How to check logs and usage (CPU/RAM/DB) of Azure function written in .NET?

Question

I wrote an Azure function that is triggered every day at 4AM. I published it and it had its first successful run today at 4AM. I am sure that it ran successfully, because it put the expected data in the database.

[FunctionName("MyFunction")]
public async Task RunAsync([TimerTrigger("0 0 4 * * *")]TimerInfo myTimer, ILogger log)
{
    // function body
}

I am using the log object to log information and error logs in the function body:

log.LogInformation("This is information log.");
// ...
log.LogError("This is error log.");

If I connect to the Log stream in Azure while the function runs, I see the logs. Where can I find them later? Only now I set the diagnostic setting to send FunctionAppLogs to Log Analytics workspace:

Will it resolve my issue?

Where can I see the details about executions (success/failure/time and maybe resource consumption) of my function? If I go to Function app, then choose functions, choose MyFunction from the list and go to the "Monitor" blade, I see only two failures (out of many!) from a few days ago. This failures were logged when the function was triggered via HTTP GET (now it's triggered by timer).

EDIT

This is the content of my hosts.json file:

{
    "version": "2.0",
    "logging": {
        "fileLoggingMode": "always",
        "applicationInsights": {
            "samplingSettings": {
                "isEnabled": true
            }
        },
        "logLevel": {
            "default": "Information",
            "Host.Results": "Error",
            "Function": "Error"
        }
    }
}

My understanding is that Application Insights should show some data (samplingSettings is enabled) and I should have the logs for my function (default is Information). I am unsure about the Function: Error setting only. In the documentation it is explained in the following way:

For logs of Host.Results or Function, only log events at Error or a higher level.
...
For all other logs, including user logs, log only Information level and higher events.

Are the logs that I create in code "user logs" or "logs for Function"?

AI logs. Check picture below. – Juanma Feliu Mar 24 '21 at 20:36 — Juanma Feliu, Mar 24 '21 at 20:36

Juanma Feliu · Answer 1 · 2021-03-29T14:34:32.463

Where can i find them later?

Where can I see the details about executions?

Azure Functions creates an internal Application insight to monitor them, you can use a host.json file to configure log levels, sampling and so on.

host.json sample:

{
    "version": "2.0",
    "aggregator": {
        "batchSize": 1000,
        "flushTimeout": "00:00:30"
    },
    "extensions": {
        "blobs": {},
        "cosmosDb": {},
        "durableTask": {},
        "eventHubs": {},
        "http": {},
        "queues": {},
        "sendGrid": {},
        "serviceBus": {}
    },
    "extensionBundle": {
        "id": "Microsoft.Azure.Functions.ExtensionBundle",
        "version": "[1.*, 2.0.0)"
    },
    "functions": [ "QueueProcessor", "GitHubWebHook" ],
    "functionTimeout": "00:05:00",
    "healthMonitor": {
        "enabled": true,
        "healthCheckInterval": "00:00:10",
        "healthCheckWindow": "00:02:00",
        "healthCheckThreshold": 6,
        "counterThreshold": 0.80
    },
    "logging": {
        "fileLoggingMode": "debugOnly",
        "logLevel": {
          "Function.MyFunction": "Trace",
          "default": "None"
        },
        "applicationInsights": {
            "samplingSettings": {
              "isEnabled": true,
              "maxTelemetryItemsPerSecond" : 20,
              "evaluationInterval": "01:00:00",
              "initialSamplingPercentage": 100.0, 
              "samplingPercentageIncreaseTimeout" : "00:00:01",
              "samplingPercentageDecreaseTimeout" : "00:00:01",
              "minSamplingPercentage": 0.1,
              "maxSamplingPercentage": 100.0,
              "movingAverageRatio": 1.0,
              "excludedTypes" : "Dependency;Event",
              "includedTypes" : "PageView;Trace"
            },
            "enableLiveMetrics": true,
            "enableDependencyTracking": true,
            "enablePerformanceCountersCollection": true,            
            "httpAutoCollectionOptions": {
                "enableHttpTriggerExtendedInfoCollection": true,
                "enableW3CDistributedTracing": true,
                "enableResponseHeaderInjection": true
            },
            "snapshotConfiguration": {
                "agentEndpoint": null,
                "captureSnapshotMemoryWeight": 0.5,
                "failedRequestLimit": 3,
                "handleUntrackedExceptions": true,
                "isEnabled": true,
                "isEnabledInDeveloperMode": false,
                "isEnabledWhenProfiling": true,
                "isExceptionSnappointsEnabled": false,
                "isLowPrioritySnapshotUploader": true,
                "maximumCollectionPlanSize": 50,
                "maximumSnapshotsRequired": 3,
                "problemCounterResetInterval": "24:00:00",
                "provideAnonymousTelemetry": true,
                "reconnectInterval": "00:15:00",
                "shadowCopyFolder": null,
                "shareUploaderProcess": true,
                "snapshotInLowPriorityThread": true,
                "snapshotsPerDayLimit": 30,
                "snapshotsPerTenMinutesLimit": 1,
                "tempFolder": null,
                "thresholdForSnapshotting": 1,
                "uploaderProxy": null
            }
        }
    },
    "managedDependency": {
        "enabled": true
    },
    "retry": {
      "strategy": "fixedDelay",
      "maxRetryCount": 5,
      "delayInterval": "00:00:05"
    },
    "singleton": {
      "lockPeriod": "00:00:15",
      "listenerLockPeriod": "00:01:00",
      "listenerLockRecoveryPollingInterval": "00:01:00",
      "lockAcquisitionTimeout": "00:01:00",
      "lockAcquisitionPollingInterval": "00:00:03"
    },
    "watchDirectories": [ "Shared", "Test" ],
    "watchFiles": [ "myFile.txt" ]
}

The aggregator indicates log flush time and limit number of executions to be logged. Azure functions use Adaptive Sampling for AI and the volume is adjusted automatically to keep within a specified maximum rate of traffic, and is controlled via the setting MaxTelemetryItemsPerSecond

To configure/disable Sampling in Azure functions for development environments you can manipulate host.json like this:

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

Change your loglevel to "trace" in your host.json.

Trace logs:

EDIT

public static class Function1
    {
        [FunctionName("Function1")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            string name = req.Query["name"];

            string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
            dynamic data = JsonConvert.DeserializeObject(requestBody);
            name = name ?? data?.name;

            string responseMessage = string.IsNullOrEmpty(name)
                ? "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response."
                : $"Hello, {name}. This HTTP triggered function executed successfully.";

            return new OkObjectResult(responseMessage);
        }
    }

Host.json:

{
    "version": "2.0",
   "logging": {
        "fileLoggingMode": "debugOnly",
        "logLevel": {
          "Function.MyFunction": "Trace",
          "default": "None"
        },
        "applicationInsights": {
            "samplingSettings": {
              "isEnabled": false,
              "maxTelemetryItemsPerSecond" : 20,
              "evaluationInterval": "01:00:00",
              "initialSamplingPercentage": 100.0, 
              "samplingPercentageIncreaseTimeout" : "00:00:01",
              "samplingPercentageDecreaseTimeout" : "00:00:01",
              "minSamplingPercentage": 0.1,
              "maxSamplingPercentage": 100.0,
              "movingAverageRatio": 1.0,
              "includedTypes" : "PageView;Trace"
            },
            "enableLiveMetrics": true,
            "enableDependencyTracking": true,
            "enablePerformanceCountersCollection": true,            
            "httpAutoCollectionOptions": {
                "enableHttpTriggerExtendedInfoCollection": true,
                "enableW3CDistributedTracing": true,
                "enableResponseHeaderInjection": true
            },
            "snapshotConfiguration": {
                "agentEndpoint": null,
                "captureSnapshotMemoryWeight": 0.5,
                "failedRequestLimit": 3,
                "handleUntrackedExceptions": true,
                "isEnabled": true,
                "isEnabledInDeveloperMode": false,
                "isEnabledWhenProfiling": true,
                "isExceptionSnappointsEnabled": false,
                "isLowPrioritySnapshotUploader": true,
                "maximumCollectionPlanSize": 50,
                "maximumSnapshotsRequired": 3,
                "problemCounterResetInterval": "24:00:00",
                "provideAnonymousTelemetry": true,
                "reconnectInterval": "00:15:00",
                "shadowCopyFolder": null,
                "shareUploaderProcess": true,
                "snapshotInLowPriorityThread": true,
                "snapshotsPerDayLimit": 30,
                "snapshotsPerTenMinutesLimit": 1,
                "tempFolder": null,
                "thresholdForSnapshotting": 1,
                "uploaderProxy": null
            }
        }
    }
}

ExcludedTypes node has been removed.

UPDATE: Function -> Functions -> click in your function -> Monitor -> configure AI

I editted my question and added my hosts.json file. I have a question regarding my configuration. Could you have a look and let me know if you know the answer? — Michal B., Mar 24 '21 at 08:55
If you are not in a production environment use: "samplingSettings": { "isEnabled": false } so you are logging everything. You can only log last 90 days in AI. — Juanma Feliu, Mar 24 '21 at 09:19
Thanks for the advice. However, I would like to log things in production and this is my problem currently. Are the logs that I create in code "user logs" or "logs for Function"? I am trying to figure out why I am missing logs for my function in Azure. — Michal B., Mar 24 '21 at 09:22
Sampling works like that. If you have 500 requests within 10 minutes with a 200 response and a 90% Sampling you will get a simplified view of your requests/response logged. https://learn.microsoft.com/en-us/azure/azure-monitor/app/sampling — Juanma Feliu, Mar 24 '21 at 09:28
Your logs should be displayed in Application Insights as "Trace". Adding a picture in the comment above. — Juanma Feliu, Mar 24 '21 at 16:12
Disable Sampling please and downgrade your log level to "Trace" — Juanma Feliu, Mar 24 '21 at 17:22
What's the easiest way to see whether the function executed successfully or failed with an exception? If I publish a function with a bug and it fails I do not see any information about it. I only know it failed, because I miss the expected data in the database... :/ — Michal B., Mar 25 '21 at 15:38
Use try catch block and log error inside your function. Log.LogError("X") You should be able to check everything in application insights -> Search button. — Juanma Feliu, Mar 25 '21 at 15:54
I see the logs after directing them to Log Analytics workspace. Can you advise me whether I should create separate Log Analytics workspaces for separate functions or rather direct logs from all functions to a single workspace? — Michal B., Mar 29 '21 at 14:00
updated: how i did to configure your function with a new or existing Application Insights. — Juanma Feliu, Mar 29 '21 at 14:35

How to check logs and usage (CPU/RAM/DB) of Azure function written in .NET?

1 Answers1