FastAPI: add redis integration

This includes the addition of the python-fakeredis package,
used for stubbing python-redis when a user does not have a
configured cache.

Signed-off-by: Kevin Morris <kevr@0cost.org>

INSTALL

@@ -57,7 +57,7 @@ read the instructions below.
 
 (FastAPI-Specific)
 
-    # pacman -S redis python-redis
+    # pacman -S redis python-redis python-fakeredis
     # systemctl enable --now redis
 
 5) Create a new MySQL database and a user and import the aurweb SQL schema:

aurweb/redis.py

@@ -0,0 +1,57 @@
+import logging
+
+import fakeredis
+
+from redis import ConnectionPool, Redis
+
+import aurweb.config
+
+logger = logging.getLogger(__name__)
+pool = None
+
+
+class FakeConnectionPool:
+    """ A fake ConnectionPool class which holds an internal reference
+    to a fakeredis handle.
+
+    We normally deal with Redis by keeping its ConnectionPool globally
+    referenced so we can persist connection state through different calls
+    to redis_connection(), and since FakeRedis does not offer a ConnectionPool,
+    we craft one up here to hang onto the same handle instance as long as the
+    same instance is alive; this allows us to use a similar flow from the
+    redis_connection() user's perspective.
+    """
+
+    def __init__(self):
+        self.handle = fakeredis.FakeStrictRedis()
+
+    def disconnect(self):
+        pass
+
+
+def redis_connection():  # pragma: no cover
+    global pool
+
+    disabled = aurweb.config.get("options", "cache") != "redis"
+
+    # If we haven't initialized redis yet, construct a pool.
+    if disabled:
+        logger.debug("Initializing fake Redis instance.")
+        if pool is None:
+            pool = FakeConnectionPool()
+        return pool.handle
+    else:
+        logger.debug("Initializing real Redis instance.")
+        if pool is None:
+            redis_addr = aurweb.config.get("options", "redis_address")
+            pool = ConnectionPool.from_url(redis_addr)
+
+    # Create a connection to the pool.
+    return Redis(connection_pool=pool)
+
+
+def kill_redis():
+    global pool
+    if pool:
+        pool.disconnect()
+        pool = None

conf/config.defaults

@@ -36,11 +36,13 @@ enable-maintenance = 1
 maintenance-exceptions = 127.0.0.1
 render-comment-cmd = /usr/local/bin/aurweb-rendercomment
 localedir = /srv/http/aurweb/aur.git/web/locale/
-# memcache or apc
+; memcache, apc, or redis
+; memcache/apc are supported in PHP, redis is supported in Python.
 cache = none
 cache_pkginfo_ttl = 86400
 memcache_servers = 127.0.0.1:11211
 salt_rounds = 12
+redis_address = redis://localhost
 
 [ratelimit]
 request_limit = 4000

conf/config.dev

@@ -28,10 +28,13 @@ enable-maintenance = 0
 localedir = YOUR_AUR_ROOT/web/locale
 ; In production, salt_rounds should be higher; suggested: 12.
 salt_rounds = 4
+; See config.defaults comment about cache.
 cache = none
 ; In docker, the memcached host is available. On a user's system,
 ; this should be set to localhost (most likely).
 memcache_servers = memcached:11211
+; If cache = 'redis' this address is used to connect to Redis.
+redis_address = redis://127.0.0.1
 
 [notifications]
 ; For development/testing, use /usr/bin/sendmail

docker/scripts/install-deps.sh

@@ -15,6 +15,6 @@ pacman -Syu --noconfirm --noprogressbar \
     python-email-validator openssh python-lxml mariadb mariadb-libs \
     python-isort flake8 cgit uwsgi uwsgi-plugin-cgi php php-fpm \
     python-asgiref uvicorn python-feedgen memcached php-memcached \
-    python-redis redis
+    python-redis redis python-fakeredis
 
 exec "$@"

test/test_asgi.py

@@ -9,6 +9,24 @@ from fastapi import HTTPException
 
 import aurweb.asgi
 import aurweb.config
+import aurweb.redis
+
+
+@pytest.mark.asyncio
+async def test_asgi_startup_session_secret_exception(monkeypatch):
+    """ Test that we get an IOError on app_startup when we cannot
+    connect to options.redis_address. """
+
+    redis_addr = aurweb.config.get("options", "redis_address")
+
+    def mock_get(section: str, key: str):
+        if section == "fastapi" and key == "session_secret":
+            return None
+        return redis_addr
+
+    with mock.patch("aurweb.config.get", side_effect=mock_get):
+        with pytest.raises(Exception):
+            await aurweb.asgi.app_startup()
 
 
 @pytest.mark.asyncio

test/test_redis.py

@@ -0,0 +1,40 @@
+from unittest import mock
+
+import pytest
+
+import aurweb.config
+
+from aurweb.redis import redis_connection
+
+
+@pytest.fixture
+def rediss():
+    """ Create a RedisStub. """
+    def mock_get(section, key):
+        return "none"
+
+    with mock.patch("aurweb.config.get", side_effect=mock_get):
+        aurweb.config.rehash()
+        redis = redis_connection()
+    aurweb.config.rehash()
+
+    yield redis
+
+
+def test_redis_stub(rediss):
+    # We don't yet have a test key set.
+    assert rediss.get("test") is None
+
+    # Set the test key to abc.
+    rediss.set("test", "abc")
+    assert rediss.get("test").decode() == "abc"
+
+    # Test expire.
+    rediss.expire("test", 0)
+    assert rediss.get("test") is None
+
+    # Now, set the test key again and use delete() on it.
+    rediss.set("test", "abc")
+    assert rediss.get("test").decode() == "abc"
+    rediss.delete("test")
+    assert rediss.get("test") is None