Cloud Datastore Client - Class DatastoreSessionHandler (1.21.2)

Reference documentation and code samples for the Cloud Datastore Client class DatastoreSessionHandler.

Custom session handler backed by Cloud Datastore.

Instead of storing the session data in a local file, this handler stores the data in Cloud Datastore. The biggest benefit of doing this is the data can be shared by multiple instances, making it suitable for cloud applications.

The downside of using Cloud Datastore is that write operations will cost you some money, so it is highly recommended to minimize the write operations while using this handler. In order to do so, keep the data in the session as limited as possible; for example, it is ok to put only signed-in state and the user id in the session with this handler. However, for example, it is definitely not recommended that you store your application's whole undo history in the session, because every user operation will cause a Datastore write, potentially costing you a lot of money.

This handler doesn't provide pessimistic lock for session data. Instead, it uses Datastore Transaction for data consistency. This means that if multiple requests are modifying the same session data simultaneously, there will be more probablity that some of the write operations will fail.

If you are building an ajax application which may issue multiple requests to the server, please design your session data carefully in order to avoid possible data contentions. Also please see the 2nd example below for how to properly handle errors on write operations.

The handler sets the Datastore namespace to the value of session.save_path, isolating the session data from your application data, it also uses the session.name as the Datastore kind, and the session id as the Datastore id. By default, it does nothing on gc for reducing the cost. Pass positive value up to 1000 for $gcLimit parameter to delete entities in gc.

Note: The datastore transaction only lasts 60 seconds. If this handler is used for long running requests, it will fail on write.

The first example automatically writes the session data. It's handy, but the code doesn't stop even if it fails to write the session data, because the write happens when the code exits. If you want to know whether the session data is correctly written to the Datastore, you need to call session_write_close() explicitly and then handle E_USER_WARNING properly. See the second example for a demonstration.

Example:

use Google\Cloud\Datastore\DatastoreClient;
use Google\Cloud\Datastore\DatastoreSessionHandler;

$datastore = new DatastoreClient();

$handler = new DatastoreSessionHandler($datastore);

session_set_save_handler($handler, true);
session_save_path('sessions');
session_start();

// Then write and read the $_SESSION array.
$_SESSION['name'] = 'Bob';
echo $_SESSION['name'];

// Session Handler with Error Handling
use Google\Cloud\Datastore\DatastoreClient;
use Google\Cloud\Datastore\DatastoreSessionHandler;

$datastore = new DatastoreClient();

$handler = new DatastoreSessionHandler($datastore);
session_set_save_handler($handler, true);
session_save_path('sessions');
session_start();

// Then read and write the $_SESSION array.
$_SESSION['name'] = 'Bob';

function handle_session_error($errNo, $errStr, $errFile, $errLine) {
    // We throw an exception here, but you can do whatever you need.
    throw new RuntimeException("$errStr in $errFile on line $errLine", $errNo);
}

set_error_handler('handle_session_error', E_USER_WARNING);
// If `write` fails for any reason, an exception will be thrown.
session_write_close();
restore_error_handler();

// You can still read the $_SESSION array after closing the session.
echo $_SESSION['name'];

Create a custom session handler backed by Cloud Datastore.

Start a session, by creating a transaction for the later write.

Just return true for this implementation.

Read the session data from Cloud Datastore.

Write the session data to Cloud Datastore.

Delete the session data from Cloud Datastore.

Delete the old session data from Cloud Datastore.