Cronet request lifecycle

Learn about the lifecycle of requests created using Cronet and how to manage them using the callback methods provided by the library.

Lifecycle overview

Network requests created using the Cronet Library are represented by the UrlRequest class. The following concepts are important to understand the UrlRequest lifecycle:

States

A state is the particular condition that the request is in at a specific time. UrlRequest objects created using the Cronet Library move through different states in their lifecycle. The request lifecycle includes an initial state, and multiple transitional and final states.

UrlRequest methods

Clients can call specific methods on UrlRequest objects depending on the state. The methods move the request from one state to another.

Callback methods

By implementing methods of the UrlRequest.Callback class, your app can receive updates about the progress of the request. You can implement the callback methods to call methods of the UrlRequest object that take the lifecycle from a state to another.

The following list describes the flow of the UrlRequest lifecycle:

1. The lifecycle is in the Started state after your app calls the start() method.
2. The server could send a redirect response, which takes the flow to the onRedirectReceived() method. In this method, you can take one of the following client actions:
   • Follow the redirect using followRedirect(). This method takes the request back to the Started state.
   • Cancel the request using cancel(). This method takes the request to the onCanceled() method where the app can perform additional operations before the request is moved to the Canceled final state.
3. After the app follows all the redirects, the server sends the response headers and the onResponseStarted() method is called. The request is in the Waiting for read() state. The app should call the read() method to attempt to read part of the response body. After read() is called, the request is in the Reading state, where there are the following possible outcomes:
   • The reading action was successful, but there is more data available. The onReadCompleted() is called and the request is in the Waiting for read() state again. The app should call the read() method again to continue reading the response body. The app could also stop reading the request by using the cancel() method .
   • The reading action was successful, and there is no more data available. The onSucceeded() method is called and the request is now in the Succeeded final state.
   • The reading action failed. The onFailed method is called and the final state of the request is now Failed.

The following diagram shows the lifecycle of a UrlRequest object:

The Cronet request lifecycle

Legend
initial state	final state
transitional state	callback methods
UrlRequest methods