Simplify Bundling of UI assets (#5917)

## Which problem is this PR solving?
- Closes #5913

## Description of the changes
- Created one file `assets.go` that holds both the `placeholder` and
`actual` assets.
- Added a helper `GetStaticFiles` to get the assets based on whether the
actual filesystem has an `index.html.gz`. If it does, we return the
assets. Otherwise, we return the placeholder `index.html` file.

## How was this change tested?
Added unit tests and performed the following manual tests
### Test 1

Makefile Target
```Makefile
.PHONY: run-all-in-one
run-all-in-one:
	go run ./cmd/all-in-one --log-level debug
```
Clearing out the `actual` directory and ran `make run-all-in-one`. Going
to `http://localhost:16686/` renders the placeholder HTML page.

### Test 2

Makefile Target
```Makefile
.PHONY: run-all-in-one
run-all-in-one: build-ui
	go run ./cmd/all-in-one --log-level debug
```
Ran `make run-all-in-one`. Going to `http://localhost:16686/` renders
the Jaeger UI.

## Checklist
- [x] I have read
https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [x] I have added unit tests for the new functionality
- [x] I have run lint and test steps successfully
  - for `jaeger`: `make lint test`
  - for `jaeger-ui`: `yarn lint` and `yarn test`

---------

Signed-off-by: Mahad Zaryab <[email protected]>

Author: mahadzaryab1

CONTRIBUTING.md

@@ -76,12 +76,6 @@ the source code for the UI assets (requires Node.js 6+).
 The assets must be compiled first with `make build-ui`, which runs Node.js build and then
 packages the assets into a Go file that is `.gitignore`-ed.
 
-The packaged assets can be enabled by providing a build tag `ui`, for example:
-
-```
-$ go run -tags ui ./cmd/all-in-one/main.go
-```
-
 `make run-all-in-one` essentially runs Jaeger all-in-one by combining both of the above
 steps into a single `make` command.
 

Makefile

@@ -186,7 +186,7 @@ lint-go: $(LINT)
 
 .PHONY: run-all-in-one
 run-all-in-one: build-ui
-	go run -tags ui ./cmd/all-in-one --log-level debug
+	go run ./cmd/all-in-one --log-level debug
 
 .PHONY: changelog
 changelog:

Makefile.BuildBinaries.mk

@@ -74,13 +74,11 @@ _build-a-binary-%:
 
 .PHONY: build-jaeger
 build-jaeger: BIN_NAME = jaeger
-build-jaeger: GO_TAGS = -tags ui
 build-jaeger: BUILD_INFO = $(BUILD_INFO_V2)
 build-jaeger: build-ui _build-a-binary-jaeger$(SUFFIX)-$(GOOS)-$(GOARCH)
 
 .PHONY: build-all-in-one
 build-all-in-one: BIN_NAME = all-in-one
-build-all-in-one: GO_TAGS = -tags ui
 build-all-in-one: build-ui _build-a-binary-all-in-one$(SUFFIX)-$(GOOS)-$(GOARCH)
 
 .PHONY: build-agent
@@ -89,7 +87,6 @@ build-agent: _build-a-binary-agent$(SUFFIX)-$(GOOS)-$(GOARCH)
 
 .PHONY: build-query
 build-query: BIN_NAME = query
-build-query: GO_TAGS = -tags ui
 build-query: build-ui _build-a-binary-query$(SUFFIX)-$(GOOS)-$(GOARCH)
 
 .PHONY: build-collector

cmd/query/app/static_handler.go

@@ -76,15 +76,11 @@ type loadedConfig struct {
 
 // NewStaticAssetsHandler returns a StaticAssetsHandler
 func NewStaticAssetsHandler(staticAssetsRoot string, options StaticAssetsHandlerOptions) (*StaticAssetsHandler, error) {
-	assetsFS := ui.StaticFiles
+	assetsFS := ui.GetStaticFiles(options.Logger)
 	if staticAssetsRoot != "" {
 		assetsFS = http.Dir(staticAssetsRoot)
 	}
 
-	if options.Logger == nil {
-		options.Logger = zap.NewNop()
-	}
-
 	h := &StaticAssetsHandler{
 		options:  options,
 		assetsFS: assetsFS,

cmd/query/app/static_handler_test.go

@@ -29,7 +29,9 @@ import (
 //go:generate mockery -all -dir ../../../pkg/fswatcher
 
 func TestNotExistingUiConfig(t *testing.T) {
-	handler, err := NewStaticAssetsHandler("/foo/bar", StaticAssetsHandlerOptions{})
+	handler, err := NewStaticAssetsHandler("/foo/bar", StaticAssetsHandlerOptions{
+		Logger: zap.NewNop(),
+	})
 	require.Error(t, err)
 	assert.Contains(t, err.Error(), "no such file or directory")
 	assert.Nil(t, handler)
@@ -155,11 +157,18 @@ func TestRegisterStaticHandler(t *testing.T) {
 }
 
 func TestNewStaticAssetsHandlerErrors(t *testing.T) {
-	_, err := NewStaticAssetsHandler("fixture", StaticAssetsHandlerOptions{UIConfigPath: "fixture/invalid-config"})
+	_, err := NewStaticAssetsHandler("fixture", StaticAssetsHandlerOptions{
+		UIConfigPath: "fixture/invalid-config",
+		Logger:       zap.NewNop(),
+	})
 	require.Error(t, err)
 
 	for _, base := range []string{"x", "x/", "/x/"} {
-		_, err := NewStaticAssetsHandler("fixture", StaticAssetsHandlerOptions{UIConfigPath: "fixture/ui-config.json", BasePath: base})
+		_, err := NewStaticAssetsHandler("fixture", StaticAssetsHandlerOptions{
+			UIConfigPath: "fixture/ui-config.json",
+			BasePath:     base,
+			Logger:       zap.NewNop(),
+		})
 		require.Errorf(t, err, "basePath=%s", base)
 		assert.Contains(t, err.Error(), "invalid base path")
 	}

cmd/query/app/ui/actual.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package ui
+
+import (
+	"embed"
+	"net/http"
+
+	"go.uber.org/zap"
+
+	"github.com/jaegertracing/jaeger/pkg/gzipfs"
+	"github.com/jaegertracing/jaeger/pkg/httpfs"
+)
+
+//go:embed actual/*
+var actualAssetsFS embed.FS
+
+//go:embed placeholder/index.html
+var placeholderAssetsFS embed.FS
+
+// GetStaticFiles gets the static assets that the Jaeger UI will serve. If the actual
+// assets are available, then this function will return them. Otherwise, a
+// non-functional index.html is returned to be used as a placeholder.
+func GetStaticFiles(logger *zap.Logger) http.FileSystem {
+	if _, err := actualAssetsFS.ReadFile("actual/index.html.gz"); err != nil {
+		logger.Warn("ui assets not embedded in the binary, using a placeholder", zap.Error(err))
+		return httpfs.PrefixedFS("placeholder", http.FS(placeholderAssetsFS))
+	}
+
+	return httpfs.PrefixedFS("actual", http.FS(gzipfs.New(actualAssetsFS)))
+}

cmd/query/app/ui/assets.go

@@ -0,0 +1,49 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package ui
+
+import (
+	"embed"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/jaegertracing/jaeger/cmd/query/app/ui/testdata"
+	"github.com/jaegertracing/jaeger/pkg/testutils"
+)
+
+func TestGetStaticFiles_ReturnsPlaceholderWhenActualNotPresent(t *testing.T) {
+	// swap out the assets FS for an empty one and then replace it back when the
+	// test completes
+	currentActualAssets := actualAssetsFS
+	actualAssetsFS = embed.FS{}
+	t.Cleanup(func() { actualAssetsFS = currentActualAssets })
+
+	logger, logBuf := testutils.NewLogger()
+	fs := GetStaticFiles(logger)
+	file, err := fs.Open("/index.html")
+	require.NoError(t, err)
+	bytes, err := io.ReadAll(file)
+	require.NoError(t, err)
+	require.Contains(t, string(bytes), "This is a placeholder for the Jaeger UI home page")
+	require.Contains(t, logBuf.String(), "ui assets not embedded in the binary, using a placeholder")
+}
+
+func TestGetStaticFiles_ReturnsActualWhenPresent(t *testing.T) {
+	// swap out the assets FS for a dummy one and then replace it back when the
+	// test completes
+	currentActualAssets := actualAssetsFS
+	actualAssetsFS = testdata.TestFS
+	t.Cleanup(func() { actualAssetsFS = currentActualAssets })
+
+	logger, logBuf := testutils.NewLogger()
+	fs := GetStaticFiles(logger)
+	file, err := fs.Open("/index.html")
+	require.NoError(t, err)
+	bytes, err := io.ReadAll(file)
+	require.NoError(t, err)
+	require.NotContains(t, string(bytes), "This is a placeholder for the Jaeger UI home page")
+	require.NotContains(t, logBuf.String(), "ui assets not embedded in the binary, using a placeholder")
+}

cmd/query/app/ui/assets_test.go

@@ -2,7 +2,6 @@
 // SPDX-License-Identifier: Apache-2.0
 
 // Package ui bundles UI assets packaged with stdlib/embed.
-// By default it imports the placeholder, non-functional index.html.
-// When building with "-tags ui", it imports the real UI assets
-// generated in build-ui Makefile target.
+// If the real UI assets are available, they are embedded and
+// used at runtime. Otherwise, the non-functional index.html is used.
 package ui