Observability with OpenTelemetry

LangChain.Databases includes built-in distributed tracing via System.Diagnostics.ActivitySource. All vector store operations emit activities that can be collected by any OpenTelemetry-compatible exporter.

Activity sources

Source name	Package
LangChain.Databases.Postgres	LangChain.Databases.Postgres
LangChain.Databases.OpenSearch	LangChain.Databases.OpenSearch

Operations traced

Both VectorStore and VectorStoreCollection operations are instrumented:

Activity name	Description
{system}.list_collections	List all collection/index names
{system}.collection_exists	Check if a collection exists
{system}.create_collection	Create a collection (table/index)
{system}.delete_collection	Delete a collection
{system}.get	Retrieve a record by key
{system}.upsert	Insert or update a single record
{system}.upsert_batch	Batch insert or update records
{system}.delete	Delete a single record
{system}.delete_batch	Batch delete records
{system}.search	Vector similarity search

Where {system} is postgresql or opensearch.

Tags (attributes)

Each activity includes OpenTelemetry Database semantic convention tags:

Tag	Description	Example
db.system.name	Database system identifier	postgresql, opensearch
db.namespace	Database name or host	mydb, localhost
db.collection.name	Table or index name	documents

Setup with .NET OpenTelemetry SDK

Install the OpenTelemetry packages:

dotnet add package OpenTelemetry
dotnet add package OpenTelemetry.Exporter.Console
# Or use OTLP exporter for Jaeger, Zipkin, etc.
dotnet add package OpenTelemetry.Exporter.OpenTelemetryProtocol

Configure tracing in your application:

using OpenTelemetry;
using OpenTelemetry.Trace;

var tracerProvider = Sdk.CreateTracerProviderBuilder()
    .AddSource("LangChain.Databases.Postgres")
    .AddSource("LangChain.Databases.OpenSearch")
    .AddConsoleExporter()  // or .AddOtlpExporter()
    .Build();

Or with ASP.NET Core dependency injection:

builder.Services.AddOpenTelemetry()
    .WithTracing(tracing => tracing
        .AddSource("LangChain.Databases.Postgres")
        .AddSource("LangChain.Databases.OpenSearch")
        .AddOtlpExporter());

Example output

With the console exporter, you'll see traces like:

Activity.TraceId:    abc123...
Activity.SpanId:     def456...
Activity.DisplayName: postgresql.search
Activity.Duration:   00:00:00.0234567
    db.system.name: postgresql
    db.namespace: mydb
    db.collection.name: documents

Metadata via GetService

Both stores expose metadata through the MEVA GetService pattern:

var store = new PostgresVectorStore(connectionString);
var metadata = store.GetService(typeof(VectorStoreMetadata)) as VectorStoreMetadata;
// metadata.VectorStoreSystemName == "postgresql"
// metadata.VectorStoreName == "mydb"

var collection = store.GetCollection<string, MyRecord>("documents");
var collMeta = collection.GetService(typeof(VectorStoreCollectionMetadata)) as VectorStoreCollectionMetadata;
// collMeta.VectorStoreSystemName == "postgresql"
// collMeta.VectorStoreName == "mydb"
// collMeta.CollectionName == "documents"