Node.js App Service application / console logs are not being streamed to event hub, but HTTP logs are

Question

Node.js App Service application / console logs are not being streamed to event hub, but HTTP logs are

Scott 0

Hi,

I have a Node.js web app running in App Services. The code contains console.log() statements.

If I click on "Log Stream" in the Azure console, I can see the outputs of those log statements. I have also configured logging to the file system under "App Service logs". Using kudu, I can see those logs files being created under "C:\home\LogFiles\Application".

I have also configured a "Diagnostic Setting" to stream the logs to an event hub. This is where I am having an issue. Even though I have selected every category of log in that setting, including "App Service Console Logs" and "App Service Application Logs", the only logs I see being streamed to the event hub are the "HTTP logs". I am observing this using the hub's Data Explorer. The event hub is deployed to the same region as my web app.

What am I missing? Why are these log types not being streamed to the event hub?

Thanks,

Scott

Scott 0 Reputation points

2025-02-27T14:05:55.59+00:00

Another point I forgot to mention - I created a second Diagnostic Setting to try sending the logs to a Log Analytics workspace, instead of streaming them to an Event Hub.

I observed a similar problem there. I see an "AppServiceHTTPLogs" table get created in that workspace and it contains the HTTP logs, but there are no tables / logs for the other log categories.
Scott 0 Reputation points

2025-02-27T14:16:47.06+00:00

Another thing - I am currently running it on Windows, so uses IISNode. Maybe that has something to do with it.

Kantamsetti Aslesha 80 Microsoft External Staff

Hi @Scott

Modify or create a web.config file in the root of your Node.js application:

<configuration>
  <system.webServer>
    <handlers>
      <add name="iisnode" path="server.js" verb="*" modules="iisnode" />
    </handlers>
    <iisnode loggingEnabled="true" logDirectory="C:\home\LogFiles\nodejs" />
  </system.webServer>
</configuration>

Kantamsetti Aslesha 80 Reputation points Microsoft External Staff

2025-03-07T11:00:53.84+00:00

Hi @Scott

Just checking in to see if the web.config update helped or if you're still facing the same issue. Let me know if you were able to verify whether logs are appearing in C:\home\LogFiles\nodejs and if the diagnostic settings are correctly configured.

Happy to troubleshoot further if needed! Looking forward to your update.
Scott 0 Reputation points

2025-03-07T17:07:07.53+00:00

Hi Kantamsetti,

Thanks for the suggestion, and sorry for not responding sooner!

I already had a web.config with most of that, minus a logDirectory. Without that setting, I could already see the console logs being written to .txt files on the file system under the C:\home\LogFiles\Application folder. I'm using the Kudu Console to see this.

The logs are being written to the file system because I have enabled that under Application Service logs. The log level is Verbose. Specifying an IIS Node log directory of C:\home\LogFiles\nodejs does not appear change this behaviour - I still see the logs being written to the file system, in that same directory. However, it does appear to completely break streaming the logs to event hub. Without a log directory set, I see the HTTP logs get streamed. With a log directory set, I see nothing getting streamed.

This is the Diagnostic Setting. As you can see, it includes the relevant log categories. It's as if it is not finding the Application / Console logs that have been written to the file system.

Thanks,

Scott
Kantamsetti Aslesha 80 Reputation points Microsoft External Staff

2025-03-10T05:18:08.8233333+00:00
Hi @Scott

If logs still don’t appear, modify console.log() calls to use structured logging:

const util = require("util"); console.log(util.inspect("Test log output"));
Kantamsetti Aslesha 80 Reputation points Microsoft External Staff

2025-03-11T05:15:49.86+00:00

Hi @Scott

Just following up to check if you were able to resolve the issue using the suggested steps. Let me know how I can assist further!
Scott 0 Reputation points

2025-03-13T11:42:34.5733333+00:00

Hi Kantamsetti,

Thanks for the suggestion but it does not make a difference.

Whether I'm outputting structured JSON logs or simple strings to the console, they all reach the file system, but are not then streamed to the event hub via the diagnostic setting. It's as if they are created, but not then picked up and forwarded on.

Scott

Your answer

Scott 0 Reputation points

2025-02-27T14:05:55.59+00:00

Another point I forgot to mention - I created a second Diagnostic Setting to try sending the logs to a Log Analytics workspace, instead of streaming them to an Event Hub.

I observed a similar problem there. I see an "AppServiceHTTPLogs" table get created in that workspace and it contains the HTTP logs, but there are no tables / logs for the other log categories.
Scott 0 Reputation points

2025-02-27T14:16:47.06+00:00

Another thing - I am currently running it on Windows, so uses IISNode. Maybe that has something to do with it.
Kantamsetti Aslesha 80 Reputation points Microsoft External Staff

2025-03-06T10:37:51.87+00:00

Hi @Scott

Modify or create a web.config file in the root of your Node.js application:

<configuration> <system.webServer> <handlers> <add name="iisnode" path="server.js" verb="*" modules="iisnode" /> </handlers> <iisnode loggingEnabled="true" logDirectory="C:\home\LogFiles\nodejs" /> </system.webServer> </configuration>
Kantamsetti Aslesha 80 Reputation points Microsoft External Staff

2025-03-07T11:00:53.84+00:00

Hi @Scott

Just checking in to see if the web.config update helped or if you're still facing the same issue. Let me know if you were able to verify whether logs are appearing in C:\home\LogFiles\nodejs and if the diagnostic settings are correctly configured.

Happy to troubleshoot further if needed! Looking forward to your update.
Scott 0 Reputation points

2025-03-07T17:07:07.53+00:00

Hi Kantamsetti,

Thanks for the suggestion, and sorry for not responding sooner!

I already had a web.config with most of that, minus a logDirectory. Without that setting, I could already see the console logs being written to .txt files on the file system under the C:\home\LogFiles\Application folder. I'm using the Kudu Console to see this.

The logs are being written to the file system because I have enabled that under Application Service logs. The log level is Verbose. Specifying an IIS Node log directory of C:\home\LogFiles\nodejs does not appear change this behaviour - I still see the logs being written to the file system, in that same directory. However, it does appear to completely break streaming the logs to event hub. Without a log directory set, I see the HTTP logs get streamed. With a log directory set, I see nothing getting streamed.

This is the Diagnostic Setting. As you can see, it includes the relevant log categories. It's as if it is not finding the Application / Console logs that have been written to the file system.

Thanks,

Scott
Kantamsetti Aslesha 80 Reputation points Microsoft External Staff

2025-03-10T05:18:08.8233333+00:00

Hi @Scott

If logs still don’t appear, modify console.log() calls to use structured logging:

const util = require("util"); console.log(util.inspect("Test log output"));
Kantamsetti Aslesha 80 Reputation points Microsoft External Staff

2025-03-11T05:15:49.86+00:00

Hi @Scott

Just following up to check if you were able to resolve the issue using the suggested steps. Let me know how I can assist further!
Scott 0 Reputation points

2025-03-13T11:42:34.5733333+00:00

Hi Kantamsetti,

Thanks for the suggestion but it does not make a difference.

Whether I'm outputting structured JSON logs or simple strings to the console, they all reach the file system, but are not then streamed to the event hub via the diagnostic setting. It's as if they are created, but not then picked up and forwarded on.

Scott

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Node.js App Service application / console logs are not being streamed to event hub, but HTTP logs are

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