feat: Add support for gzipped event payloads (#213)

docs/service_spec.md

@@ -72,6 +72,10 @@ This means that the SDK has the ability to construct and compare two contexts fo
 
 This means that the SDK supports caching of the e-tag header between client restarts. Typical SDKs track the polling e-tag header and send it between subsequent requests. SDKs supporting this capability are able to persist that e-tag header for use even between complete client restarts.
 
+#### Capability `"event-gzip"`
+
+This means that the SDK supports gzip compression of event payloads.
+
 #### Capability `"event-sampling"`
 
 This means that the SDK supports event sampling; the SDK can limit the number of certain events based on payloads received from upstream services.

mockld/events_service.go

@@ -1,9 +1,11 @@
 package mockld
 
 import (
+	"compress/gzip"
 	"encoding/json"
 	"io/ioutil"
 	"net/http"
+	"strings"
 	"sync"
 	"time"
 
@@ -32,7 +34,7 @@ type EventsService struct {
 	lock                   sync.Mutex
 }
 
-func NewEventsService(sdkKind SDKKind, logger framework.Logger) *EventsService {
+func NewEventsService(sdkKind SDKKind, logger framework.Logger, requireGzip bool) *EventsService {
 	s := &EventsService{
 		AnalyticsEventPayloads: make(chan Events, eventsChannelBufferSize),
 		sdkKind:                sdkKind,
@@ -42,6 +44,10 @@ func NewEventsService(sdkKind SDKKind, logger framework.Logger) *EventsService {
 	}
 
 	router := mux.NewRouter()
+	if requireGzip {
+		router.Use(gzipMiddleware)
+	}
+
 	switch sdkKind {
 	case ServerSideSDK, PHPSDK:
 		router.HandleFunc("/bulk", s.postEvents).Methods("POST")
@@ -62,6 +68,22 @@ func NewEventsService(sdkKind SDKKind, logger framework.Logger) *EventsService {
 	return s
 }
 
+func gzipMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if strings.Contains(r.Header.Get("Content-Encoding"), "gzip") {
+			gr, err := gzip.NewReader(r.Body)
+			if err != nil {
+				http.Error(w, "Failed to read gzipped request body", http.StatusBadRequest)
+				return
+			}
+			r.Body = gr
+			next.ServeHTTP(w, r)
+		} else {
+			http.Error(w, "Failed to provide a gzipped payload", http.StatusBadRequest)
+		}
+	})
+}
+
 func (s *EventsService) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	s.logger.Printf("Received %s %s", r.Method, r.URL)
 	s.handler.ServeHTTP(w, r)

sdktests/common_tests_events_request.go

@@ -37,6 +37,10 @@ func (c CommonEventTests) RequestMethodAndHeaders(t *ldtest.T, credential string
 					headersMatcher,
 					c.authorizationHeaderMatcher(credential),
 				))
+
+				if t.Capabilities().Has(servicedef.CapabilityEventGzip) {
+					m.In(t).For("request headers").Assert(request.Headers, Header("Content-Encoding").Should(m.StringContains("gzip")))
+				}
 			})
 		}
 	})

sdktests/testapi_sdk_events.go

@@ -42,7 +42,10 @@ type SDKEventSink struct {
 // sink will be attached to this test scope, and also to any of its subtests that are active when the
 // output is generated.
 func NewSDKEventSink(t *ldtest.T) *SDKEventSink {
-	eventsService := mockld.NewEventsService(requireContext(t).sdkKind, t.DebugLogger())
+	eventsService := mockld.NewEventsService(
+		requireContext(t).sdkKind,
+		t.DebugLogger(),
+		t.Capabilities().Has(servicedef.CapabilityEventGzip))
 	eventsEndpoint := requireContext(t).harness.NewMockEndpoint(eventsService, t.DebugLogger(),
 		harness.MockEndpointDescription("events service"))
 

servicedef/service_params.go

@@ -30,6 +30,7 @@ const (
 	CapabilityAutoEnvAttributes  = "auto-env-attributes"
 	CapabilityMigrations         = "migrations"
 	CapabilityEventSampling      = "event-sampling"
+	CapabilityEventGzip          = "event-gzip"
 	CapabilityETagCaching        = "etag-caching"
 	CapabilityInlineContext      = "inline-context"
 	CapabilityAnonymousRedaction = "anonymous-redaction"