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Diffstat (limited to 'iredis/data/commands/client-pause.md')
| -rw-r--r-- | iredis/data/commands/client-pause.md | 38 |
1 files changed, 31 insertions, 7 deletions
diff --git a/iredis/data/commands/client-pause.md b/iredis/data/commands/client-pause.md index bdbdda0..3de6beb 100644 --- a/iredis/data/commands/client-pause.md +++ b/iredis/data/commands/client-pause.md @@ -3,14 +3,28 @@ 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. - However interactions with replicas will continue normally. +- 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. + +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. + 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: @@ -21,11 +35,16 @@ system administrator could do the following: - Turn one of the replicas into a master. - Reconfigure clients to connect with the new master. -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 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. 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 @@ -36,3 +55,8 @@ but also from the point of view of internal operations. @simple-string-reply: The command returns OK or an error if the timeout is invalid. + +@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. |