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Diffstat (limited to 'iredis/data/commands/cluster-set-config-epoch.md')
| -rw-r--r-- | iredis/data/commands/cluster-set-config-epoch.md | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/iredis/data/commands/cluster-set-config-epoch.md b/iredis/data/commands/cluster-set-config-epoch.md new file mode 100644 index 0000000..b64fffa --- /dev/null +++ b/iredis/data/commands/cluster-set-config-epoch.md @@ -0,0 +1,25 @@ +This command sets a specific _config epoch_ in a fresh node. It only works when: + +1. The nodes table of the node is empty. +2. The node current _config epoch_ is zero. + +These prerequisites are needed since usually, manually altering the +configuration epoch of a node is unsafe, we want to be sure that the node with +the higher configuration epoch value (that is the last that failed over) wins +over other nodes in claiming the hash slots ownership. + +However there is an exception to this rule, and it is when a new cluster is +created from scratch. Redis Cluster _config epoch collision resolution_ +algorithm can deal with new nodes all configured with the same configuration at +startup, but this process is slow and should be the exception, only to make sure +that whatever happens, two more nodes eventually always move away from the state +of having the same configuration epoch. + +So, using `CONFIG SET-CONFIG-EPOCH`, when a new cluster is created, we can +assign a different progressive configuration epoch to each node before joining +the cluster together. + +@return + +@simple-string-reply: `OK` if the command was executed successfully, otherwise +an error is returned. |