Michał Michalski created CASSANDRA-6768:
-------------------------------------------
Summary: Refresh permissions cache in ClientState periodically to
avoid cache miss stampede effect
Key: CASSANDRA-6768
URL: https://issues.apache.org/jira/browse/CASSANDRA-6768
Project: Cassandra
Issue Type: Improvement
Reporter: Michał Michalski
Assignee: Aleksey Yeschenko
h3. Background
We want to password-protect Cassandra by using the built-in
PasswordAuthenticator and PasswordAuthorizer. In general we are happy with this
solution, but after reviewing the code we're a bit afraid of default
permissionsCache behaviour in org.apache.cassandra.service.ClientState.
h3. Problem
>From what I understand, at the moment cache expires every N seconds (2 by
>default) and it gets repopulated when permissionsCache.get() is being called.
>However, as we're talking about at least a few hundreds requests to Cassandra
>per second, we're afraid of the "stampede" effect once the cache expires and a
>number of queries will "trigger" its reload simultaneously during the short
>period of time when it will be empty.
h3. Proposed Solution
Therefore, instead of the current solution, we'd prefer this cache to be
reloaded "in background" every N seconds, so it's only a single request every N
seconds, rather than tens (hundreds?) of them just after the cache expires
during the period when it's empty.
In other words, we're thinking about replacing this:
{code}expireAfterWrite(validityPeriod, TimeUnit.MILLISECONDS){code}
with:
{code}refreshAfterWrite(refreshPeriod, TimeUnit.MILLISECONDS){code}
Default refreshPeriod could be the same as the validityPeriod, for example.
Are there any reasons that make this idea a bad one ("you misunderstood Guava's
Cache" counts too!)?
[~iamaleksey], I've let myself to assign this issue directly to you, as you're
the author of current solution.
--
This message was sent by Atlassian JIRA
(v6.1.5#6160)
