add appengine/bigquery sample

appengine/bigquery/README.md

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+# Accessing BigQuery from App Engine
+
+This code has been written to support this [blog post][1].
+
+You can run this application locally or deploy it to App Engine app servers.
+To do so you will need the `goapp` tool included in the [Go App Engine SDK][2].
+
+- get all the dependencies for this code snippet
+
+	goapp get .
+
+- deploy to App Engine servers
+
+	goapp deploy --application=[your-application-id] .
+
+[1]: https://medium.com/@francesc/accessing-bigquery-from-app-engine-d01823de81ee
+[2]: https://cloud.google.com/appengine/downloads?hl=en

appengine/bigquery/app.go

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+// Copyright 2015 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+// This App Engine application uses its default service account to list all
+// the BigQuery datasets accessible via the BigQuery REST API.
+package sample
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"golang.org/x/net/context"
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google"
+	"google.golang.org/api/bigquery/v2"
+	"google.golang.org/appengine"
+	"google.golang.org/appengine/urlfetch"
+)
+
+func init() {
+	http.HandleFunc("/", handle)
+}
+
+func handle(w http.ResponseWriter, r *http.Request) {
+	if r.URL.Path != "/" {
+		http.NotFound(w, r)
+		return
+	}
+
+	// create a new App Engine context from the request.
+	ctx := appengine.NewContext(r)
+
+	// obtain the list of dataset names.
+	names, err := datasets(ctx)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "text")
+
+	if len(names) == 0 {
+		fmt.Fprintf(w, "no datasets visible")
+	} else {
+		fmt.Fprintf(w, "datasets:\n\t"+strings.Join(names, "\n\t"))
+	}
+}
+
+// datasets returns a list with the ids of all the Big Query datasets visible
+// with the given context.
+func datasets(ctx context.Context) ([]string, error) {
+	// create a new authenticated HTTP client over urlfetch.
+	client := &http.Client{
+		Transport: &oauth2.Transport{
+			Source: google.AppEngineTokenSource(ctx, bigquery.BigqueryScope),
+			Base:   &urlfetch.Transport{Context: ctx},
+		},
+	}
+
+	// create the BigQuery service.
+	bq, err := bigquery.New(client)
+	if err != nil {
+		return nil, fmt.Errorf("could not create service: %v", err)
+	}
+
+	// obtain the current application id, the BigQuery id is the same.
+	appID := appengine.AppID(ctx)
+
+	// prepare the list of ids.
+	var ids []string
+	datasets, err := bq.Datasets.List(appID).Do()
+	if err != nil {
+		return nil, fmt.Errorf("could not list datasets for %q: %v", appID, err)
+	}
+	for _, d := range datasets.Datasets {
+		ids = append(ids, d.Id)
+	}
+	return ids, nil
+}

appengine/bigquery/app.yaml

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+version: 1
+runtime: go
+api_version: go1
+
+handlers:
+- url: /.*
+  script: _go_app