diff --git a/dev/reference/performance/follower-read.md b/dev/reference/performance/follower-read.md index 883dd41b96217..91a27a3feec73 100644 --- a/dev/reference/performance/follower-read.md +++ b/dev/reference/performance/follower-read.md @@ -10,7 +10,7 @@ When a read hotspot appears in a Region, the Region leader can become a read bot ## Overview -The Follower Read feature refers to using any follower replica of a Region to serve a read request under the premise of strongly consistent reads. This feature improves the throughput of the TiDB cluster and reduces the load of the leader. It contains a series of load balancing mechanisms that offload TiKV read loads from the leader replica to the follower replica in a Region. TiKV's Follower Read implementation guarantees the linearizability of single-row data reading. Combined with Snapshot Isolation in TiDB, this implementation also provides users with strongly consistent reads. +The Follower Read feature refers to using any follower replica of a Region to serve a read request under the premise of strongly consistent reads. This feature improves the throughput of the TiDB cluster and reduces the load of the leader. It contains a series of load balancing mechanisms that offload TiKV read loads from the leader replica to the follower replica in a Region. TiKV's Follower Read implementation guarantees the linearizability of data reading; combined with Snapshot Isolation in TiDB, this implementation provides users with strongly consistent reads. > **Note:** > @@ -37,7 +37,7 @@ This variable is used to set the data read mode expected by the current session. ## Implementation mechanism -Before the Follower Read feature was introduced, TiDB applied the strong leader policy and submitted all read and write requests to the leader node of a Region to handle. Although TiKV can distribute Regions evenly on multiple physical nodes, for each Region, only the leader can provide external services. The other followers can do nothing to handle read requests but receive the data replicated from the leader at all times and prepare for voting to elect a leader in case of a failover. +Before the Follower Read feature was introduced, TiDB applied the strong leader principle and submitted all read and write requests to the leader node of a Region to handle. Although TiKV can distribute Regions evenly on multiple physical nodes, for each Region, only the leader can provide external services. The other followers can do nothing to handle read requests but receive the data replicated from the leader at all times and prepare for voting to elect a leader in case of a failover. To allow data reading in the follower node without violating linearizability or affecting Snapshot Isolation in TiDB, the follower node needs to use `ReadIndex` of the Raft protocol to ensure that the read request can read the latest data that has been committed on the leader. At the TiDB level, the Follower Read feature simply needs to send the read request of a Region to a follower replica based on the load balancing policy. diff --git a/v3.1/reference/performance/follower-read.md b/v3.1/reference/performance/follower-read.md index 883dd41b96217..91a27a3feec73 100644 --- a/v3.1/reference/performance/follower-read.md +++ b/v3.1/reference/performance/follower-read.md @@ -10,7 +10,7 @@ When a read hotspot appears in a Region, the Region leader can become a read bot ## Overview -The Follower Read feature refers to using any follower replica of a Region to serve a read request under the premise of strongly consistent reads. This feature improves the throughput of the TiDB cluster and reduces the load of the leader. It contains a series of load balancing mechanisms that offload TiKV read loads from the leader replica to the follower replica in a Region. TiKV's Follower Read implementation guarantees the linearizability of single-row data reading. Combined with Snapshot Isolation in TiDB, this implementation also provides users with strongly consistent reads. +The Follower Read feature refers to using any follower replica of a Region to serve a read request under the premise of strongly consistent reads. This feature improves the throughput of the TiDB cluster and reduces the load of the leader. It contains a series of load balancing mechanisms that offload TiKV read loads from the leader replica to the follower replica in a Region. TiKV's Follower Read implementation guarantees the linearizability of data reading; combined with Snapshot Isolation in TiDB, this implementation provides users with strongly consistent reads. > **Note:** > @@ -37,7 +37,7 @@ This variable is used to set the data read mode expected by the current session. ## Implementation mechanism -Before the Follower Read feature was introduced, TiDB applied the strong leader policy and submitted all read and write requests to the leader node of a Region to handle. Although TiKV can distribute Regions evenly on multiple physical nodes, for each Region, only the leader can provide external services. The other followers can do nothing to handle read requests but receive the data replicated from the leader at all times and prepare for voting to elect a leader in case of a failover. +Before the Follower Read feature was introduced, TiDB applied the strong leader principle and submitted all read and write requests to the leader node of a Region to handle. Although TiKV can distribute Regions evenly on multiple physical nodes, for each Region, only the leader can provide external services. The other followers can do nothing to handle read requests but receive the data replicated from the leader at all times and prepare for voting to elect a leader in case of a failover. To allow data reading in the follower node without violating linearizability or affecting Snapshot Isolation in TiDB, the follower node needs to use `ReadIndex` of the Raft protocol to ensure that the read request can read the latest data that has been committed on the leader. At the TiDB level, the Follower Read feature simply needs to send the read request of a Region to a follower replica based on the load balancing policy.