From 0590d9198f653ff2170e0f26790056bef4f056fe Mon Sep 17 00:00:00 2001
From: Stan Hu <stanhu@gmail.com>
Date: Sat, 19 Sep 2020 03:34:49 -0700
Subject: Make it possible to propagate correlation ID across processes

Previously, gitlab-shell did not pass a context through the application.
Correlation IDs were generated down the call stack, since we don't pass
the context around from the start execution.

This has several potential downsides:

1. It's easier for programming mistakes to be made in future which lead
to multiple correlation IDs being generated for a single request.
2. Correlation IDs cannot be passed in from upstream requests
3. Other advantages of context passing, such as distributed tracing is
not possible.

This commit changes the behavior:

1. Extract the correlation ID from the environment at the start of
the application.
2. If no correlation ID exists, generate a random one.
3. Pass the correlation ID to the GitLabNet API requests.

This change also enables other clients of GitLabNet (e.g. Gitaly) to
pass along the correlation ID in the internal API requests
(https://gitlab.com/gitlab-org/gitaly/-/issues/2725).

Fixes https://gitlab.com/gitlab-org/gitlab-shell/-/issues/474
---
 client/gitlabnet.go | 28 +++++++++++-----------------
 1 file changed, 11 insertions(+), 17 deletions(-)

(limited to 'client/gitlabnet.go')

diff --git a/client/gitlabnet.go b/client/gitlabnet.go
index 0657ca0..b908d04 100644
--- a/client/gitlabnet.go
+++ b/client/gitlabnet.go
@@ -11,8 +11,9 @@ import (
 	"strings"
 	"time"
 
-	log "github.com/sirupsen/logrus"
 	"gitlab.com/gitlab-org/labkit/correlation"
+
+	log "github.com/sirupsen/logrus"
 )
 
 const (
@@ -59,7 +60,7 @@ func normalizePath(path string) string {
 	return path
 }
 
-func newRequest(method, host, path string, data interface{}) (*http.Request, string, error) {
+func newRequest(ctx context.Context, method, host, path string, data interface{}) (*http.Request, string, error) {
 	var jsonReader io.Reader
 	if data != nil {
 		jsonData, err := json.Marshal(data)
@@ -70,20 +71,13 @@ func newRequest(method, host, path string, data interface{}) (*http.Request, str
 		jsonReader = bytes.NewReader(jsonData)
 	}
 
-	correlationID, err := correlation.RandomID()
-	ctx := context.Background()
-
-	if err != nil {
-		log.WithError(err).Warn("unable to generate correlation ID")
-	} else {
-		ctx = correlation.ContextWithCorrelation(ctx, correlationID)
-	}
-
 	request, err := http.NewRequestWithContext(ctx, method, host+path, jsonReader)
 	if err != nil {
 		return nil, "", err
 	}
 
+	correlationID := correlation.ExtractFromContext(ctx)
+
 	return request, correlationID, nil
 }
 
@@ -102,16 +96,16 @@ func parseError(resp *http.Response) error {
 
 }
 
-func (c *GitlabNetClient) Get(path string) (*http.Response, error) {
-	return c.DoRequest(http.MethodGet, normalizePath(path), nil)
+func (c *GitlabNetClient) Get(ctx context.Context, path string) (*http.Response, error) {
+	return c.DoRequest(ctx, http.MethodGet, normalizePath(path), nil)
 }
 
-func (c *GitlabNetClient) Post(path string, data interface{}) (*http.Response, error) {
-	return c.DoRequest(http.MethodPost, normalizePath(path), data)
+func (c *GitlabNetClient) Post(ctx context.Context, path string, data interface{}) (*http.Response, error) {
+	return c.DoRequest(ctx, http.MethodPost, normalizePath(path), data)
 }
 
-func (c *GitlabNetClient) DoRequest(method, path string, data interface{}) (*http.Response, error) {
-	request, correlationID, err := newRequest(method, c.httpClient.Host, path, data)
+func (c *GitlabNetClient) DoRequest(ctx context.Context, method, path string, data interface{}) (*http.Response, error) {
+	request, correlationID, err := newRequest(ctx, method, c.httpClient.Host, path, data)
 	if err != nil {
 		return nil, err
 	}
-- 
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