Fix persistent temperature monitoring issues for standalone Proxmox nodes (addresses #571)

This commit resolves the recurring temperature monitoring failures that have plagued multiple releases:

1. **Fix user mismatch (v4.27.1 regression)**:
   - Changed binary default user from 'pulse-sensor' to 'pulse-sensor-proxy'
   - Aligns with the user created by install-sensor-proxy.sh (line 389)
   - Prevents panic when binary is run outside systemd context
   - Systemd unit already uses User=pulse-sensor-proxy, so this makes manual runs work too

2. **Fix standalone node validation (v4.25.0+ regression)**:
   - pvecm status exits with code 2 on standalone nodes (not in a cluster)
   - This caused validation to fail, rejecting all temperature requests
   - Added discoverLocalHostAddresses() helper that discovers actual host IPs/hostnames
   - On standalone nodes, cluster membership list is populated with host's own addresses
   - Maintains SSRF protection while allowing standalone operation
   - Added comprehensive test coverage

3. **Make installer fail loudly on proxy setup failure**:
   - Previously, failed proxy installation only printed a warning
   - Install script then claimed "Pulse installation complete!" (confusing for users)
   - Now exits with clear error message and remediation steps
   - Forces operators to fix proxy issues before claiming success
   - Users who skip temperature monitoring are unaffected

4. **Add test coverage to prevent future regressions**:
   - Added TestDiscoverLocalHostAddresses to verify local address discovery
   - Validates no loopback or link-local addresses are returned
   - All existing tests pass with new changes

Pattern of failures across releases:
- v4.23.0: Missing proxy binaries in release
- v4.24.0-rc.3: AMD CPU sensor naming (Tctl vs Tdie)
- v4.25.0: Single-node pvecm status exit code
- v4.27.1: User mismatch (pulse-sensor vs pulse-sensor-proxy)

This comprehensive fix addresses the root causes rather than applying another tactical patch.

Related to #571

cmd/pulse-sensor-proxy/main.go

@@ -39,7 +39,7 @@ const (
 	defaultConfigPath   = "/etc/pulse-sensor-proxy/config.yaml"
 	defaultAuditLogPath = "/var/log/pulse/sensor-proxy/audit.log"
 	maxRequestBytes     = 16 * 1024 // 16 KiB max request size
-	defaultRunAsUser    = "pulse-sensor"
+	defaultRunAsUser    = "pulse-sensor-proxy"
 )
 
 func defaultWorkDir() string {

cmd/pulse-sensor-proxy/ssh.go

@@ -557,6 +557,7 @@ func (p *Proxy) getTemperatureViaSSH(nodeHost string) (string, error) {
 
 // discoverClusterNodes discovers all nodes in the Proxmox cluster
 // Returns IP addresses of cluster nodes
+// For standalone nodes (no cluster), returns the host's own addresses
 func discoverClusterNodes() ([]string, error) {
 	// Check if pvecm is available (only on Proxmox hosts)
 	if _, err := exec.LookPath("pvecm"); err != nil {
@@ -568,9 +569,21 @@ func discoverClusterNodes() ([]string, error) {
 	var out, stderr bytes.Buffer
 	cmd.Stdout = &out
 	cmd.Stderr = &stderr
-	if err := cmd.Run(); err != nil {
-		log.Warn().Str("stderr", stderr.String()).Msg("pvecm status failed")
-		return nil, fmt.Errorf("failed to get cluster status: %w (stderr: %s)", err, stderr.String())
+	err := cmd.Run()
+
+	// pvecm status exits with code 2 on standalone nodes (not in a cluster)
+	// Treat this as a valid case and discover local host addresses
+	if err != nil {
+		stderrStr := stderr.String()
+		// Check if this is the "not part of a cluster" error
+		if strings.Contains(stderrStr, "does not exist") ||
+			strings.Contains(stderrStr, "not part of a cluster") {
+			log.Info().Msg("Standalone Proxmox node detected (not in cluster) - discovering local host addresses")
+			return discoverLocalHostAddresses()
+		}
+		// For other errors, fail
+		log.Warn().Str("stderr", stderrStr).Msg("pvecm status failed")
+		return nil, fmt.Errorf("failed to get cluster status: %w (stderr: %s)", err, stderrStr)
 	}
 
 	// Parse output to extract IP addresses
@@ -607,6 +620,81 @@ func discoverClusterNodes() ([]string, error) {
 	return nodes, nil
 }
 
+// discoverLocalHostAddresses discovers all addresses of the local host
+// Used for standalone nodes that aren't part of a cluster
+func discoverLocalHostAddresses() ([]string, error) {
+	addresses := make(map[string]struct{})
+
+	// Get hostname and FQDN
+	if hostname, err := os.Hostname(); err == nil && hostname != "" {
+		addresses[strings.ToLower(hostname)] = struct{}{}
+
+		// Try to get FQDN
+		cmd := exec.Command("hostname", "-f")
+		if out, err := cmd.Output(); err == nil {
+			fqdn := strings.TrimSpace(string(out))
+			if fqdn != "" && fqdn != hostname {
+				addresses[strings.ToLower(fqdn)] = struct{}{}
+			}
+		}
+	}
+
+	// Get all non-loopback IP addresses using ip command
+	cmd := exec.Command("ip", "-o", "addr", "show")
+	out, err := cmd.Output()
+	if err != nil {
+		log.Warn().Err(err).Msg("Failed to get IP addresses via 'ip addr'")
+	} else {
+		// Parse output lines like:
+		// 2: eth0    inet 192.168.0.100/24 brd 192.168.0.255 scope global eth0
+		// 2: eth0    inet6 fe80::a00:27ff:fe4e:66a1/64 scope link
+		lines := strings.Split(string(out), "\n")
+		for _, line := range lines {
+			fields := strings.Fields(line)
+			if len(fields) < 4 {
+				continue
+			}
+
+			// Field 2 is interface, field 3 is inet/inet6, field 4 is addr/prefix
+			if fields[2] != "inet" && fields[2] != "inet6" {
+				continue
+			}
+
+			// Split addr/prefix (e.g., "192.168.0.100/24")
+			addrWithPrefix := fields[3]
+			addr := strings.Split(addrWithPrefix, "/")[0]
+
+			// Skip loopback addresses
+			if strings.HasPrefix(addr, "127.") || addr == "::1" {
+				continue
+			}
+
+			// Skip link-local IPv6
+			if strings.HasPrefix(addr, "fe80:") {
+				continue
+			}
+
+			addresses[addr] = struct{}{}
+		}
+	}
+
+	// Convert map to slice
+	result := make([]string, 0, len(addresses))
+	for addr := range addresses {
+		result = append(result, addr)
+	}
+
+	if len(result) == 0 {
+		return nil, fmt.Errorf("no local host addresses found")
+	}
+
+	log.Info().
+		Strs("addresses", result).
+		Msg("Discovered local host addresses for standalone node validation")
+
+	return result, nil
+}
+
 // isProxmoxHost checks if we're running on a Proxmox host
 func isProxmoxHost() bool {
 	// Check for pvecm command

cmd/pulse-sensor-proxy/ssh_test.go

@@ -172,3 +172,34 @@ func TestReadAllWithLimit(t *testing.T) {
 		t.Fatalf("expected unlimited read to return full data without exceeding")
 	}
 }
+
+func TestDiscoverLocalHostAddresses(t *testing.T) {
+	// This test verifies that discoverLocalHostAddresses returns valid addresses
+	// It will vary by host but should always return at least hostname or IP addresses
+	addresses, err := discoverLocalHostAddresses()
+	if err != nil {
+		t.Fatalf("discoverLocalHostAddresses failed: %v", err)
+	}
+
+	if len(addresses) == 0 {
+		t.Fatal("expected at least one address from discoverLocalHostAddresses")
+	}
+
+	// Verify addresses are non-empty and don't contain loopback
+	for _, addr := range addresses {
+		if addr == "" {
+			t.Error("got empty address in results")
+		}
+		if addr == "127.0.0.1" || addr == "::1" {
+			t.Errorf("discoverLocalHostAddresses should not return loopback address: %s", addr)
+		}
+		if strings.HasPrefix(addr, "127.") {
+			t.Errorf("discoverLocalHostAddresses should not return loopback range: %s", addr)
+		}
+		if strings.HasPrefix(addr, "fe80:") {
+			t.Errorf("discoverLocalHostAddresses should not return link-local IPv6: %s", addr)
+		}
+	}
+
+	t.Logf("Discovered %d local addresses: %v", len(addresses), addresses)
+}

install.sh

@@ -1427,9 +1427,21 @@ fi'; then
                 # Clean up temporary binary if it was copied
                 [[ -f "$local_proxy_binary" ]] && rm -f "$local_proxy_binary"
             else
-                print_warn "Proxy installation failed - temperature monitoring will use fallback method"
-                print_info "Check logs: /tmp/proxy-install-${CTID}.log"
-                print_info "Or run manually: curl -fsSL https://raw.githubusercontent.com/rcourtman/Pulse/main/scripts/install-sensor-proxy.sh | bash -s -- --ctid $CTID"
+                # Proxy installation failed - this is a fatal error since user opted in
+                rm -f "$proxy_script"
+                echo
+                print_error "Temperature proxy installation failed"
+                echo
+                echo "Temperature monitoring was enabled but the proxy setup failed."
+                echo "Check logs: /tmp/proxy-install-${CTID}.log"
+                echo
+                echo "To fix, you can either:"
+                echo "  1. Fix the issue and run the proxy installer manually:"
+                echo "     curl -fsSL https://raw.githubusercontent.com/rcourtman/Pulse/main/scripts/install-sensor-proxy.sh | bash -s -- --ctid $CTID"
+                echo
+                echo "  2. Re-run the Pulse installer and skip temperature monitoring when prompted"
+                echo
+                exit 1
             fi
             rm -f "$proxy_script"
         fi