Monitoring Azure Cosmos DB
This document provides a comprehensive guide to monitoring your Azure Cosmos DB instances, covering key metrics, tools, and best practices for ensuring performance, availability, and cost-effectiveness.
Effective monitoring is crucial for understanding the health and performance of your Azure Cosmos DB database. It helps you proactively identify potential issues, optimize resource utilization, and ensure your applications meet their performance targets.
Key Metrics to Monitor
Azure Cosmos DB exposes a rich set of metrics that provide insights into various aspects of your database's operation. Here are some of the most important ones:
Throughput and Performance Metrics
- Request Unit Consumption: Tracks the number of Request Units (RUs) consumed by your operations. Monitoring this helps identify performance bottlenecks and optimize RU allocation.
- Max RU/s: The maximum throughput provisioned for a container or database.
- Provisioned RU/s: The current RU/s available for a container or database.
- Actual RU/s: The actual RU/s consumed by requests.
- Successful Requests: The number of successful operations completed within a given time frame.
- Failed Requests: The number of operations that failed. Look for specific error codes like 429 (Too Many Requests) or 5xx server errors.
- Latency: The average time taken for requests to be processed. High latency can indicate performance issues.
Storage Metrics
- Total Document Size: The total size of all documents stored in your container or database.
- Data Usage: The amount of storage consumed by your data.
Availability and Errors
- Availability: The percentage of time your Cosmos DB service is operational and accessible.
- Http 4xx Errors: Client-side errors.
- Http 5xx Errors: Server-side errors.
Monitoring Tools and Services
Azure provides several integrated services to help you monitor Cosmos DB:
Azure Monitor
Azure Monitor is the primary service for collecting, analyzing, and acting on telemetry from your Azure and on-premises environments. For Cosmos DB, Azure Monitor offers:
- Metrics Explorer: Visualize and analyze metrics in real-time or historically. You can create charts, set alerts, and export data.
- Log Analytics: Collect and analyze diagnostic logs from Cosmos DB for deeper troubleshooting. Enable diagnostic settings to send logs to Log Analytics.
- Alerts: Configure alerts based on metric thresholds or log query results. Alerts can trigger actions like sending emails, invoking webhooks, or creating tickets.
Tip:
Configure diagnostic settings to send operation and diagnostic logs to Log Analytics or storage accounts for long-term analysis and auditing.
Azure Portal
The Azure portal provides a graphical interface for monitoring your Cosmos DB accounts. The Metrics and Diagnostic logs sections within your Cosmos DB account blade offer quick access to key performance indicators and logs.
Azure CLI and PowerShell
You can use Azure Command-Line Interface (CLI) or Azure PowerShell to programmatically retrieve metrics and diagnostic logs, enabling automated monitoring and reporting.
# Example using Azure CLI to get RU consumption metric
az cosmosdb cosmos metric list --account-name <your-cosmosdb-account-name> --resource-group <your-resource-group> --metric-names DocumentRUC.Total && \
--interval-granularity 5min --timespan <start-time>/<end-time>Setting Up Alerts
Alerts are essential for proactive issue detection. Consider setting up alerts for the following conditions:
- High Request Unit consumption (e.g., consistently exceeding 80% of provisioned RUs).
- Increased latency for read or write operations.
- High rates of 4xx or 5xx client or server errors.
- Low availability.
- Significant spikes in document size or data usage.
Best Practices for Monitoring
- Understand Your Workload: Know your application's typical read/write patterns and RU consumption to set meaningful alert thresholds.
- Monitor Across Regions: If using multi-region writes, monitor metrics for each region.
- Correlate Metrics with Logs: When an alert fires, use diagnostic logs to pinpoint the exact cause of the issue.
- Regularly Review Dashboards: Create custom Azure Monitor dashboards to get a consolidated view of your Cosmos DB performance and health.
- Capacity Planning: Use historical monitoring data to forecast future capacity needs and avoid performance degradation due to insufficient throughput.
Note:
Request Unit (RU) consumption is the primary cost driver for Cosmos DB. Monitoring RUs closely is key to managing costs effectively.
Troubleshooting Common Monitoring Issues
- High RU Consumption (429 Errors): Indicates that your provisioned throughput is insufficient for the current workload. Scale up RU/s or optimize queries.
- Increased Latency: Could be due to network issues, inefficient queries, or insufficient throughput.
- 5xx Server Errors: Often temporary, but persistent errors may require contacting Azure support.
By implementing a robust monitoring strategy using Azure Monitor and understanding the key metrics, you can ensure your Azure Cosmos DB environment remains healthy, performant, and cost-effective.