From b55bb4839b43c501b021d3a60639803db7ab4b0a Mon Sep 17 00:00:00 2001
From: Andre Medeiros <me@andremedeiros.info>
Date: Wed, 7 Jul 2021 22:19:02 -0400
Subject: [PATCH] measure reddit connections

---
 cmd/apollo-api/main.go    | 12 +++++++++++-
 cmd/apollo-worker/main.go |  8 ++++++--
 internal/reddit/client.go | 20 +++++++++++++++++++-
 3 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/cmd/apollo-api/main.go b/cmd/apollo-api/main.go
index 085315e..72b1909 100644
--- a/cmd/apollo-api/main.go
+++ b/cmd/apollo-api/main.go
@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"os"
 
+	"github.com/DataDog/datadog-go/statsd"
 	"github.com/joho/godotenv"
 	_ "github.com/lib/pq"
 
@@ -46,7 +47,16 @@ func main() {
 	}
 	defer db.Close()
 
-	rc := reddit.NewClient(os.Getenv("REDDIT_CLIENT_ID"), os.Getenv("REDDIT_CLIENT_SECRET"))
+	statsd, err := statsd.New("127.0.0.1:8125")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	rc := reddit.NewClient(
+		os.Getenv("REDDIT_CLIENT_ID"),
+		os.Getenv("REDDIT_CLIENT_SECRET"),
+		statsd,
+	)
 
 	app := &application{
 		cfg,
diff --git a/cmd/apollo-worker/main.go b/cmd/apollo-worker/main.go
index d91cf59..2389f47 100644
--- a/cmd/apollo-worker/main.go
+++ b/cmd/apollo-worker/main.go
@@ -182,8 +182,6 @@ func main() {
 		logger.Printf("Couldn't find .env so I will read from existing ENV.")
 	}
 
-	rc := reddit.NewClient(os.Getenv("REDDIT_CLIENT_ID"), os.Getenv("REDDIT_CLIENT_SECRET"))
-
 	dburl, ok := os.LookupEnv("DATABASE_CONNECTION_POOL_URL")
 	if !ok {
 		dburl = os.Getenv("DATABASE_URL")
@@ -204,6 +202,12 @@ func main() {
 		log.Fatal(err)
 	}
 
+	rc := reddit.NewClient(
+		os.Getenv("REDDIT_CLIENT_ID"),
+		os.Getenv("REDDIT_CLIENT_SECRET"),
+		statsd,
+	)
+
 	// This is a very conservative value -- seen as most of the work that is done in these jobs is
 	//
 	runtime.GOMAXPROCS(workers)
diff --git a/internal/reddit/client.go b/internal/reddit/client.go
index e6c055d..2f394c8 100644
--- a/internal/reddit/client.go
+++ b/internal/reddit/client.go
@@ -4,9 +4,11 @@ import (
 	"encoding/json"
 	"io/ioutil"
 	"net/http"
+	"net/http/httptrace"
 	"strings"
 	"time"
 
+	"github.com/DataDog/datadog-go/statsd"
 	"github.com/valyala/fastjson"
 )
 
@@ -18,14 +20,26 @@ type Client struct {
 	id     string
 	secret string
 	client *http.Client
+	tracer *httptrace.ClientTrace
 	parser *fastjson.Parser
+	statsd *statsd.Client
 }
 
-func NewClient(id, secret string) *Client {
+func NewClient(id, secret string, statsd *statsd.Client) *Client {
 	tr := &http.Transport{
 		MaxIdleConnsPerHost: 128,
 	}
 
+	tracer := &httptrace.ClientTrace{
+		GotConn: func(info httptrace.GotConnInfo) {
+			if info.Reused {
+				statsd.Incr("reddit.api.connections.reused", []string{}, 0.1)
+			} else {
+				statsd.Incr("reddit.api.connections.created", []string{}, 0.1)
+			}
+		},
+	}
+
 	client := &http.Client{Transport: tr}
 
 	parser := &fastjson.Parser{}
@@ -34,7 +48,9 @@ func NewClient(id, secret string) *Client {
 		id,
 		secret,
 		client,
+		tracer,
 		parser,
+		statsd,
 	}
 }
 
@@ -56,6 +72,8 @@ func (rac *AuthenticatedClient) request(r *Request) ([]byte, error) {
 		return nil, err
 	}
 
+	req = req.WithContext(httptrace.WithClientTrace(req.Context(), rac.tracer))
+
 	resp, err := rac.client.Do(req)
 	if err != nil {
 		return nil, err