Django database router, based on django-balancer, that sends reads for the specified models to the RoundRobinMasterSlaveRouter router in django-balancer. Uses thread locals to determine whether or not the it has been enabled for the current request. Will raise an exception if views or other code attempt to use it for write queries.

decorators.py

from functools import wraps

from routers import ForceReadForModelsRouter

__all__ = ['uses_forced_read_router']


def uses_forced_read_router(func):
    @wraps(func)
    def wrapper(req, *args, **kwargs):
        try:
            ForceReadForModelsRouter.enable()
            return func(req, *args, **kwargs)
        finally:
            ForceReadForModelsRouter.disable()
    return wrapper

routers.py

import threading

from balancer.routers import RoundRobinMasterSlaveRouter


class ForceReadForModelsRouter(RoundRobinMasterSlaveRouter):
    """
    Router that sends reads for the specified models to the
    RoundRobinMasterSlaveRouter router in django-balancer.  Uses thread locals
    to determine whether or not the it has been enabled for the current request.
    Will raise an exception if views or other code attempt to use it for write
    queries.
    """
    _locals = threading.local()

    app_models = {
        'appname': [
            'Model1',
            'Model2',
        ],
    }

    @classmethod
    def enable(cls):
        cls._locals.enabled = True

    @classmethod
    def disable(cls):
        cls._locals.enabled = False

    @classmethod
    def is_enabled(cls):
        return getattr(cls._locals, 'enabled', False)

    def _should_handle(self, model):
        return ForceReadForModelsRouter.is_enabled() and\
               model._meta.app_label in self.app_models and\
               model._meta.object_name in self.app_models[model._meta.app_label]

    def db_for_read(self, model, **hints):
        if self._should_handle(model):
            return super(ForceReadForModelsRouter, self).db_for_read(model, **hints)

    def db_for_write(self, model, **hints):
        if self._should_handle(model):
            model_name = '.'.join([model._meta.app_label,
                                   model._meta.object_name])
            raise ValueError('The {0} model is marked as read-only'.format(model_name))