feat: create standalone samples that run against emulator (#30)

* feat: create standalone samples that run against emulator

* samples: refactor transactions sample to use emulator

examples/README.md

@@ -0,0 +1,21 @@
+# Spanner Go Sql Examples
+
+This directory contains samples for how to use the Spanner go-sql driver. Each sample can be executed
+as a standalone application without the need for any prior setup, other than that Docker must be installed
+on your system. Each sample will automatically:
+1. Download and start the [Spanner Emulator](https://cloud.google.com/spanner/docs/emulator) in a Docker container.
+2. Create a sample database and execute the sample on the sample database.
+3. Shutdown the Docker container that is running the emulator.
+
+Running a sample is done by navigating to the corresponding sample directory and executing the following command:
+
+```shell
+# Change the 'helloword' directory below to any of the samples in this directory.
+cd helloworld
+go run main.go
+```
+
+## Prerequisites
+
+Your system must have [Docker installed](https://docs.docker.com/get-docker/) for these samples to be executed,
+as each sample will automatically start the Spanner Emulator in a Docker container.

examples/emulator_runner.go

@@ -0,0 +1,162 @@
+// Copyright 2021 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package examples
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	database "cloud.google.com/go/spanner/admin/database/apiv1"
+	instance "cloud.google.com/go/spanner/admin/instance/apiv1"
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/container"
+	"github.com/docker/docker/client"
+	"github.com/docker/go-connections/nat"
+	databasepb "google.golang.org/genproto/googleapis/spanner/admin/database/v1"
+	instancepb "google.golang.org/genproto/googleapis/spanner/admin/instance/v1"
+)
+
+var cli *client.Client
+var containerId string
+
+func RunSampleOnEmulator(sample func(string, string, string) error, ddlStatements ...string) {
+	var err error
+	if err = startEmulator(); err != nil {
+		log.Fatalf("failed to start emulator: %v", err)
+	}
+	projectId, instanceId, databaseId := "my-project", "my-instance", "my-database"
+	if err = createInstance(projectId, instanceId); err != nil {
+		stopEmulator()
+		log.Fatalf("failed to create instance on emulator: %v", err)
+	}
+	if err = createSampleDB(projectId, instanceId, databaseId, ddlStatements...); err != nil {
+		stopEmulator()
+		log.Fatalf("failed to create database on emulator: %v", err)
+	}
+	err = sample(projectId, instanceId, databaseId)
+	stopEmulator()
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func startEmulator() error {
+	ctx := context.Background()
+	if err := os.Setenv("SPANNER_EMULATOR_HOST", "localhost:9010"); err != nil {
+		return err
+	}
+
+	// Initialize a Docker client.
+	var err error
+	cli, err = client.NewClientWithOpts(client.FromEnv, client.WithAPIVersionNegotiation())
+	if err != nil {
+		return err
+	}
+	// Pull the Spanner Emulator docker image.
+	if _, err := cli.ImagePull(ctx, "gcr.io/cloud-spanner-emulator/emulator", types.ImagePullOptions{}); err != nil {
+		return err
+	}
+	// Create and start a container with the emulator.
+	resp, err := cli.ContainerCreate(ctx, &container.Config{
+		Image:        "gcr.io/cloud-spanner-emulator/emulator",
+		ExposedPorts: nat.PortSet{"9010": {}},
+	}, &container.HostConfig{
+		PortBindings: map[nat.Port][]nat.PortBinding{"9010": {{HostIP: "0.0.0.0", HostPort: "9010"}}},
+	}, nil, nil, "")
+	if err != nil {
+		return err
+	}
+	containerId = resp.ID
+	if err := cli.ContainerStart(ctx, containerId, types.ContainerStartOptions{}); err != nil {
+		return err
+	}
+	// Wait max 10 seconds or until the emulator is running.
+	for c := 0; c < 20; c++ {
+		// Always wait at least 500 milliseconds to ensure that the emulator is actually ready, as the
+		// state can be reported as ready, while the emulator (or network interface) is actually not ready.
+		<-time.After(500 * time.Millisecond)
+		resp, err := cli.ContainerInspect(ctx, containerId)
+		if err != nil {
+			return fmt.Errorf("failed to inspect container state: %v", err)
+		}
+		if resp.State.Running {
+			break
+		}
+	}
+
+	return nil
+}
+
+func createInstance(projectId, instanceId string) error {
+	ctx := context.Background()
+	instanceAdmin, err := instance.NewInstanceAdminClient(ctx)
+	if err != nil {
+		return err
+	}
+	defer instanceAdmin.Close()
+	op, err := instanceAdmin.CreateInstance(ctx, &instancepb.CreateInstanceRequest{
+		Parent:     fmt.Sprintf("projects/%s", projectId),
+		InstanceId: instanceId,
+		Instance: &instancepb.Instance{
+			Config:      fmt.Sprintf("projects/%s/instanceConfigs/%s", projectId, "emulator-config"),
+			DisplayName: instanceId,
+			NodeCount:   1,
+		},
+	})
+	if err != nil {
+		return fmt.Errorf("could not create instance %s: %v", fmt.Sprintf("projects/%s/instances/%s", projectId, instanceId), err)
+	}
+	// Wait for the instance creation to finish.
+	if _, err := op.Wait(ctx); err != nil {
+		return fmt.Errorf("waiting for instance creation to finish failed: %v", err)
+	}
+	return nil
+}
+
+func createSampleDB(projectId, instanceId, databaseId string, statements ...string) error {
+	ctx := context.Background()
+	databaseAdminClient, err := database.NewDatabaseAdminClient(ctx)
+	if err != nil {
+		return err
+	}
+	defer databaseAdminClient.Close()
+	opDB, err := databaseAdminClient.CreateDatabase(ctx, &databasepb.CreateDatabaseRequest{
+		Parent:          fmt.Sprintf("projects/%s/instances/%s", projectId, instanceId),
+		CreateStatement: fmt.Sprintf("CREATE DATABASE `%s`", databaseId),
+		ExtraStatements: statements,
+	})
+	if err != nil {
+		return err
+	}
+	// Wait for the database creation to finish.
+	if _, err := opDB.Wait(ctx); err != nil {
+		return fmt.Errorf("waiting for database creation to finish failed: %v", err)
+	}
+	return nil
+}
+
+func stopEmulator() {
+	if cli == nil || containerId == "" {
+		return
+	}
+	ctx := context.Background()
+	timeout := 10 * time.Second
+	if err := cli.ContainerStop(ctx, containerId, &timeout); err != nil {
+		log.Printf("failed to stop emulator: %v\n", err)
+	}
+}

examples/go.mod

@@ -0,0 +1,17 @@
+module github.com/cloudspannerecosystem/go-sql-spanner/examples
+
+go 1.14
+
+replace github.com/cloudspannerecosystem/go-sql-spanner => ../
+
+require (
+	cloud.google.com/go/spanner v1.23.1-0.20210727075241-3d6c6c7873e1
+	github.com/cloudspannerecosystem/go-sql-spanner v0.0.0-00010101000000-000000000000
+	github.com/containerd/containerd v1.5.5 // indirect
+	github.com/docker/docker v20.10.8+incompatible
+	github.com/docker/go-connections v0.4.0
+	github.com/gorilla/mux v1.8.0 // indirect
+	github.com/moby/term v0.0.0-20210619224110-3f7ff695adc6 // indirect
+	github.com/morikuni/aec v1.0.0 // indirect
+	google.golang.org/genproto v0.0.0-20210726143408-b02e89920bf0
+)