Some Metrics Work Individually but Not in Combined Queries

[nc-star]

Description

I encountered an issue while using azure-metrics-exporter for Cosmos DB where specific metrics work correctly when queried individually but fail to provide a response when queried together in a combined request. Below, I describe the steps I followed, the results I observed, and the problematic behavior.

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Steps to Reproduce

1. Setup Environment:

   • Installed and configured azure-metrics-exporter.
   • Verified that the exporter is reachable at http://localhost:8080.

2. Queried Metrics Individually:

   This approach worked for the following metrics:

   • AvailableStorage
   • DataUsage
   • DocumentCount
   • DocumentQuota
   • IndexUsage
   • MetadataRequests
   • NormalizedRUConsumption
   • PhysicalPartitionSizeInfo
   • ServerSideLatency
   • ServerSideLatencyGateway
   • ServiceAvailability
   • TotalRequests
   • TotalRequestsPreview
   • TotalRequestUnits
   • TotalRequestUnitsPreview

3. Combined Query:

   When I attempted to query these metrics in a combined request, some metrics did not return any data.

   Example Request:

   curl -X GET "http://localhost:8080/probe/metrics/list?name=azure_metric&subscription=xxxx-xxxx-xxxx-xxxx&resourceType=Microsoft.DocumentDB/DatabaseAccounts&metric=AvailableStorage,DataUsage,DocumentCount,DocumentQuota,IndexUsage,MetadataRequests,NormalizedRUConsumption,PhysicalPartitionSizeInfo,ServerSideLatency,ServerSideLatencyGateway,ServiceAvailability,TotalRequests,TotalRequestsPreview,TotalRequestUnits,TotalRequestUnitsPreview&interval=PT1H&timespan=PT1H&aggregation=average&metricTop=10&validateDimensions=true"
   
   
   ### Result
   

• Some metrics returned valid data, but others had no response or empty results.
• No specific error message was provided.

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Observations

• Individual metric queries work consistently.
• When combining metrics, some fail to provide a response without clear feedback.
• The issue seems to occur when specific metrics are queried together.

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Expected Behavior

• Combined metric queries should work the same way as individual queries, returning data for all specified metrics.

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Actual Behavior

• Some metrics fail to return data in combined queries.

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Request for Support

Could you help identify why combined metric queries fail for some metrics when querying Cosmos DB? If there are specific configurations or limitations regarding combined requests, it would be helpful to document them.

[WhitneyLampkin]

Hi @nc-star, I ran into this same issue recently with CosmosDB metrics and notice it is a common issue. The quick answer to this is that Azure Monitor doesn't support requests for metrics with different time grains. I see in your request that you're using PT1H for your time grain. Unfortunately, there are some CosmosDB metrics that don't support this time grain, such as TotalRequests, which only has the PT1M time grain available.

Check out my response for Issue 95 for more details. Hope this helps.