I have setup up Redis master slave configuration having one master (6379 port) and 3 slaves (6380,6381,6382) running in the same machine. Looks like cluster is setup properly as I can see the following output on running info command:
# Replication
role:master
connected_slaves:3
slave0:ip=127.0.0.1,port=6380,state=online,offset=29,lag=1
slave1:ip=127.0.0.1,port=6381,state=online,offset=29,lag=1
slave2:ip=127.0.0.1,port=6382,state=online,offset=29,lag=1
master_repl_offset:43
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:42
But wherever I try to add new key in master, I get the following error:
(error) CLUSTERDOWN Hash slot not served
Using redis-3.0.7 in Mac OS X Yosemite.
I had the same issue, turned out I forgot to run the create cluster:
cd /path/to/utils/create-cluster
./create-cluster create
http://redis.io/topics/cluster-tutorial#creating-a-redis-cluster-using-the-create-cluster-script
To fix slots issue while insertion:
redis-cli --cluster fix localhost:6379
You can use ruby script buddled with redis for creating clusters as mentioned below :
/usr/local/redis-3.2.11/src/redis-trib.rb create --replicas 1 192.168.142.128:7001 192.168.142.128:7002 192.168.142.128:7003 192.168.142.128:7004 192.168.142.128:7005 192.168.142.128:7006
There is a hash slot not allotted to any master. Check the hash slots by looking at the column 9 in the output of following command (column 9 will be empty if no hash slots for that node):
redis-cli -h masterIP -p masterPORT CLUSTER NODES
The hash slots can be allotted by using the following command.
redis-cli -h masterIP -p masterPORT CLUSTER ADDSLOTS SLOTNNUMBER
But this has to be done for every slot number individually without missing. Use a bat script to include it in for loop. something like,
for /L %a in (0,1,5400) Do redis-cli -h 127.0.0.1 -p 7001 cluster addslots %a
Also, this command works before assigning slaves to master. After this ADDSLOTS step and completing the setup, the SET and GET worked fine. Remember to use -c along with redis-cli before SET to enable cluster support.
The issue comes when one or more Redis nodes gets corrupted and can no longer serve its configured hash slots.
You will have to bootstrap the cluster again to make sure the nodes agree on the hash slots to serve.
If the Redis nodes contain data or a key in the database 0, you will have to clear this data before rerunning the bootstrap.
Related
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 (i.e: 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!
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 explained here, 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.
When I scan the Redis using below command:
redis-cli -h <redis_master_ip> -p 6379 --scan --pattern '*'
it returns keys which belong to this node, but it also returns many keys which belong to another redis node. Therefore if I run below command:
redis-cli -h <redis_master_ip> -p 6379 object freq <some_keys_from_scan>
I get error like Error: MOVED 90 <another_redis_master_ip>:6379
Due to the same reason, I get the same error when running:
redis-cli -h <redis_master_ip> -p 6379 --hotkeys
Note both the <redis_master_ip> and <another_redis_master_ip> are a part of redis cluster.
The document https://redis.io/commands/scan defines scan as: "iterates the set of keys in the currently selected Redis database". My understanding is it should only scan the keys belong to the current node. my redis cluster is 6.0.10.
Does anybody know why executing scan return the keys of another node? I am only interested in getting the keys of this node.
I see another link mentioned the same issue but no solution yet: https://github.com/redis/redis/issues/4810
When a Redis instance is setup and running, the dataset size (in bytes) can be retrieved from output of the below command by looking at used_memory_dataset field.
./redis-cli -h <ip address> -p <port> info
However, when I have multiple instances running in the cluster mode, how do I retrieve the dataset size across the cluster? Can redis-cli tool still be used for such cluster-based commands?
As of Redis v5 the cli includes cluster-smarts. You can use the following form to call a command, e.g. INFO, on all nodes:
redis-cli --cluster call ip:port command
To calculate the dataset's total size, you'd have to add up the different replies.
I am trying to test my cache was implemented with redis clustering (cluster by server not client).
I have to flush redis every time I run a unit test.
when I try to run flushdb command I got this error:
Cannot use 'FLUSHDB' with redis-cluster.
it seems that I can run flushdb command in cluster mode only when I set the slot but I do not know how to do it. (I have overridden redis wrapper of laravel so laravel is not the case If you learn me how to use predis I can adopt it with laravel)
For deleting by pattern:
redis-cli --raw keys "$PATTERN" | xargs redis-cli del
for example:
redis-cli KEYS "prefix:*" | xargs redis-cli DEL
For deleting all keys from one db:
redis-cli flushdb
For deleting all keys from all dbs:
redis-cli flushall
For cluster mode you need to use this bash script:
https://gist.github.com/yaud/85e0382d26c189bdf84f0297cd54f479
to remove all nodes from master nodes (slave nodes will be synced)
How does one upgrade to a newer version of Redis with zero downtime? Redis slaves are read-only, so it seems like you'd have to take down the master and your site would be read-only for 45 seconds or more while you waited for it to reload the DB.
Is there a way around this?
Redis Team has very good documentation on this
Core Steps:
Setup your new Redis instance as a slave for your current Redis instance. In order to do so you need a different server, or a server that has enough RAM to keep two instances of Redis running at the same time.
If you use a single server, make sure that the slave is started in a different port than the master instance, otherwise the slave will not be able to start at all.
Wait for the replication initial synchronization to complete (check the slave log file).
Make sure using INFO that there are the same number of keys in the master and in the slave. Check with redis-cli that the slave is working as you wish and is replying to your commands.
Configure all your clients in order to use the new instance (that is, the slave).
Once you are sure that the master is no longer receiving any query (you can check this with the MONITOR command), elect the slave to master using the SLAVEOF NO ONE command, and shut down your master.
Full Documentation:
Upgrading or restarting a Redis instance without downtime
When taking the node offline, promote the slave to master using the SLAVEOF command, then when you bring it back online you set it up as a slave and it will copy all data from the online node.
You may also need to make sure your client can handle changed/missing master nodes appropriately.
If you want to get really fancy, you can set up your client to promote a slave if it detects an error writing to the master.
You can use Redis Sentinel for doing this, the sentinel will automatically promote a slave as new master.
you can find more info here http://redis.io/topics/sentinel.
Sentinel is a system used to manage redis servers , it monitors the redis master and slaves continuously, and whenever a master goes down it will automatically promote a slave in to master. and when the old master is UP it will be made as slave of the new master.
Here there will be no downtime or manual configuration of config file is needed.
You can visit above link to find out how to configure sentinel for your redis servers.
Note, you may have to check and set the following config to write to your slave.
("Since Redis 2.6 by default slaves are read-only")
redis-cli config set slave-read-only no
-- Example
-bash-4.1$ redis-cli info
Server
redis_version:2.6.9
-bash-4.1$ redis-cli slaveof admin2.mypersonalsite.com 6379
OK
-bash-4.1$ redis-cli set temp 42
(error) READONLY You can't write against a read only slave.
-bash-4.1$ redis-cli slaveof no one
OK
-bash-4.1$ redis-cli set temp 42
OK
-bash-4.1$ redis-cli get temp
"42"
-bash-4.1$ redis-cli config set slave-read-only no
OK
-bash-4.1$ redis-cli slaveof admin2.mypersonalsite.com 6379
OK
-bash-4.1$ redis-cli set temp 42
OK
-bash-4.1$ redis-cli get temp
"42"