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Graceful fallback for Redis failures
- Author Ridemonkey
- Creation date
Q: Can't this just be a plugin?
A: No, XenForo initializes and accesses the cache layer before any plugins are called. Core code would have to change in order to alter this behavior, or you could write your own adapter and reference it.
Q: Will logged-in users be affected by the session cache going offline?
A: Users who have selected "Stay logged in," or Admin CP users, are unaffected. Users who are temporarily logged in (have unchecked "Stay logged in") will be logged out. If that is intolerable then you could consider leaving user sessions out of Redis.
Q: So this handles all Redis errors?
A: No. This only handles instances where the Redis server goes offline. If Redis is available but serving bad data (e.g. a bug), the site will still reflect that error state.
Q: Why doesn't XenForo handle this already?
A: There are reasons why you might want to fail quickly if your cache goes offline, but IMO it should be a configuration setting and not forced. In general, I think forcing an application to fail when the cache layer is degraded is bad practice. XenForo should handle this, but does not.
A: No, XenForo initializes and accesses the cache layer before any plugins are called. Core code would have to change in order to alter this behavior, or you could write your own adapter and reference it.
Q: Will logged-in users be affected by the session cache going offline?
A: Users who have selected "Stay logged in," or Admin CP users, are unaffected. Users who are temporarily logged in (have unchecked "Stay logged in") will be logged out. If that is intolerable then you could consider leaving user sessions out of Redis.
Q: So this handles all Redis errors?
A: No. This only handles instances where the Redis server goes offline. If Redis is available but serving bad data (e.g. a bug), the site will still reflect that error state.
Q: Why doesn't XenForo handle this already?
A: There are reasons why you might want to fail quickly if your cache goes offline, but IMO it should be a configuration setting and not forced. In general, I think forcing an application to fail when the cache layer is degraded is bad practice. XenForo should handle this, but does not.