Troubleshooting CI Failures Elasticsearch FullClusterRestartIT TestShrink Cluster UPGRADED

by StackCamp Team 91 views

Hey everyone! We've got a situation where the FullClusterRestartIT test, specifically the testShrink {cluster=UPGRADED} method, is failing in our Continuous Integration (CI) environment for Elasticsearch. Let's dive into the details, figure out what's going on, and explore potential solutions.

Understanding the Issue: FullClusterRestartIT Test Failure

The Problem: Intermittent Test Failure

We are seeing failures in the testShrink {cluster=UPGRADED} method within the FullClusterRestartIT test suite. This test is designed to verify the functionality of Elasticsearch during a full cluster restart scenario, specifically when shrinking the cluster after an upgrade. The intermittent nature of these failures makes it a bit tricky to nail down the root cause immediately.

As of the latest reports, there have been 3 failures in the testShrink {cluster=UPGRADED} method out of 1000 executions, which translates to a 0.3% fail rate. While this might seem like a small percentage, it's enough to warrant investigation, as it indicates potential instability or edge-case scenarios that our tests are uncovering. These types of intermittent failures can be particularly troublesome because they can mask underlying issues and lead to unexpected behavior in production environments.

Key Information and Context

To effectively tackle this issue, let's gather and dissect the key information we have at hand:

  • Build Scans: The build scans provide a treasure trove of information about the test execution environment, dependencies, and any potential build-related issues. We have links to build scans for different Elasticsearch versions:
    • elasticsearch-intake #29532 / 10.0.0_lucene-compat
    • elasticsearch-periodic-java-ea #41 / 8.2.3_bwc
    • elasticsearch-periodic-java-ea #41 / 8.10.4_bwc
  • Reproduction Line: This is a crucial piece of the puzzle. The provided Gradle command allows us to reproduce the failure locally, which is a huge step in debugging. Here’s the command:
    ./gradlew ":qa:full-cluster-restart:luceneBwcTest" -Dtests.class="org.elasticsearch.upgrades.FullClusterRestartIT" -Dtests.method="testShrink {cluster=UPGRADED}" -Dtests.seed=1D222D634C4BC05B -Dtests.bwc.main.version=9.0.0 -Dtests.bwc.refspec.main=10352e57d85505984582616e1e38530d3ec6ca59 -Dtests.locale=ar-IQ -Dtests.timezone=Africa/Bissau -Druntime.java=25
    Breaking this down, we can see it's running a Lucene BWC test for the FullClusterRestartIT class, specifically targeting the testShrink method with the cluster=UPGRADED configuration. It also includes a seed for reproducibility, specifies the BWC version, locale, timezone, and Java runtime.
  • Applicable Branches: The issue is affecting the main branch, indicating that this is a concern for the current development efforts.
  • Reproduces Locally?: Currently, it's marked as N/A, but our goal is to change this by using the reproduction line to try and reproduce it locally.
  • Failure History: The dashboard link gives us insights into the historical failure patterns, helping us understand if this is a recurring issue or a new one.
  • Failure Message: The error message, java.lang.RuntimeException: An error occurred while checking cluster 'test-cluster' status, suggests that there's a problem verifying the cluster's health or state during the test. This could be due to a variety of reasons, such as nodes not joining correctly, data inconsistencies, or timing issues.
  • Issue Reasons: The summary indicates 3 failures in the specified test method, with a 0.3% failure rate out of 1000 executions. This provides a quantitative measure of the issue's prevalence.

Importance of FullClusterRestartIT

The FullClusterRestartIT test suite is a critical part of Elasticsearch's testing framework. It ensures that Elasticsearch clusters can be upgraded and restarted without data loss or service interruption. These tests simulate real-world upgrade scenarios, where clusters might be running older versions of Elasticsearch and need to be upgraded to newer versions. The testShrink method, in particular, focuses on the scenario where a cluster is scaled down (shrunk) after an upgrade. This is a common operation in production environments, as users might want to reduce resource consumption after an upgrade or adjust the cluster size based on changing workloads.

The fact that this test is failing intermittently suggests that there might be subtle issues in the upgrade or cluster-shrinking process that are not always triggered but can lead to failures under certain conditions. Addressing these issues is crucial to maintaining the reliability and stability of Elasticsearch upgrades.

Reproducing the Failure Locally

Why Reproducing Locally is Key

The first step in tackling any flaky test is to reproduce it locally. Why? Because debugging in a controlled environment is much easier than trying to decipher logs from a remote CI system. Local reproduction allows us to:

  • Set breakpoints and step through the code.
  • Modify the test and quickly rerun it.
  • Use debuggers and profilers to identify performance bottlenecks or race conditions.
  • Isolate the problem without the noise of the CI environment.

Using the Reproduction Line

The provided reproduction line is our golden ticket here. Fire up your terminal, navigate to the Elasticsearch project directory, and paste this command:

./gradlew ":qa:full-cluster-restart:luceneBwcTest" -Dtests.class="org.elasticsearch.upgrades.FullClusterRestartIT" -Dtests.method="testShrink {cluster=UPGRADED}" -Dtests.seed=1D222D634C4BC05B -Dtests.bwc.main.version=9.0.0 -Dtests.bwc.refspec.main=10352e57d85505984582616e1e38530d3ec6ca59 -Dtests.locale=ar-IQ -Dtests.timezone=Africa/Bissau -Druntime.java=25

Important Considerations:

  • Sufficient Resources: Ensure your machine has enough resources (CPU, memory, disk space) to run the test. Elasticsearch can be resource-intensive, especially during BWC tests.
  • Java Version: The -Druntime.java=25 parameter specifies the Java version. Make sure you have a compatible Java Development Kit (JDK) installed and configured.
  • Gradle Setup: Ensure Gradle is properly set up in your environment. You might need to configure environment variables or use a Gradle wrapper.
  • Patience: BWC tests can take a while to run, especially the full cluster restart tests. Be patient and let the test complete. Use the -Dtests.seed to make sure we are using the same seed that failed in CI.

Analyzing the Failure

If the test fails locally (and hopefully, it will!), you'll get a stack trace and error messages. This is where the real investigation begins:

  1. Read the Stack Trace: The stack trace points you to the exact location in the code where the exception occurred. Start from the top (the most recent call) and work your way down.
  2. Examine the Error Message: The error message often provides clues about the nature of the problem. In this case, `