Using Cloud Spanner with Cloud Functions

Cloud Spanner

Objectives

Write, deploy, and trigger an HTTP Cloud Function that accesses Spanner.

Costs

This topic uses Spanner and Cloud Functions, which are billable components of the Google Cloud.

Before you begin

  1. This topic assumes you have a Spanner instance named test-instance and a database named example-db that uses the music application schema. For instructions on creating an instance and database with the music application schema, see Quickstart using the console or the tutorials for Getting Started in Go, Java, Node.js, or Python.

  2. Enable the Cloud Functions API.

    Enable the API

  3. Install and initialize the Cloud SDK.

  4. Update gcloud components:

    gcloud components update

  5. Prepare your development environment:

Prepare the application

  1. Clone the sample app repository to your local machine:

    Node.js 

    git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

    Python 

    git clone https://github.com/GoogleCloudPlatform/python-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

    Go 

    git clone https://github.com/GoogleCloudPlatform/golang-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

  2. Change to the directory that contains the Cloud Functions sample code for accessing Spanner:

    Node.js 

    cd nodejs-docs-samples/functions/spanner/

    Python 

    cd python-docs-samples/functions/spanner/

    Go 

    cd golang-samples/functions/spanner/

  3. Take a look at the sample code:

    Node.js

    functions/spanner/index.js 
    // Imports the Google Cloud client library
const {Spanner} = require('@google-cloud/spanner');

// Instantiates a client
const spanner = new Spanner();

// Your Cloud Spanner instance ID
const instanceId = 'test-instance';

// Your Cloud Spanner database ID
const databaseId = 'example-db';

/**
 * HTTP Cloud Function.
 *
 * @param {Object} req Cloud Function request context.
 * @param {Object} res Cloud Function response context.
 */
exports.get = async (req, res) => {
  // Gets a reference to a Cloud Spanner instance and database
  const instance = spanner.instance(instanceId);
  const database = instance.database(databaseId);

  // The query to execute
  const query = {
    sql: 'SELECT * FROM Albums',
  };

  // Execute the query
  try {
    const results = await database.run(query);
    const rows = results[0].map(row => row.toJSON());
    rows.forEach(row => {
      res.write(
        `SingerId: ${row.SingerId}, ` +
          `AlbumId: ${row.AlbumId}, ` +
          `AlbumTitle: ${row.AlbumTitle}\n`
      );
    });
    res.status(200).end();
  } catch (err) {
    res.status(500).send(`Error querying Spanner: ${err}`);
  }
};

    Python

    functions/spanner/main.py 
    from google.cloud import spanner

instance_id = 'test-instance'
database_id = 'example-db'

client = spanner.Client()
instance = client.instance(instance_id)
database = instance.database(database_id)


def spanner_read_data(request):
    query = 'SELECT * FROM Albums'

    outputs = []
    with database.snapshot() as snapshot:
        results = snapshot.execute_sql(query)

        for row in results:
            output = 'SingerId: {}, AlbumId: {}, AlbumTitle: {}'.format(*row)
            outputs.append(output)

    return '\n'.join(outputs)

    Go

    functions/spanner/spanner.go 
    
// Package spanner contains an example of using Spanner from a Cloud Function.
package spanner

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"sync"

	"cloud.google.com/go/spanner"
	"google.golang.org/api/iterator"
)

// client is a global Spanner client, to avoid initializing a new client for
// every request.
var client *spanner.Client
var clientOnce sync.Once

// db is the name of the database to query.
var db = "projects/my-project/instances/my-instance/databases/example-db"

// HelloSpanner is an example of querying Spanner from a Cloud Function.
func HelloSpanner(w http.ResponseWriter, r *http.Request) {
	clientOnce.Do(func() {
		// Declare a separate err variable to avoid shadowing client.
		var err error
		client, err = spanner.NewClient(context.Background(), db)
		if err != nil {
			http.Error(w, "Error initializing database", http.StatusInternalServerError)
			log.Printf("spanner.NewClient: %v", err)
			return
		}
	})

	fmt.Fprintln(w, "Albums:")
	stmt := spanner.Statement{SQL: `SELECT SingerId, AlbumId, AlbumTitle FROM Albums`}
	iter := client.Single().Query(r.Context(), stmt)
	defer iter.Stop()
	for {
		row, err := iter.Next()
		if err == iterator.Done {
			return
		}
		if err != nil {
			http.Error(w, "Error querying database", http.StatusInternalServerError)
			log.Printf("iter.Next: %v", err)
			return
		}
		var singerID, albumID int64
		var albumTitle string
		if err := row.Columns(&singerID, &albumID, &albumTitle); err != nil {
			http.Error(w, "Error parsing database response", http.StatusInternalServerError)
			log.Printf("row.Columns: %v", err)
			return
		}
		fmt.Fprintf(w, "%d %d %s\n", singerID, albumID, albumTitle)
	}
}

    The function sends a SQL query to fetch all Albums data from your database. The function is executed when you make an HTTP request to the function's endpoint.

Deploy the function

To deploy the function with an HTTP trigger, run the following command in the spanner directory:

Node.js 

gcloud functions deploy get --runtime nodejs8 --trigger-http
You can use the following values for the --runtime flag to specify your preferred Node.js version:
  • nodejs6 (deprecated)
  • nodejs8
  • nodejs10 (beta)

Python 

gcloud functions deploy spanner_read_data --runtime python37 --trigger-http

Go 

gcloud functions deploy HelloSpanner --runtime go111 --trigger-http
You can use the following values for the --runtime flag to specify your preferred Go version:
  • go111
  • go113 (beta)

Function deployment may take up to 2 minutes.

Note the url value returned when your function finishes deploying. You will use it when you trigger the function.

You can view your deployed functions on the Cloud Functions page in the Google Cloud Console. You can also create and edit functions on that page, and get details and diagnostics for your functions.

Trigger the function

Make an HTTP request to your function:

Node.js 

curl "https://REGION-PROJECT_ID.cloudfunctions.net/get" --trigger-http

Python 

curl "https://REGION-PROJECT_ID.cloudfunctions.net/spanner_read_data" --trigger-http

Go 

curl "https://REGION-PROJECT_ID.cloudfunctions.net/HelloSpanner" --trigger-http

where REGION and PROJECT_ID match the values that are visible in your terminal when your function finishes deploying. You should see output that shows the results of the SQL query, assuming you worked through a Getting Started tutorial and populated the database:

SingerId: 2, AlbumId: 2, AlbumTitle: Forever Hold Your Peace
SingerId: 1, AlbumId: 2, AlbumTitle: Go, Go, Go
SingerId: 2, AlbumId: 1, AlbumTitle: Green
SingerId: 2, AlbumId: 3, AlbumTitle: Terrified
SingerId: 1, AlbumId: 1, AlbumTitle: Total Junk

You can also visit the function's URL in your browser to see the result of your SQL query.

Cleanup

To avoid incurring additional charges to your Google Cloud account for the Spanner and Cloud Functions resources used in this topic:

  1. Delete the instance:

    gcloud spanner instances delete test-instance

  2. Delete the function that you deployed:

    Node.js 

    gcloud functions delete get --trigger-http

    Python 

    gcloud functions delete spanner_read_data --trigger-http

    Go 

    gcloud functions delete HelloSpanner --trigger-http

What's next