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Clarify the WAIT command and acknowledgment #479

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Merged
andy1li merged 1 commit into from
Dec 15, 2025
Merged

Clarify the WAIT command and acknowledgment #479

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6 changes: 3 additions & 3 deletions stage_descriptions/replication-16-my8.md
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Expand Up @@ -2,17 +2,17 @@ In this stage, you’ll implement support for the `WAIT` command on the master.

### The `WAIT` command

The `WAIT` command is used to check how many replicas have acknowledged a write command. This allows a client to measure the durability of a write command before considering it successful.
The `WAIT` command is used to check how many replicas have acknowledged all previous write commands. This allows a client to measure the durability of a write command before considering it successful.

The command format is:
The command format is:

```bash
WAIT <numreplicas> <timeout>
```

Here's what each argument means:

- `<numreplicas>`: The minimum number of replicas that must acknowledge the write command.
- `<numreplicas>`: The minimum number of replicas that must acknowledge all previous write commands.
- `<timeout>`: The maximum time (in milliseconds) the client is willing to wait.

For example:
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5 changes: 3 additions & 2 deletions stage_descriptions/replication-18-na2.md
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Expand Up @@ -3,6 +3,7 @@ In this stage, you’ll extend your `WAIT` implementation to handle the case whe
### `WAIT` with propagated commands

In previous stages, we handled the cases where:

- No replicas were connected, and the master could safely return `0`.
- Replicas were connected, but hadn't received any write commands.

Expand All @@ -12,10 +13,10 @@ To do this, the master must send `REPLCONF GETACK *` to replicas if there are pe

The `WAIT` command should complete when either:

- The required number of replicas has acknowledged the last write command, or
- The required number of replicas has acknowledged all previous write commands, or
- The timeout expires.

Either way, the master should return the number of replicas that acknowledged the command as a [RESP integer](https://redis.io/docs/latest/develop/reference/protocol-spec/#integers).
Either way, the master should return the number of replicas that acknowledged all previous write commands as a [RESP integer](https://redis.io/docs/latest/develop/reference/protocol-spec/#integers).

### Tests

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