RGW Kafka Notification Test Failure: Signature Mismatch

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RGW Kafka Notification Test Failure: Signature Mismatch

Introduction

Hey guys, we've hit a snag with the test_rgw_kafka_notifications test, and it's throwing a SignatureDoesNotMatch error when trying to create a bucket. This article dives into the details of this issue, why it's happening, and the steps we're taking to resolve it. We'll break down the error logs, pinpoint the problematic code, and explore potential solutions. So, buckle up and let's get to the bottom of this!

This issue specifically arises within the Red Hat Storage and OCS-CI (OpenShift Container Storage - Continuous Integration) environments. Understanding the root cause is crucial for maintaining the stability and reliability of our storage solutions. Let's dig deep into the error logs and code snippets to figure out what's causing this signature mismatch during bucket creation.

Problem Description

The test_rgw_kafka_notifications test is failing with a SignatureDoesNotMatch error during the CreateBucket operation. This indicates an issue with the authentication process when the test attempts to create a new bucket in the RGW (Rados Gateway). The error logs point to a problem with the signature used to authenticate the request, suggesting a potential mismatch between the signature generated by the client and the signature expected by the server. This could stem from various reasons, such as incorrect credentials, timestamp issues, or problems with the signing algorithm itself.

Here's a breakdown of the key symptoms:

  • The test consistently fails at the bucket creation step.
  • The error message explicitly mentions SignatureDoesNotMatch.
  • The issue is observed in the context of RGW Kafka notifications, implying a connection to the notification setup.

To illustrate, let's look at the traceback provided in the original issue report. It clearly shows the error occurring within the botocore library, which is used for interacting with AWS services (and in this case, the S3-compatible RGW). The traceback highlights the create_bucket operation as the point of failure, reinforcing the signature mismatch problem. Analyzing these logs is the first step in diagnosing the root cause.

Deep Dive into the Error

Let's dissect the error message and the code snippet to understand what's going on under the hood. The core issue is the botocore.exceptions.ClientError: An error occurred (SignatureDoesNotMatch) when calling the CreateBucket operation: None. This basically means the signature calculated by the client (the test script) doesn't match what the RGW server expects.

Several factors could contribute to this:

  1. Incorrect Credentials: The access key ID or secret access key might be wrong or outdated. This is the most common culprit.
  2. Timestamp Skew: If the client's clock is significantly out of sync with the server's clock, the signature calculation will be off.
  3. Incorrect Region: While not explicitly mentioned in the logs, specifying the wrong region can sometimes lead to signature mismatches.
  4. Signing Algorithm Issues: There might be a bug in the signing algorithm implementation on either the client or the server side.
  5. Network Issues: Though less likely, network hiccups could corrupt the request and lead to a signature mismatch.

The provided code snippet shows the test setting up an AMQ cluster, creating a Kafka topic, and deploying a Kafkadrop pod. It then attempts to create a bucket using the rgw_bucket_factory. Critically, it retrieves RGW credentials and uses them to initialize a boto3 S3 resource. The put_object operation succeeds, but the subsequent notification setup fails during bucket creation. This suggests the initial credentials might be valid for basic operations, but something goes awry during the notification configuration.

Code Analysis and Potential Causes

Okay, let's break down the code snippet provided and see if we can pinpoint where the signature might be going wrong. The test sets up an AMQ cluster, creates a Kafka topic, and deploys a Kafkadrop pod – all standard procedure. The interesting part starts when it tries to create a bucket and configure RGW notifications.

The code retrieves RGW credentials using rgw_obj.get_credentials(). It then initializes a boto3 S3 resource with these credentials. A key piece of code is this:

s3_resource = boto3.resource(
    "s3",
    verify=retrieve_verification_mode(),
    endpoint_url=rgw_endpoint,
    aws_access_key_id=obc_obj.access_key_id,
    aws_secret_access_key=obc_obj.access_key,
)
s3_client = s3_resource.meta.client

This is where the connection to the RGW is established. The endpoint_url, aws_access_key_id, and aws_secret_access_key are crucial for authentication. If any of these are incorrect, we'll get a SignatureDoesNotMatch error.

The code then attempts to put an object into the bucket, which succeeds:

assert s3_client.put_object(
    Bucket=bucketname, Key="key-1", Body=data
), "Failed: Put object: key-1"

This is a bit of a red herring, as it suggests the credentials are at least partially valid. However, the issue arises later when the notification configuration is attempted using the notify_cmd. This command executes a Python script (notify.py) that likely uses the same credentials to create or configure bucket notifications. This discrepancy – the ability to put an object but failure to configure notifications – suggests a potential issue with the specific API calls used for notification setup or with the way the signing is handled in that script.

Let's look at the command being executed:

notify_cmd = (
    f"python {notify_path} -e {rgw_endpoint} -a {obc_obj.access_key_id} "
    f"-s {obc_obj.access_key} -b {bucketname} -ke {constants.KAFKA_ENDPOINT} -t {self.kafka_topic.name}"
)

This command passes the endpoint, access key ID, secret access key, bucket name, Kafka endpoint, and topic name to the notify.py script. It's crucial to ensure that the notify.py script is correctly using these parameters to sign its requests. A potential cause could be a subtle difference in how the boto3 client is configured or used within the notify.py script compared to the main test script.

Reproducing the Issue

To effectively troubleshoot, we need to reproduce the issue reliably. Here's how we can try to replicate the error:

  1. Environment Setup: Ensure we have a similar environment to the one where the test is failing (Red Hat Storage, OCS-CI). This includes the correct versions of software and libraries.
  2. Run the Test: Execute the test_rgw_kafka_notifications test directly.
  3. Isolate the Problem: If the test fails, try to isolate the bucket creation and notification setup steps. Run them separately to see if the failure is specific to notification configuration.
  4. Debug the Script: If the issue lies within the notify.py script, add logging statements to track the credentials, endpoint, and signature being used.
  5. Check Clock Synchronization: Verify that the client and server clocks are synchronized using ntp or similar tools.
  6. Manual Bucket Creation: Try creating a bucket manually using the same credentials via the aws CLI or s3cmd to rule out any issues with the boto3 library.

By systematically reproducing the error, we can gather more information and narrow down the possible causes.

Potential Solutions and Mitigation Steps

Alright, so we've identified the problem and dissected the code. Now, let's brainstorm some potential solutions and steps we can take to mitigate this SignatureDoesNotMatch error:

  1. Credential Verification:
    • Double-check the access key ID and secret access key. Ensure they are the correct and most up-to-date credentials.
    • Verify that the credentials have the necessary permissions to create buckets and configure notifications. A missing permission could lead to a signature mismatch.
  2. Clock Synchronization:
    • Ensure the client and server clocks are synchronized. Use NTP or a similar time synchronization protocol.
    • Investigate any potential clock drift issues on the client or server.
  3. Endpoint URL:
    • Confirm the RGW endpoint URL is correct. A typo or incorrect endpoint can cause signature mismatches.
    • Ensure the endpoint is reachable from the client.
  4. Signing Algorithm and Region:
    • Verify the signing algorithm being used by boto3. Ensure it's compatible with the RGW server.
    • Explicitly specify the region in the boto3 client configuration. While not always necessary, it can sometimes resolve signature issues.
  5. Debugging the notify.py script:
    • Add logging statements to the script to track the credentials, endpoint, and signature being used.
    • Compare the signing process in the script to the signing process in the main test script.
    • Look for any subtle differences in how the boto3 client is configured or used.
  6. Boto3 Configuration:
    • Check for any environment variables that might be affecting the boto3 configuration (e.g., AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_DEFAULT_REGION).
    • Ensure that the boto3 version being used is compatible with the RGW server.
  7. Temporary Workaround (if applicable):
    • If possible, try creating the bucket manually before running the test. This might bypass the immediate error and allow the rest of the test to proceed (though it doesn't solve the underlying issue).

By systematically addressing these potential causes, we should be able to narrow down the root cause and implement a proper fix.

Steps Taken and Current Status

So, where are we in the troubleshooting process? Here’s a rundown of the steps we've taken so far and the current status:

  1. Initial Investigation: We started by analyzing the error logs and traceback, identifying the SignatureDoesNotMatch error during the CreateBucket operation.
  2. Code Review: We examined the relevant code snippets, focusing on the RGW credential retrieval and the boto3 client configuration.
  3. Reproducing the Issue: We're actively working on reproducing the issue in a controlled environment to facilitate debugging.
  4. Potential Causes: We've brainstormed a list of potential causes, including incorrect credentials, clock skew, endpoint issues, and signing algorithm problems.
  5. Mitigation Steps: We've outlined several mitigation steps, such as verifying credentials, synchronizing clocks, and debugging the notify.py script.

Currently, we are focusing on:

  • Reproducing the error reliably.
  • Adding detailed logging to the notify.py script to inspect the signing process.
  • Comparing the boto3 configuration in the script with the main test script.

We'll keep you updated as we make progress. Our goal is to identify the root cause and implement a robust solution to prevent this issue from recurring.

Conclusion

The SignatureDoesNotMatch error in the test_rgw_kafka_notifications test is a tricky one, but by systematically investigating the code, logs, and environment, we can get to the bottom of it. We've explored potential causes ranging from credential issues to clock skew and signing algorithm problems. The next steps involve reproducing the error reliably, adding detailed logging, and comparing the signing process in different parts of the code.

Remember, debugging is like detective work. We gather clues, form hypotheses, and test them until we find the culprit. We're committed to resolving this issue and ensuring the stability of our storage solutions. Stay tuned for further updates, and thanks for following along!