Monorail client in Go

go/src/infra/monorail/endpoints.go

Index: go/src/infra/monorail/endpoints.go
diff --git a/go/src/infra/monorail/endpoints.go b/go/src/infra/monorail/endpoints.go
new file mode 100644
index 0000000000000000000000000000000000000000..fe7de9f0d4b0284fdb4e4529a9daa9ec04e7378e
--- /dev/null
+++ b/go/src/infra/monorail/endpoints.go
@@ -0,0 +1,97 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package monorail
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+
+	"github.com/luci/luci-go/common/errors"
+	"github.com/luci/luci-go/common/logging"
+
+	"infra/httputil"
+)
+
+// epClient implements MonorailClient by sending requests to Monorail's
+// Cloud Endpoints API.
+// See https://monorail-staging.appspot.com/_ah/api/explorer#p/monorail/v1/
+type epClient struct {
+	HTTP *http.Client
+	Host string
+}
+
+// NewEndpointsClient creates a MonorailClient that send requests to Monorail's
+// Cloud Endpoints.
+func NewEndpointsClient(client *http.Client, host string) MonorailClient {
+	return &epClient{HTTP: client, Host: host}
+}
+
+func (c *epClient) call(ctx context.Context, urlSuffix string, request, response interface{}) error {
+	var buf bytes.Buffer
+	if err := json.NewEncoder(&buf).Encode(request); err != nil {
+		return err
+	}
+	reqBytes := buf.Bytes()
+
+	u := fmt.Sprintf("https://%s/_ah/api/monorail/v1/%s", c.Host, urlSuffix)
+	req, err := http.NewRequest("POST", u, nil)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Accept", "application/json")
+
+	logging.Debugf(ctx, "POST %s %s", u, reqBytes)
+
+	return httputil.RetryRequest(ctx, c.HTTP, req, reqBytes, func(res *http.Response) error {
+		if res.StatusCode != http.StatusOK {
+			text, _ := ioutil.ReadAll(io.LimitReader(res.Body, 1024))
+			err := fmt.Errorf("unexpected status %q. Response: %s", res.Status, text)
+			if res.StatusCode == http.StatusNotFound {
+				// Occasionally Cloud Endpoints returns 404.

[seanmccullough1, 2016/06/03 18:45:33]

Even when it really should be a 500 :)

[nodir, 2016/06/03 18:56:12]

yes!

+				err = errors.WrapTransient(err)
+			}
+			return err
+		}
+		if response == nil {
+			return nil
+		}
+		return json.NewDecoder(res.Body).Decode(response)
+	})
+}
+
+func (c *epClient) InsertIssue(ctx context.Context, req *InsertIssueRequest, options ...grpc.CallOption) (*InsertIssueResponse, error) {

[seanmccullough1, 2016/06/03 18:45:33]

Godoc here and below. Mention that even though the signature accepts
...grpc.CallOption that actually passing any will cause an error. Either that or
don't accept CallOptions at all.

[nodir, 2016/06/03 18:56:12]

these functions are internal, so nobody will see their docstrings.

Mentioned CallOption in NewEndpointsClient docstring

+	if err := checkOptions(options); err != nil {
+		return nil, err
+	}
+	if err := req.Validate(); err != nil {
+		return nil, err
+	}
+	url := fmt.Sprintf("projects/%s/issues?sendEmail=%v", req.ProjectId, req.SendEmail)
+	res := &InsertIssueResponse{&Issue{}}
+	return res, c.call(ctx, url, &req.Issue, res.Issue)
+}
+
+func (c *epClient) InsertComment(ctx context.Context, req *InsertCommentRequest, options ...grpc.CallOption) (*InsertCommentResponse, error) {
+	if err := checkOptions(options); err != nil {
+		return nil, err
+	}
+	url := fmt.Sprintf("projects/%s/issues/%d/comments", req.Issue.ProjectId, req.Issue.IssueId)
+	return &InsertCommentResponse{}, c.call(ctx, url, req.Comment, nil)
+}
+
+func checkOptions(options []grpc.CallOption) error {
+	if len(options) > 0 {
+		return errGrpcOptions
+	}
+	return nil
+}