perf: enable backend and render optimizations by default

README.md

@@ -32,8 +32,8 @@ Remove `.build/zlib-ng` (or run `make clean`) to rebuild the dependency.
 
 `make build TAGS='-tags cairo,nativegzip'` retains system-zlib decoding.
 `make nocairo` retains the portable Go decoder without either native dependency.
-The existing `CARBONAPI_NATIVE_GZIP` and `CARBONAPI_STREAM_RENDER` startup flags
-still control use of native backend decoding.
+Backend streaming and native gzip decoding are enabled by default. Builds without
+native gzip support use the portable Go decoder automatically.
 
 To build the binaries with debug symbols, run:
 
@@ -61,6 +61,26 @@ interested in those.
 
 ## Run
 
+The following performance paths are enabled by default. No environment overrides
+are needed to enable them. Set an individual variable to `0` before starting the
+process to use its previous path; unset, empty and `1` all leave it enabled.
+
+| Environment variable | Default path | Path with `0` |
+| --- | --- | --- |
+| `CARBONAPI_SYNC_BACKEND_HTTP` | Synchronous backend HTTP transport | Go HTTP transport |
+| `CARBONAPI_STREAM_RENDER` | Stream backend render responses | Buffer responses before decoding |
+| `CARBONAPI_NATIVE_GZIP` | Native backend gzip decoder, when built in | Go gzip decoder |
+| `CARBONAPI_PACK_BACKEND_POINTS` | Packed backend points for replica merging | Separate values and absence arrays |
+| `CARBONAPI_STABLE_RENDER_BATCH` | Stable groups when render batching is configured | Previous render batching |
+
+These switches retain their existing scope: native gzip requires a native-enabled
+build, packed points require streaming, and stable batching follows the configured
+globbing mode and batch size. Changing a switch requires a process restart.
+
+When removing existing `=1` overrides from a service manager, first deploy a binary
+with these defaults. Restore the overrides before rolling back to an older binary
+if the optimized paths should remain enabled.
+
 Run the full stack `carbonapi` -> `zipper` -> `go-carbon` with:
 
 ```

pkg/app/carbonapi/app.go

@@ -79,7 +79,7 @@ func New(config cfg.API, lg *zap.Logger, buildVersion string) (*App, error) {
 	ms := newPrometheusMetrics(config)
 	app := &App{
 		config:            config,
-		stableRenderBatch: os.Getenv("CARBONAPI_STABLE_RENDER_BATCH") == "1",
+		stableRenderBatch: os.Getenv("CARBONAPI_STABLE_RENDER_BATCH") != "0",
 		queryCache:        cache.NullCache{},
 		findCache:         cache.NullCache{},
 		defaultTimeZone:   time.Local,
@@ -333,7 +333,7 @@ func InitBackends(config cfg.Zipper, zms *ZipperPrometheusMetrics, ms *Prometheu
 			KeepAlive: config.KeepAliveInterval,
 		}).DialContext,
 	}
-	if os.Getenv("CARBONAPI_SYNC_BACKEND_HTTP") == "1" {
+	if os.Getenv("CARBONAPI_SYNC_BACKEND_HTTP") != "0" {
 		client.Transport = bnet.NewSyncTransport(client.Transport.(*http.Transport))
 	}
 

pkg/backend/net/net.go

@@ -128,9 +128,9 @@ func New(cfg Config) (*NetBackend, error) {
 		b.client = http.DefaultClient
 	}
 	b.requestGzip = transportCompresses(b.client)
-	b.streamRender = os.Getenv("CARBONAPI_STREAM_RENDER") == "1"
-	b.nativeGzip = os.Getenv("CARBONAPI_NATIVE_GZIP") == "1"
-	b.packRender = os.Getenv("CARBONAPI_PACK_BACKEND_POINTS") == "1"
+	b.streamRender = os.Getenv("CARBONAPI_STREAM_RENDER") != "0"
+	b.nativeGzip = os.Getenv("CARBONAPI_NATIVE_GZIP") != "0"
+	b.packRender = os.Getenv("CARBONAPI_PACK_BACKEND_POINTS") != "0"
 
 	b.responsesCount = cfg.Responses
 

pkg/backend/net/net_test.go

@@ -7,11 +7,42 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"os"
 	"strings"
 	"testing"
 	"time"
 )
 
+func TestPerformanceDefaultsAndIndependentOptOuts(t *testing.T) {
+	flags := []string{"CARBONAPI_STREAM_RENDER", "CARBONAPI_NATIVE_GZIP", "CARBONAPI_PACK_BACKEND_POINTS"}
+	for _, flag := range flags {
+		t.Setenv(flag, "")
+		if err := os.Unsetenv(flag); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, disabled := range append([]string{""}, flags...) {
+		t.Run("disabled="+disabled, func(t *testing.T) {
+			if disabled != "" {
+				t.Setenv(disabled, "0")
+			}
+			b, err := New(Config{Address: "localhost:8080"})
+			if err != nil {
+				t.Fatal(err)
+			}
+			for flag, enabled := range map[string]bool{
+				flags[0]: b.streamRender,
+				flags[1]: b.nativeGzip,
+				flags[2]: b.packRender,
+			} {
+				if enabled != (flag != disabled) {
+					t.Errorf("%s enabled=%v with %s disabled", flag, enabled, disabled)
+				}
+			}
+		})
+	}
+}
+
 func TestAddress(t *testing.T) {
 	b, err := New(Config{
 		Address: "localhost:8080",

pkg/backend/net/stream_render_test.go

@@ -169,11 +169,21 @@ func TestStreamingRenderMatchesBuffered(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
+		base.streamRender = false // Keep the buffered decoder as the reference.
 		request := types.NewRenderRequest([]string{"fixture.*"}, 0, 1)
 		want, err := base.Render(context.Background(), request)
 		if err != nil {
 			t.Fatal(err)
 		}
+		defaults, err := New(Config{Address: srv.URL})
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err := defaults.Render(context.Background(), request)
+		if err != nil {
+			t.Fatal(err)
+		}
+		equalStreamResults(t, got, want)
 		for _, native := range []bool{false, true} {
 			be, err := New(Config{Address: srv.URL})
 			if err != nil {