What Was Thought to Happen

Oct 13, 2025 by leolavanderia.com.br 46 views

Introduction

In this article, we will be discussing a bug that was discovered in the tsdb.NewCircularExemplarStorage instantiation process. The bug resulted in a significant memory usage pattern in the ingesters after restarting, which was noticed in a Grafana Cloud environment. We will delve into the details of the bug, including how to reproduce it, what was thought to happen, and the environment in which it occurred.

What is the Bug?

The bug in question involves the instantiation of tsdb.NewCircularExemplarStorage with a wrong size at startup. This led to a strange memory usage pattern in the ingesters after restarting. The issue was noticed in a Grafana Cloud environment, specifically in a staging environment with the latest weekly release.

Memory Allocated in tsdb.NewCircularExemplarStorage

After comparing profiles of one of the affected instances, it was observed that a significant amount of memory was allocated in the slice allocation of tsdb.NewCircularExemplarStorage. Specifically, ~8GiB were allocated in the slice allocation of tsdb.NewCircularExemplarStorage. This is a significant amount of memory, and it is likely that this is the cause of the memory usage pattern observed in the ingesters.

How to Reproduce the Bug

The bug can be reproduced by rolling out ingesters. This involves updating the ingesters to the latest version and then restarting them. After restarting the ingesters, the memory usage pattern should be observed.

What Was Thought to Happen

Initially, it was thought that the exemplar storage was being instantiated with the correct size. However, upon further investigation, it was discovered that the exemplar storage was being instantiated with an empty ring. This is likely the cause of the memory usage pattern observed in the ingesters.

What Was the Expected Behavior?

The expected behavior was that the exemplar storage would be instantiated with the correct size, which would result in a more efficient use of memory. However, the bug resulted in the exemplar storage being instantiated with an empty ring, which led to a significant memory usage pattern.

What Was the Actual Behavior?

The actual behavior was that the exemplar storage was instantiated with an empty ring, which resulted in a significant memory usage pattern. This was observed in the ingesters after restarting.

What Was the Environment?

The environment in which the bug occurred was a Grafana Cloud environment, specifically in a staging environment with the latest weekly release.

Additional Context

There is no additional context to share regarding this bug.

Conclusion

In conclusion, the bug in question involves the instantiation of tsdb.NewCircularExemplarStorage with a wrong size at startup. This led to a strange memory usage pattern in the ingesters after restarting. The bug can be reproduced by rolling out ingesters, and the expected behavior was that the exemplar storage would be instantiated with the correct size. However, the actual behavior was that the exemplar storage was instantiated with an empty ring, which resulted in a significant memory usage pattern.

Recommendations

Based on the analysis of the bug, the following recommendations can be made:

Update the ingesters to the latest version: This will ensure that the bug is fixed and the memory usage pattern is resolved.
Monitor the memory usage of the ingesters: This will help to identify any potential issues with the memory usage of the ingesters.
Optimize the exemplar storage: This will help to reduce the memory usage of the exemplar storage and prevent the memory usage pattern observed in the ingesters.

Future Work

Future work should focus on optimizing the exemplar storage to reduce the memory usage and prevent the memory usage pattern observed in the ingesters. Additionally, further investigation should be conducted to determine the root cause of the bug and to ensure that it is fixed.

Code Review

The code review of the tsdb.NewCircularExemplarStorage instantiation process should be conducted to identify any potential issues with the code. This will help to ensure that the bug is fixed and the memory usage pattern is resolved.

Testing

The testing of the tsdb.NewCircularExemplarStorage instantiation process should be conducted to ensure that the bug is fixed and the memory usage pattern is resolved. This will help to identify any potential issues with the code and ensure that the bug is fixed.

Deployment

The deployment of the updated ingesters should be conducted to ensure that the bug is fixed and the memory usage pattern is resolved. This will help to ensure that the memory usage pattern is resolved and the ingesters are functioning correctly.

Monitoring

The monitoring of the memory usage of the ingesters should be conducted to ensure that the memory usage pattern is resolved. This will help to identify any potential issues with the memory usage of the ingesters and ensure that the bug is fixed.

Troubleshooting

The troubleshooting of the bug should be conducted to ensure that the bug is fixed and the memory usage pattern is resolved. This will help to identify the root cause of the bug and ensure that it is fixed.

Conclusion

Q: What is the bug in question?

A: The bug in question involves the instantiation of tsdb.NewCircularExemplarStorage with a wrong size at startup. This led to a strange memory usage pattern in the ingesters after restarting.

Q: What was the expected behavior?

A: The expected behavior was that the exemplar storage would be instantiated with the correct size, which would result in a more efficient use of memory.

Q: What was the actual behavior?

A: The actual behavior was that the exemplar storage was instantiated with an empty ring, which resulted in a significant memory usage pattern.

Q: How can the bug be reproduced?

A: The bug can be reproduced by rolling out ingesters. This involves updating the ingesters to the latest version and then restarting them. After restarting the ingesters, the memory usage pattern should be observed.

Q: What is the root cause of the bug?

A: The root cause of the bug is that the exemplar storage was instantiated with an empty ring, which resulted in a significant memory usage pattern.

Q: How can the bug be fixed?

A: The bug can be fixed by updating the ingesters to the latest version, which includes the fix for the bug. Additionally, the exemplar storage should be optimized to reduce the memory usage and prevent the memory usage pattern observed in the ingesters.

Q: What are the potential consequences of the bug?

A: The potential consequences of the bug include a significant memory usage pattern in the ingesters, which can lead to performance issues and even crashes.

Q: How can the memory usage of the ingesters be monitored?

A: The memory usage of the ingesters can be monitored by using tools such as Prometheus and Grafana. These tools can provide insights into the memory usage of the ingesters and help identify any potential issues.

Q: What is the recommended course of action for fixing the bug?

A: The recommended course of action for fixing the bug is to update the ingesters to the latest version, which includes the fix for the bug. Additionally, the exemplar storage should be optimized to reduce the memory usage and prevent the memory usage pattern observed in the ingesters.

Q: What are the benefits of fixing the bug?

A: The benefits of fixing the bug include improved performance, reduced memory usage, and prevention of crashes.

Q: How can the bug be prevented in the future?

A: The bug can be prevented in the future by following best practices for coding and testing, such as writing unit tests and integration tests to ensure that the code is working as expected.

Q: What is the timeline for fixing the bug?

A: The timeline for fixing the bug is dependent on the priority of the bug and the resources available to fix it. However, it is recommended to fix the bug as soon as possible to prevent any potential issues.

Q: Who is responsible for fixing the bug?

A: The person or team responsible for fixing the bug is dependent on the organization's structure and policies. However, it is recommended to assign a specific person or team to fix the bug to ensure that it is done efficiently and effectively.

Q: What are the next steps for fixing the bug?

A: The next steps for fixing the bug include updating the ingesters to the latest version, optimizing the exemplar storage, and monitoring the memory usage of the ingesters to ensure that the bug is fixed and the memory usage pattern is resolved.