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This article mainly introduces the Redisl cluster 3 more than what is used, has a certain reference value, the need for friends can refer to the next. I hope you all have a lot of success after reading this article. Let's take a look at it together.

Redisl cluster more than 3 is to improve the accuracy of fault judgment by increasing the number of sentinel nodes, because the leader election needs at least half plus 1 node, and odd nodes can save one node on the basis of meeting this condition.

Simply put: if there are 3 nodes of sentinel when a redis problem, sentinel will immediately vote, only more than half of the votes before subjective offline oh! Finally objective offline, so we need 3 sentinel nodes.

The sentinel pattern is a special pattern. First Redis provides the sentinel command. The sentinel is an independent process. As a process, it will run independently. The principle is that sentries monitor multiple running Redis instances by sending commands and waiting for Redis servers to respond.

The sentries here serve two purposes.

By sending commands, Redis servers return to monitor their health status, both master and slave.

When the sentinel detects that the master is down, it will automatically switch the slave to the master, and then notify the other slave servers through the publish subscription mode to modify the configuration file and let them switch hosts.

However, a single sentinel process monitoring Redis servers may cause problems, so we can use multiple sentinels to monitor. There is also monitoring between sentries, thus forming a multi-sentinel model.

Describe the failover process in words.

Assuming that the primary server is down and Sentinel 1 detects this result first, the system does not immediately perform the failover process, but Sentinel 1 subjectively believes that the primary server is unavailable, and this phenomenon becomes subjective offline. When the following sentries also detect that the primary server is unavailable, and the number reaches a certain value, then a vote will be held among the sentries, and the result of the vote will be initiated by a sentinel for failover operation. After the switch is successful, each sentinel will switch the slave server monitored by itself to the host through the publish-subscribe mode. This process is called objective offline. This way, everything is transparent to the client.

Thank you for reading this article carefully. I hope Xiaobian can share more than 3 Redisl clusters. What content is useful to everyone? At the same time, I hope everyone will support you more. Pay attention to the industry information channel. If you encounter problems, find detailed solutions waiting for you to learn!

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