Add fetch flags

README.md

@@ -235,6 +235,14 @@ for the content fetched by the `fetchContent` javascript function and inserted i
 
 ![cmd line](/images/cmd_line.png)
 
+## Flags
+Operator can look at the flags that are set in cli context by the user to launch Erigon node. The corresponding code in Erigon is in the file `diagnostics/flags.go`. This is particularly useful when user launches Erigon using a config file with `--config` and [Command line arguments](#command-line-arguments) cannot fully capture the true state of the 'launch setting'. The returned flags are the result after parsing command line argument and config file by Erigon.
+
+The code on the side of the diagnostics system is spread across files `cmd/ui_handler.go` (invocation of `processFlags` function), `cmd/flags.go`, `assests/template/session.html` (html template the part where the button `Fetch Flags` is defined with the javascript handler), `assests/script/session.js` (function `fetchContent`), `assets/template/flags.html` (html template for the content fetched by the `fetchContent` javascript function and inserted into the HTML div element).
+
+![flags](/images/flags.png)
+
+
 ## Logs
 
 Since version 2.43.0, Erigon nodes write logs by default with `INFO` level into `<datadir>/logs` directory, there is log rotation. Using diagnostics system,

assets/template/flags.html

@@ -0,0 +1,12 @@
+<table>
+    <tr>
+        <th>Flag</th>
+        <th>Value</th>
+    </tr>
+    {{range $key, $value := .FlagPayload}}
+        <tr>
+            <td><code>{{$key}}</code></td>
+            <td><code>{{$value}}</code></td>
+        </tr>
+    {{end}}
+</table>

assets/template/session.html

@@ -44,6 +44,10 @@ <h2>SESSION: {{.SessionName}} PIN: {{.SessionPin}}</h2>
                         <button type="button" onclick="fetchContent('{{.SessionName}}', 'command line args', '/ui/cmd_line', 'cmdlineargs')">Fetch Command Line</button>
                         <div id="cmdlineargs"></div>
                     </div>
+                    <div>
+                        <button type="button" onclick="fetchContent('{{.SessionName}}', 'context flags', '/ui/flags', 'flags')">Fetch Flags</button>
+                        <div id="flags"></div>
+                    </div>
                     <div>
                         <button type="button" onclick="fetchContent('{{.SessionName}}', 'log list', '/ui/log_list', 'loglist')">Fetch Log List</button>
                         <div id="loglist"></div>

cmd/flags.go

@@ -0,0 +1,56 @@
+package cmd
+
+import (
+	"fmt"
+	"html/template"
+	"net/http"
+	"strings"
+)
+
+type Flags struct {
+	Success     bool
+	Error       string
+	FlagPayload map[string]string
+}
+
+func processFlags(w http.ResponseWriter, templ *template.Template, success bool, result string, versions Versions) {
+
+	if !versions.Success {
+		fmt.Fprintf(w, "Unable to process flag due to inability to get node version: %s", versions.Error)
+		return
+	}
+
+	if versions.NodeVersion < 2 {
+		fmt.Fprintf(w, "Flags only support version >= 2. Node version: %d", versions.NodeVersion)
+		return
+	}
+
+	var flags Flags
+	flags.FlagPayload = make(map[string]string)
+	if success {
+		lines := strings.Split(result, "\n")
+		if len(lines) > 0 && strings.HasPrefix(lines[0], successLine) {
+			flags.Success = true
+
+			for _, line := range lines[1:] {
+				if len(line) > 0 {
+					flagName, flagValue, found := strings.Cut(line, "=")
+					if !found {
+						flags.Error = fmt.Sprintf("fail to parse line %s", line)
+						flags.Success = false
+					} else {
+						flags.FlagPayload[flagName] = flagValue
+					}
+				}
+			}
+		} else {
+			flags.Error = fmt.Sprintf("incorrect response (first line needs to be SUCCESS): %v", lines)
+		}
+	} else {
+		flags.Error = result
+	}
+	if err := templ.ExecuteTemplate(w, "flags.html", flags); err != nil {
+		fmt.Fprintf(w, "Executing flags template: %v", err)
+		return
+	}
+}

cmd/ui_handler.go

@@ -22,7 +22,7 @@ import (
 const sessionIdCookieName = "sessionId"
 const sessionIdCookieDuration = 30 * 24 * 3600 // 30 days
 
-var uiRegex = regexp.MustCompile("^/ui/(cmd_line|log_list|log_head|log_tail|log_download|versions|reorgs|bodies_download|)$")
+var uiRegex = regexp.MustCompile("^/ui/(cmd_line|flags|log_list|log_head|log_tail|log_download|versions|reorgs|bodies_download|)$")
 
 func (uih *UiHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	m := uiRegex.FindStringSubmatch(r.URL.Path)
@@ -71,6 +71,12 @@ func (uih *UiHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		success, result := uih.fetch("/cmdline\n", requestChannel)
 		processCmdLineArgs(w, uih.uiTemplate, success, result)
 		return
+	case "flags":
+		versionCallSuccess, versionCallResult := uih.fetch("/version\n", requestChannel)
+		versions := processVersions(w, uih.uiTemplate, versionCallSuccess, versionCallResult, true)
+		success, result := uih.fetch("/flags\n", requestChannel)
+		processFlags(w, uih.uiTemplate, success, result, versions)
+		return
 	case "log_list":
 		success, result := uih.fetch("/logs/list\n", requestChannel)
 		processLogList(w, uih.uiTemplate, success, uiSession.SessionName, result)

cmd/versions.go

@@ -17,8 +17,19 @@ type Versions struct {
 	GitCommit      string
 }
 
-func processVersions(w http.ResponseWriter, templ *template.Template, success bool, result string) {
+func processVersions(w http.ResponseWriter, templ *template.Template, success bool, result string, skipUpdateHTML ...bool) Versions {
+	versions := processVersionsResponse(w, templ, success, result)
+
+	if len(skipUpdateHTML) == 0 || !skipUpdateHTML[0] {
+		updateHTML(w, templ, versions)
+	}
+
+	return versions
+}
+
+func processVersionsResponse(w http.ResponseWriter, templ *template.Template, success bool, result string) Versions {
 	var versions Versions
+
 	if success {
 		lines := strings.Split(result, "\n")
 		if len(lines) > 0 && strings.HasPrefix(lines[0], successLine) {
@@ -49,8 +60,12 @@ func processVersions(w http.ResponseWriter, templ *template.Template, success bo
 	} else {
 		versions.Error = result
 	}
+
+	return versions
+}
+
+func updateHTML(w http.ResponseWriter, templ *template.Template, versions Versions) {
 	if err := templ.ExecuteTemplate(w, "versions.html", versions); err != nil {
 		fmt.Fprintf(w, "Executing versions template: %v", err)
-		return
 	}
 }