Cosmos DB: Network level Metrics

[sourabh1007]

Area(s)

area:db

Is your change request related to a problem? Please describe.

In the Cosmos DB SDK, a single operation involves several network calls. Currently, if something goes wrong (e.g., high latency) with these network calls, customers rely solely on the logs they have implemented in their applications. When investigating such issues, we are dependent on the information provided by the customer and backend telemetry. To improve monitoring and make it more aligned with potential errors, I am proposing a set of metrics that the SDK should collect to enhance observability.

Describe the solution you'd like

Proposing below list of metrics for network calls, SDK make 2 kinds of network calls

1. Gateway (i.e. HTTP)
2. TCP (i.e. RNTBD, proprietary to Microsoft)

Gateway (Meter name: Azure.Cosmos.Client.Request)

We cannot use the HTTP default metrics because we would need our custom dimensions for these metrics. Below is the proposed metrics with dimensions:

Dimensions

Tag/dimension name	Sample value
db.system	cosmodb
db.collection.name	myCollectionName
db.namespace	myDatabaseName
server.address	myaccountname.documents.azure.com
server.port	443
db.operation.name	query_items
db.response.status_code	200 or 429 etc.
db.cosmosdb.sub_status_code	1002 etc.
db.cosmosdb.consistency_level	Eventual, ConsistentPrefix, BoundedStaleness, Strong or Session
network.protocol.name	http for gateway mode, rntbd for direct mode
network.protocol.host	host from http://<host> : <port>
network.protocol.port	port from http://<host>:<port>
cloud.region	region name, where request was sent
db.cosmosdb.network.response.status_code	200 or 429 etc.
db.cosmosdb.network.response.sub_status_code	1002 etc.
db.cosmosdb.network.routing_id (opt-in)	pkrangeid (gateway mode), partionid/replicaid (direct mode)

Metrics

Name	Unit	Type	Description
db.client.cosmosdb.request.duration	{seconds}	Histogram	Duration of client requests.
db.client.cosmosdb.request.count	{requests}	Histogram	Number of requests made
db.client.cosmosdb.request.body.size	By	Histogram	Size of client request bodies.
db.client.cosmosdb.response.body.size	By	Histogram	Size of client response bodies.
db.client.cosmosdb.request.channel_aquisition.duration	{seconds}	Histogram	The duration of the successfully established outbound TCP connections. i.e. Channel Aquisition Time (for direct mode)
db.server.cosmosdb.request.duration db.client.cosmosdb.request.service_duration	{seconds}	Histogram	Backend Latency (for direct mode)
db.client.cosmosdb.request.pipelined.duration	{seconds}	Histogram	Time spent on "pipelined" stage (for direct mode)
db.client.cosmosdb.request.transit.duration	{seconds}	Histogram	Time spent on the wire (for direct mode)
db.client.cosmosdb.request.received.duration	{seconds}	Histogram	Time spent on "Received" stage (for direct mode)
db.client.cosmosdb.request.completed.duration	{seconds}	Histogram	Time spent on "Completed" stage (for direct mode)
db.client.cosmosdb.request.failed.duration	{seconds}	Histogram	Time spent on "Failed" stage (for direct mode)

Describe alternatives you've considered

No response

Additional context

Ref. java SDK metrics : https://github.com/Azure/azure-sdk-for-java/blob/main/sdk/cosmos/azure-cosmos/docs/Metrics.md

[joaopgrassi]

CC @open-telemetry/semconv-db-approvers