implement set on client/server

chord/client.go

@@ -13,13 +13,15 @@ type Client interface {
 	// If the ID is not associated with a key, the result must be the empty
 	// string with a nil error.
 	Find(ctx context.Context, s Peer, id ID) (Peer, string, error)
+	// Set asks s to save a value for an ID.
+	Set(ctx context.Context, s Peer, id ID, v string) error
 	// Notify tells s we believe n to be its predecessor.
 	Notify(ctx context.Context, n *Node, s Peer) error
 	// Neighbors requests a peer's beliefs about its own neighbors.
 	Neighbors(ctx context.Context, p Peer) (pred Peer, succ []Peer, err error)
 }
 
-// TODO(branden): FindSuccessor should be plural; if we have multiple keys to
+// TODO(branden): Find should be plural; if we have multiple keys to
 // search, we shouldn't have to do the whole query for all of them, especially
 // considering we can sort by increasing distance from the origin and then do
 // the query in linear time.
@@ -33,6 +35,18 @@ func Find(ctx context.Context, cl Client, n *Node, id ID) (Peer, string, error)
 	return p, s, err
 }
 
+// TODO(branden): Set should be plural for the same reasons. It should also
+// return an error if the key isn't local to the peer.
+
+// Set saves a value in the Chord network.
+func Set(ctx context.Context, cl Client, n *Node, key ID, val string) error {
+	p, _, err := Find(ctx, cl, n, key)
+	if err != nil {
+		return fmt.Errorf("couldn't find peer to save key: %w", err)
+	}
+	return cl.Set(ctx, p, key, val)
+}
+
 // Join creates a new node joining an existing Chord network by communicating
 // with any peer already in the network.
 func Join(ctx context.Context, cl Client, addr netip.AddrPort, np Peer) (*Node, error) {

chord/httpnode/client.go

@@ -2,11 +2,13 @@ package httpnode
 
 import (
 	"context"
+	"encoding/base64"
 	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
 	"path"
+	"strings"
 
 	"git.sunturtle.xyz/zephyr/chord/chord"
 )
@@ -27,8 +29,7 @@ func (cl *Client) Find(ctx context.Context, s chord.Peer, id chord.ID) (chord.Pe
 	url := url.URL{
 		Scheme: "http",
 		Host:   addr.String(),
-		Path:     path.Join("/", cl.APIBase, "succ"),
+		Path:   path.Join("/", cl.APIBase, "key", id.String()),
-		RawQuery: url.Values{"s": {id.String()}}.Encode(),
 	}
 	req, err := http.NewRequestWithContext(ctx, "GET", url.String(), nil)
 	if err != nil {
@@ -45,6 +46,29 @@ func (cl *Client) Find(ctx context.Context, s chord.Peer, id chord.ID) (chord.Pe
 	return chord.Address(p.Peer), p.Value, nil
 }
 
+func (cl *Client) Set(ctx context.Context, s chord.Peer, id chord.ID, v string) error {
+	_, addr := s.Values()
+	url := url.URL{
+		Scheme: "http",
+		Host:   addr.String(),
+		Path:   path.Join("/", cl.APIBase, "key", id.String()),
+	}
+	body := strings.NewReader(base64.StdEncoding.EncodeToString([]byte(v)))
+	req, err := http.NewRequestWithContext(ctx, "POST", url.String(), body)
+	if err != nil {
+		return err
+	}
+	resp, err := cl.HTTP.Do(req)
+	if err != nil {
+		return err
+	}
+	if resp.StatusCode >= 400 {
+		_, err := readResponse[struct{}](resp)
+		return err
+	}
+	return nil
+}
+
 // Notify tells s we believe n to be its predecessor.
 func (cl *Client) Notify(ctx context.Context, n *chord.Node, s chord.Peer) error {
 	_, addr := s.Values()

chord/httpnode/server.go

@@ -2,8 +2,10 @@ package httpnode
 
 import (
 	"context"
+	"encoding/base64"
 	"errors"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"net/netip"
@@ -45,7 +47,8 @@ func New(l net.Listener, cl chord.Client) (*Node, error) {
 // Router creates a handler for the Chord HTTP endpoints.
 func (n *Node) Router() http.Handler {
 	m := http.NewServeMux()
-	m.HandleFunc("GET /key", n.key)
+	m.HandleFunc("GET /key/{id}", n.key)
+	m.HandleFunc("POST /key/{id}", n.set)
 	m.HandleFunc("POST /pred", n.notify)
 	m.HandleFunc("GET /neighbors", n.neighbors)
 	return m
@@ -66,7 +69,7 @@ func (n *Node) Check(ctx context.Context) error {
 }
 
 func (n *Node) key(w http.ResponseWriter, r *http.Request) {
-	s := r.FormValue("s")
+	s := r.PathValue("id")
 	id, err := chord.ParseID(s)
 	if err != nil {
 		writeError(w, http.StatusBadRequest, err.Error())
@@ -82,6 +85,25 @@ func (n *Node) key(w http.ResponseWriter, r *http.Request) {
 	writeOk(w, pv)
 }
 
+func (n *Node) set(w http.ResponseWriter, r *http.Request) {
+	s := r.PathValue("id")
+	id, err := chord.ParseID(s)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	val, err := io.ReadAll(base64.NewDecoder(base64.StdEncoding, r.Body))
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	if !n.self.SetLocal(id, string(val)) {
+		writeError(w, http.StatusNotFound, "id does not belong to this peer")
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
 func (n *Node) notify(w http.ResponseWriter, r *http.Request) {
 	s := r.FormValue("p")
 	addr, err := netip.ParseAddrPort(s)

chord/topology.go

@@ -47,9 +47,15 @@ func (n *Node) Neighbors(s []Peer) (Peer, []Peer) {
 	return n.pred, append(s, n.succ...)
 }
 
+func (n *Node) localLocked(id ID) bool {
+	return contains(n.self.id, n.succ[0].id, id)
+}
+
 // IsLocal reports whether this node owns the given key.
 func (n *Node) IsLocal(id ID) bool {
-	return contains(n.self.id, n.Successor().id, id)
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	return n.localLocked(id)
 }
 
 // Closest finds the locally known peer which is the closest predecessor of key.
@@ -85,19 +91,26 @@ func (n *Node) Closest(id ID) Peer {
 	return n.self
 }
 
-// Get obtains the value for a key owned by the node.
+// GetLocal obtains the value for a key if it is local to and owned by the node.
-func (n *Node) Get(k ID) (v string, found bool) {
+func (n *Node) GetLocal(k ID) (v string, found bool) {
 	n.mu.Lock()
 	defer n.mu.Unlock()
+	if n.localLocked(k) {
 		v, found = n.data[k]
+	}
 	return v, found
 }
 
-// Set sets the value for a key.
+// SetLocal sets the value for a key.
-func (n *Node) Set(k ID, v string) {
+// Returns false if the key is not owned by the node.
+func (n *Node) SetLocal(k ID, v string) bool {
 	n.mu.Lock()
 	defer n.mu.Unlock()
+	if n.localLocked(k) {
 		n.data[k] = v
+		return true
+	}
+	return false
 }
 
 // Peer is the ID and address of a node.