From c78fcd29ba5a46859becf6148401c8e5f1388210 Mon Sep 17 00:00:00 2001
From: Julien Pivotto <roidelapluie@inuits.eu>
Date: Tue, 30 Nov 2021 11:21:07 +0100
Subject: [PATCH] Adapt UI for Prometheus Agent (#9851)

* Adapt UI for Prometheus Agent

UI is not my strongest skill, but I'd like to have something minimal for
the initial release of the agent.

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

* Address review comments

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

* Add tests

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

* Add tests, serve only current mode paths

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

* Update js style, add agent test

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>
---
 web/ui/react-app/public/index.html         |  3 +-
 web/ui/react-app/src/App.test.tsx          |  4 +-
 web/ui/react-app/src/App.tsx               | 12 +++--
 web/ui/react-app/src/Navbar.tsx            | 55 +++++++++++++---------
 web/ui/react-app/src/index.tsx             |  4 +-
 web/ui/react-app/src/pages/agent/Agent.tsx | 16 +++++++
 web/ui/react-app/src/pages/index.ts        |  3 ++
 web/web.go                                 | 36 +++++++++++---
 web/web_test.go                            |  3 ++
 9 files changed, 102 insertions(+), 34 deletions(-)
 create mode 100644 web/ui/react-app/src/pages/agent/Agent.tsx

diff --git a/web/ui/react-app/public/index.html b/web/ui/react-app/public/index.html
index eac493853..a3f7b7a85 100755
--- a/web/ui/react-app/public/index.html
+++ b/web/ui/react-app/public/index.html
@@ -15,10 +15,11 @@
         It will render a "Consoles" link in the navbar when it is non-empty.
       - PROMETHEUS_AGENT_MODE is replaced by a boolean indicating if Prometheus is running in agent mode.
         It true, it will disable querying capacities in the UI and generally adapt the UI to the agent mode.
+        It has to be represented as a string, because booleans can be mangled to !1 in production builds.
     -->
     <script>
       const GLOBAL_CONSOLES_LINK='CONSOLES_LINK_PLACEHOLDER';
-      const GLOBAL_PROMETHEUS_AGENT_MODE=PROMETHEUS_AGENT_MODE_PLACEHOLDER;
+      const GLOBAL_AGENT_MODE='AGENT_MODE_PLACEHOLDER';
     </script>
 
     <!--
diff --git a/web/ui/react-app/src/App.test.tsx b/web/ui/react-app/src/App.test.tsx
index 9e7a6d744..af23fc2f5 100755
--- a/web/ui/react-app/src/App.test.tsx
+++ b/web/ui/react-app/src/App.test.tsx
@@ -5,6 +5,7 @@ import Navigation from './Navbar';
 import { Container } from 'reactstrap';
 import { Route } from 'react-router-dom';
 import {
+  AgentPage,
   AlertsPage,
   ConfigPage,
   FlagsPage,
@@ -24,6 +25,7 @@ describe('App', () => {
   });
   it('routes', () => {
     [
+      AgentPage,
       AlertsPage,
       ConfigPage,
       FlagsPage,
@@ -37,7 +39,7 @@ describe('App', () => {
       const c = app.find(component);
       expect(c).toHaveLength(1);
     });
-    expect(app.find(Route)).toHaveLength(9);
+    expect(app.find(Route)).toHaveLength(10);
     expect(app.find(Container)).toHaveLength(1);
   });
 });
diff --git a/web/ui/react-app/src/App.tsx b/web/ui/react-app/src/App.tsx
index 49f0c6439..8c96a3f73 100755
--- a/web/ui/react-app/src/App.tsx
+++ b/web/ui/react-app/src/App.tsx
@@ -4,6 +4,7 @@ import { Container } from 'reactstrap';
 
 import { BrowserRouter as Router, Redirect, Switch, Route } from 'react-router-dom';
 import {
+  AgentPage,
   AlertsPage,
   ConfigPage,
   FlagsPage,
@@ -22,14 +23,16 @@ import useMedia from './hooks/useMedia';
 
 interface AppProps {
   consolesLink: string | null;
+  agentMode: boolean;
 }
 
-const App: FC<AppProps> = ({ consolesLink }) => {
+const App: FC<AppProps> = ({ consolesLink, agentMode }) => {
   // This dynamically/generically determines the pathPrefix by stripping the first known
   // endpoint suffix from the window location path. It works out of the box for both direct
   // hosting and reverse proxy deployments with no additional configurations required.
   let basePath = window.location.pathname;
   const paths = [
+    '/agent',
     '/graph',
     '/alerts',
     '/status',
@@ -70,14 +73,17 @@ const App: FC<AppProps> = ({ consolesLink }) => {
       <Theme />
       <PathPrefixContext.Provider value={basePath}>
         <Router basename={basePath}>
-          <Navigation consolesLink={consolesLink} />
+          <Navigation consolesLink={consolesLink} agentMode={agentMode} />
           <Container fluid style={{ paddingTop: 70 }}>
             <Switch>
-              <Redirect exact from="/" to={`graph`} />
+              <Redirect exact from="/" to={agentMode ? '/agent' : '/graph'} />
               {/*
               NOTE: Any route added here needs to also be added to the list of
               React-handled router paths ("reactRouterPaths") in /web/web.go.
             */}
+              <Route path="/agent">
+                <AgentPage />
+              </Route>
               <Route path="/graph">
                 <PanelListPage />
               </Route>
diff --git a/web/ui/react-app/src/Navbar.tsx b/web/ui/react-app/src/Navbar.tsx
index 277cef46a..3963c2e31 100644
--- a/web/ui/react-app/src/Navbar.tsx
+++ b/web/ui/react-app/src/Navbar.tsx
@@ -17,17 +17,18 @@ import { ThemeToggle } from './Theme';
 
 interface NavbarProps {
   consolesLink: string | null;
+  agentMode: boolean;
 }
 
-const Navigation: FC<NavbarProps> = ({ consolesLink }) => {
+const Navigation: FC<NavbarProps> = ({ consolesLink, agentMode }) => {
   const [isOpen, setIsOpen] = useState(false);
   const toggle = () => setIsOpen(!isOpen);
   const pathPrefix = usePathPrefix();
   return (
     <Navbar className="mb-3" dark color="dark" expand="md" fixed="top">
       <NavbarToggler onClick={toggle} className="mr-2" />
-      <Link className="pt-0 navbar-brand" to="/graph">
-        Prometheus
+      <Link className="pt-0 navbar-brand" to={agentMode ? '/agent' : '/graph'}>
+        Prometheus{agentMode && ' Agent'}
       </Link>
       <Collapse isOpen={isOpen} navbar style={{ justifyContent: 'space-between' }}>
         <Nav className="ml-0" navbar>
@@ -36,16 +37,20 @@ const Navigation: FC<NavbarProps> = ({ consolesLink }) => {
               <NavLink href={consolesLink}>Consoles</NavLink>
             </NavItem>
           )}
-          <NavItem>
-            <NavLink tag={Link} to="/alerts">
-              Alerts
-            </NavLink>
-          </NavItem>
-          <NavItem>
-            <NavLink tag={Link} to="/graph">
-              Graph
-            </NavLink>
-          </NavItem>
+          {!agentMode && (
+            <>
+              <NavItem>
+                <NavLink tag={Link} to="/alerts">
+                  Alerts
+                </NavLink>
+              </NavItem>
+              <NavItem>
+                <NavLink tag={Link} to="/graph">
+                  Graph
+                </NavLink>
+              </NavItem>
+            </>
+          )}
           <UncontrolledDropdown nav inNavbar>
             <DropdownToggle nav caret>
               Status
@@ -54,18 +59,22 @@ const Navigation: FC<NavbarProps> = ({ consolesLink }) => {
               <DropdownItem tag={Link} to="/status">
                 Runtime & Build Information
               </DropdownItem>
-              <DropdownItem tag={Link} to="/tsdb-status">
-                TSDB Status
-              </DropdownItem>
+              {!agentMode && (
+                <DropdownItem tag={Link} to="/tsdb-status">
+                  TSDB Status
+                </DropdownItem>
+              )}
               <DropdownItem tag={Link} to="/flags">
                 Command-Line Flags
               </DropdownItem>
               <DropdownItem tag={Link} to="/config">
                 Configuration
               </DropdownItem>
-              <DropdownItem tag={Link} to="/rules">
-                Rules
-              </DropdownItem>
+              {!agentMode && (
+                <DropdownItem tag={Link} to="/rules">
+                  Rules
+                </DropdownItem>
+              )}
               <DropdownItem tag={Link} to="/targets">
                 Targets
               </DropdownItem>
@@ -77,9 +86,11 @@ const Navigation: FC<NavbarProps> = ({ consolesLink }) => {
           <NavItem>
             <NavLink href="https://prometheus.io/docs/prometheus/latest/getting_started/">Help</NavLink>
           </NavItem>
-          <NavItem>
-            <NavLink href={`${pathPrefix}/classic/graph${window.location.search}`}>Classic UI</NavLink>
-          </NavItem>
+          {!agentMode && (
+            <NavItem>
+              <NavLink href={`${pathPrefix}/classic/graph${window.location.search}`}>Classic UI</NavLink>
+            </NavItem>
+          )}
         </Nav>
       </Collapse>
       <ThemeToggle />
diff --git a/web/ui/react-app/src/index.tsx b/web/ui/react-app/src/index.tsx
index a2db57b66..a798d1b62 100755
--- a/web/ui/react-app/src/index.tsx
+++ b/web/ui/react-app/src/index.tsx
@@ -10,8 +10,10 @@ import { isPresent } from './utils';
 
 // Declared/defined in public/index.html, value replaced by Prometheus when serving bundle.
 declare const GLOBAL_CONSOLES_LINK: string;
+declare const GLOBAL_AGENT_MODE: string;
 
 let consolesLink: string | null = GLOBAL_CONSOLES_LINK;
+const agentMode: string | null = GLOBAL_AGENT_MODE;
 
 if (
   GLOBAL_CONSOLES_LINK === 'CONSOLES_LINK_PLACEHOLDER' ||
@@ -21,4 +23,4 @@ if (
   consolesLink = null;
 }
 
-ReactDOM.render(<App consolesLink={consolesLink} />, document.getElementById('root'));
+ReactDOM.render(<App consolesLink={consolesLink} agentMode={agentMode === 'true'} />, document.getElementById('root'));
diff --git a/web/ui/react-app/src/pages/agent/Agent.tsx b/web/ui/react-app/src/pages/agent/Agent.tsx
new file mode 100644
index 000000000..2590a0a35
--- /dev/null
+++ b/web/ui/react-app/src/pages/agent/Agent.tsx
@@ -0,0 +1,16 @@
+import React, { FC } from 'react';
+
+const Agent: FC = () => {
+  return (
+    <>
+      <h2>Prometheus Agent</h2>
+      <p>
+        This Prometheus instance is running in <strong>agent mode</strong>. In this mode, Prometheus is only used to scrape
+        discovered targets and forward them to remote write endpoints.
+      </p>
+      <p>Some features are not available in this mode, such as querying and alerting.</p>
+    </>
+  );
+};
+
+export default Agent;
diff --git a/web/ui/react-app/src/pages/index.ts b/web/ui/react-app/src/pages/index.ts
index c51466337..fbe727833 100644
--- a/web/ui/react-app/src/pages/index.ts
+++ b/web/ui/react-app/src/pages/index.ts
@@ -1,3 +1,4 @@
+import Agent from './agent/Agent';
 import Alerts from './alerts/Alerts';
 import Config from './config/Config';
 import Flags from './flags/Flags';
@@ -9,6 +10,7 @@ import PanelList from './graph/PanelList';
 import TSDBStatus from './tsdbStatus/TSDBStatus';
 import { withStartingIndicator } from '../components/withStartingIndicator';
 
+const AgentPage = withStartingIndicator(Agent);
 const AlertsPage = withStartingIndicator(Alerts);
 const ConfigPage = withStartingIndicator(Config);
 const FlagsPage = withStartingIndicator(Flags);
@@ -21,6 +23,7 @@ const PanelListPage = withStartingIndicator(PanelList);
 
 // prettier-ignore
 export {
+  AgentPage,
   AlertsPage,
   ConfigPage,
   FlagsPage,
diff --git a/web/web.go b/web/web.go
index 01014f426..5aba8896d 100644
--- a/web/web.go
+++ b/web/web.go
@@ -71,18 +71,27 @@ import (
 
 // Paths that are handled by the React / Reach router that should all be served the main React app's index.html.
 var reactRouterPaths = []string{
-	"/alerts",
 	"/config",
 	"/flags",
-	"/graph",
-	"/rules",
 	"/service-discovery",
 	"/status",
 	"/targets",
-	"/tsdb-status",
 	"/starting",
 }
 
+// Paths that are handled by the React router when the Agent mode is set.
+var reactRouterAgentPaths = []string{
+	"/agent",
+}
+
+// Paths that are handled by the React router when the Agent mode is not set.
+var reactRouterServerPaths = []string{
+	"/alerts",
+	"/graph",
+	"/rules",
+	"/tsdb-status",
+}
+
 // withStackTrace logs the stack trace in case the request panics. The function
 // will re-raise the error which will then be handled by the net/http package.
 // It is needed because the go-kit log package doesn't manage properly the
@@ -346,10 +355,15 @@ func New(logger log.Logger, o *Options) *Handler {
 		router = router.WithPrefix(o.RoutePrefix)
 	}
 
+	homePage := "/graph"
+	if o.IsAgent {
+		homePage = "/agent"
+	}
+
 	readyf := h.testReady
 
 	router.Get("/", func(w http.ResponseWriter, r *http.Request) {
-		http.Redirect(w, r, path.Join(o.ExternalURL.Path, "/graph"), http.StatusFound)
+		http.Redirect(w, r, path.Join(o.ExternalURL.Path, homePage), http.StatusFound)
 	})
 	router.Get("/classic/", func(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, path.Join(o.ExternalURL.Path, "/classic/graph"), http.StatusFound)
@@ -409,7 +423,7 @@ func New(logger log.Logger, o *Options) *Handler {
 		}
 		replacedIdx := bytes.ReplaceAll(idx, []byte("CONSOLES_LINK_PLACEHOLDER"), []byte(h.consolesPath()))
 		replacedIdx = bytes.ReplaceAll(replacedIdx, []byte("TITLE_PLACEHOLDER"), []byte(h.options.PageTitle))
-		replacedIdx = bytes.ReplaceAll(replacedIdx, []byte("PROMETHEUS_AGENT_MODE_PLACEHOLDER"), []byte(strconv.FormatBool(h.options.IsAgent)))
+		replacedIdx = bytes.ReplaceAll(replacedIdx, []byte("AGENT_MODE_PLACEHOLDER"), []byte(strconv.FormatBool(h.options.IsAgent)))
 		w.Write(replacedIdx)
 	}
 
@@ -418,6 +432,16 @@ func New(logger log.Logger, o *Options) *Handler {
 		router.Get(p, serveReactApp)
 	}
 
+	if h.options.IsAgent {
+		for _, p := range reactRouterAgentPaths {
+			router.Get(p, serveReactApp)
+		}
+	} else {
+		for _, p := range reactRouterServerPaths {
+			router.Get(p, serveReactApp)
+		}
+	}
+
 	// The favicon and manifest are bundled as part of the React app, but we want to serve
 	// them on the root.
 	for _, p := range []string{"/favicon.ico", "/manifest.json"} {
diff --git a/web/web_test.go b/web/web_test.go
index 874972508..636cc3dab 100644
--- a/web/web_test.go
+++ b/web/web_test.go
@@ -585,6 +585,8 @@ func TestAgentAPIEndPoints(t *testing.T) {
 		"/query",
 		"/query_range",
 		"/query_exemplars",
+		"/graph",
+		"/rules",
 	} {
 		w := httptest.NewRecorder()
 		req, err := http.NewRequest("GET", baseURL+u, nil)
@@ -595,6 +597,7 @@ func TestAgentAPIEndPoints(t *testing.T) {
 
 	// Test for available endpoints in the Agent mode.
 	for _, u := range []string{
+		"/agent",
 		"/targets",
 		"/status",
 	} {