apache / apache/iotdb

[Feature request] CLI should support automatic reconnection when connection is lost during interactive session

Open
#17,179 1 comment 0 reactions 0 assignees View on GitHub
Dominant language
Java
Stars
6.4k
Forks
1.2k
Avg merge
1d 23h
Merged PRs (30d)
115

Description

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/iotdb/issues) and found nothing similar.

### Motivation

I am always frustrated when the IoTDB CLI exits as soon as the connection to the server is lost (e.g. server restart, network blip, or idle timeout). I have to reconnect manually, re-enter connection parameters, and lose my session context.

Other IoTDB clients already support reconnection: the Session API (Java), JDBC (via callWithRetryAndReconnect in IoTDBStatement), and the C++/Python clients all retry and reconnect on connection failure. The CLI is the only major client that does not—it holds a single connection for the entire interactive session and exits on any connection-related error. Adding automatic reconnection to the CLI would align its behaviour with the rest of the client stack and improve the experience for long-lived interactive sessions (e.g. over SSH or after server restarts).

### Solution

**Proposed behaviour**

1. **Detect connection loss**
When a command fails with a connection-related error (e.g. SQLException caused by connection refused, timeout, or closed connection), do not exit immediately.

2. **Attempt reconnection**
Try to establish a new connection using the same parameters (host, port, user, password, and options) that were used at login. Reuse the same logic as the initial connection (e.g. DriverManager.getConnection with the same URL and properties).

3. **Retry the command**
After a successful reconnection, retry the same user command (the current line/statement that failed) with the new connection, with a bounded number of retries (e.g. 3) and optional backoff.

4. **User feedback**
On successful reconnection, print a short message such as: "Connection lost. Reconnected. Retrying command." and continue the interactive loop with the new connection.

5. **Failure handling**
If reconnection fails after all retries, exit with a clear error message, e.g. "Could not reconnect after N attempts. Please check that the server is running and try again."

**Relevant code**

- `iotdb-client/cli/src/main/java/org/apache/iotdb/cli/Cli.java`:
- `receiveCommands()` opens one connection and runs a `while (true)` loop; any SQLException is caught at the top level and the process exits (lines 215–217).
- Change: catch connection-related failures inside the loop (or around `processCommand`), attempt reconnection, then retry the command or continue with the new connection.

- `iotdb-client/jdbc`:
- `IoTDBConnection.reconnect()` and `IoTDBStatement.callWithRetryAndReconnect()` can be used as reference for retry/reconnect behaviour.

**Optional**

- Make retry count and interval configurable (e.g. CLI options or environment variables) for consistency with Session/JDBC.

### Alternatives

1. **No retry, only reconnect**
On connection loss, attempt reconnection and, on success, continue the session without retrying the failed command (user re-enters it). Simpler to implement but less convenient than retrying the last command.

2. **Prompt user**
On connection loss, prompt: "Connection lost. Reconnect? (y/n)". If yes, reconnect and optionally retry the command. Gives control but adds friction for automated or scripted use.

3. **Leave as-is**
Keep current behaviour (exit on connection loss). This preserves simplicity but leaves the CLI as the only client without reconnection support and worsens UX for long sessions and unstable networks.

### Are you willing to submit a PR?

- [x] I'm willing to submit a PR!

Contributor guide

Open the contributing guide

Research direction

Start in iotdb-client/cli/src/main/java/org/apache/iotdb/cli/Cli.java, especially receiveCommands() and processCommand, then read IoTDBConnection.reconnect() and IoTDBStatement.callWithRetryAndReconnect() under iotdb-client/jdbc. Done means connection-related failures are retried with bounded reconnection attempts, successful recovery retries the command with feedback, and failed recovery exits clearly.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
cli, databases
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.