Transient data¶
Introduction¶
In the context of Websauna transient data primarly means
Visitor session data (authentication, shopping carts, etc.)
Cache
Other non-critical, fast and frequently accessed data
Websauna defaults to Redis key value store for transient data storage.
Differences between persistent data (SQL) and transient data (Redis)¶
Transient data properties are along the lines of
Which might not be around forever - does not satisfy ACID guarantees
Might be cache-like data
Might be user session data
Is optimized for speed instead of persistence
Might not be tied to normal database transaction lifecycle
Might not have complex query properties like SQL, but is more key-value like
Using session data¶
Session data is available for both logged in and anonymous users. Examples:
request.session["my_key"] = "value" # Set a session value
print(request.session["my_key"]) # Get a session value
print(request.session.get("my_key") # Get a session value, defaults to None if not yet set
See also flash messages and websauna.system.Initializer.configure_sessions().
For more information see Sessions in Pyramid.
Getting Redis client¶
Getting a hold a Redis client can be done with websauna.system.core.redis.get_redis() call.
Storing data¶
Redis stores all data, including numbers, internally as byte strings. For unicode strings (default Python strings), you must encode values yourself:
from websauna.system.core.redis import get_redis
def my_view(request):
redis = get_redis(request)
redis.set("foo", "ÅÄÖ".encode("utf-8"))
assert redis.get("foo").decode("utf-8") == "ÅÄÖ"
For more advanced example, see SMS login.
Exploring Redis database¶
If you want to explore Redis database you can use
Clearing Redis data in tests¶
By default tests do not clear Redis database between tests run.
You can manually clear Redis at the beginning of your test code:
from websauna.system.core.redis import get_redis
def test_brand_data(dbsession, test_request):
"""Verify brand data."""
# Clear redis data for proper cache testing,
# make sure we don't have existing data from previous test runs
redis = get_redis(test_request)
redis.flushdb()
Default Redis database numbering¶
Redis database 1 is configured for local development/staging/production session and cache data.
Redis database 3 is configured for local development/staging/production Celery jobs.
Redis database 14 is configured for unit test session data.
Redis database 15 is configured for unit test Celery jobs.
Redis settings can be found in base.ini and test.ini.
Also see Celery config for more information.
Increasing session timeout¶
To make user sessions persistent, as in no need to relogin, you can set session timeout to a long value.
Add to your production.ini:
#
# Session
#
# Set cookie time out to one year
redis.sessions.cookie_max_age = 31536000
# Set redis session key timeout to one year
redis.sessions.timeout = 31536000
# No JavaScript access to cookies
redis.sessions.cookie_secure = True
# Only server session cookie over HTTPS
redis.sessions.cookie_httponly = True