Azure Cosmos DB Troubleshooting Guide
This document provides guidance and common solutions for troubleshooting issues encountered with Azure Cosmos DB. We cover a range of topics, from performance bottlenecks to connectivity problems and error handling.
Common Issues and Solutions
1. Request Unit (RU) Throttling and High Latency
One of the most common issues is exceeding your provisioned Request Units (RUs). This can lead to throttled requests and increased latency.
- Monitor RU Consumption: Regularly check the "Request Units consumed" metric in the Azure portal.
- Analyze Queries: Identify long-running or inefficient queries. Use the Azure Cosmos DB SQL query metrics to understand query costs.
- Optimize Partitioning: Ensure your partition key is well-distributed to avoid hot partitions.
- Scale Throughput: If your workload consistently requires more RUs, consider increasing the provisioned throughput (either manually or by enabling autoscale).
- Request Charge Optimization: For read operations, consider using consistent prefix for partitioning and selecting only necessary fields. For writes, batch operations where possible.
SELECT TOP 100
c.id,
c.propertyName
FROM
c
WHERE
c.partitionKey = 'someValue'
2. Connectivity Issues
Problems connecting to your Azure Cosmos DB account can stem from network configurations, firewall rules, or service availability.
- Check Firewall Rules: Ensure your IP address or virtual network is allowed access in the Cosmos DB account's firewall settings.
- DNS Resolution: Verify that your application can resolve the Cosmos DB endpoint's DNS name.
- Service Availability: Check the Azure Service Health dashboard for any ongoing incidents affecting Azure Cosmos DB in your region.
- SDK Version: Ensure you are using an up-to-date version of the Azure Cosmos DB SDK.
- Timeouts: Review application-level timeouts and connection pool settings.
3. Data Consistency and Replication Problems
While Azure Cosmos DB offers configurable consistency levels, understanding their implications is crucial.
- Understand Consistency Levels: Choose the appropriate consistency level (e.g., Strong, Bounded Staleness, Session, Consistent Prefix, Eventual) based on your application's requirements.
- Replication Lag: If using a multi-region setup, be aware of potential replication lag, especially with stronger consistency levels.
- Conflict Resolution: Implement robust conflict resolution strategies if using last-writer-wins (LWW) or custom resolvers.
4. Error Handling and Troubleshooting Specific Errors
Familiarize yourself with common HTTP status codes and Cosmos DB-specific error codes.
- 400 Bad Request: Often indicates an issue with the query syntax or invalid input.
- 401 Unauthorized: Check your account key or Azure AD token.
- 403 Forbidden: May be related to insufficient permissions or throttling.
- 429 Too Many Requests: Indicates throttling. See RU Throttling section.
- 5xx Server Errors: Usually indicate a transient issue on the Azure Cosmos DB service side. Retry the operation with exponential backoff.
Advanced Troubleshooting Techniques
1. Diagnostic Logs and Metrics
Leverage Azure Monitor for detailed insights into your Cosmos DB account's performance and health.
- Activity Log: Tracks resource management operations.
- Diagnostic Logs: Provides detailed logs for requests, query metrics, and other operational data.
- Metrics: Offers key performance indicators like RU consumption, latency, and request rates.
2. Azure Cosmos DB Emulator
For local development and testing, the Azure Cosmos DB Emulator can help reproduce and debug issues before deploying to the cloud.
3. Support and Community
If you're unable to resolve an issue, don't hesitate to reach out for help.
- Azure Support: Open a support ticket for critical issues.
- Microsoft Q&A: Search for answers or post your questions.
- GitHub Repositories: Check the official Cosmos DB SDK repositories for known issues and discussions.