wp-metacache/main.go

package main

import (
	"bufio"
	"database/sql"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"github.com/elliotchance/phpserialize"
	_ "github.com/go-sql-driver/mysql"
	"log"
	"net"
	"net/textproto"
	"os"
	"sort"
	"sync"
	"time"
)

// Globals...

var sockpath *string
var dsn *string
var db *sql.DB

type metadataValues struct {
	Values []string `php:"v"`
}

type metadataObject struct {
	lastHit time.Time
	entries map[string]metadataValues
	lock    sync.RWMutex
	loading sync.Once
}
type MetadataCache struct {
	objects    map[int64]metadataObject
	lock       sync.RWMutex
	objectType string
	sizeLimit  int
}

type age struct {
	key     int64
	lastHit time.Time
}

func (c *MetadataCache) Purge() {
	if len(c.objects) < c.sizeLimit {
		// We aren't full so let's not run
		return
	}
	var ages []age
	for x := range c.objects {
		var a age
		a.key = x
		a.lastHit = c.objects[x].lastHit
		ages = append(ages, a)
	}
	// Sort by age
	sort.Slice(ages, func(a, b int) bool { return ages[a].lastHit.After(ages[b].lastHit) })
	// Now we remove all entries from the 90% age mark up
	purgeto := int(float64(c.sizeLimit) * 0.9)
	for x := purgeto; x < len(ages); x++ {
		delete(c.objects, ages[x].key)
	}
}

func (c *MetadataCache) Delete(o int64) {
	// We could be selective about what we purge but let's see if it matters before we do that
	c.lock.Lock()
	delete(c.objects, o)
	c.lock.Unlock()
}

func (c *MetadataCache) Get(o int64, k string) ([]string, error) {
	log.Printf("Get %d, %s.\n", o, k)
	// Check cache for entry
	c.lock.RLock()
	object, ok := c.objects[o]
	if !ok {
		// Object is not in the cache so let's load it up
		var tmpobject metadataObject
		c.objects[o] = tmpobject
		tmpobject.loading.Do(func() {
			// Only do this once even if concurrent requests come in
			tmpobject.entries = loadDbEntries(c.objectType, o)
		})
		object = tmpobject

	}
	c.lock.RUnlock()

	object.lock.RLock()
	entries, ok := object.entries[k]
	object.lock.RUnlock()

	object.lock.Lock()
	object.lastHit = time.Now()
	object.lock.Unlock()
	c.lock.Lock()
	c.objects[o] = object
	c.lock.Unlock()
	if !ok {
		// Value does not exist! Send it back.
		return nil, errors.New("Value not found")
	}
	return entries.Values, nil
}

func loadDbEntries(ot string, id int64) map[string]metadataValues {
	log.Println("loadDbEntries")
	var entries map[string]metadataValues
	entries = make(map[string]metadataValues)
	var table string
	var column string
	if ot == "u" {
		table = "wp_usermeta"
		column = "user_id"
	} else if ot == "p" {
		table = "wp_postmeta"
		column = "post_id"
	} else {
		log.Printf("Invalid object type: %s", ot)
		return entries
	}
	query := fmt.Sprintf("select meta_key, meta_value from %s where %s = ?", table, column)
	log.Println(query)
	rows, err := db.Query(query, id)
	if err != nil {
		log.Printf("db.Query: %s\n", err.Error())
		return entries
	}

	for rows.Next() {
		var key string
		var value string
		rows.Scan(&key, &value)
		values, _ := entries[key]
		values.Values = append(values.Values, value)
		entries[key] = values
	}
	return entries
}

func init() {
	// Get database and socket running
	dsn = flag.String("dsn", "", "Database connection string")
	sockpath = flag.String("sock", "", "Unix socket path")
	flag.Parse()
	var err error
	db, err = sql.Open("mysql", *dsn)
	if err != nil {
		log.Fatalf("sql.Open: %s", err.Error())
	}
	err = db.Ping()
	if err != nil {
		log.Fatalf("sql.Ping: %s", err.Error())
	}
}

func main() {
	var UC MetadataCache
	UC.objects = make(map[int64]metadataObject)
	UC.sizeLimit = 100
	UC.objectType = "u"
	var PC MetadataCache
	PC.objects = make(map[int64]metadataObject)
	PC.sizeLimit = 100
	PC.objectType = "p"

	if err := os.RemoveAll(*sockpath); err != nil {
		log.Fatal(err)
	}
	unixListener, err := net.Listen("unix", *sockpath)
	if err != nil {
		log.Fatal(err)
	}
	os.Chmod(*sockpath, 0777)
	for {
		conn, err := unixListener.Accept()
		if err != nil {
			// handle error
		}
		go handleConnection(conn, UC, PC)
	}
}

type cachecommand struct {
	ObjectType string `json:"t"`
	ObjectId   int64  `json:"i"`
	Key        string `json:"k"`
	Command    string `json:"c"`
}

func handleConnection(conn net.Conn, UC MetadataCache, PC MetadataCache) {
	log.Println("handleConnection started")
	var m *MetadataCache
	reader := bufio.NewReader(conn)
	tp := textproto.NewReader(reader)
	for {
		buf, err := tp.ReadLine()
		if err != nil {
			conn.Close()
			return
		}
		var c cachecommand
		err = json.Unmarshal([]byte(buf), &c)
		if err != nil {
			log.Printf("json.Unmarshal: %s returned %s", buf, err.Error())
		}
		var values []string
		if c.ObjectType == "u" {
			m = &UC
		} else if c.ObjectType == "p" {
			m = &PC
		}
		if c.Command == "g" {
			values, err = m.Get(c.ObjectId, c.Key)
			if err != nil {
				conn.Write([]byte("404"))
			} else {
				p, err := phpserialize.Marshal(values, nil)
				if err != nil {
					log.Fatalf("phpserialize.Marshal: %s", err.Error())
				}
				conn.Write(p)
			}
		} else if c.Command == "d" {
			m.Delete(c.ObjectId)
			conn.Write([]byte("200"))
		}
		conn.Write([]byte("\n"))
	}

}