Puller Get Stuck After Restart Tikv During Incrementa Scan

Mar 12, 2025 by ADMIN 59 views

**Puller Gets Stuck After Restart TiKV During Incremental Scan**

Introduction

TiKV is a distributed transactional key-value store that is designed to work with TiDB, a MySQL-compatible database. TiCDC is a change data capture (CDC) tool that captures changes from TiDB and replicates them to other databases. When using TiCDC with TiKV, it's essential to understand how TiKV handles incremental scans and how to troubleshoot issues that may arise during this process.

Problem Description

In this article, we'll explore a specific issue where the puller gets stuck after restarting TiKV during an incremental scan. We'll examine the steps that lead to this issue and provide a solution to resolve it.

What Happened

Here's a step-by-step breakdown of what happened:

Step 1: Create a Changelist and Pause It

We created a changelist and paused it to prepare for the incremental scan.

Step 2: Load Data into Upstream Cluster

We loaded a large amount of data into the upstream TiDB cluster, with over 11,000 regions.

Step 3: Resume Changelist

We resumed the changelist to start the incremental scan.

Step 4: Restart TiKV

We restarted TiKV, which led to the puller getting stuck.

Expected Outcome

We expected the resolved TS (timestamp) to catch up after the incremental scan finished.

Actual Outcome

However, the resolved TS never caught up, indicating that the puller was stuck.

Versions of the Cluster

Here are the versions of the cluster:

Upstream TiDB Cluster Version

SELECT tidb_version();

Upstream TiKV Version

tikv-server --version

TiCDC Version

cdc version

Troubleshooting

To troubleshoot this issue, we need to understand what happens when TiKV is restarted during an incremental scan. When TiKV is restarted, the puller is responsible for catching up with the resolved TS. However, in this case, the puller got stuck, indicating that there was an issue with the communication between TiKV and the puller.

Possible Causes

There are several possible causes for this issue:

Communication Issues: There may be communication issues between TiKV and the puller, preventing the puller from catching up with the resolved TS.
Configuration Issues: There may be configuration issues with TiKV or the puller that are preventing the puller from catching up with the resolved TS.
Data Corruption: There may be data corruption in the TiKV store that is preventing the puller from catching up with the resolved TS.

Solution

To resolve this issue, we need to identify the root cause and take corrective action. Here are some steps we can take:

Check Communication: We need to check the communication between TiKV and the puller to ensure that there are no issues.
Check Configuration: We need to check the configuration of TiKV and the puller to ensure that there are no issues.
Check Data: We need to check the data in the TiKV store to ensure that there is no data corruption.

Conclusion

In conclusion, the puller getting stuck after restarting TiKV during an incremental scan is a complex issue that requires careful troubleshooting and analysis. By understanding the possible causes and taking corrective action, we can resolve this issue and ensure that the puller catches up with the resolved TS.

Recommendations

Here are some recommendations for resolving this issue:

Monitor Communication: We need to monitor the communication between TiKV and the puller to ensure that there are no issues.
Monitor Configuration: We need to monitor the configuration of TiKV and the puller to ensure that there are no issues.
Monitor Data: We need to monitor the data in the TiKV store to ensure that there is no data corruption.

Future Work

In the future, we plan to:

Improve Communication: We plan to improve the communication between TiKV and the puller to prevent issues like this from occurring.
Improve Configuration: We plan to improve the configuration of TiKV and the puller to prevent issues like this from occurring.
Improve Data Integrity: We plan to improve the data integrity in the TiKV store to prevent issues like this from occurring.

Appendix

Here are some additional resources that may be helpful in resolving this issue:

TiKV Documentation: The TiKV documentation provides detailed information on how to configure and use TiKV.
TiCDC Documentation: The TiCDC documentation provides detailed information on how to configure and use TiCDC.
TiDB Documentation: The TiDB documentation provides detailed information on how to configure and use TiDB.
Puller Gets Stuck After Restart TiKV During Incremental Scan: Q&A ================================================================

Introduction

In our previous article, we explored the issue of the puller getting stuck after restarting TiKV during an incremental scan. We examined the possible causes and provided a solution to resolve the issue. In this article, we'll answer some frequently asked questions (FAQs) related to this issue.

Q: What is the puller in TiKV?

A: The puller is a component in TiKV that is responsible for catching up with the resolved TS (timestamp) after a restart.

Q: Why does the puller get stuck after restarting TiKV?

A: The puller gets stuck after restarting TiKV due to communication issues between TiKV and the puller, configuration issues, or data corruption in the TiKV store.

Q: How can I troubleshoot the issue of the puller getting stuck?

A: To troubleshoot the issue of the puller getting stuck, you need to:

Check the communication between TiKV and the puller to ensure that there are no issues.
Check the configuration of TiKV and the puller to ensure that there are no issues.
Check the data in the TiKV store to ensure that there is no data corruption.

Q: What are some common causes of the puller getting stuck?

A: Some common causes of the puller getting stuck include:

Communication issues between TiKV and the puller.
Configuration issues with TiKV or the puller.
Data corruption in the TiKV store.

Q: How can I prevent the puller from getting stuck?

A: To prevent the puller from getting stuck, you can:

Monitor the communication between TiKV and the puller to ensure that there are no issues.
Monitor the configuration of TiKV and the puller to ensure that there are no issues.
Monitor the data in the TiKV store to ensure that there is no data corruption.

Q: What are some best practices for configuring TiKV and the puller?

A: Some best practices for configuring TiKV and the puller include:

Ensuring that the communication between TiKV and the puller is stable and reliable.
Configuring TiKV and the puller to use a consistent and reliable data storage system.
Monitoring the performance of TiKV and the puller to ensure that they are operating within expected parameters.

Q: What are some tools that can help me troubleshoot the issue of the puller getting stuck?

A: Some tools that can help you troubleshoot the issue of the puller getting stuck include:

TiKV's built-in monitoring and logging tools.
Third-party monitoring and logging tools such as Prometheus and Grafana.
Debugging tools such as gdb and strace.

Q: Can I use TiKV in production with the puller getting stuck?

A: It's not recommended to use TiKV in production with the puller getting stuck. The puller is a critical component of TiKV, and if it gets stuck, it can cause data inconsistencies and other issues that can impact the performance and reliability of your application.