Flaky Test: Storage/storage.test.lua

Mar 12, 2025 by ADMIN 37 views

Introduction

Flaky tests are a common issue in software development, particularly in distributed systems like Tarantool. A flaky test is one that fails intermittently, making it difficult to identify and fix the underlying issue. In this article, we will investigate a flaky test in the Tarantool storage module, specifically the storage/storage.test.lua test.

Understanding the Test Failure

The test failure is indicated by the following log message:

[001] storage/storage.test.lua                        memtx           
[001] 
[001] [Instance "storage_1_a" returns with non-zero exit code: 1]

This message indicates that the test instance storage_1_a failed with a non-zero exit code, which is a common indicator of a test failure.

Analyzing the Log Output

Let's take a closer look at the log output to understand what might be causing the test failure:

2025-03-12 16:18:51.504 [208738] main/110/checkpoint_daemon gc.c:643 I> scheduled next checkpoint for Wed Mar 12 18:14:19 2025
2025-03-12 16:18:51.504 [208738] main/125/applier/storage@127.0.0.1:3302 applier.cc:673 I> remote master 3de2e3e1-9ebe-4d0d-abb1-26d301b84633 at 127.0.0.1:3302 running Tarantool 3.4.0
2025-03-12 16:18:51.504 [208738] main/124/applier/storage@127.0.0.1:3301 applier.cc:673 I> remote master 8a274925-a26d-47fc-9e1b-af88ce939412 at 127.0.0.1:3301 running Tarantool 3.4.0
2025-03-12 16:18:51.521 [208738] main main.cc:1074 I> entering the event loop
2025-03-12 16:18:51.522 [208738] main/124/applier/storage@127.0.0.1:3301 box.cc:588 I> leaving orphan mode
2025-03-12 16:18:51.522 [208738] main/125/applier/storage@127.0.0.1:3302 applier.cc:759 I> authenticated
2025-03-12 16:18:51.522 [208738] main/125/applier/storage@127.0.0.1:3302 applier.cc:2425 I> subscribed
2025-03-12 16:18:51.522 [208738] main/125/applier/storage@127.0.0.1:3302 applier.cc:2428 I> remote vclock {1: 152} local vclock {0: 4, 1: 153}
2025-03-12 16:18:51.522 [208738] main/125/applier/storage@127.0.0.1:3302 raft.c:507 I> RAFT: message {term: 1, state: follower} from 2
2025-03-12 16:18:51.522 [208738] main/125/applier/storage@127.0.0.1:3302 box.cc:588 I> leaving orphan mode
2025-03-12 16:18:51.522 [208738] main/118/main box.cc:5039 I> subscribed replica 3de2e3e1-9ebe-4d0d-abb1-26d301b84633 at fd 36, aka 127.0.0.1:3301, peer of 127.0.0.1:58208
2025-03-12 16:18:51.522 [208738] main/118/main box.cc:5041 I> remote vclock {1: 152} local vclock {0: 5, 1: 153}
2025-03-12 16:18:51.522 [208738] relay/127.0.0.1:58208/101/main recovery.cc:370 I> recover from `/tmp/t/001_storage/storage_1_a/00000000000000000156.xlog'
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51.588 [208738] main say.c:85 F> cfg_get('read_only')
2025-03-12 16:18:51<br/>
**Flaky Test: Storage/Storage.test.lua**
=====================================

**Q&A: Understanding the Flaky Test**
-----------------------------------

### Q: What is a flaky test?

A: A flaky test is a test that fails intermittently, making it difficult to identify and fix the underlying issue.

### Q: What is the cause of the flaky test in the storage/storage.test.lua test?

A: The cause of the flaky test is not immediately apparent from the log output. However, we can see that the test is failing with a non-zero exit code, and the log output is showing a series of `cfg_get` calls that are failing.

### Q: What is the purpose of the `cfg_get` calls in the test?

A: The `cfg_get` calls are used to retrieve configuration settings from the Tarantool instance. In this case, the calls are failing, which is causing the test to fail.

### Q: How can we troubleshoot the flaky test?

A: To troubleshoot the flaky test, we can start by examining the log output more closely. We can look for any patterns or clues that might indicate what is causing the test to fail. We can also try running the test with different configurations or settings to see if that makes a difference.

### Q: What are some common causes of flaky tests?

A: Some common causes of flaky tests include:

* **Timing issues**: Tests that rely on timing or synchronization can be prone to flakiness.
* **Randomness**: Tests that use random numbers or other randomizing factors can be flaky.
* **External dependencies**: Tests that rely on external dependencies, such as network connections or file systems, can be flaky.
* **Concurrency**: Tests that run concurrently with other tests or processes can be flaky.

### Q: How can we prevent flaky tests?

A: To prevent flaky tests, we can:

* **Use deterministic testing**: Use testing frameworks that provide deterministic testing, such as JUnit or TestNG.
* **Use mocking**: Use mocking libraries to isolate dependencies and reduce the risk of flakiness.
* **Use synchronization**: Use synchronization mechanisms, such as locks or semaphores, to ensure that tests run in a predictable order.
* **Use retry mechanisms**: Use retry mechanisms, such as exponential backoff, to handle temporary failures.

### Q: What are some best practices for writing flaky tests?

A: Some best practices for writing flaky tests include:

* **Keep tests simple**: Keep tests simple and focused on a single piece of functionality.
* **Use clear and concise language**: Use clear and concise language in test names and descriptions.
* **Use meaningful test data**: Use meaningful test data that is representative of real-world scenarios.
* **Use assertions**: Use assertions to verify that the expected behavior is occurring.

### Q: How can we debug flaky tests?

A: To debug flaky tests, we can:

* **Use a debugger**: Use a debugger to step through the test code and identify the source of the flakiness.
* **Use logging**: Use logging to capture detailed information about the test execution and identify the source of the flakiness.
* **Use profiling**: Use profiling tools to identify performance bottlenecks and optimize the test code.
* **Use testing frameworks**: Use testing frameworks that provide built-in support for debugging and troubleshooting flaky tests.