Fixing Kibana Serverless Search Test Failure

We've got a bit of a situation, guys! A test in the Kibana serverless search functionality is failing. Specifically, it's the discover/esql discover esql view sorting should sort correctly test within the 6.x-pack/platform/test/serverless/functional/test_suites/discover/esql/_esql_view.ts file. This article will break down the error, explore potential causes, and outline steps to resolve it. Let's get this sorted!

Understanding the Error

First, let's dissect the error message:

Error: timed out waiting for first cell contains the same highest value after reopening -- last error: TimeoutError: Waiting for element to be located By(css selector, [data-test-subj="euiDataGridBody"] [data-test-subj="dataGridRowCell"][data-gridcell-column-index="0"][data-gridcell-visible-row-index="0"])
Wait timed out after 10032ms
    at /opt/buildkite-agent/builds/bk-agent-prod-gcp-1762285545116643820/elastic/kibana-on-merge/kibana/node_modules/selenium-webdriver/lib/webdriver.js:929:22
    at processTicksAndRejections (node:internal/process/task_queues:105:5)
    at onFailure (retry_for_truthy.ts:40:13)
    at retryForSuccess (retry_for_success.ts:91:7)
    at retryForTruthy (retry_for_truthy.ts:28:3)
    at RetryService.waitFor (retry.ts:93:5)
    at Context.<anonymous> (_esql_view.ts:538:9)
    at Object.apply (wrap_function.js:74:16)

This error indicates a timeout issue during the test execution. The test is using Selenium WebDriver to interact with the Kibana UI. It's trying to locate a specific cell in the data grid (euiDataGridBody) – the cell in the first column and first visible row – after reopening something (likely a view or panel). The test expects this cell to contain the same highest value after the reopening. The timeout of 10032ms (approximately 10 seconds) was exceeded before the element was found, or the expected value was present. The stack trace points to the _esql_view.ts file, specifically line 538, suggesting the problem lies within the ES|QL view sorting functionality. This timeout is a critical symptom, indicating a potential problem with the rendering of the data grid, the sorting mechanism in ES|QL, or the interaction between the two. A possible root cause could be that the server is taking too long to return the sorted data, or that the client-side rendering of the data grid is slow. Investigating network performance and server-side query execution times is crucial. Furthermore, the stability of the Kibana environment itself can influence the results of UI tests, making it necessary to ensure the test environment is properly configured and maintained. The flakiness could also be caused by external factors such as concurrent processes consuming resources, which can affect the responsiveness of the Kibana application. To address this, it's helpful to monitor the resource utilization of the server during test execution and identify potential bottlenecks.

Possible Causes

Several factors could be contributing to this failure:

1. Slow ES|QL Query: The ES|QL query used for sorting might be taking longer than expected to execute. This could be due to the complexity of the query, the size of the data being queried, or issues with the Elasticsearch cluster itself. Check Elasticsearch cluster health and query performance.
2. Data Grid Rendering Issues: The EUI data grid might be slow to render, especially with large datasets. This could be due to inefficient rendering logic or browser performance limitations. Consider optimizing the data grid configuration and rendering process.
3. Kibana Server Load: High load on the Kibana server could be slowing down the entire process, leading to timeouts. Monitor server CPU, memory, and disk I/O.
4. Timing Issues: There might be subtle timing issues in the test itself. For example, the test might be trying to access the data grid before it has fully rendered or populated with data. Review the test code for potential race conditions or incorrect wait conditions.
5. Environment Instability: The test environment itself (e.g., the Buildkite agent) could be experiencing issues, leading to intermittent failures. Ensure the test environment is stable and properly configured.
6. Flaky Test: Sometimes, tests fail intermittently due to various factors like network glitches or resource contention. Consider re-running the test multiple times to see if it consistently fails.

Troubleshooting Steps

Here's a systematic approach to troubleshoot this issue:

1. Reproduce the Error Locally: Try to reproduce the error locally. This will allow you to debug the test more easily and isolate the problem. Use the same Kibana version and configuration as the Buildkite environment.
2. Examine ES|QL Query Performance: Use the Elasticsearch profiling API to analyze the performance of the ES|QL query. Identify any slow parts of the query and optimize them. You can use Kibana's Dev Tools to execute the query and analyze its performance. Pay attention to the query execution time and resource consumption.
3. Optimize Data Grid Rendering: If the data grid is slow to render, explore ways to optimize it. For example, you could try using virtualization to render only the visible rows. Experiment with different data grid configurations and rendering options. Another potential area for optimization lies in the data itself. Large string fields or complex data structures can increase the rendering time. Truncating or simplifying the data displayed in the grid can significantly improve performance. It's important to strike a balance between providing sufficient information and optimizing rendering speed. If the issue persists, consider upgrading the EUI data grid library to the latest version, as newer versions often include performance improvements and bug fixes.
4. Monitor Server Resources: Use system monitoring tools to track the CPU, memory, and disk I/O usage on the Kibana server. Identify any resource bottlenecks that could be contributing to the slowdown. Consider increasing server resources if necessary.
5. Review Test Code: Carefully review the test code for any potential timing issues or race conditions. Ensure that the test is waiting for the data grid to fully render and populate before attempting to access its contents. Use explicit waits instead of implicit waits to ensure that the test is waiting for the expected condition to be met. Add more logging to the test to help diagnose the issue.
6. Increase Timeout: As a temporary workaround, you could try increasing the timeout value in the test. However, this is not a long-term solution and should only be used for debugging purposes. If increasing the timeout resolves the issue, it suggests that the underlying problem is related to performance. Address the root cause of the performance issue rather than simply increasing the timeout.
7. Check Elasticsearch Cluster Health: Ensure that the Elasticsearch cluster is healthy and not experiencing any performance issues. Use the Elasticsearch cluster health API to check the status of the cluster. Address any issues identified by the cluster health API.
8. Investigate Network Latency: Analyze network latency between the Kibana server and the Elasticsearch cluster. High latency can contribute to slow query execution times. Use network monitoring tools to measure latency. Optimize network configuration to reduce latency.
9. Update Dependencies: Ensure that all dependencies, including Kibana, Elasticsearch, and the EUI library, are up to date. Newer versions often include bug fixes and performance improvements. Regularly update dependencies to maintain a stable and performant environment.

Proposed Solution and Code Example

Based on the error message and troubleshooting steps, a likely cause is a timing issue within the test. The test might be attempting to access the data grid before it's fully rendered after reopening the view. Here's a proposed solution, focusing on adding a more robust wait condition:

// Existing code...

await retry.waitFor(
  'first cell contains the same highest value after reopening',
  async () => {
    const firstCell = await findTestSubject('euiDataGridBody')
      .find(By.css('[data-test-subj="dataGridRowCell"][data-gridcell-column-index="0"][data-gridcell-visible-row-index="0"]'))
      .getVisibleText();

    // Add logging to inspect the value
    console.log(`First cell value: ${firstCell}`);

    return firstCell === expectedHighestValue;
  },
  { timeout: 20000 } // Increase timeout for good measure
);

// Existing code...

Explanation of changes:

• Increased Timeout: The timeout in the retry.waitFor function is increased to 20000ms (20 seconds). This gives the data grid more time to render.
• Explicit Wait Condition: The code now explicitly waits for the first cell to contain the expectedHighestValue. This is a more reliable approach than simply waiting for the element to be present.
• Logging: Added console.log to inspect the value of firstCell. This will provide valuable debugging information if the test continues to fail. Remember to remove or comment out this logging in production code.

Important Considerations:

• Replace expectedHighestValue with the actual variable that holds the expected value. It's critical to ensure that the expectedHighestValue is being correctly calculated and passed to the retry.waitFor function.
• This solution assumes that the expectedHighestValue is available at this point in the test. If it's not, you'll need to adjust the code accordingly. *Verify that the expectedHighestValue is initialized before the retry.waitFor call.
• Thoroughly test this solution locally before deploying it to the Buildkite environment. Run the test multiple times to ensure that it consistently passes.

Conclusion

Debugging failing tests in complex systems like Kibana can be challenging. By systematically analyzing the error message, exploring potential causes, and implementing targeted solutions, you can effectively resolve the issue. Remember to focus on improving the reliability and performance of your tests to prevent future failures. Good luck, and happy debugging!

By following these troubleshooting steps and implementing the proposed solution, you should be able to resolve the failing test and improve the stability of your Kibana serverless search functionality. Remember to monitor your test environment and address any underlying performance issues to prevent future failures. Effective testing is an ongoing process that requires continuous attention and optimization.