From 745299bce5c3e7df22894fdcecc8882a6296e1fa Mon Sep 17 00:00:00 2001
From: Asim Aslam <asim@aslam.me>
Date: Mon, 14 Oct 2019 21:39:25 +0100
Subject: [PATCH] add http lock implementation

---
 sync/lock/http/http.go          | 135 ++++++++++++++++++++++++++++++++
 sync/lock/http/server/server.go |  45 +++++++++++
 2 files changed, 180 insertions(+)
 create mode 100644 sync/lock/http/http.go
 create mode 100644 sync/lock/http/server/server.go

diff --git a/sync/lock/http/http.go b/sync/lock/http/http.go
new file mode 100644
index 00000000..892be138
--- /dev/null
+++ b/sync/lock/http/http.go
@@ -0,0 +1,135 @@
+// Package http adds a http lock implementation
+package http
+
+import (
+	"errors"
+	"fmt"
+	"hash/crc32"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"path/filepath"
+	"strings"
+
+	"github.com/micro/go-micro/sync/lock"
+)
+
+var (
+	DefaultPath    = "/sync/lock"
+	DefaultAddress = "localhost:8080"
+)
+
+type httpLock struct {
+	opts lock.Options
+}
+
+func (h *httpLock) url(id string) (string, error) {
+	sum := crc32.ChecksumIEEE([]byte(id))
+	node := h.opts.Nodes[sum%uint32(len(h.opts.Nodes))]
+
+	// parse the host:port or whatever
+	uri, err := url.Parse(node)
+	if err != nil {
+		return "", err
+	}
+
+	if len(uri.Scheme) == 0 {
+		uri.Scheme = "http"
+	}
+
+	// set path
+	// build path
+	path := filepath.Join(DefaultPath, h.opts.Prefix, id)
+	uri.Path = path
+
+	// return url
+	return uri.String(), nil
+}
+
+func (h *httpLock) Acquire(id string, opts ...lock.AcquireOption) error {
+	var options lock.AcquireOptions
+	for _, o := range opts {
+		o(&options)
+	}
+
+	uri, err := h.url(id)
+	if err != nil {
+		return err
+	}
+
+	ttl := fmt.Sprintf("%d", int64(options.TTL.Seconds()))
+	wait := fmt.Sprintf("%d", int64(options.Wait.Seconds()))
+
+	rsp, err := http.PostForm(uri, url.Values{
+		"id":   {id},
+		"ttl":  {ttl},
+		"wait": {wait},
+	})
+	if err != nil {
+		return err
+	}
+	defer rsp.Body.Close()
+
+	b, err := ioutil.ReadAll(rsp.Body)
+	if err != nil {
+		return err
+	}
+
+	// success
+	if rsp.StatusCode == 200 {
+		return nil
+	}
+
+	// return error
+	return errors.New(string(b))
+}
+
+func (h *httpLock) Release(id string) error {
+	uri, err := h.url(id)
+	if err != nil {
+		return err
+	}
+
+	vals := url.Values{
+		"id": {id},
+	}
+
+	req, err := http.NewRequest("DELETE", uri, strings.NewReader(vals.Encode()))
+	if err != nil {
+		return err
+	}
+
+	rsp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer rsp.Body.Close()
+
+	b, err := ioutil.ReadAll(rsp.Body)
+	if err != nil {
+		return err
+	}
+
+	// success
+	if rsp.StatusCode == 200 {
+		return nil
+	}
+
+	// return error
+	return errors.New(string(b))
+}
+
+func NewLock(opts ...lock.Option) lock.Lock {
+	var options lock.Options
+	for _, o := range opts {
+		o(&options)
+	}
+
+	if len(options.Nodes) == 0 {
+		options.Nodes = []string{DefaultAddress}
+	}
+
+	return &httpLock{
+		opts: options,
+	}
+}
diff --git a/sync/lock/http/server/server.go b/sync/lock/http/server/server.go
new file mode 100644
index 00000000..49298547
--- /dev/null
+++ b/sync/lock/http/server/server.go
@@ -0,0 +1,45 @@
+// Package server implements the sync http server
+package server
+
+import (
+	"net/http"
+
+	"github.com/micro/go-micro/sync/lock"
+	lkhttp "github.com/micro/go-micro/sync/lock/http"
+)
+
+func Handler(lk lock.Lock) http.Handler {
+	mux := http.NewServeMux()
+
+	mux.HandleFunc(lkhttp.DefaultPath, func(w http.ResponseWriter, r *http.Request) {
+		r.ParseForm()
+
+		id := r.Form.Get("id")
+		if len(id) == 0 {
+			return
+		}
+
+		switch r.Method {
+		case "POST":
+			err := lk.Acquire(id)
+			if err != nil {
+				http.Error(w, err.Error(), 500)
+			}
+		case "DELETE":
+			err := lk.Release(id)
+			if err != nil {
+				http.Error(w, err.Error(), 500)
+			}
+		}
+	})
+
+	return mux
+}
+
+func Server(lk lock.Lock) *http.Server {
+	server := &http.Server{
+		Addr:    lkhttp.DefaultAddress,
+		Handler: Handler(lk),
+	}
+	return server
+}