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Diffstat (limited to 'iredis/data/commands/client-pause.md')
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diff --git a/iredis/data/commands/client-pause.md b/iredis/data/commands/client-pause.md index 3de6beb..6f778da 100644 --- a/iredis/data/commands/client-pause.md +++ b/iredis/data/commands/client-pause.md @@ -1,62 +1,44 @@ -`CLIENT PAUSE` is a connections control command able to suspend all the Redis -clients for the specified amount of time (in milliseconds). +`CLIENT PAUSE` is a connections control command able to suspend all the Redis clients for the specified amount of time (in milliseconds). The command performs the following actions: -- It stops processing all the pending commands from normal and pub/sub clients - for the given mode. However interactions with replicas will continue normally. - Note that clients are formally paused when they try to execute a command, so - no work is taken on the server side for inactive clients. -- However it returns OK to the caller ASAP, so the `CLIENT PAUSE` command - execution is not paused by itself. -- When the specified amount of time has elapsed, all the clients are unblocked: - this will trigger the processing of all the commands accumulated in the query - buffer of every client during the pause. +* It stops processing all the pending commands from normal and pub/sub clients for the given mode. However interactions with replicas will continue normally. Note that clients are formally paused when they try to execute a command, so no work is taken on the server side for inactive clients. +* However it returns OK to the caller ASAP, so the `CLIENT PAUSE` command execution is not paused by itself. +* When the specified amount of time has elapsed, all the clients are unblocked: this will trigger the processing of all the commands accumulated in the query buffer of every client during the pause. Client pause currently supports two modes: -- `ALL`: This is the default mode. All client commands are blocked. -- `WRITE`: Clients are only blocked if they attempt to execute a write command. +* `ALL`: This is the default mode. All client commands are blocked. +* `WRITE`: Clients are only blocked if they attempt to execute a write command. For the `WRITE` mode, some commands have special behavior: -- `EVAL`/`EVALSHA`: Will block client for all scripts. -- `PUBLISH`: Will block client. -- `PFCOUNT`: Will block client. -- `WAIT`: Acknowledgements will be delayed, so this command will appear blocked. +* `EVAL`/`EVALSHA`: Will block client for all scripts. +* `PUBLISH`: Will block client. +* `PFCOUNT`: Will block client. +* `WAIT`: Acknowledgments will be delayed, so this command will appear blocked. -This command is useful as it makes able to switch clients from a Redis instance -to another one in a controlled way. For example during an instance upgrade the -system administrator could do the following: +This command is useful as it makes able to switch clients from a Redis instance to another one in a controlled way. For example during an instance upgrade the system administrator could do the following: -- Pause the clients using `CLIENT PAUSE` -- Wait a few seconds to make sure the replicas processed the latest replication - stream from the master. -- Turn one of the replicas into a master. -- Reconfigure clients to connect with the new master. +* Pause the clients using `CLIENT PAUSE` +* Wait a few seconds to make sure the replicas processed the latest replication stream from the master. +* Turn one of the replicas into a master. +* Reconfigure clients to connect with the new master. -Since Redis 6.2, the recommended mode for client pause is `WRITE`. This mode -will stop all replication traffic, can be aborted with the `CLIENT UNPAUSE` -command, and allows reconfiguring the old master without risking accepting -writes after the failover. This is also the mode used during cluster failover. +Since Redis 6.2, the recommended mode for client pause is `WRITE`. This mode will stop all replication traffic, can be +aborted with the `CLIENT UNPAUSE` command, and allows reconfiguring the old master without risking accepting writes after the +failover. This is also the mode used during cluster failover. -For versions before 6.2, it is possible to send `CLIENT PAUSE` in a MULTI/EXEC -block together with the `INFO replication` command in order to get the current -master offset at the time the clients are blocked. This way it is possible to -wait for a specific offset in the replica side in order to make sure all the -replication stream was processed. +For versions before 6.2, it is possible to send `CLIENT PAUSE` in a MULTI/EXEC block together with the `INFO replication` command in order to get the current master offset at the time the clients are blocked. This way it is possible to wait for a specific offset in the replica side in order to make sure all the replication stream was processed. Since Redis 3.2.10 / 4.0.0, this command also prevents keys to be evicted or expired during the time clients are paused. This way the dataset is guaranteed -to be static not just from the point of view of clients not being able to write, -but also from the point of view of internal operations. +to be static not just from the point of view of clients not being able to write, but also from the point of view of internal operations. @return -@simple-string-reply: The command returns OK or an error if the timeout is -invalid. +@simple-string-reply: The command returns OK or an error if the timeout is invalid. -@history +## Behavior change history -- `>= 3.2.10`: Client pause prevents client pause and key eviction as well. -- `>= 6.2`: CLIENT PAUSE WRITE mode added along with the `mode` option. +* `>= 3.2.0`: Client pause prevents client pause and key eviction as well.
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