From 157b276638d21ceed5a396a279ae3530f55ec7ef Mon Sep 17 00:00:00 2001
From: Paulo Zenida <paulo.zenida@olx.com>
Date: Wed, 16 Mar 2022 10:43:47 +0000
Subject: [PATCH 1/8] add support for methods using contexts

---
 .gitignore           |   1 +
 memcache/conn.go     |  37 ++++
 memcache/errors.go   |  46 ++++
 memcache/helpers.go  |  79 +++++++
 memcache/item.go     |  22 ++
 memcache/memcache.go | 516 +++++++++++++++++++------------------------
 memcache/selector.go |  11 +-
 7 files changed, 415 insertions(+), 297 deletions(-)
 create mode 100644 memcache/conn.go
 create mode 100644 memcache/errors.go
 create mode 100644 memcache/helpers.go
 create mode 100644 memcache/item.go

diff --git a/.gitignore b/.gitignore
index 02c604d7..b4a2d1c8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 _*
 *.out
 *~
+.idea
diff --git a/memcache/conn.go b/memcache/conn.go
new file mode 100644
index 00000000..1c6eb273
--- /dev/null
+++ b/memcache/conn.go
@@ -0,0 +1,37 @@
+package memcache
+
+import (
+	"bufio"
+	"net"
+	"time"
+)
+
+// conn is a connection to a server.
+type conn struct {
+	nc   net.Conn
+	rw   *bufio.ReadWriter
+	addr net.Addr
+	c    *Client
+}
+
+// release returns this connection back to the client's free pool
+func (cn *conn) release() {
+	cn.c.putFreeConn(cn.addr, cn)
+}
+
+func (cn *conn) extendDeadline() {
+	cn.nc.SetDeadline(time.Now().Add(cn.c.netTimeout()))
+}
+
+// condRelease releases this connection if the error pointed to by err
+// is nil (not an error) or is only a protocol level error (e.g. a
+// cache miss).  The purpose is to not recycle TCP connections that
+// are bad.
+func (cn *conn) condRelease(err *error) {
+	if *err == nil || resumableError(*err) {
+		cn.release()
+	} else {
+		cn.nc.Close()
+	}
+}
+
diff --git a/memcache/errors.go b/memcache/errors.go
new file mode 100644
index 00000000..eb8e4932
--- /dev/null
+++ b/memcache/errors.go
@@ -0,0 +1,46 @@
+package memcache
+
+import (
+	"errors"
+	"net"
+)
+
+var (
+	// ErrCacheMiss means that a Get failed because the item wasn't present.
+	ErrCacheMiss = errors.New("memcache: cache miss")
+
+	// ErrCASConflict means that a CompareAndSwap call failed due to the
+	// cached value being modified between the Get and the CompareAndSwap.
+	// If the cached value was simply evicted rather than replaced,
+	// ErrNotStored will be returned instead.
+	ErrCASConflict = errors.New("memcache: compare-and-swap conflict")
+
+	// ErrNotStored means that a conditional write operation (i.e. Add or
+	// CompareAndSwap) failed because the condition was not satisfied.
+	ErrNotStored = errors.New("memcache: item not stored")
+
+	// ErrServerError means that a server error occurred.
+	ErrServerError = errors.New("memcache: server error")
+
+	// ErrNoStats means that no statistics were available.
+	ErrNoStats = errors.New("memcache: no statistics available")
+
+	// ErrMalformedKey is returned when an invalid key is used.
+	// Keys must be at maximum 250 bytes long and not
+	// contain whitespace or control characters.
+	ErrMalformedKey = errors.New("malformed: key is too long or contains invalid characters")
+
+	// ErrNoServers is returned when no servers are configured or available.
+	ErrNoServers = errors.New("memcache: no servers configured or available")
+)
+
+// ConnectTimeoutError is the error type used when it takes
+// too long to connect to the desired host. This level of
+// detail can generally be ignored.
+type ConnectTimeoutError struct {
+	Addr net.Addr
+}
+
+func (cte *ConnectTimeoutError) Error() string {
+	return "memcache: connect timeout to " + cte.Addr.String()
+}
\ No newline at end of file
diff --git a/memcache/helpers.go b/memcache/helpers.go
new file mode 100644
index 00000000..46402cde
--- /dev/null
+++ b/memcache/helpers.go
@@ -0,0 +1,79 @@
+package memcache
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+)
+
+// resumableError returns true if err is only a protocol-level cache error.
+// This is used to determine whether or not a server connection should
+// be re-used or not. If an error occurs, by default we don't reuse the
+// connection, unless it was just a cache error.
+func resumableError(err error) bool {
+	switch err {
+	case ErrCacheMiss, ErrCASConflict, ErrNotStored, ErrMalformedKey:
+		return true
+	}
+	return false
+}
+
+func legalKey(key string) bool {
+	if len(key) > 250 {
+		return false
+	}
+	for i := 0; i < len(key); i++ {
+		if key[i] <= ' ' || key[i] == 0x7f {
+			return false
+		}
+	}
+	return true
+}
+
+// scanGetResponseLine populates it and returns the declared size of the item.
+// It does not read the bytes of the item.
+func scanGetResponseLine(line []byte, it *Item) (size int, err error) {
+	pattern := "VALUE %s %d %d %d\r\n"
+	dest := []interface{}{&it.Key, &it.Flags, &size, &it.casid}
+	if bytes.Count(line, space) == 3 {
+		pattern = "VALUE %s %d %d\r\n"
+		dest = dest[:3]
+	}
+	n, err := fmt.Sscanf(string(line), pattern, dest...)
+	if err != nil || n != len(dest) {
+		return -1, fmt.Errorf("memcache: unexpected line in get response: %q", line)
+	}
+	return size, nil
+}
+
+func writeReadLine(rw *bufio.ReadWriter, format string, args ...interface{}) ([]byte, error) {
+	_, err := fmt.Fprintf(rw, format, args...)
+	if err != nil {
+		return nil, err
+	}
+	if err := rw.Flush(); err != nil {
+		return nil, err
+	}
+	line, err := rw.ReadSlice('\n')
+	return line, err
+}
+
+func writeExpectf(rw *bufio.ReadWriter, expect []byte, format string, args ...interface{}) error {
+	line, err := writeReadLine(rw, format, args...)
+	if err != nil {
+		return err
+	}
+	switch {
+	case bytes.Equal(line, resultOK):
+		return nil
+	case bytes.Equal(line, expect):
+		return nil
+	case bytes.Equal(line, resultNotStored):
+		return ErrNotStored
+	case bytes.Equal(line, resultExists):
+		return ErrCASConflict
+	case bytes.Equal(line, resultNotFound):
+		return ErrCacheMiss
+	}
+	return fmt.Errorf("memcache: unexpected response line: %q", string(line))
+}
diff --git a/memcache/item.go b/memcache/item.go
new file mode 100644
index 00000000..69ec3cae
--- /dev/null
+++ b/memcache/item.go
@@ -0,0 +1,22 @@
+package memcache
+
+// Item is an item to be got or stored in a memcached server.
+type Item struct {
+	// Key is the Item's key (250 bytes maximum).
+	Key string
+
+	// Value is the Item's value.
+	Value []byte
+
+	// Flags are server-opaque flags whose semantics are entirely
+	// up to the app.
+	Flags uint32
+
+	// Expiration is the cache expiration time, in seconds: either a relative
+	// time from now (up to 1 month), or an absolute Unix epoch time.
+	// Zero means the Item has no expiration time.
+	Expiration int32
+
+	// Compare and swap ID.
+	casid uint64
+}
diff --git a/memcache/memcache.go b/memcache/memcache.go
index 28eccf03..4f94420a 100644
--- a/memcache/memcache.go
+++ b/memcache/memcache.go
@@ -20,6 +20,7 @@ package memcache
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -34,35 +35,6 @@ import (
 // Similar to:
 // https://godoc.org/google.golang.org/appengine/memcache
 
-var (
-	// ErrCacheMiss means that a Get failed because the item wasn't present.
-	ErrCacheMiss = errors.New("memcache: cache miss")
-
-	// ErrCASConflict means that a CompareAndSwap call failed due to the
-	// cached value being modified between the Get and the CompareAndSwap.
-	// If the cached value was simply evicted rather than replaced,
-	// ErrNotStored will be returned instead.
-	ErrCASConflict = errors.New("memcache: compare-and-swap conflict")
-
-	// ErrNotStored means that a conditional write operation (i.e. Add or
-	// CompareAndSwap) failed because the condition was not satisfied.
-	ErrNotStored = errors.New("memcache: item not stored")
-
-	// ErrServer means that a server error occurred.
-	ErrServerError = errors.New("memcache: server error")
-
-	// ErrNoStats means that no statistics were available.
-	ErrNoStats = errors.New("memcache: no statistics available")
-
-	// ErrMalformedKey is returned when an invalid key is used.
-	// Keys must be at maximum 250 bytes long and not
-	// contain whitespace or control characters.
-	ErrMalformedKey = errors.New("malformed: key is too long or contains invalid characters")
-
-	// ErrNoServers is returned when no servers are configured or available.
-	ErrNoServers = errors.New("memcache: no servers configured or available")
-)
-
 const (
 	// DefaultTimeout is the default socket read/write timeout.
 	DefaultTimeout = 100 * time.Millisecond
@@ -74,30 +46,6 @@ const (
 
 const buffered = 8 // arbitrary buffered channel size, for readability
 
-// resumableError returns true if err is only a protocol-level cache error.
-// This is used to determine whether or not a server connection should
-// be re-used or not. If an error occurs, by default we don't reuse the
-// connection, unless it was just a cache error.
-func resumableError(err error) bool {
-	switch err {
-	case ErrCacheMiss, ErrCASConflict, ErrNotStored, ErrMalformedKey:
-		return true
-	}
-	return false
-}
-
-func legalKey(key string) bool {
-	if len(key) > 250 {
-		return false
-	}
-	for i := 0; i < len(key); i++ {
-		if key[i] <= ' ' || key[i] == 0x7f {
-			return false
-		}
-	}
-	return true
-}
-
 var (
 	crlf            = []byte("\r\n")
 	space           = []byte(" ")
@@ -150,54 +98,233 @@ type Client struct {
 	freeconn map[string][]*conn
 }
 
-// Item is an item to be got or stored in a memcached server.
-type Item struct {
-	// Key is the Item's key (250 bytes maximum).
-	Key string
-
-	// Value is the Item's value.
-	Value []byte
+// FlushAll flushes all from all servers
+func (c *Client) FlushAll() error {
+	return c.FlushAllWithContext(context.Background())
+}
 
-	// Flags are server-opaque flags whose semantics are entirely
-	// up to the app.
-	Flags uint32
+// FlushAllWithContext flushes all from all servers
+func (c *Client) FlushAllWithContext(ctx context.Context) error {
+	return c.selector.Each(ctx, c.flushAllFromAddr)
+}
 
-	// Expiration is the cache expiration time, in seconds: either a relative
-	// time from now (up to 1 month), or an absolute Unix epoch time.
-	// Zero means the Item has no expiration time.
-	Expiration int32
+// Get gets the item for the given key. ErrCacheMiss is returned for a
+// memcache cache miss. The key must be at most 250 bytes in length.
+func (c *Client) Get(key string) (item *Item, err error) {
+	return c.GetWithContext(context.Background(), key)
+}
 
-	// Compare and swap ID.
-	casid uint64
+// GetWithContext gets the item for the given key. ErrCacheMiss is returned for a
+// memcache cache miss. The key must be at most 250 bytes in length.
+func (c *Client) GetWithContext(ctx context.Context, key string) (item *Item, err error) {
+	err = c.withKeyAddr(ctx, key, func(addr net.Addr) error {
+		return c.getFromAddr(addr, []string{key}, func(it *Item) { item = it })
+	})
+	if err == nil && item == nil {
+		err = ErrCacheMiss
+	}
+	return
 }
 
-// conn is a connection to a server.
-type conn struct {
-	nc   net.Conn
-	rw   *bufio.ReadWriter
-	addr net.Addr
-	c    *Client
+// Touch updates the expiry for the given key. The seconds parameter is either
+// a Unix timestamp or, if seconds is less than 1 month, the number of seconds
+// into the future at which time the item will expire. Zero means the item has
+// no expiration time. ErrCacheMiss is returned if the key is not in the cache.
+// The key must be at most 250 bytes in length.
+func (c *Client) Touch(key string, seconds int32) (err error) {
+	return c.TouchWithContext(context.Background(), key, seconds)
 }
 
-// release returns this connection back to the client's free pool
-func (cn *conn) release() {
-	cn.c.putFreeConn(cn.addr, cn)
+// TouchWithContext updates the expiry for the given key. The seconds parameter
+// is either a Unix timestamp or, if seconds is less than 1 month, the number of
+// seconds into the future at which time the item will expire. Zero means the item
+// has no expiration time. ErrCacheMiss is returned if the key is not in the cache.
+// The key must be at most 250 bytes in length.
+func (c *Client) TouchWithContext(ctx context.Context, key string, seconds int32) (err error) {
+	return c.withKeyAddr(ctx, key, func(addr net.Addr) error {
+		return c.touchFromAddr(addr, []string{key}, seconds)
+	})
 }
 
-func (cn *conn) extendDeadline() {
-	cn.nc.SetDeadline(time.Now().Add(cn.c.netTimeout()))
+// GetMulti is a batch version of Get. The returned map from keys to
+// items may have fewer elements than the input slice, due to memcache
+// cache misses. Each key must be at most 250 bytes in length.
+// If no error is returned, the returned map will also be non-nil.
+func (c *Client) GetMulti(keys []string) (map[string]*Item, error) {
+	return c.GetMultiWithContext(context.Background(), keys)
 }
 
-// condRelease releases this connection if the error pointed to by err
-// is nil (not an error) or is only a protocol level error (e.g. a
-// cache miss).  The purpose is to not recycle TCP connections that
-// are bad.
-func (cn *conn) condRelease(err *error) {
-	if *err == nil || resumableError(*err) {
-		cn.release()
-	} else {
-		cn.nc.Close()
+// GetMultiWithContext is a batch version of Get. The returned map from keys to
+// items may have fewer elements than the input slice, due to memcache
+// cache misses. Each key must be at most 250 bytes in length.
+// If no error is returned, the returned map will also be non-nil.
+func (c *Client) GetMultiWithContext(ctx context.Context, keys []string) (map[string]*Item, error) {
+	var lk sync.Mutex
+	m := make(map[string]*Item)
+	addItemToMap := func(it *Item) {
+		lk.Lock()
+		defer lk.Unlock()
+		m[it.Key] = it
+	}
+
+	keyMap := make(map[net.Addr][]string)
+	for _, key := range keys {
+		if !legalKey(key) {
+			return nil, ErrMalformedKey
+		}
+		addr, err := c.selector.PickServer(ctx, key)
+		if err != nil {
+			return nil, err
+		}
+		keyMap[addr] = append(keyMap[addr], key)
 	}
+
+	ch := make(chan error, buffered)
+	for addr, keys := range keyMap {
+		go func(addr net.Addr, keys []string) {
+			ch <- c.getFromAddr(addr, keys, addItemToMap)
+		}(addr, keys)
+	}
+
+	var err error
+	for _ = range keyMap {
+		if ge := <-ch; ge != nil {
+			err = ge
+		}
+	}
+	return m, err
+}
+
+// Set writes the given item, unconditionally.
+func (c *Client) Set(item *Item) error {
+	return c.SetWithContext(context.Background(), item)
+}
+
+// SetWithContext writes the given item, unconditionally.
+func (c *Client) SetWithContext(ctx context.Context, item *Item) error {
+	return c.onItem(ctx, item, (*Client).set)
+}
+
+// Add writes the given item, if no value already exists for its
+// key. ErrNotStored is returned if that condition is not met.
+func (c *Client) Add(item *Item) error {
+	return c.AddWithContext(context.Background(), item)
+}
+
+// AddWithContext writes the given item, if no value already exists for its
+// key. ErrNotStored is returned if that condition is not met.
+func (c *Client) AddWithContext(ctx context.Context, item *Item) error {
+	return c.onItem(ctx, item, (*Client).add)
+}
+
+// Replace writes the given item, but only if the server *does*
+// already hold data for this key
+func (c *Client) Replace(item *Item) error {
+	return c.ReplaceWithContext(context.Background(), item)
+}
+
+// ReplaceWithContext writes the given item, but only if the server *does*
+// already hold data for this key
+func (c *Client) ReplaceWithContext(ctx context.Context, item *Item) error {
+	return c.onItem(ctx, item, (*Client).replace)
+}
+
+// CompareAndSwap writes the given item that was previously returned
+// by Get, if the value was neither modified or evicted between the
+// Get and the CompareAndSwap calls. The item's Key should not change
+// between calls but all other item fields may differ. ErrCASConflict
+// is returned if the value was modified in between the
+// calls. ErrNotStored is returned if the value was evicted in between
+// the calls.
+func (c *Client) CompareAndSwap(item *Item) error {
+	return c.CompareAndSwapWithContext(context.Background(), item)
+}
+
+// CompareAndSwapWithContext writes the given item that was previously returned
+// by Get, if the value was neither modified or evicted between the
+// Get and the CompareAndSwap calls. The item's Key should not change
+// between calls but all other item fields may differ. ErrCASConflict
+// is returned if the value was modified in between the
+// calls. ErrNotStored is returned if the value was evicted in between
+// the calls.
+func (c *Client) CompareAndSwapWithContext(ctx context.Context, item *Item) error {
+	return c.onItem(ctx, item, (*Client).cas)
+}
+
+// Delete deletes the item with the provided key. The error ErrCacheMiss is
+// returned if the item didn't already exist in the cache.
+func (c *Client) Delete(key string) error {
+	return c.DeleteWithContext(context.Background(), key)
+}
+
+// DeleteWithContext deletes the item with the provided key. The error ErrCacheMiss is
+// returned if the item didn't already exist in the cache.
+func (c *Client) DeleteWithContext(ctx context.Context, key string) error {
+	return c.withKeyRw(ctx, key, func(rw *bufio.ReadWriter) error {
+		return writeExpectf(rw, resultDeleted, "delete %s\r\n", key)
+	})
+}
+
+// DeleteAll deletes all items in the cache.
+func (c *Client) DeleteAll() error {
+	return c.DeleteAllWithContext(context.Background())
+}
+
+// DeleteAllWithContext deletes all items in the cache.
+func (c *Client) DeleteAllWithContext(ctx context.Context) error {
+	return c.withKeyRw(ctx, "", func(rw *bufio.ReadWriter) error {
+		return writeExpectf(rw, resultDeleted, "flush_all\r\n")
+	})
+}
+
+// Ping checks all instances if they are alive. Returns error if any
+// of them is down.
+func (c *Client) Ping() error {
+	return c.PingWithContext(context.Background())
+}
+
+// PingWithContext checks all instances if they are alive. Returns error if any
+// of them is down.
+func (c *Client) PingWithContext(ctx context.Context) error {
+	return c.selector.Each(ctx, c.ping)
+}
+
+// Increment atomically increments key by delta. The return value is
+// the new value after being incremented or an error. If the value
+// didn't exist in memcached the error is ErrCacheMiss. The value in
+// memcached must be an decimal number, or an error will be returned.
+// On 64-bit overflow, the new value wraps around.
+func (c *Client) Increment(key string, delta uint64) (newValue uint64, err error) {
+	return c.IncrementWithContext(context.Background(), key, delta)
+}
+
+// IncrementWithContext atomically increments key by delta. The return value is
+// the new value after being incremented or an error. If the value
+// didn't exist in memcached the error is ErrCacheMiss. The value in
+// memcached must be an decimal number, or an error will be returned.
+// On 64-bit overflow, the new value wraps around.
+func (c *Client) IncrementWithContext(ctx context.Context, key string, delta uint64) (newValue uint64, err error) {
+	return c.incrDecr(ctx, "incr", key, delta)
+}
+
+// Decrement atomically decrements key by delta. The return value is
+// the new value after being decremented or an error. If the value
+// didn't exist in memcached the error is ErrCacheMiss. The value in
+// memcached must be an decimal number, or an error will be returned.
+// On underflow, the new value is capped at zero and does not wrap
+// around.
+func (c *Client) Decrement(key string, delta uint64) (newValue uint64, err error) {
+	return c.DecrementWithContext(context.Background(), key, delta)
+}
+
+// DecrementWithContext atomically decrements key by delta. The return value is
+// the new value after being decremented or an error. If the value
+// didn't exist in memcached the error is ErrCacheMiss. The value in
+// memcached must be an decimal number, or an error will be returned.
+// On underflow, the new value is capped at zero and does not wrap
+// around.
+func (c *Client) DecrementWithContext(ctx context.Context, key string, delta uint64) (newValue uint64, err error) {
+	return c.incrDecr(ctx, "decr", key, delta)
 }
 
 func (c *Client) putFreeConn(addr net.Addr, cn *conn) {
@@ -243,17 +370,6 @@ func (c *Client) maxIdleConns() int {
 	return DefaultMaxIdleConns
 }
 
-// ConnectTimeoutError is the error type used when it takes
-// too long to connect to the desired host. This level of
-// detail can generally be ignored.
-type ConnectTimeoutError struct {
-	Addr net.Addr
-}
-
-func (cte *ConnectTimeoutError) Error() string {
-	return "memcache: connect timeout to " + cte.Addr.String()
-}
-
 func (c *Client) dial(addr net.Addr) (net.Conn, error) {
 	nc, err := net.DialTimeout(addr.Network(), addr.String(), c.netTimeout())
 	if err == nil {
@@ -287,8 +403,8 @@ func (c *Client) getConn(addr net.Addr) (*conn, error) {
 	return cn, nil
 }
 
-func (c *Client) onItem(item *Item, fn func(*Client, *bufio.ReadWriter, *Item) error) error {
-	addr, err := c.selector.PickServer(item.Key)
+func (c *Client) onItem(ctx context.Context, item *Item, fn func(*Client, *bufio.ReadWriter, *Item) error) error {
+	addr, err := c.selector.PickServer(ctx, item.Key)
 	if err != nil {
 		return err
 	}
@@ -303,38 +419,11 @@ func (c *Client) onItem(item *Item, fn func(*Client, *bufio.ReadWriter, *Item) e
 	return nil
 }
 
-func (c *Client) FlushAll() error {
-	return c.selector.Each(c.flushAllFromAddr)
-}
-
-// Get gets the item for the given key. ErrCacheMiss is returned for a
-// memcache cache miss. The key must be at most 250 bytes in length.
-func (c *Client) Get(key string) (item *Item, err error) {
-	err = c.withKeyAddr(key, func(addr net.Addr) error {
-		return c.getFromAddr(addr, []string{key}, func(it *Item) { item = it })
-	})
-	if err == nil && item == nil {
-		err = ErrCacheMiss
-	}
-	return
-}
-
-// Touch updates the expiry for the given key. The seconds parameter is either
-// a Unix timestamp or, if seconds is less than 1 month, the number of seconds
-// into the future at which time the item will expire. Zero means the item has
-// no expiration time. ErrCacheMiss is returned if the key is not in the cache.
-// The key must be at most 250 bytes in length.
-func (c *Client) Touch(key string, seconds int32) (err error) {
-	return c.withKeyAddr(key, func(addr net.Addr) error {
-		return c.touchFromAddr(addr, []string{key}, seconds)
-	})
-}
-
-func (c *Client) withKeyAddr(key string, fn func(net.Addr) error) (err error) {
+func (c *Client) withKeyAddr(ctx context.Context, key string, fn func(net.Addr) error) (err error) {
 	if !legalKey(key) {
 		return ErrMalformedKey
 	}
-	addr, err := c.selector.PickServer(key)
+	addr, err := c.selector.PickServer(ctx, key)
 	if err != nil {
 		return err
 	}
@@ -350,8 +439,8 @@ func (c *Client) withAddrRw(addr net.Addr, fn func(*bufio.ReadWriter) error) (er
 	return fn(cn.rw)
 }
 
-func (c *Client) withKeyRw(key string, fn func(*bufio.ReadWriter) error) error {
-	return c.withKeyAddr(key, func(addr net.Addr) error {
+func (c *Client) withKeyRw(ctx context.Context, key string, fn func(*bufio.ReadWriter) error) error {
+	return c.withKeyAddr(ctx, key, func(addr net.Addr) error {
 		return c.withAddrRw(addr, fn)
 	})
 }
@@ -444,47 +533,6 @@ func (c *Client) touchFromAddr(addr net.Addr, keys []string, expiration int32) e
 	})
 }
 
-// GetMulti is a batch version of Get. The returned map from keys to
-// items may have fewer elements than the input slice, due to memcache
-// cache misses. Each key must be at most 250 bytes in length.
-// If no error is returned, the returned map will also be non-nil.
-func (c *Client) GetMulti(keys []string) (map[string]*Item, error) {
-	var lk sync.Mutex
-	m := make(map[string]*Item)
-	addItemToMap := func(it *Item) {
-		lk.Lock()
-		defer lk.Unlock()
-		m[it.Key] = it
-	}
-
-	keyMap := make(map[net.Addr][]string)
-	for _, key := range keys {
-		if !legalKey(key) {
-			return nil, ErrMalformedKey
-		}
-		addr, err := c.selector.PickServer(key)
-		if err != nil {
-			return nil, err
-		}
-		keyMap[addr] = append(keyMap[addr], key)
-	}
-
-	ch := make(chan error, buffered)
-	for addr, keys := range keyMap {
-		go func(addr net.Addr, keys []string) {
-			ch <- c.getFromAddr(addr, keys, addItemToMap)
-		}(addr, keys)
-	}
-
-	var err error
-	for _ = range keyMap {
-		if ge := <-ch; ge != nil {
-			err = ge
-		}
-	}
-	return m, err
-}
-
 // parseGetResponse reads a GET response from r and calls cb for each
 // read and allocated Item
 func parseGetResponse(r *bufio.Reader, cb func(*Item)) error {
@@ -516,62 +564,18 @@ func parseGetResponse(r *bufio.Reader, cb func(*Item)) error {
 	}
 }
 
-// scanGetResponseLine populates it and returns the declared size of the item.
-// It does not read the bytes of the item.
-func scanGetResponseLine(line []byte, it *Item) (size int, err error) {
-	pattern := "VALUE %s %d %d %d\r\n"
-	dest := []interface{}{&it.Key, &it.Flags, &size, &it.casid}
-	if bytes.Count(line, space) == 3 {
-		pattern = "VALUE %s %d %d\r\n"
-		dest = dest[:3]
-	}
-	n, err := fmt.Sscanf(string(line), pattern, dest...)
-	if err != nil || n != len(dest) {
-		return -1, fmt.Errorf("memcache: unexpected line in get response: %q", line)
-	}
-	return size, nil
-}
-
-// Set writes the given item, unconditionally.
-func (c *Client) Set(item *Item) error {
-	return c.onItem(item, (*Client).set)
-}
-
 func (c *Client) set(rw *bufio.ReadWriter, item *Item) error {
 	return c.populateOne(rw, "set", item)
 }
 
-// Add writes the given item, if no value already exists for its
-// key. ErrNotStored is returned if that condition is not met.
-func (c *Client) Add(item *Item) error {
-	return c.onItem(item, (*Client).add)
-}
-
 func (c *Client) add(rw *bufio.ReadWriter, item *Item) error {
 	return c.populateOne(rw, "add", item)
 }
 
-// Replace writes the given item, but only if the server *does*
-// already hold data for this key
-func (c *Client) Replace(item *Item) error {
-	return c.onItem(item, (*Client).replace)
-}
-
 func (c *Client) replace(rw *bufio.ReadWriter, item *Item) error {
 	return c.populateOne(rw, "replace", item)
 }
 
-// CompareAndSwap writes the given item that was previously returned
-// by Get, if the value was neither modified or evicted between the
-// Get and the CompareAndSwap calls. The item's Key should not change
-// between calls but all other item fields may differ. ErrCASConflict
-// is returned if the value was modified in between the
-// calls. ErrNotStored is returned if the value was evicted in between
-// the calls.
-func (c *Client) CompareAndSwap(item *Item) error {
-	return c.onItem(item, (*Client).cas)
-}
-
 func (c *Client) cas(rw *bufio.ReadWriter, item *Item) error {
 	return c.populateOne(rw, "cas", item)
 }
@@ -617,81 +621,9 @@ func (c *Client) populateOne(rw *bufio.ReadWriter, verb string, item *Item) erro
 	return fmt.Errorf("memcache: unexpected response line from %q: %q", verb, string(line))
 }
 
-func writeReadLine(rw *bufio.ReadWriter, format string, args ...interface{}) ([]byte, error) {
-	_, err := fmt.Fprintf(rw, format, args...)
-	if err != nil {
-		return nil, err
-	}
-	if err := rw.Flush(); err != nil {
-		return nil, err
-	}
-	line, err := rw.ReadSlice('\n')
-	return line, err
-}
-
-func writeExpectf(rw *bufio.ReadWriter, expect []byte, format string, args ...interface{}) error {
-	line, err := writeReadLine(rw, format, args...)
-	if err != nil {
-		return err
-	}
-	switch {
-	case bytes.Equal(line, resultOK):
-		return nil
-	case bytes.Equal(line, expect):
-		return nil
-	case bytes.Equal(line, resultNotStored):
-		return ErrNotStored
-	case bytes.Equal(line, resultExists):
-		return ErrCASConflict
-	case bytes.Equal(line, resultNotFound):
-		return ErrCacheMiss
-	}
-	return fmt.Errorf("memcache: unexpected response line: %q", string(line))
-}
-
-// Delete deletes the item with the provided key. The error ErrCacheMiss is
-// returned if the item didn't already exist in the cache.
-func (c *Client) Delete(key string) error {
-	return c.withKeyRw(key, func(rw *bufio.ReadWriter) error {
-		return writeExpectf(rw, resultDeleted, "delete %s\r\n", key)
-	})
-}
-
-// DeleteAll deletes all items in the cache.
-func (c *Client) DeleteAll() error {
-	return c.withKeyRw("", func(rw *bufio.ReadWriter) error {
-		return writeExpectf(rw, resultDeleted, "flush_all\r\n")
-	})
-}
-
-// Ping checks all instances if they are alive. Returns error if any
-// of them is down.
-func (c *Client) Ping() error {
-	return c.selector.Each(c.ping)
-}
-
-// Increment atomically increments key by delta. The return value is
-// the new value after being incremented or an error. If the value
-// didn't exist in memcached the error is ErrCacheMiss. The value in
-// memcached must be an decimal number, or an error will be returned.
-// On 64-bit overflow, the new value wraps around.
-func (c *Client) Increment(key string, delta uint64) (newValue uint64, err error) {
-	return c.incrDecr("incr", key, delta)
-}
-
-// Decrement atomically decrements key by delta. The return value is
-// the new value after being decremented or an error. If the value
-// didn't exist in memcached the error is ErrCacheMiss. The value in
-// memcached must be an decimal number, or an error will be returned.
-// On underflow, the new value is capped at zero and does not wrap
-// around.
-func (c *Client) Decrement(key string, delta uint64) (newValue uint64, err error) {
-	return c.incrDecr("decr", key, delta)
-}
-
-func (c *Client) incrDecr(verb, key string, delta uint64) (uint64, error) {
+func (c *Client) incrDecr(ctx context.Context, verb, key string, delta uint64) (uint64, error) {
 	var val uint64
-	err := c.withKeyRw(key, func(rw *bufio.ReadWriter) error {
+	err := c.withKeyRw(ctx, key, func(rw *bufio.ReadWriter) error {
 		line, err := writeReadLine(rw, "%s %s %d\r\n", verb, key, delta)
 		if err != nil {
 			return err
diff --git a/memcache/selector.go b/memcache/selector.go
index 89ad81e0..e1337268 100644
--- a/memcache/selector.go
+++ b/memcache/selector.go
@@ -17,6 +17,7 @@ limitations under the License.
 package memcache
 
 import (
+	"context"
 	"hash/crc32"
 	"net"
 	"strings"
@@ -31,8 +32,8 @@ import (
 type ServerSelector interface {
 	// PickServer returns the server address that a given item
 	// should be shared onto.
-	PickServer(key string) (net.Addr, error)
-	Each(func(net.Addr) error) error
+	PickServer(ctx context.Context, key string) (net.Addr, error)
+	Each(ctx context.Context, fn func(net.Addr) error) error
 }
 
 // ServerList is a simple ServerSelector. Its zero value is usable.
@@ -90,11 +91,11 @@ func (ss *ServerList) SetServers(servers ...string) error {
 }
 
 // Each iterates over each server calling the given function
-func (ss *ServerList) Each(f func(net.Addr) error) error {
+func (ss *ServerList) Each(_ context.Context, fn func(net.Addr) error) error {
 	ss.mu.RLock()
 	defer ss.mu.RUnlock()
 	for _, a := range ss.addrs {
-		if err := f(a); nil != err {
+		if err := fn(a); nil != err {
 			return err
 		}
 	}
@@ -111,7 +112,7 @@ var keyBufPool = sync.Pool{
 	},
 }
 
-func (ss *ServerList) PickServer(key string) (net.Addr, error) {
+func (ss *ServerList) PickServer(_ context.Context, key string) (net.Addr, error) {
 	ss.mu.RLock()
 	defer ss.mu.RUnlock()
 	if len(ss.addrs) == 0 {

From 2a9ae78f6674b40b20f4c4057620ac6ae5825744 Mon Sep 17 00:00:00 2001
From: Paulo Zenida <paulo.zenida@olx.com>
Date: Wed, 16 Mar 2022 10:50:24 +0000
Subject: [PATCH 2/8] update go.mod

---
 go.mod | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/go.mod b/go.mod
index 0d0eed2c..f7f4a483 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
-module github.com/bradfitz/gomemcache
+module github.com/paulo.zenida/gomemcache
 
-go 1.12
+go 1.17

From bef8c2afe5041c91326697d6f50e4a63e45d5a8f Mon Sep 17 00:00:00 2001
From: Paulo Zenida <paulo.zenida@olx.com>
Date: Wed, 16 Mar 2022 10:53:58 +0000
Subject: [PATCH 3/8] update go.mod

---
 go.mod | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/go.mod b/go.mod
index f7f4a483..c74c12b6 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
-module github.com/paulo.zenida/gomemcache
+module github.com/paulozenida/gomemcache
 
 go 1.17

From 88ab6197902148dcf3c2cebd645b502c2fce2f99 Mon Sep 17 00:00:00 2001
From: Paulo Zenida <paulo.zenida@olx.com>
Date: Wed, 16 Mar 2022 17:35:39 +0000
Subject: [PATCH 4/8] update readme

---
 README.md | 36 +-----------------------------------
 1 file changed, 1 insertion(+), 35 deletions(-)

diff --git a/README.md b/README.md
index f987363c..01020dae 100644
--- a/README.md
+++ b/README.md
@@ -1,37 +1,3 @@
 ## About
 
-This is a memcache client library for the Go programming language
-(http://golang.org/).
-
-## Installing
-
-### Using *go get*
-
-    $ go get github.com/bradfitz/gomemcache/memcache
-
-After this command *gomemcache* is ready to use. Its source will be in:
-
-    $GOPATH/src/github.com/bradfitz/gomemcache/memcache
-
-## Example
-
-    import (
-            "github.com/bradfitz/gomemcache/memcache"
-    )
-
-    func main() {
-         mc := memcache.New("10.0.0.1:11211", "10.0.0.2:11211", "10.0.0.3:11212")
-         mc.Set(&memcache.Item{Key: "foo", Value: []byte("my value")})
-
-         it, err := mc.Get("foo")
-         ...
-    }
-
-## Full docs, see:
-
-See https://godoc.org/github.com/bradfitz/gomemcache/memcache
-
-Or run:
-
-    $ godoc github.com/bradfitz/gomemcache/memcache
-
+This is a fork from github.com/bradfitz/gomemcache.

From 761568a9e16a14df0a625095c714cc4abf9d967f Mon Sep 17 00:00:00 2001
From: Paulo Zenida <paulo.zenida@olx.com>
Date: Thu, 17 Mar 2022 12:00:39 +0000
Subject: [PATCH 5/8] update readme and go.mod for upstream fork

---
 README.md | 36 +++++++++++++++++++++++++++++++++++-
 go.mod    |  4 ++--
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 01020dae..f987363c 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,37 @@
 ## About
 
-This is a fork from github.com/bradfitz/gomemcache.
+This is a memcache client library for the Go programming language
+(http://golang.org/).
+
+## Installing
+
+### Using *go get*
+
+    $ go get github.com/bradfitz/gomemcache/memcache
+
+After this command *gomemcache* is ready to use. Its source will be in:
+
+    $GOPATH/src/github.com/bradfitz/gomemcache/memcache
+
+## Example
+
+    import (
+            "github.com/bradfitz/gomemcache/memcache"
+    )
+
+    func main() {
+         mc := memcache.New("10.0.0.1:11211", "10.0.0.2:11211", "10.0.0.3:11212")
+         mc.Set(&memcache.Item{Key: "foo", Value: []byte("my value")})
+
+         it, err := mc.Get("foo")
+         ...
+    }
+
+## Full docs, see:
+
+See https://godoc.org/github.com/bradfitz/gomemcache/memcache
+
+Or run:
+
+    $ godoc github.com/bradfitz/gomemcache/memcache
+
diff --git a/go.mod b/go.mod
index c74c12b6..0d0eed2c 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
-module github.com/paulozenida/gomemcache
+module github.com/bradfitz/gomemcache
 
-go 1.17
+go 1.12

From c35fade5485eb7680a42f65d685cfd5303b7cc8e Mon Sep 17 00:00:00 2001
From: Paulo Zenida <paulo.zenida@olx.com>
Date: Thu, 17 Mar 2022 12:05:39 +0000
Subject: [PATCH 6/8] fix tests

---
 memcache/memcache_test.go | 3 ++-
 memcache/selector_test.go | 7 +++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/memcache/memcache_test.go b/memcache/memcache_test.go
index b94a30ca..f0077f90 100644
--- a/memcache/memcache_test.go
+++ b/memcache/memcache_test.go
@@ -19,6 +19,7 @@ package memcache
 
 import (
 	"bufio"
+	"context"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -287,6 +288,6 @@ func BenchmarkOnItem(b *testing.B) {
 	dummyFn := func(_ *Client, _ *bufio.ReadWriter, _ *Item) error { return nil }
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		c.onItem(&item, dummyFn)
+		c.onItem(context.Background(), &item, dummyFn)
 	}
 }
diff --git a/memcache/selector_test.go b/memcache/selector_test.go
index 65a2c4dd..4241d560 100644
--- a/memcache/selector_test.go
+++ b/memcache/selector_test.go
@@ -16,7 +16,10 @@ limitations under the License.
 
 package memcache
 
-import "testing"
+import (
+	"context"
+	"testing"
+)
 
 func BenchmarkPickServer(b *testing.B) {
 	// at least two to avoid 0 and 1 special cases:
@@ -32,7 +35,7 @@ func benchPickServer(b *testing.B, servers ...string) {
 	var ss ServerList
 	ss.SetServers(servers...)
 	for i := 0; i < b.N; i++ {
-		if _, err := ss.PickServer("some key"); err != nil {
+		if _, err := ss.PickServer(context.Background(), "some key"); err != nil {
 			b.Fatal(err)
 		}
 	}

From 4269599f33e989e3c151debfda177c3aa6a7f4f5 Mon Sep 17 00:00:00 2001
From: Paulo Zenida <paulo.zenida@olx.com>
Date: Thu, 17 Mar 2022 12:26:48 +0000
Subject: [PATCH 7/8] passing context to the connection method as well

---
 memcache/memcache.go | 39 +++++++++++++++++++++++----------------
 memcache/selector.go |  6 +++---
 2 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/memcache/memcache.go b/memcache/memcache.go
index 4f94420a..8b6f8e3b 100644
--- a/memcache/memcache.go
+++ b/memcache/memcache.go
@@ -118,7 +118,7 @@ func (c *Client) Get(key string) (item *Item, err error) {
 // memcache cache miss. The key must be at most 250 bytes in length.
 func (c *Client) GetWithContext(ctx context.Context, key string) (item *Item, err error) {
 	err = c.withKeyAddr(ctx, key, func(addr net.Addr) error {
-		return c.getFromAddr(addr, []string{key}, func(it *Item) { item = it })
+		return c.getFromAddr(ctx, addr, []string{key}, func(it *Item) { item = it })
 	})
 	if err == nil && item == nil {
 		err = ErrCacheMiss
@@ -142,7 +142,7 @@ func (c *Client) Touch(key string, seconds int32) (err error) {
 // The key must be at most 250 bytes in length.
 func (c *Client) TouchWithContext(ctx context.Context, key string, seconds int32) (err error) {
 	return c.withKeyAddr(ctx, key, func(addr net.Addr) error {
-		return c.touchFromAddr(addr, []string{key}, seconds)
+		return c.touchFromAddr(ctx, addr, []string{key}, seconds)
 	})
 }
 
@@ -182,7 +182,7 @@ func (c *Client) GetMultiWithContext(ctx context.Context, keys []string) (map[st
 	ch := make(chan error, buffered)
 	for addr, keys := range keyMap {
 		go func(addr net.Addr, keys []string) {
-			ch <- c.getFromAddr(addr, keys, addItemToMap)
+			ch <- c.getFromAddr(ctx, addr, keys, addItemToMap)
 		}(addr, keys)
 	}
 
@@ -383,7 +383,14 @@ func (c *Client) dial(addr net.Addr) (net.Conn, error) {
 	return nil, err
 }
 
-func (c *Client) getConn(addr net.Addr) (*conn, error) {
+func (c *Client) getConn(ctx context.Context, addr net.Addr) (*conn, error) {
+	// Check if the context is expired.
+	select {
+	default:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+
 	cn, ok := c.getFreeConn(addr)
 	if ok {
 		cn.extendDeadline()
@@ -408,7 +415,7 @@ func (c *Client) onItem(ctx context.Context, item *Item, fn func(*Client, *bufio
 	if err != nil {
 		return err
 	}
-	cn, err := c.getConn(addr)
+	cn, err := c.getConn(ctx, addr)
 	if err != nil {
 		return err
 	}
@@ -430,8 +437,8 @@ func (c *Client) withKeyAddr(ctx context.Context, key string, fn func(net.Addr)
 	return fn(addr)
 }
 
-func (c *Client) withAddrRw(addr net.Addr, fn func(*bufio.ReadWriter) error) (err error) {
-	cn, err := c.getConn(addr)
+func (c *Client) withAddrRw(ctx context.Context, addr net.Addr, fn func(*bufio.ReadWriter) error) (err error) {
+	cn, err := c.getConn(ctx, addr)
 	if err != nil {
 		return err
 	}
@@ -441,12 +448,12 @@ func (c *Client) withAddrRw(addr net.Addr, fn func(*bufio.ReadWriter) error) (er
 
 func (c *Client) withKeyRw(ctx context.Context, key string, fn func(*bufio.ReadWriter) error) error {
 	return c.withKeyAddr(ctx, key, func(addr net.Addr) error {
-		return c.withAddrRw(addr, fn)
+		return c.withAddrRw(ctx, addr, fn)
 	})
 }
 
-func (c *Client) getFromAddr(addr net.Addr, keys []string, cb func(*Item)) error {
-	return c.withAddrRw(addr, func(rw *bufio.ReadWriter) error {
+func (c *Client) getFromAddr(ctx context.Context, addr net.Addr, keys []string, cb func(*Item)) error {
+	return c.withAddrRw(ctx, addr, func(rw *bufio.ReadWriter) error {
 		if _, err := fmt.Fprintf(rw, "gets %s\r\n", strings.Join(keys, " ")); err != nil {
 			return err
 		}
@@ -461,8 +468,8 @@ func (c *Client) getFromAddr(addr net.Addr, keys []string, cb func(*Item)) error
 }
 
 // flushAllFromAddr send the flush_all command to the given addr
-func (c *Client) flushAllFromAddr(addr net.Addr) error {
-	return c.withAddrRw(addr, func(rw *bufio.ReadWriter) error {
+func (c *Client) flushAllFromAddr(ctx context.Context, addr net.Addr) error {
+	return c.withAddrRw(ctx, addr, func(rw *bufio.ReadWriter) error {
 		if _, err := fmt.Fprintf(rw, "flush_all\r\n"); err != nil {
 			return err
 		}
@@ -484,8 +491,8 @@ func (c *Client) flushAllFromAddr(addr net.Addr) error {
 }
 
 // ping sends the version command to the given addr
-func (c *Client) ping(addr net.Addr) error {
-	return c.withAddrRw(addr, func(rw *bufio.ReadWriter) error {
+func (c *Client) ping(ctx context.Context, addr net.Addr) error {
+	return c.withAddrRw(ctx, addr, func(rw *bufio.ReadWriter) error {
 		if _, err := fmt.Fprintf(rw, "version\r\n"); err != nil {
 			return err
 		}
@@ -507,8 +514,8 @@ func (c *Client) ping(addr net.Addr) error {
 	})
 }
 
-func (c *Client) touchFromAddr(addr net.Addr, keys []string, expiration int32) error {
-	return c.withAddrRw(addr, func(rw *bufio.ReadWriter) error {
+func (c *Client) touchFromAddr(ctx context.Context, addr net.Addr, keys []string, expiration int32) error {
+	return c.withAddrRw(ctx, addr, func(rw *bufio.ReadWriter) error {
 		for _, key := range keys {
 			if _, err := fmt.Fprintf(rw, "touch %s %d\r\n", key, expiration); err != nil {
 				return err
diff --git a/memcache/selector.go b/memcache/selector.go
index e1337268..47ded8fa 100644
--- a/memcache/selector.go
+++ b/memcache/selector.go
@@ -33,7 +33,7 @@ type ServerSelector interface {
 	// PickServer returns the server address that a given item
 	// should be shared onto.
 	PickServer(ctx context.Context, key string) (net.Addr, error)
-	Each(ctx context.Context, fn func(net.Addr) error) error
+	Each(ctx context.Context, fn func(context.Context, net.Addr) error) error
 }
 
 // ServerList is a simple ServerSelector. Its zero value is usable.
@@ -91,11 +91,11 @@ func (ss *ServerList) SetServers(servers ...string) error {
 }
 
 // Each iterates over each server calling the given function
-func (ss *ServerList) Each(_ context.Context, fn func(net.Addr) error) error {
+func (ss *ServerList) Each(ctx context.Context, fn func(context.Context, net.Addr) error) error {
 	ss.mu.RLock()
 	defer ss.mu.RUnlock()
 	for _, a := range ss.addrs {
-		if err := fn(a); nil != err {
+		if err := fn(ctx, a); nil != err {
 			return err
 		}
 	}

From 923d02dad59d0878ebddf2d067d40f883999bd54 Mon Sep 17 00:00:00 2001
From: Paulo Zenida <paulo.zenida@olx.com>
Date: Thu, 17 Mar 2022 12:28:43 +0000
Subject: [PATCH 8/8] update unit test

---
 memcache/memcache_test.go | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/memcache/memcache_test.go b/memcache/memcache_test.go
index f0077f90..47a0d36e 100644
--- a/memcache/memcache_test.go
+++ b/memcache/memcache_test.go
@@ -278,9 +278,10 @@ func BenchmarkOnItem(b *testing.B) {
 		}
 	}()
 
+	ctx := context.Background()
 	addr := fakeServer.Addr()
 	c := New(addr.String())
-	if _, err := c.getConn(addr); err != nil {
+	if _, err := c.getConn(ctx, addr); err != nil {
 		b.Fatal("failed to initialize connection to fake server")
 	}
 
@@ -288,6 +289,6 @@ func BenchmarkOnItem(b *testing.B) {
 	dummyFn := func(_ *Client, _ *bufio.ReadWriter, _ *Item) error { return nil }
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		c.onItem(context.Background(), &item, dummyFn)
+		c.onItem(ctx, &item, dummyFn)
 	}
 }