bookwyrm/bookwyrm/redis_store.py

""" access the activity stores stored in redis """
from abc import ABC, abstractmethod
import redis

from bookwyrm import settings

r = redis.Redis(
    host=settings.REDIS_ACTIVITY_HOST, port=settings.REDIS_ACTIVITY_PORT, db=0
)


class RedisStore(ABC):
    """ sets of ranked, related objects, like statuses for a user's feed """
    max_length = settings.MAX_STREAM_LENGTH

    def get_value(self, obj):
        """ the object and rank """
        return {obj.id: self.get_rank(obj)}

    def add_object_to_related_stores(self, obj, execute=True):
        """ add an object to all suitable stores """
        value = self.get_value(obj)
        # we want to do this as a bulk operation, hence "pipeline"
        pipeline = r.pipeline()
        for store in self.get_stores_for_object(obj):
            # add the status to the feed
            pipeline.zadd(store, value)
            # trim the store
            pipeline.zremrangebyrank(
                store, 0, -1 * self.max_length
            )
        if not execute:
            return pipeline
        # and go!
        return pipeline.execute()

    def remove_object_from_related_stores(self, obj):
        """ remove an object from all stores """
        pipeline = r.pipeline()
        for store in self.get_stores_for_object(obj):
            pipeline.zrem(store, -1, obj.id)
        pipeline.execute()

    def bulk_add_objects_to_store(self, objs, store):
        """ add a list of objects to a given store """
        pipeline = r.pipeline()
        for obj in objs[:self.max_length]:
            pipeline.zadd(store, self.get_value(obj))
        if objs:
            pipeline.zremrangebyrank(
                store, 0, -1 * self.max_length
            )
        pipeline.execute()

    def bulk_remove_objects_from_store(self, objs, store):
        """ remoev a list of objects from a given store """
        pipeline = r.pipeline()
        for obj in objs[:self.max_length]:
            pipeline.zrem(store, -1, obj.id)
        pipeline.execute()

    def get_store(self, store):  # pylint: disable=no-self-use
        """ load the values in a store """
        return r.zrevrange(store, 0, -1)

    def populate_store(self, store):
        """ go from zero to a store """
        pipeline = r.pipeline()
        queryset = self.get_objects_for_store(store)

        for obj in queryset[:self.max_length]:
            pipeline.zadd(store, self.get_value(obj))

        # only trim the store if objects were added
        if queryset.exists():
            pipeline.zremrangebyrank(
                store, 0, -1 * self.max_length
            )
        pipeline.execute()

    @abstractmethod
    def get_objects_for_store(self, store):
        """ a queryset of what should go in a store, used for populating it """

    @abstractmethod
    def get_stores_for_object(self, obj):
        """ the stores that an object belongs in """

    @abstractmethod
    def get_rank(self, obj):
        """ how to rank an object """