08-12 02:49:07.488))
| where Level == "Warning" or Level == "Error"
| project TimeGenerated, HostInstanceId, Level, Message, ExceptionType, ExceptionMessage, FunctionInvocationId, FunctionName
| sort by TimeGenerated asc

To review execution results for function invocations:

FunctionAppLogs
| where TimeGenerated between (datetime(2026-08-12 02:45:07.485) .. datetime(2026-08-12 02:49:07.488))
| where Category startswith "Function." and Message startswith "Executed "
| parse Message with "Executed '" Name "' (" Result ", Id=" Id ", Duration=" Duration:long "ms)"
| project TimeGenerated, Name, Result, Id, Duration, FunctionInvocationId, _ResourceId
| sort by TimeGenerated asc

If logs stop after "Validation successful completion", check these areas:

• Sampling may be enabled and can limit telemetry sent to Application Insights.
• Log verbosity may be too low. Azure Functions logging can be controlled through host.json categories and log levels.
• If the Function App is integrated with a virtual network, outbound port 443 must be open so telemetry can reach Application Insights endpoints.
• Use Diagnose and solve problems → Connectivity Troubleshooter to check outbound restrictions, DNS, storage, and firewall issues.

If diagnostic settings are configured, the Azure Functions-specific resource log is FunctionAppLogs.

Useful columns for this investigation are:

• TimeGenerated
• Level
• Category
• Message
• FunctionInvocationId
• FunctionName
• ExceptionType
• ExceptionMessage
• HostInstanceId

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• Application Insights logs are missing or incorrect for Azure Function App
• Application Insights logs are missing or incorrect for Azure Function App
• Queries for the FunctionAppLogs table
• Resolve "Function App Down or Reporting Errors" issues
• FunctionAppLogs
• Azure Functions monitoring data reference
• Viewing logs of Azure functions - Microsoft Q&A