---
title: "Connect Database Monitoring with APM Traces"
description: "Link PostgreSQL query samples to the APM services and traces that sent them by adding W3C traceparent comments to SQL with sqlcommenter."
section: "APM"
breadcrumb: "APM > Database Monitoring > Connect with APM Traces"
canonical: "https://docs.middleware.io/features/apm/database-monitoring/connect-apm-traces"
---
# Connect Database Monitoring with APM Traces

Connecting Database Monitoring with APM shows which service and trace sent each PostgreSQL query. You can start from a slow query and see the services calling it, or start from a query sample and open the full request trace.

This feature is available for **PostgreSQL**.

## How It Works

1. Your application is instrumented with APM, so every database call runs inside a trace span.
2. A SQL commenter library appends the current trace context to each query as a comment:

   ```sql
   SELECT * FROM users WHERE id = $1 /*traceparent='00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01'*/
   ```
3. When the agent samples `pg_stat_activity`, it reads the `traceparent` from the query text and stores the trace ID and span ID with the sample.
4. Middleware matches the span ID to your APM traces and shows the calling service and trace next to the query.

## Prerequisites

1. **APM instrumentation** that sends traces to Middleware. See the [APM setup guides](/get-started/apm).
2. **Query Sample Collection** turned on in the PostgreSQL integration. See [Set Up PostgreSQL](/get-started/database/postgresql).
3. The latest **Middleware Agent** version.

## Add Trace Context to SQL Queries

Turn on SQL commenter in the database instrumentation of your application:

#### Go

Use [sqlcommenter for `database/sql`](https://github.com/google/sqlcommenter/tree/master/go/database/sql) to open the database connection:

```go
import (
    gosql "github.com/google/sqlcommenter/go/database/sql"
    sqlcommentercore "github.com/google/sqlcommenter/go/core"
    _ "github.com/lib/pq"
)

db, err := gosql.Open("postgres", "<connection-string>", sqlcommentercore.CommenterOptions{
    Config: sqlcommentercore.CommenterConfig{
        EnableTraceparent: true, // append traceparent to every query
    },
})
```

#### Node.js

Turn on the SQL commenter option of the OpenTelemetry `pg` instrumentation:

```javascript
const { PgInstrumentation } = require("@opentelemetry/instrumentation-pg");

new PgInstrumentation({
  addSqlCommenterCommentToQueries: true,
});
```

#### Python

Turn on the commenter in the OpenTelemetry `psycopg2` instrumentation:

```python
from opentelemetry.instrumentation.psycopg2 import Psycopg2Instrumentor

Psycopg2Instrumentor().instrument(enable_commenter=True)
```

Any library that appends a W3C `traceparent` comment in the [sqlcommenter format](https://google.github.io/sqlcommenter/) works the same way.

## Verify the Connection

1. Send some traffic through your application.
2. Open **APM → Database → Samples**. Click **Customize** and add the **Calling Service**, **Trace ID**, and **Span ID** columns. New samples show your service name and IDs.
3. Open a sample. The **Calling Service** section shows the service, and the **Trace** tab shows the linked trace.

## Where Correlation Appears

- **Query details → Upstream → Calling Services**: every sample of the query linked to an APM service.
- **Query details → Upstream → Traces**: the linked spans. Click **Open in Traces** to continue in the [Trace Explorer](/features/apm/traces).
- **Sample details**: the **Calling Service** section and the **Trace** tab.
- **Instance Summary → Calling Services**: linked samples for the whole instance.

![Query details Upstream tab showing the Traces view with spans from the calling service](/images/apm/database-monitoring/pg-query-upstream-traces.png)

If nothing is linked, the Calling Services view shows "Please configure your application to link APM Services to Database Monitoring to see the data".

## Limitations

- **Sampled, not every execution**: a query is linked only if it is visible in `pg_stat_activity` when the agent takes a sample. Very fast queries may be linked only some of the time.
- **Long queries**: PostgreSQL stores only the first `track_activity_query_size` bytes of query text (1024 by default). The comment is added at the end, so it can be cut off on long queries. Increase the setting (for example, to `4096`) and restart PostgreSQL if long queries are not linked.
- **MongoDB**: correlation with APM traces is not available for MongoDB.

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