django-readwrite 0.0.1

This library is not ready for use yet.

Read/write database splitting for Django, based on the HTTP request method.

Tested against Django 1.2.x

Features:

• Makes Django use a configured database for an entire HTTP request according to configured HTTP methods (GET, POST, etc) and URL paths.
• Chooses a random connection if there are multiple databases configured for a request - poor man's database load balancing.
• Raises an error if a view tries to write to a read-only database.
• No issues with database replica latency, and reading data before it has been synchronized.
• No need to specify any database with using= in all of your model/transaction code.
• No need to set up database routers.
• Database transactions work as expectd; reads won't read from a different transaction to the writes.
• Read-only command to force all requests to use a read-only database connection.

Extras:

• @pre_commit and @post_commit function decorators.

Usage

1. Add django_readwrite to the top of your INSTALLED_APPS setting.
2. Replaces TransactionMiddleware in MIDDLEWARE_CLASSES with:
   • django_readwrite.middleware.MultiDBMiddleware
   • django_readwrite.middleware.ReadOnlyMiddleware
   • django_readwrite.middleware.MultiDBTransactionMiddleware
3. Update your database settings to include:
   • HTTP_PATHS
   • HTTP_METHODS
   • READ_ONLY or READ_ONLY_WARNING

Example:

DATABASES = {
    'default': {
        'ENGINE': engine,
        'HOST': primary_host,
        'PORT': primary_port,
        'NAME': primary_database,
        'USER': primary_user,
        'PASSWORD': primary_password,

        # Set HTTP_PATHS to force request paths to use a database.
        # This ensures that the admin always uses the primary database.
        'HTTP_PATHS': ['/admin/'],

    },
    'readonly1': {
        'ENGINE': engine,
        'HOST': replica1_host,
        'PORT': replica1_post,
        'NAME': replica1_name,
        'USER': replica1_user,
        'PASSWORD': replica1_password,

        # Set HTTP_METHODS to force request methods to use a database.
        # This ensures that GET and HEAD requests use the read-only replica.
        # Adding None to the list means that it will also be used outside
        # of requests (e.g. if your application access the database during
        # process initialization).
        'HTTP_METHODS': ('GET', 'HEAD', None),

        # Set READ_ONLY to disable write SQL queries on a database.
        'READ_ONLY': True,

        # Enable autocommit avoid creating transactions
        # on databases which will never have writes.
        'OPTIONS': {
            'autocommit': True,
        }
    }
    'readonly2': {...}
}