feat(kit/feature): add feature flag package (#17851)

* feat(kit/feature): add feature flag package

* refactor(kit/feature/_codegen): simplify with fmt.Errorf

* chore(kit/feature): tidy comments

.circleci/config.yml

@@ -275,6 +275,42 @@ jobs:
           destination: raw-test-output
       - store_test_results: # Upload test results for display in Test Summary: https://circleci.com/docs/2.0/collect-test-data/
           path: /tmp/test-results
+
+  lint-feature-flags:
+    docker:
+      - image: circleci/golang:1.13
+    environment:
+      GOCACHE: /tmp/go-cache
+      GOFLAGS: "-mod=readonly -p=2" # Go on Circle thinks 32 CPUs are available, but there aren't.
+    working_directory: /go/src/github.com/influxdata/influxdb
+    steps:
+      - checkout
+      # Populate GOCACHE.
+      - restore_cache:
+          name: Restoring GOCACHE
+          keys:
+            - influxdb-gocache-{{ .Branch }}-{{ .Revision }} # Matches when retrying a single run.
+            - influxdb-gocache-{{ .Branch }}- # Matches a new commit on an existing branch.
+            - influxdb-gocache- # Matches a new branch.
+      # Populate GOPATH/pkg.
+      - restore_cache:
+          name: Restoring GOPATH/pkg/mod
+          keys:
+            - influxdb-gomod-{{ checksum "go.sum" }} # Matches based on go.sum checksum.
+      - run: ./scripts/ci/lint/flags.bash
+      - skip_if_not_master
+      - save_cache:
+          name: Saving GOCACHE
+          key: influxdb-gocache-{{ .Branch }}-{{ .Revision }}
+          paths:
+            - /tmp/go-cache
+          when: always
+      - save_cache:
+          name: Saving GOPATH/pkg/mod
+          key: influxdb-gomod-{{ checksum "go.sum" }}
+          paths:
+            - /go/pkg/mod
+          when: always
   golint:
     docker:
       - image: circleci/golang:1.13

CHANGELOG.md

@@ -14,6 +14,8 @@
 
 ### Features
 
+1. [17851](https://github.com/influxdata/influxdb/pull/17851): Add feature flag package capability and flags endpoint
+
 ### Bug Fixes
 
 1. [17618](https://github.com/influxdata/influxdb/pull/17618): Add index for URM by user ID to improve lookup performance

Makefile

@@ -206,5 +206,9 @@ protoc:
 	unzip -o -d /go /tmp/protoc.zip
 	chmod +x /go/bin/protoc
 
+# generate feature flags
+flags:
+	$(GO_GENERATE) ./kit/feature
+
 # .PHONY targets represent actions that do not create an actual file.
-.PHONY: all $(SUBDIRS) run fmt checkfmt tidy checktidy checkgenerate test test-go test-js test-go-race bench clean node_modules vet nightly chronogiraffe dist ping protoc e2e run-e2e influxd libflux
+.PHONY: all $(SUBDIRS) run fmt checkfmt tidy checktidy checkgenerate test test-go test-js test-go-race bench clean node_modules vet nightly chronogiraffe dist ping protoc e2e run-e2e influxd libflux flags

cmd/influxd/launcher/launcher.go

@@ -27,6 +27,8 @@ import (
 	"github.com/influxdata/influxdb/v2/inmem"
 	"github.com/influxdata/influxdb/v2/internal/fs"
 	"github.com/influxdata/influxdb/v2/kit/cli"
+	"github.com/influxdata/influxdb/v2/kit/feature"
+	overrideflagger "github.com/influxdata/influxdb/v2/kit/feature/override"
 	"github.com/influxdata/influxdb/v2/kit/prom"
 	"github.com/influxdata/influxdb/v2/kit/signals"
 	"github.com/influxdata/influxdb/v2/kit/tracing"
@@ -303,8 +305,12 @@ func buildLauncherCommand(l *Launcher, cmd *cobra.Command) {
 			Default: 10,
 			Desc:    "the number of queries that are allowed to be awaiting execution before new queries are rejected",
 		},
+		{
+			DestP: &l.featureFlags,
+			Flag:  "feature-flags",
+			Desc:  "feature flag overrides",
+		},
 	}
-
 	cli.BindOptions(cmd, opts)
 	cmd.AddCommand(inspect.NewCommand())
 }
@@ -332,6 +338,8 @@ type Launcher struct {
 
 	enableNewMetaStore bool
 
+	featureFlags map[string]string
+
 	// Query options.
 	concurrencyQuota                int
 	initialMemoryBytesQuotaPerQuery int
@@ -843,6 +851,18 @@ func (m *Launcher) run(ctx context.Context) (err error) {
 		Addr: m.httpBindAddress,
 	}
 
+	flagger := feature.DefaultFlagger()
+	if len(m.featureFlags) > 0 {
+		f, err := overrideflagger.Make(m.featureFlags)
+		if err != nil {
+			m.log.Error("Failed to configure feature flag overrides",
+				zap.Error(err), zap.Any("overrides", m.featureFlags))
+			return err
+		}
+		m.log.Info("Running with feature flag overrides", zap.Any("config", m.featureFlags))
+		flagger = f
+	}
+
 	m.apibackend = &http.APIBackend{
 		AssetsPath:           m.assetsPath,
 		HTTPErrorHandler:     kithttp.ErrorHandler(0),
@@ -885,6 +905,7 @@ func (m *Launcher) run(ctx context.Context) (err error) {
 		OrgLookupService:                m.kvService,
 		WriteEventRecorder:              infprom.NewEventRecorder("write"),
 		QueryEventRecorder:              infprom.NewEventRecorder("query"),
+		Flagger:                         flagger,
 	}
 
 	m.reg.MustRegister(m.apibackend.PrometheusCollectors()...)

flags.yml

@@ -0,0 +1,28 @@
+# This file defines feature flags.
+#
+# It is used for code generation in the ./kit/feature package.
+# If you change this file, run `make flags` to regenerate.
+#
+# Format details:
+#
+# - name:         Human-readable name
+#   description:  Human-readable description
+#   key:          Programmatic name
+#   default:      Used when unable to reach server and to infer flag type
+#   contact:      Contact for information or issues regarding the flag
+#   lifetime:     Expected lifetime of the flag; temporary or permanent, default temporary
+#   expose:       Boolean indicating whether the flag should be exposed to callers; default false
+
+- name: Backend Example
+  description: A permanent backend example boolean flag
+  key: backendExample
+  default: false
+  contact: Gavin Cabbage
+  lifetime: permanent
+
+- name: Frontend Example
+  description: A temporary frontend example integer flag
+  key: frontendExample
+  default: 42
+  contact: Gavin Cabbage
+  expose: true

http/api_handler.go

@@ -8,6 +8,7 @@ import (
 	"github.com/influxdata/influxdb/v2/authorizer"
 	"github.com/influxdata/influxdb/v2/chronograf/server"
 	"github.com/influxdata/influxdb/v2/http/metric"
+	"github.com/influxdata/influxdb/v2/kit/feature"
 	"github.com/influxdata/influxdb/v2/kit/prom"
 	kithttp "github.com/influxdata/influxdb/v2/kit/transport/http"
 	"github.com/influxdata/influxdb/v2/query"
@@ -82,6 +83,7 @@ type APIBackend struct {
 	DocumentService                 influxdb.DocumentService
 	NotificationRuleStore           influxdb.NotificationRuleStore
 	NotificationEndpointService     influxdb.NotificationEndpointService
+	Flagger                         feature.Flagger
 }
 
 // PrometheusCollectors exposes the prometheus collectors associated with an APIBackend.
@@ -203,6 +205,7 @@ func NewAPIHandler(b *APIBackend, opts ...APIHandlerOptFn) *APIHandler {
 	userHandler := NewUserHandler(b.Logger, userBackend)
 	h.Mount(prefixMe, userHandler)
 	h.Mount(prefixUsers, userHandler)
+	h.Mount("/api/v2/flags", serveFlagsHandler(b.HTTPErrorHandler))
 
 	variableBackend := NewVariableBackend(b.Logger.With(zap.String("handler", "variable")), b)
 	variableBackend.VariableService = authorizer.NewVariableService(b.VariableService)
@@ -236,6 +239,7 @@ var apiLinks = map[string]interface{}{
 	"external": map[string]string{
 		"statusFeed": "https://www.influxdata.com/feed/json",
 	},
+	"flags":                 "/api/v2/flags",
 	"labels":                "/api/v2/labels",
 	"variables":             "/api/v2/variables",
 	"me":                    "/api/v2/me",
@@ -277,3 +281,16 @@ func serveLinksHandler(errorHandler influxdb.HTTPErrorHandler) http.Handler {
 	}
 	return http.HandlerFunc(fn)
 }
+
+func serveFlagsHandler(errorHandler influxdb.HTTPErrorHandler) http.Handler {
+	fn := func(w http.ResponseWriter, r *http.Request) {
+		var (
+			ctx   = r.Context()
+			flags = feature.ExposedFlagsFromContext(ctx)
+		)
+		if err := encodeResponse(ctx, w, http.StatusOK, flags); err != nil {
+			errorHandler.HandleHTTPError(ctx, err, w)
+		}
+	}
+	return http.HandlerFunc(fn)
+}

http/platform_handler.go

@@ -4,6 +4,7 @@ import (
 	"net/http"
 	"strings"
 
+	"github.com/influxdata/influxdb/v2/kit/feature"
 	kithttp "github.com/influxdata/influxdb/v2/kit/transport/http"
 )
 
@@ -17,7 +18,7 @@ type PlatformHandler struct {
 // NewPlatformHandler returns a platform handler that serves the API and associated assets.
 func NewPlatformHandler(b *APIBackend, opts ...APIHandlerOptFn) *PlatformHandler {
 	h := NewAuthenticationHandler(b.Logger, b.HTTPErrorHandler)
-	h.Handler = NewAPIHandler(b, opts...)
+	h.Handler = feature.NewHandler(b.Logger, b.Flagger, feature.Flags(), NewAPIHandler(b, opts...))
 	h.AuthorizationService = b.AuthorizationService
 	h.SessionService = b.SessionService
 	h.SessionRenewDisabled = b.SessionRenewDisabled

http/swagger.yml

@@ -4936,6 +4936,27 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/Error"
+  /flags:
+    get:
+      operationId: GetFlags
+      tags:
+        - Users
+      summary: Return the feature flags for the currently authenticated user
+      parameters:
+        - $ref: '#/components/parameters/TraceSpan'
+      responses:
+        '200':
+          description: Feature flags for the currently authenticated user
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Flags"
+        default:
+          description: Unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
   /me:
     get:
       operationId: GetMe
@@ -8138,6 +8159,9 @@ components:
           type: array
           items:
             $ref: "#/components/schemas/User"
+    Flags:
+      type: object
+      additionalProperties: true
     ResourceMember:
       allOf:
         - $ref: "#/components/schemas/User"
@@ -8223,6 +8247,9 @@ components:
         me:
           type: string
           format: uri
+        flags:
+          type: string
+          format: uri
         orgs:
           type: string
           format: uri

kit/cli/viper.go

@@ -150,6 +150,18 @@ func BindOptions(cmd *cobra.Command, opts []Opt) {
 			}
 			mustBindPFlag(o.Flag, flagset)
 			*destP = viper.GetStringSlice(envVar)
+		case *map[string]string:
+			var d map[string]string
+			if o.Default != nil {
+				d = o.Default.(map[string]string)
+			}
+			if hasShort {
+				flagset.StringToStringVarP(destP, o.Flag, string(o.Short), d, o.Desc)
+			} else {
+				flagset.StringToStringVar(destP, o.Flag, d, o.Desc)
+			}
+			mustBindPFlag(o.Flag, flagset)
+			*destP = viper.GetStringMapString(envVar)
 		case pflag.Value:
 			if hasShort {
 				flagset.VarP(destP, o.Flag, string(o.Short), o.Desc)