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Hits with Errors

When a browser requests a webpage and related web resources (JavaScripts, images, stylesheets, ...), it sends HTTP requests to the different servers on which these resources reside. A request to a web resource is called a "hit". There may be many hits per page view since an HTML page can contain multiple files.

For each hit, the browser sends an HTTP request to the server, which responds back with an HTTP response. The HTTP response header contains a status code, which indicates whether the HTTP request has been successfully completed. Responses are grouped in five classes:

  1. Informational responses (100 to 199)
  2. Successful responses (200 to 299)
  3. Redirects (300 to 399)
  4. Client errors (400 to 499)
  5. Server errors (500 to 599)

As you can see, all status codes below 400 are related to successful requests. The main client errors you may encountered are the following:

Status code Description
400 - Bad Request The server could not understand the request due to invalid syntax
401 - Unauthorized Although the HTTP standard specifies "unauthorized", semantically this response means "unauthenticated". That is, the client must authenticate itself to get the requested response.
403 - Forbidden The client does not have access rights to the content; that is, it is unauthorized, so the server is refusing to give the requested resource. Unlike 401, the client's identity is known to the server.
404 - Not Found The server cannot find the requested resource

The main server errors you may encountered are the following:

Status code Description
500 - Internal Server Error The server has encountered a situation it doesn't know how to handle
502 - Bad Gateway This error response means that the server, while working as a gateway to get a response needed to handle the request, got an invalid response.
503 - Service Unavailable The server is not ready to handle the request. Common causes are a server that is down for maintenance or that is overloaded.
504 - Gateway Timeout This error response is given when the server is acting as a gateway and cannot get a response in time
505 - HTTP Version Not Supported The HTTP version used in the request is not supported by the server

The number of hits with errors reported by Kadiska corresponds to all HTTP requests for which the HTTP response status codes are above 399 as well as all resources fetch processes that fail without the server responding to the client at all.
The Kadiska interface provides this value as a percentage of errors, taking all hits occurrences into account. The example below shows the main performance metrics for a specific application. You can see here that 0.19% of the hits that are linked to this application generated errors.

If you need more details about the hits in errors, you can find this information in all tables of the "Resources" analysis section. For example, the following table shows the percentage of hits in error per initiator type:

If you want to identify the error codes themselves, these are provided in the Waterfall view of the "Activity" dashboard.
The following example shows:

  • errors that are related to a whole fetching process failure (4 occurrences)
  • one successful API call (status code 200):

The HTTP status codes are only provided for fetch and xmlhttprequest initiator types and when using the User-Watcher. They are not provided for other initiator types or when using App-Watcher.

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