From c477633c9b17981ccbfa0b86d28b9cd6b7202888 Mon Sep 17 00:00:00 2001
From: Ben Johnson <benbjohnson@yahoo.com>
Date: Wed, 4 Oct 2023 11:01:35 -0600
Subject: [PATCH] Add primary hostname to /info endpoint (#411)

---
 cmd/litefs/run.go |  4 ++--
 http/server.go    |  9 +++++++--
 lease.go          |  5 +++++
 litefs.go         | 41 ++++-------------------------------------
 mock/lease.go     |  5 +++++
 5 files changed, 23 insertions(+), 41 deletions(-)

diff --git a/cmd/litefs/run.go b/cmd/litefs/run.go
index 5530c34..2c8c70d 100644
--- a/cmd/litefs/run.go
+++ b/cmd/litefs/run.go
@@ -121,7 +121,7 @@ func (c *RunCommand) Run(ctx context.Context) (err error) {
 
 	// Attempt to promote local node to be the primary node via lease handoff.
 	if c.Promote {
-		if info.Primary {
+		if info.IsPrimary {
 			log.Printf("node is already primary, skipping promotion")
 		} else {
 			log.Printf("promoting node to primary")
@@ -143,7 +143,7 @@ func (c *RunCommand) Run(ctx context.Context) (err error) {
 		}
 
 		// Attempt to lock the database.
-		if f, err = os.OpenFile(c.WithHaltLockOn+"-lock", os.O_RDWR, 0666); os.IsNotExist(err) {
+		if f, err = os.OpenFile(c.WithHaltLockOn+"-lock", os.O_RDWR, 0o666); os.IsNotExist(err) {
 			return fmt.Errorf("lock file not available, are you sure %q is a LiteFS mount?", filepath.Dir(c.WithHaltLockOn))
 		} else if err != nil {
 			return err
diff --git a/http/server.go b/http/server.go
index f8d28a7..cefddf3 100644
--- a/http/server.go
+++ b/http/server.go
@@ -270,12 +270,17 @@ func (s *Server) handleDebugRand(w http.ResponseWriter, r *http.Request) {
 
 func (s *Server) handleGetInfo(w http.ResponseWriter, r *http.Request) {
 	var info litefs.NodeInfo
-	info.ID = s.store.ID()
 	info.ClusterID = s.store.ClusterID()
-	info.Primary = s.store.IsPrimary()
+	info.IsPrimary = s.store.IsPrimary()
 	info.Candidate = s.store.Candidate()
 	info.Path = s.store.Path()
 
+	if isPrimary, primaryInfo := s.store.PrimaryInfo(); isPrimary {
+		info.Primary.Hostname = s.store.Leaser.Hostname()
+	} else if primaryInfo != nil {
+		info.Primary.Hostname = primaryInfo.Hostname
+	}
+
 	if buf, err := json.MarshalIndent(info, "", "  "); err != nil {
 		Error(w, r, err, http.StatusInternalServerError)
 		return
diff --git a/lease.go b/lease.go
index e5092ab..9115f5c 100644
--- a/lease.go
+++ b/lease.go
@@ -14,6 +14,7 @@ type Leaser interface {
 	// Type returns the name of the leaser.
 	Type() string
 
+	Hostname() string
 	AdvertiseURL() string
 
 	// Acquire attempts to acquire the lease to become the primary.
@@ -91,6 +92,10 @@ func (l *StaticLeaser) Close() (err error) { return nil }
 // Type returns "static".
 func (l *StaticLeaser) Type() string { return "static" }
 
+func (l *StaticLeaser) Hostname() string {
+	return l.hostname
+}
+
 // AdvertiseURL returns the primary URL if this is the primary.
 // Otherwise returns blank.
 func (l *StaticLeaser) AdvertiseURL() string {
diff --git a/litefs.go b/litefs.go
index 653fd0f..028c8e9 100644
--- a/litefs.go
+++ b/litefs.go
@@ -5,7 +5,6 @@ import (
 	"context"
 	"crypto/rand"
 	"encoding/binary"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -60,46 +59,14 @@ func ValidateClusterID(id string) error {
 
 // NodeInfo represents basic info about a node.
 type NodeInfo struct {
-	ID        uint64 `json:"id"`                  // node ID
 	ClusterID string `json:"clusterID,omitempty"` // cluster ID
-	Primary   bool   `json:"primary"`             // if true, node is currently primary
+	IsPrimary bool   `json:"isPrimary"`           // if true, node is currently primary
 	Candidate bool   `json:"candidate"`           // if true, node is eligible to be primary
 	Path      string `json:"path"`                // data directory
-}
-
-type nodeInfoJSON struct {
-	ID        string `json:"id"`
-	ClusterID string `json:"clusterID,omitempty"`
-	Primary   bool   `json:"primary"`
-	Candidate bool   `json:"candidate"`
-	Path      string `json:"path"`
-}
-
-// MarshalJSON marshals info to JSON. Converts the ID to and from its string representation.
-func (i NodeInfo) MarshalJSON() ([]byte, error) {
-	return json.Marshal(nodeInfoJSON{
-		ID:        FormatNodeID(i.ID),
-		ClusterID: i.ClusterID,
-		Primary:   i.Primary,
-		Candidate: i.Candidate,
-		Path:      i.Path,
-	})
-}
 
-// UnmarshalJSON unmarshals info from JSON.
-func (i *NodeInfo) UnmarshalJSON(data []byte) (err error) {
-	var v nodeInfoJSON
-	if err := json.Unmarshal(data, &v); err != nil {
-		return err
-	}
-	if i.ID, err = ParseNodeID(v.ID); err != nil {
-		return err
-	}
-	i.ClusterID = v.ClusterID
-	i.Primary = v.Primary
-	i.Candidate = v.Candidate
-	i.Path = v.Path
-	return nil
+	Primary struct {
+		Hostname string `json:"hostname"`
+	} `json:"primary"`
 }
 
 // Environment represents an interface for interacting with the host environment.
diff --git a/mock/lease.go b/mock/lease.go
index eadab47..ad5b402 100644
--- a/mock/lease.go
+++ b/mock/lease.go
@@ -11,6 +11,7 @@ var _ litefs.Leaser = (*Leaser)(nil)
 
 type Leaser struct {
 	CloseFunc           func() error
+	HostnameFunc        func() string
 	AdvertiseURLFunc    func() string
 	AcquireFunc         func(ctx context.Context) (litefs.Lease, error)
 	AcquireExistingFunc func(ctx context.Context, leaseID string) (litefs.Lease, error)
@@ -25,6 +26,10 @@ func (l *Leaser) Close() error {
 
 func (l *Leaser) Type() string { return "mock" }
 
+func (l *Leaser) Hostname() string {
+	return l.HostnameFunc()
+}
+
 func (l *Leaser) AdvertiseURL() string {
 	return l.AdvertiseURLFunc()
 }