Service to handle messages delivered by a Cloud Pub/Sub Push subscription.

## Explore further


For detailed documentation that includes this code sample, see the following:

- [Use Pub/Sub with Cloud Run tutorial](https://docs.cloud.google.com/run/docs/tutorials/pubsub)

## Code sample

### C#


To authenticate to Cloud Run, set up Application Default Credentials.
For more information, see

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    app.MapPost("/", (Envelope envelope) =>
    {
        if (envelope?.Message?.Data == null)
        {
            app.Logger.LogWarning("Bad Request: Invalid Pub/Sub message format.");
            return Results.BadRequest();
        }

        var data = Convert.FromBase64String(envelope.Message.Data);
        var target = System.Text.Encoding.UTF8.GetString(data);

        app.Logger.LogInformation($"Hello {target}!");

        return Results.NoContent();
    });

### Go


To authenticate to Cloud Run, set up Application Default Credentials.
For more information, see

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).


    // WrappedMessage is the payload of a Pub/Sub event.
    //
    // For more information about receiving messages from a Pub/Sub event
    // see: https://cloud.google.com/pubsub/docs/push#receive_push
    type WrappedMessage struct {
    	Message struct {
    		Data []byte `json:"data,omitempty"`
    		ID   string `json:"id"`
    	} `json:"message"`
    	Subscription string `json:"subscription"`
    }

    // HelloPubSub receives and processes a Pub/Sub push message.
    func HelloPubSub(w http.ResponseWriter, r *http.Request) {
    	var m WrappedMessage
    	body, err := io.ReadAll(r.Body)
    	defer r.Body.Close()
    	if err != nil {
    		log.Printf("io.ReadAll: %v", err)
    		http.Error(w, "Bad Request", http.StatusBadRequest)
    		return
    	}
    	// byte slice unmarshalling handles base64 decoding.
    	if err := json.Unmarshal(body, &m); err != nil {
    		log.Printf("json.Unmarshal: %v", err)
    		http.Error(w, "Bad Request", http.StatusBadRequest)
    		return
    	}

    	name := string(m.Message.Data)
    	if name == "" {
    		name = "World"
    	}
    	log.Printf("Hello %s!", name)
    }

### Java


To authenticate to Cloud Run, set up Application Default Credentials.
For more information, see

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    import com.example.cloudrun.Body;
    import java.util.Base64;
    import org.apache.commons.lang3.StringUtils;
    import org.springframework.http.HttpStatus;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;

    // PubsubController consumes a Pub/Sub message.
    @RestController
    public class PubSubController {
      @RequestMapping(value = "/", method = RequestMethod.POST)
      public ResponseEntity<String> receiveMessage(@RequestBody Body body) {
        // Get PubSub message from request body.
        Body.Message message = body.getMessage();
        if (message == null) {
          String msg = "Bad Request: invalid Pub/Sub message format";
          System.out.println(msg);
          return new ResponseEntity<>(msg, HttpStatus.BAD_REQUEST);
        }

        String data = message.getData();
        String target =
            !StringUtils.isEmpty(data) ? new String(Base64.getDecoder().decode(data)) : "World";
        String msg = "Hello " + target + "!";

        System.out.println(msg);
        return new ResponseEntity<>(msg, HttpStatus.OK);
      }
    }

### Node.js


To authenticate to Cloud Run, set up Application Default Credentials.
For more information, see

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    app.post('/', (req, res) => {
      if (!req.body) {
        const msg = 'no Pub/Sub message received';
        console.error(`error: ${msg}`);
        res.status(400).send(`Bad Request: ${msg}`);
        return;
      }
      if (!req.body.message) {
        const msg = 'invalid Pub/Sub message format';
        console.error(`error: ${msg}`);
        res.status(400).send(`Bad Request: ${msg}`);
        return;
      }

      const pubSubMessage = req.body.message;
      const name = pubSubMessage.data
        ? Buffer.from(pubSubMessage.data, 'base64').toString().trim()
        : 'World';

      console.log(`Hello ${name}!`);
      res.status(204).send();
    });

### Python


To authenticate to Cloud Run, set up Application Default Credentials.
For more information, see

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    @app.route("/", methods=["POST"])
    def index():
        """Receive and parse Pub/Sub messages."""
        envelope = request.get_json()
        if not envelope:
            msg = "no Pub/Sub message received"
            print(f"error: {msg}")
            return f"Bad Request: {msg}", 400

        if not isinstance(envelope, dict) or "message" not in envelope:
            msg = "invalid Pub/Sub message format"
            print(f"error: {msg}")
            return f"Bad Request: {msg}", 400

        pubsub_message = envelope["message"]

        name = "World"
        if isinstance(pubsub_message, dict) and "data" in pubsub_message:
            name = base64.b64decode(pubsub_message["data"]).decode("utf-8").strip()

        print(f"Hello {name}!")

        return ("", 204)

## What's next


To search and filter code samples for other Google Cloud products, see the
[Google Cloud sample browser](https://docs.cloud.google.com/docs/samples?product=cloudrun).