Validate event json

Feb 11, 2016 · 2 min read

Application Insights endpoint now supports events validation. It’s very easy to use - just post your telemetry item json to this endpoint and if response code is not 200 response text will contain the error message.

In C# code will look like this:

static async Task<bool> IsEventCorrect(string json)
{
    json = json.Replace("duration", "durationMs");

    HttpClient client = new HttpClient();
    var result = await client.PostAsync(
        "https://dc.services.visualstudio.com/v2/validate", 
        new ByteArrayContent(Encoding.UTF8.GetBytes(json)));

    Console.WriteLine(result.StatusCode);

    if (result.StatusCode != HttpStatusCode.OK)
    {
        var response = await result.Content.ReadAsStringAsync();
        Console.WriteLine(response);
        return await Task.FromResult(false);
    }
    return await Task.FromResult(true);
}

Result of execution will be something like this:

BadRequest
{
  "itemsReceived": 1,
  "itemsAccepted": 0,
  "errors": [
    {
      "index": 0,
      "statusCode": 400,
      "message": "106: Field 'duration' on type 'RequestData' is of 
                    incorrect type. Expected: string, Actual: undefined"
    }
  ]
}

Validation that this endpoint provides is not 100% strict. It guarantees that event is well-formed and has all the required fields. So it will be accepted by the /track endpoint. However, today it will allow sending some extra fields in json payload that will never be saved in backend.

With the .NET SDK it’s easy to generate test JSON. You’ll need to construct telemetry type of interest. In this example - RequestTelemetry. Then use JsonSerializer class to get byte array:

RequestTelemetry rt = new RequestTelemetry();

rt.Context.InstrumentationKey = "c92059c3-9428-43e7-9b85-a96fb7c9488f";

rt.Name = "RequestName";
rt.StartTime = DateTimeOffset.Now;
rt.Duration = TimeSpan.FromSeconds(10);

string json = Encoding.Default.GetString(
    JsonSerializer.Serialize(new List<ITelemetry>() { rt }, false));

json = json.Replace("duration", "durationMs");

var t = IsEventCorrect(json);

You can also fill out all the properties:

// Host context
rt.Context.Cloud.RoleName = "Role Name";
rt.Context.Cloud.RoleInstance = "Role Instance";

// Application context
rt.Context.Component.Version = "Application Version";

// Custom properties - limit 200 per application
rt.Context.Properties["DeploymentUnit"] = "SouthUS";

// Application user context
rt.Context.Location.Ip = "127.0.0.1";
rt.Context.Operation.SyntheticSource = "Test in production";

// Session context
rt.Context.User.Id = "Anonymous User Id";
rt.Context.Session.Id = "Anonymous Session Id";

rt.Context.User.AccountId = "Account Id";
rt.Context.User.AuthenticatedUserId = "Authenticated user id";

// Operation context
rt.Context.Operation.Id = "Root operatioin id";
rt.Context.Operation.ParentId = "Parent Operation Id";
rt.Context.Operation.Name = "Operation name";

Using C# JSON serialization and validation endpoint it is easier to understand why json formed by any other SDK is not being accepted by Application Insights endpoint.

Validate event json

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