[FEAT] Serve Assets from Docker FileSystem

[bbengfort]

Scope of changes

Serves static assets from the filesystem rather than building them into the binary.

Estimated PR Size:

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• Small
• Medium
• Large
• Huge

Acceptance criteria

This PR will be merged without review.

Author checklist

• I have manually tested the change and/or added automation in the form of unit tests or integration tests
• I have updated the dependencies list
• I have added new test fixtures as needed to support added tests
• I have added or updated the documentation
• I have run go generate to update generated code

---

Note

Medium Risk
Changes how static assets are packaged and served (Docker image + runtime routing/config), so misconfiguration or missing files could break UI assets in production. Validation and tests reduce risk, but it affects runtime behavior and deployment defaults.

Overview
Updates the service to serve static assets from the container filesystem instead of embedding them in the Go binary.

The Docker image now copies pkg/web/static into /var/www/html, exposes port 8000, and sets new env defaults (UPTIME_STATIC_SERVE, UPTIME_STATIC_ROOT, UPTIME_STATIC_URL). Runtime routing switches /static (plus /favicon.ico and /robots.txt) to be served via os.DirFS when enabled, and configuration adds/validates a new Static section (including URL vs filesystem constraints) with accompanying unit tests.

^{Written by Cursor Bugbot for commit af34fe9. Configure here.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Template helper uses hardcoded path ignoring configurable URL
  • Updated the template static helper to build URLs from the configured Static.URL (with /static fallback) and wired that value through renderer initialization with tests for custom and CDN URLs.

Or push these changes by commenting:

@cursor push 33bfa46b60

Preview (33bfa46b60)

diff --git a/pkg/server/routes.go b/pkg/server/routes.go
--- a/pkg/server/routes.go
+++ b/pkg/server/routes.go
@@ -14,7 +14,7 @@
 
 func (s *Server) setupRoutes() (err error) {
 	// Setup HTML template renderer.
-	if s.router.HTMLRender, err = web.NewRender(web.Templates()); err != nil {
+	if s.router.HTMLRender, err = web.NewRender(web.Templates(), s.conf.Static.URL); err != nil {
 		return err
 	}
 

diff --git a/pkg/web/web.go b/pkg/web/web.go
--- a/pkg/web/web.go
+++ b/pkg/web/web.go
@@ -7,6 +7,7 @@
 	"html/template"
 	"io/fs"
 	"log/slog"
+	"net/url"
 	"path/filepath"
 	"strings"
 	"time"
@@ -43,9 +44,10 @@
 }
 
 // Creates a new template renderer from the default templates.
-func NewRender(fsys fs.FS) (render *Render, err error) {
+func NewRender(fsys fs.FS, staticURL string) (render *Render, err error) {
 	render = &Render{
 		templates: make(map[string]*template.Template),
+		staticURL: staticURL,
 	}
 
 	// Add the pages patterns
@@ -77,6 +79,7 @@
 type Render struct {
 	templates map[string]*template.Template
 	funcs     template.FuncMap
+	staticURL string
 }
 
 var _ render.HTMLRender = (*Render)(nil)
@@ -119,7 +122,7 @@
 func (r *Render) FuncMap() template.FuncMap {
 	if r.funcs == nil {
 		r.funcs = template.FuncMap{
-			"static":      static,
+			"static":      r.static,
 			"titlecase":   titlecase,
 			"lowercase":   lowercase,
 			"uppercase":   uppercase,
@@ -150,10 +153,21 @@
 	return t.Format("January 2, 2006 3:04 PM")
 }
 
-func static(path string) string {
-	return filepath.Join("/static", path)
+func (r *Render) static(path string) string {
+	return staticURL(r.staticURL, path)
 }
 
+func staticURL(base, path string) string {
+	if base == "" {
+		base = "/static"
+	}
+
+	if joined, err := url.JoinPath(base, path); err == nil {
+		return joined
+	}
+	return strings.TrimSuffix(base, "/") + "/" + strings.TrimPrefix(path, "/")
+}
+
 func currentYear() int {
 	return time.Now().Year()
 }

diff --git a/pkg/web/web_test.go b/pkg/web/web_test.go
--- a/pkg/web/web_test.go
+++ b/pkg/web/web_test.go
@@ -9,7 +9,7 @@
 )
 
 func TestRender(t *testing.T) {
-	renderer, err := web.NewRender(web.Templates())
+	renderer, err := web.NewRender(web.Templates(), "/static")
 	require.NoError(t, err)
 	require.NotNil(t, renderer)
 }
@@ -104,4 +104,23 @@
 			require.Equal(t, testCase.expected, f(testCase.input))
 		}
 	})
+
+	t.Run("static configurable base url", func(t *testing.T) {
+		renderer, err := web.NewRender(web.Templates(), "/assets")
+		require.NoError(t, err)
+		funcMap := renderer.FuncMap()
+
+		f := funcMap["static"].(func(string) string)
+		require.Equal(t, "/assets/favicon.ico", f("/favicon.ico"))
+		require.Equal(t, "/assets/css/style.css", f("css/style.css"))
+	})
+
+	t.Run("static configurable remote url", func(t *testing.T) {
+		renderer, err := web.NewRender(web.Templates(), "https://cdn.example.com/uptime")
+		require.NoError(t, err)
+		funcMap := renderer.FuncMap()
+
+		f := funcMap["static"].(func(string) string)
+		require.Equal(t, "https://cdn.example.com/uptime/img/logo.png", f("img/logo.png"))
+	})
 }

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