universal error handling in api pkg by returning errs from http handlers

pkg/api/auth.go

@@ -25,7 +25,7 @@ type login struct {
 var store = sessions.NewCookieStore([]byte(os.Getenv("ANA_SECRET_KEY")))
 
 // URL: POST /api/session
-var LoginHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var LoginHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 
 	// check login creds
 	var l login
@@ -36,27 +36,31 @@ var LoginHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request)
 	// compare pwd
 	if err != nil || bcrypt.CompareHashAndPassword([]byte(u.HashedPassword), []byte(l.Password)) != nil {
 		w.WriteHeader(http.StatusUnauthorized)
-		respond(w, envelope{Error: "invalid_credentials"})
+		return respond(w, envelope{Error: "invalid_credentials"})
-		return
 	}
 
 	session, _ := store.Get(r, "auth")
 	session.Values["user_id"] = u.ID
 	err = session.Save(r, w)
-	checkError(err)
+	if err != nil {
+		return err
+	}
 
-	respond(w, envelope{Data: true})
+	return respond(w, envelope{Data: true})
 })
 
 // URL: DELETE /api/session
-var LogoutHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var LogoutHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	session, _ := store.Get(r, "auth")
 	if !session.IsNew {
 		session.Options.MaxAge = -1
-		session.Save(r, w)
+		err := session.Save(r, w)
+		if err != nil {
+			return err
+		}
 	}
 
-	respond(w, envelope{Data: true})
+	return respond(w, envelope{Data: true})
 })
 
 /* middleware */

pkg/api/browsers.go

@@ -6,8 +6,8 @@ import (
 )
 
 // URL: /api/browsers
-var GetBrowsersHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetBrowsersHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 	results := count.Browsers(before, after, getRequestedLimit(r))
-	respond(w, envelope{Data: results})
+	return respond(w, envelope{Data: results})
 })

pkg/api/collect.go

@@ -11,28 +11,23 @@ import (
 	"github.com/mssola/user_agent"
 	"github.com/usefathom/fathom/pkg/datastore"
 	"github.com/usefathom/fathom/pkg/models"
+
+	log "github.com/sirupsen/logrus"
 )
 
 var buffer []*models.Pageview
 var bufferSize = 250
 var timeout = 100 * time.Millisecond
 
-func getRequestIp(r *http.Request) string {
-	ipAddress := r.RemoteAddr
-
-	headerForwardedFor := r.Header.Get("X-Forwarded-For")
-	if headerForwardedFor != "" {
-		ipAddress = headerForwardedFor
-	}
-
-	return ipAddress
-}
-
 func persistPageviews() {
 	if len(buffer) > 0 {
 		err := datastore.SavePageviews(buffer)
+		if err != nil {
+			log.Errorf("error saving pageviews: %s", err)
+		}
+
+		// clear buffer regardless of error... this means data loss, but better than filling the buffer for now
 		buffer = buffer[:0]
-		checkError(err)
 	}
 }
 
@@ -55,12 +50,12 @@ func NewCollectHandler() http.Handler {
 	pageviews := make(chan *models.Pageview, 100)
 	go processBuffer(pageviews)
 
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	return HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
-		ua := user_agent.New(r.UserAgent())
 
 		// abort if this is a bot.
+		ua := user_agent.New(r.UserAgent())
 		if ua.Bot() {
-			return
+			return nil
 		}
 
 		q := r.URL.Query()
@@ -75,7 +70,9 @@ func NewCollectHandler() http.Handler {
 			}
 
 			err = datastore.SavePage(page)
-			checkError(err)
+			if err != nil {
+				return err
+			}
 		}
 
 		// find or insert visitor.
@@ -98,7 +95,9 @@ func NewCollectHandler() http.Handler {
 			visitor.BrowserName, visitor.BrowserVersion = ua.Browser()
 			visitor.BrowserName = parseMajorMinor(visitor.BrowserName)
 			err = datastore.SaveVisitor(visitor)
-			checkError(err)
+			if err != nil {
+				return err
+			}
 		}
 
 		pageview := &models.Pageview{
@@ -127,6 +126,7 @@ func NewCollectHandler() http.Handler {
 		// 1x1 px transparent GIF
 		b, _ := base64.StdEncoding.DecodeString("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7")
 		w.Write(b)
+		return nil
 	})
 }
 

pkg/api/http.go

@@ -0,0 +1,43 @@
+package api
+
+import (
+	"encoding/json"
+	log "github.com/sirupsen/logrus"
+	"net/http"
+)
+
+// Handler is our custom HTTP handler with error returns
+type Handler func(w http.ResponseWriter, r *http.Request) error
+
+func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if err := h(w, r); err != nil {
+		HandleError(w, r, err)
+	}
+}
+
+// HandlerFunc takes a custom Handler func and converts it to http.HandlerFunc
+func HandlerFunc(fn Handler) http.HandlerFunc {
+	return http.HandlerFunc(Handler(fn).ServeHTTP)
+}
+
+// HandleError handles errors
+func HandleError(w http.ResponseWriter, r *http.Request, err error) {
+	log.WithFields(log.Fields{
+		"request": r.Method + " " + r.RequestURI,
+		"error":   err,
+	}).Error("error handling request")
+
+	w.Header().Set("Content-Type", "application/json")
+	w.Write([]byte("false"))
+}
+
+type envelope struct {
+	Data  interface{}
+	Error interface{} `json:"omitempty"`
+}
+
+func respond(w http.ResponseWriter, d interface{}) error {
+	w.Header().Set("Content-Type", "application/json")
+	err := json.NewEncoder(w).Encode(d)
+	return err
+}

pkg/api/languages.go

@@ -7,8 +7,8 @@ import (
 )
 
 // URL: /api/languages
-var GetLanguagesHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetLanguagesHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 	results := count.Languages(before, after, getRequestedLimit(r))
-	respond(w, envelope{Data: results})
+	return respond(w, envelope{Data: results})
 })

pkg/api/pageviews.go

@@ -15,7 +15,7 @@ type pageviews struct {
 }
 
 // URL: /api/pageviews
-var GetPageviewsHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetPageviewsHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 
 	stmt, err := datastore.DB.Prepare(`
@@ -30,38 +30,46 @@ var GetPageviewsHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.R
 		GROUP BY p.path, p.hostname
 		ORDER BY count DESC
 		LIMIT ?`)
-
+	if err != nil {
-	checkError(err)
+		return err
+	}
 	defer stmt.Close()
 
 	rows, err := stmt.Query(before, after, defaultLimit)
-	checkError(err)
+	if err != nil {
+		return err
+	}
 	defer rows.Close()
 
 	results := make([]pageviews, 0)
 	for rows.Next() {
 		var p pageviews
 		err = rows.Scan(&p.Hostname, &p.Path, &p.Count, &p.CountUnique)
-		checkError(err)
+		if err != nil {
+			return err
+		}
+
 		results = append(results, p)
 	}
 
 	err = rows.Err()
-	checkError(err)
+	if err != nil {
+		return err
+	}
 
-	respond(w, envelope{Data: results})
+	return respond(w, envelope{Data: results})
 })
 
 // URL: /api/pageviews/count
-var GetPageviewsCountHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetPageviewsCountHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 	result := count.Pageviews(before, after)
-	respond(w, envelope{Data: result})
+	return respond(w, envelope{Data: result})
 })
 
 // URL: /api/pageviews/group/day
-var GetPageviewsPeriodCountHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetPageviewsPeriodCountHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 	results := count.PageviewsPerDay(before, after)
-	respond(w, envelope{Data: results})
+	return respond(w, envelope{Data: results})
 })

pkg/api/params.go

@@ -1,8 +1,6 @@
 package api
 
 import (
-	"encoding/json"
-	"log"
 	"net/http"
 	"strconv"
 	"strings"
@@ -12,25 +10,6 @@ import (
 const defaultPeriod = 7
 const defaultLimit = 10
 
-type envelope struct {
-	Data  interface{}
-	Error interface{}
-}
-
-func respond(w http.ResponseWriter, d interface{}) {
-	w.Header().Set("Content-Type", "application/json")
-	enc := json.NewEncoder(w)
-	err := enc.Encode(d)
-	checkError(err)
-}
-
-// log fatal errors
-func checkError(err error) {
-	if err != nil {
-		log.Fatal(err)
-	}
-}
-
 func getRequestedLimit(r *http.Request) int {
 	limit, err := strconv.Atoi(r.URL.Query().Get("limit"))
 	if err != nil || limit == 0 {
@@ -64,3 +43,14 @@ func parseMajorMinor(v string) string {
 	}
 	return v
 }
+
+func getRequestIp(r *http.Request) string {
+	ipAddress := r.RemoteAddr
+
+	headerForwardedFor := r.Header.Get("X-Forwarded-For")
+	if headerForwardedFor != "" {
+		ipAddress = headerForwardedFor
+	}
+
+	return ipAddress
+}

pkg/api/referrers.go

@@ -7,8 +7,8 @@ import (
 )
 
 // URL: /api/referrers
-var GetReferrersHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetReferrersHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 	results := count.Referrers(before, after, getRequestedLimit(r))
-	respond(w, envelope{Data: results})
+	return respond(w, envelope{Data: results})
 })

pkg/api/screens.go

@@ -7,8 +7,8 @@ import (
 )
 
 // URL: /api/screen-resolutions
-var GetScreenResolutionsHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetScreenResolutionsHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 	results := count.Screens(before, after, getRequestedLimit(r))
-	respond(w, envelope{Data: results})
+	return respond(w, envelope{Data: results})
 })

pkg/api/visitors.go

@@ -7,21 +7,21 @@ import (
 )
 
 // URL: /api/visitors/count
-var GetVisitorsCountHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetVisitorsCountHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 	result := count.Visitors(before, after)
-	respond(w, envelope{Data: result})
+	return respond(w, envelope{Data: result})
 })
 
 // URL: /api/visitors/count/realtime
-var GetVisitorsRealtimeCountHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetVisitorsRealtimeCountHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	result := count.RealtimeVisitors()
-	respond(w, envelope{Data: result})
+	return respond(w, envelope{Data: result})
 })
 
 // URL: /api/visitors/count/group/:period
-var GetVisitorsPeriodCountHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+var GetVisitorsPeriodCountHandler = HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
 	before, after := getRequestedPeriods(r)
 	results := count.VisitorsPerDay(before, after)
-	respond(w, envelope{Data: results})
+	return respond(w, envelope{Data: results})
 })