# `TiCDC` Cluster Architecture

+ **`High Availability`** relies on `etcd` in the `Placement Driver` cluster 
+ A **`Capture`** is one stateless `TiCDC` instance
+ Multiple **`Capture`** form a `TiCDC` cluster that replicates `KV` change logs

![`smart`](TiCDCPI_aa_003_20220622.png)

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The `TiCDC` runtime is a stateless instance with high availability capability. `TiCDC` cluster achieves high availability through `etcd` in `PD` cluster. The `TiCDC` cluster supports creating multiple replication tasks to replicate data to multiple downstream platforms.

`capture:` The operating process of `TiCDC`. Multiple `capture` form a `TiCDC` cluster that replicates `KV` change logs.
- Each capture pulls a part of `KV` change logs.
- Sorts the pulled `KV` change log(s).
- Restores the transaction to downstream or outputs the log based on the `TiCDC Open Protocol`.

`etcd` is a distributed, reliable key-value store for distributed systems