https://bugs.exim.org/show_bug.cgi?id=2248
Bug ID: 2248
Summary: Lightweight redis cluster redirect method
Product: Exim
Version: 4.90
Hardware: x86
OS: All
Status: NEW
Severity: wishlist
Priority: medium
Component: Lookups
Assignee: nigel@???
Reporter: graeme@???
CC: exim-dev@???
Created attachment 1072
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https://bugs.exim.org/attachment.cgi?id=1072&action=edit
DEFER rather than ERROR on redis cluster MOVED response.
Patch against 4.90.1 lookups/redis.c
Synopsis: DEFER rather than ERROR on redis cluster MOVED response.
This is a "cheap" way of following 'MOVED' cluster redirect in Redis Cluster.
When redis_servers is set to a list of > 1 element, and the Redis servers in
that list are in cluster configuration (not describing that here), a query -
whether a lookup or setting anything - against the first or subsequent server
in the list can receive a response of the form:
MOVED 7506 192.168.76.5:7002
i.e. MOVED [shard] [server]:[port]
In order to not put full redis cluster client functionality into Exim, this
patch turns the REDIS_REPLY_ERROR case of MOVED into a DEFER case instead, thus
moving the query onto the next server in the list.
Eventually, depending on the number of servers in the cluster, the lookup will
land on the server with that shard and will then complete the lookup.
NOTE: For a cluster of N elements, all N servers must be defined in
redis_servers.
This is soak testing on live traffic as I type and has generated no errors.
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