Leverage DevOps Guru for RDS to detect anomalies and resolve operational issues

The Relational Database Management System (RDBMS) is a popular choice among organizations running critical applications that supports online transaction processing (OLTP) use-cases. But managing the RDBMS database comes with its own challenges. AWS has made it easier for organizations to operate these databases in the cloud, thereby addressing the undifferentiated heavy lifting with managed databases (Amazon Aurora, Amazon RDS). Although using managed services has freed up engineering from provisioning hardware, database setup, patching, and backups, they still face the challenges that come with running a highly performant database. As applications scale in size and sophistication, it becomes increasingly challenging for customers to detect and resolve relational database performance bottlenecks and other operational issues quickly.

Amazon RDS Performance Insights is a database performance tuning and monitoring feature, that lets you quickly assess your database load and determine when and where to take action. Performance Insights lets non-experts in database administration diagnose performance problems with an easy-to-understand dashboard that visualizes database load. Furthermore, Performance Insights expands on the existing Amazon RDS monitoring features to illustrate database performance and help analyze any issues that affect it. The Performance Insights dashboard also lets you visualize the database load and filter the load by waits, SQL statements, hosts, or users.

On Dec 1st, 2021, we announced Amazon DevOps Guru for RDS, a new capability for Amazon DevOps Guru. It’s a fully-managed machine learning (ML)-powered service that detects operational and performance related issues for Amazon Aurora engines. It uses the data that it collects from Performance Insights, and then automatically detects and alerts customers of application issues, including database problems. When DevOps Guru detects an issue in an RDS database, it publishes an insight in the DevOps Guru dashboard. The insight contains an anomaly for the resource AWS/RDS. If DevOps Guru for RDS is turned on for your instances, then the anomaly contains a detailed analysis of the problem. DevOps Guru for RDS also recommends that you perform an investigation, or it provides a specific corrective action. For example, the recommendation might be to investigate a specific high-load SQL statement or to scale database resources.

In this post, we’ll deep-dive into some of the common issues that you may encounter while running your workloads against Amazon Aurora MySQL-Compatible Edition databases, with simulated performance issues. We’ll also look at how DevOps Guru for RDS can help identify and resolve these issues. Simulating a performance issue is resource intensive, and it will cost you money to run these tests. If you choose the default options that are provided, and clean up your resources using the following clean-up instructions, then it will cost you approximately $15 to run the first test only. If you wish to run all of the tests, then you can choose “all” in the Tests parameter choice. This will cost you approximately $28 to run all three tests.

Prerequisites

To follow along with this walkthrough, you must have the following prerequisites:

• An AWS account with a role that has sufficient access to provision the required infrastructure. The account should also not have exceeded its quota for the resources being deployed (VPCs, Amazon Aurora, etc.).
• Credentials that enable you to interact with your AWS account.
• If you already have Amazon DevOps Guru turned on, then make sure that it’s tagged properly to detect issues for the resource being deployed.

Solution overview

You will clone the project from GitHub and deploy an AWS CloudFormation template, which will set up the infrastructure required to run the tests. If you choose to use the defaults, then you can run only the first test. If you would like to run all of the tests, then choose the “all” option under Tests parameter.

We simulate some common scenarios that your database might encounter when running enterprise applications. The first test simulates locking issues. The second test simulates the behavior when the AUTOCOMMIT property of the database driver is set to: True. This could result in statement latency. The third test simulates performance issues when an index is missing on a large table.

Solution walk through

Clone the repo and deploy resources

1. Utilize the following command to clone the GitHub repository that contains the CloudFormation template and the scripts necessary to simulate the database load. Note that by default, we’ve provided the command to run only the first test.

   git clone https://github.com/aws-samples/amazon-devops-guru-rds.git
   cd amazon-devops-guru-rds
   
   aws cloudformation create-stack --stack-name DevOpsGuru-Stack \
       --template-body file://DevOpsGuruMySQL.yaml \
       --capabilities CAPABILITY_IAM \
       --parameters ParameterKey=Tests,ParameterValue=one \
   ParameterKey=EnableDevOpsGuru,ParameterValue=y

   If you wish to run all four of the tests, then flip the ParameterValue of the Tests ParameterKey to “all”.

   If Amazon DevOps Guru is already enabled in your account, then change the ParameterValue of the EnableDevOpsGuru ParameterKey to “n”.

   It may take up to 30 minutes for CloudFormation to provision the necessary resources. Visit the CloudFormation console (make sure to choose the region where you have deployed your resources), and make sure that DevOpsGuru-Stack is in the CREATE_COMPLETE state before proceeding to the next step.

2. Navigate to AWS Cloud9, then choose Your environments. Next, choose DevOpsGuruMySQLInstance followed by Open IDE. This opens a cloud-based IDE environment where you will be running your tests. Note that in this setup, AWS Cloud9 inherits the credentials that you used to deploy the CloudFormation template.
3. Open a new terminal window which you will be using to clone the repository where the scripts are located.

4. Clone the repo into your Cloud9 environment, then navigate to the directory where the scripts are located, and run initial setup.

git clone https://github.com/aws-samples/amazon-devops-guru-rds.git
cd amazon-devops-guru-rds/scripts
sh setup.sh 
# NOTE: If you are running all test cases, use sh setup.sh all command instead. 
source ~/.bashrc

5. Initialize databases for all of the test cases, and add random data into them. The script to insert random data takes approximately five hours to complete. Your AWS Cloud9 instance is set up to run for up to 24 hours before shutting down. You can exit the browser and return between 5–24 hours to validate that the script ran successfully, then continue to the next step.

source ./connect.sh test 1
USE devopsgurusource;
CREATE TABLE IF NOT EXISTS test1 (id int, filler char(255), timer timestamp);
exit;
python3 ct.py

If you chose to run all test cases, and you ran the sh setup.sh all command in Step 4, open two new terminal windows and run the following commands to insert random data for test cases 2 and 3.

# Test case 2 – Open a new terminal window to run the commands
cd amazon-devops-guru-rds/scripts
source ./connect.sh test 2
USE devopsgurusource;
CREATE TABLE IF NOT EXISTS test1 (id int, filler char(255), timer timestamp);
exit;
python3 ct.py
# Test case 3 - Open a new terminal window to run the commands
cd amazon-devops-guru-rds/scripts
source ./connect.sh test 3
USE devopsgurusource;
CREATE TABLE IF NOT EXISTS test1 (id int, filler char(255), timer timestamp);
exit;
python3 ct.py

6. Return between 5-24 hours to run the next set of commands.

7. Add an index to the first database.

source ./connect.sh test 1
CREATE UNIQUE INDEX test1_pk ON test1(id);
INSERT INTO test1 VALUES (-1, 'locker', current_timestamp);
exit;

source ./connect.sh test 2
CREATE UNIQUE INDEX test1_pk ON test1(id);
INSERT INTO test1 VALUES (-1, 'locker', current_timestamp);
exit;

9. Allow two days before you start running the following tests.

Scenario 1: Locking Issues

In this scenario, multiple sessions compete for the same (“locked”) record, and they must wait for each other.
In real life, this often happens when:

• A database session gets disconnected due to a (i.e., temporary network) malfunction, while still holding a critical lock.
• Other sessions become stuck while waiting for the lock to be released.
• The problem is often exacerbated by the application connection manager that keeps spawning additional sessions (because the existing sessions don’t complete the work on time), thus creating a distinct “inclined slope” pattern that you’ll see in this scenario.

Here’s how you can reproduce it:

1. Connect to the database.

cd amazon-devops-guru-rds/scripts
source ./connect.sh test 1

2. In your MySQL, enter the following SQL, and don’t exit the shell.

START TRANSACTION;
UPDATE test1 SET timer=current_timestamp WHERE id=-1;
-- Do NOT exit!

2. Open a new terminal, and run the command to simulate competing transactions. Give it approximately five minutes before you run the commands in this step.

cd amazon-devops-guru-rds/scripts
source ./connect.sh test 1
exit;
python3 locking_scenario.py 1 1200 2

3. After the program completes its execution, navigate to the Amazon DevOps Guru console, choose Insights, and then choose RDS DB Load Anomalous. You’ll notice a summary of the insight under Description.

4. Choose the View Recommendations link on the top right, and observe the databases for which it’s showing the recommendations.
5. Next, choose View detailed analysis for database performance anomaly for the following resources.
6. Under To view a detailed analysis, choose a resource name, choose the database associated with the first test.

6. Observe the recommendations under Analysis and recommendations. It provides you with analysis, recommendations, and links to troubleshooting documentation.

In this example, DevOps Guru for RDS has detected a high and unusual spike of database load, and then marked it as “performance anomaly”.

Note that the relative size of the anomaly is significant: 490 times higher than the “typical” database load, which is why it’s deemed: “HIGH severity”.

In the analysis section, note that a single “wait event”, wait/synch/mutex/innodb/aurora_lock_thread_slot_futex, is dominating the entire spike. Moreover, a single SQL is “responsible” (or more precisely: “suffering”) from this wait event at the time of the problem. Select the wait event name and see a simple explanation of what’s happening in the database. For example, it’s “record locking”, where multiple sessions are competing for the same database records. Additionally, you can select the SQL hash and see the exact text of the SQL that’s responsible for the issue.

If you’re interested in why DevOps Guru for RDS detected this problem, and why these particular wait events and an SQL were selected, the Why is this a problem? and Why do we recommend this? links will provide the answer.

Finally, the most relevant part of this analysis is a View troubleshooting doc link. It references a document that contains a detailed explanation of the likely causes for this problem, as well as the actions that you can take to troubleshoot and address it.

Scenario 2: Autocommit: ON

In this scenario, we must run multiple batch updates, and we’re using a fairly popular driver setting: AUTOCOMMIT: ON.

This setting can sometimes lead to performance issues as it causes each UPDATE statement in a batch to be “encased” in its own “transaction”. This leads to data changes being frequently synchronized to disk, thus dramatically increasing batch latency.

Here’s how you can reproduce the scenario:

1. On your Cloud9 terminal, run the following commands:

cd amazon-devops-guru-rds/scripts
source ./connect.sh test 2
exit;
python3 batch_autocommit.py 50 1200 1000 10000000

2. Once the program completes its execution, or after an hour, navigate to the Amazon DevOps Guru console, choose Insights, and then choose RDS DB Load Anomalous. Then choose Recommendations and choose View detailed analysis for database performance anomaly for the following resources. Under To view a detailed analysis, choose a resource name, choose the database associated with the second test.

3. Observe the recommendations under Analysis and recommendations. It provides you with analysis, recommendations, and links to troubleshooting documentation.

Note that DevOps Guru for RDS detected a significant (and unusual) spike of database load and marked it as a HIGH severity anomaly.

The spike looks similar to the previous example (albeit, “smaller”), but it describes a different database problem (“COMMIT slowdowns”). This is because of a different database wait event that dominates the spike: wait/io/aurora_redo_log_flush.

As in the previous example, you can select the wait event name to see a simple description of what’s going on, and you can select the SQL hash to see the actual statement that is slow. Furthermore, just as before, the View troubleshooting doc link references the document that describes what you can do to troubleshoot the problem further and address it.

Scenario 3: Missing index

Have you ever wondered what would happen if you drop a frequently accessed index on a large table?

In this relatively simple scenario, we’re testing exactly that – an index gets dropped causing queries to switch from fast index lookups to slow full table scans, thus dramatically increasing latency and resource use.

Here’s how you can reproduce this problem and see it for yourself:

1. On your Cloud9 terminal, run the following commands:

cd amazon-devops-guru-rds/scripts
source ./connect.sh test 3
exit;
python3 no_index.py 50 1200 1000 10000000

2. Once the program completes its execution, or after an hour, navigate to the Amazon DevOps Guru console, choose Insights, and then choose RDS DB Load Anomalous. Then choose Recommendations and choose View detailed analysis for database performance anomaly for the following resources. Under To view a detailed analysis, choose a resource name, choose the database associated with the third test.

3. Observe the recommendations under Analysis and recommendations. It provides you with analysis, recommendations, and links to troubleshooting documentation.

As with the previous examples, DevOps Guru for RDS detected a high and unusual spike of database load (in this case, ~ 50 times larger than the “typical” database load). It also identified that a single wait event, wait/io/table/sql/handler, and a single SQL, are responsible for this issue.

The analysis highlights the SQL that you must pay attention to, and it links a detailed troubleshooting document that lists the likely causes and recommended actions for the problems that you see. While it doesn’t tell you that the “missing index” is the real root cause of the issue (this is planned in future versions), it does offer many relevant details that can help you come to that conclusion yourself.

Cleanup

On your terminal where you originally ran the AWS Command Line Interface (AWS CLI) command to create the CloudFormation resources, run the following command:

aws cloudformation delete-stack --stack-name DevOpsGuru-Stack

Conclusion

In this post, you learned how to leverage DevOps Guru for RDS to alert you of any operational issues with recommendations. You simulated some of the commonly encountered, real-world production issues, such as locking contentions, AUTOCOMMIT, and missing indexes. Moreover, you saw how DevOps Guru for RDS helped you detect and resolve these issues. Try this out, and let us know how DevOps Guru for RDS was able to address your use-case.

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