Metadata¶

Read Lambda execution-environment information from the Lambda Metadata Service (LMDS).

Install¶

Use Go 1.27 or newer:

CGO_ENABLED=0 go get github.com/rambow-cloud/powertools-lambda-go/commons/metadata@v1.2.0
CGO_ENABLED=0 go get github.com/rambow-cloud/powertools-lambda-go/logger@v1.2.0

Read execution-environment metadata¶

This program logs the returned metadata object with Logger. Outside Lambda, metadata is empty and no request is sent.

Input

Local process, outside Lambda

Code

package main

import (
    "context"
    "os"
    "time"

    "github.com/rambow-cloud/powertools-lambda-go/commons/metadata"
    "github.com/rambow-cloud/powertools-lambda-go/logger"
)

func main() {
    appLog := logger.New(logger.WithServiceName("orders"))
    if err := run(appLog); err != nil {
        if logErr := appLog.Error("Application failed", err); logErr != nil {
            panic(logErr)
        }
        os.Exit(1)
    }
}

func run(appLog *logger.Logger) error {
    value, err := metadata.GetMetadata(context.Background(),
        metadata.Options{Timeout: 500 * time.Millisecond})
    if err != nil {
        return err
    }
    return appLog.Info("Metadata retrieved", logger.Fields{"metadata": value})
}

The Logger timestamp varies on each run.

Output

{
  "level": "INFO",
  "message": "Metadata retrieved",
  "timestamp": "2026-10-15T00:00:00.000Z",
  "service": "orders",
  "sampling_rate": 0,
  "metadata": {}
}

Read metadata in Lambda¶

Use the invocation context so timeouts and cancellation apply:

value, err := metadata.GetMetadata(ctx,
    metadata.Options{Timeout: 500 * time.Millisecond})

Example service result

{
  "AvailabilityZoneID": "example-az1"
}

The available fields and values depend on the execution environment. Unknown response fields are retained.

Control caching¶

Successful nonempty results are cached across warm calls. Use ClearMetadataCache() to clear the default cache, or create an explicit client with metadata.New(metadata.Config{...}) and call ClearCache() on that client.

Things to know¶

This is Lambda metadata, not the EC2 Instance Metadata Service.
Logger and Tracer do not fetch it automatically.
The default client uses AWS_LAMBDA_METADATA_API and AWS_LAMBDA_METADATA_TOKEN; never log the token.
An unavailable service, timeout or malformed response returns an error.

Next steps¶

See the API and behavior notes for advanced options, and module installation for dependencies.