在启用集群模式的情况下批量上传到 Elasticache 时，redis-cli --pipe 会产生 MOVED 错误

Question

I am trying to use redis-cli --pipe to bulk upload some commands to my AWS Elasticache for redis cluster. The commands come from parsing a file via a custom awk command, which helps generate some HSET commands. The awk command is in a custom shell script. When my Elasticache for redis server had cluster-mode disabled, doing something like the following worked like a charm:

sh script_containing_awk.sh $FILE_TO_PARSE | redis-cli -h <Primary_endpoint> -p <port> --tls --cacert <path/to/cert> --pipe

Due to an internal project requirement, the Elasticache for Redis server has been re-created with cluster-mode enabled, and hence I am adding the -c flag to the above command to specify as such.

I see the following results when trying to work with my Elasticache for Redis server with cluster-mode enabled:

• I can connect to the cluster via the configuration endpoint no problem!
• Single command uploads work (ie: redis-cli -h <config_endpoint> -p <port> -c --tls --cacert <path/to/certs> SET key value )

It would be extremely convenient to just pipe output from my script to the cli:

sh script_containing_awk.sh $FILE_TO_PARSE | redis-cli -h <config_endpoint> -p <port> -c --tls --cacert <path/to/cert> --pipe

but adding the --pipe flag results in "MOVED" errors.

I have tried modifying the script to include {} (ex: HSET {user1}:hash field1 val1 field2 val2... brackets to try to force keys to the same CLUSTER SLOTS, but I still get the "MOVED" errors and I am attempting to bulk upload millions of keys so I don't think they would all fit in the same slot anyway.

Does anyone have experience getting --pipe to work with cluster-mode enabled Redis/Elasticache?

Thanks!

Answer 1

I am sure you understand that the core difference between Cluster Mode Disabled and Cluster Mode Enabled is that there is a split in your total Key slots.

Just to put in context; CMD - Let's say we have 4 node cluster with 1 Primary and 3 Replicas. if we have 100 key slots - All the 100 key slots will be there in all the nodes. 3 of them will serve Read only commands and 1 of the node will serve all the commands.

CME - Let's say we have 4 nodes split in 2 shards - 1 replica and 1 primary each. We can look at them as logical sub-clusters ie. they will have different sets of key-slots. Ideally a 50-50 split.

Now, the MOVED message is not necessarily an error. When you connect to the configuration endpoint, by default you are being connected with one of the primary nodes (chosen at random, at first). when you make a command, the client sends that command and the primary node decides if it has the correct hash-slot to serve that command.

As explainedhere , if the node does not have the hash-slot that your client is looking for, it will redirect you with a MOVED message.

So, I would assume MOVED messages are somewhat expected with CME clusters.