abi/fastly,configstore: protect valueBuf with a mutex

cee-dub · cee-dub · commit fbda32d65005 · 2024-06-21T13:54:16.000-07:00
diff --git a/configstore/configstore.go b/configstore/configstore.go
@@ -61,8 +61,8 @@ func Open(name string) (*Store, error) {
 	return &Store{d}, nil
 }
 
-// Has checks to see if the item exists in the config store, without allocating
-// any space to read it.
+// Has returns true if the key exists in the config store, without allocating
+// space to read a value.
 func (s *Store) Has(key string) (bool, error) {
 	if s == nil {
 		return false, ErrKeyNotFound
@@ -86,7 +86,7 @@ func (s *Store) Has(key string) (bool, error) {
 	return v, nil
 }
 
-// GetBytes returns the item in the config store with the given key, as a byte slice.
+// GetBytes returns the value in the config store for the given key, if it exists, as a byte slice.
 func (s *Store) GetBytes(key string) ([]byte, error) {
 	if s == nil {
 		return nil, ErrKeyNotFound
@@ -106,17 +106,14 @@ func (s *Store) GetBytes(key string) ([]byte, error) {
 			return nil, err
 		}
 	}
-	p := make([]byte, len(v))
-	copy(p, v)
-	return p, nil
+	return v, nil
 }
 
-// Get returns the item in the config store with the given key.
+// Get returns the value in the config store with the given key, if it exists.
 func (s *Store) Get(key string) (string, error) {
 	buf, err := s.GetBytes(key)
 	if err != nil {
 		return "", err
 	}
-
 	return string(buf), nil
 }
diff --git a/integration_tests/config_store/configstore.json b/integration_tests/config_store/configstore.json
@@ -1,6 +1,11 @@
 {
   "twitter": "https://twitter.com/fastly",
   "empty-value": "",
+  "concurrent 0": "0",
+  "concurrent 1": "11",
+  "concurrent 2": "222",
+  "concurrent 3": "3333",
+  "concurrent 4": "44444",
   "maximum-length-asciiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii-1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000-2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000": 
     "10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000070000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000900000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000030000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000060000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000007000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000090000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000050000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000009000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111110000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000070000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000900000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000030000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000060000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000007000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000090000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000050000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000009000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111110000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000070000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000900000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000030000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000060000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000007000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000090000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111",
   "ゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝゝ":
diff --git a/integration_tests/config_store/main_test.go b/integration_tests/config_store/main_test.go
@@ -6,7 +6,9 @@ package main
 
 import (
 	"bytes"
+	"strconv"
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/fastly/compute-sdk-go/configstore"
@@ -62,7 +64,8 @@ func TestConfigStore(t *testing.T) {
 		t.Errorf("Body = %q, want %q", got, want)
 	}
 
-	max, err := d.Get("maximum-length-asciiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii-1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000-2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")
+	maxKey := "maximum-length-asciiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii-1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000-2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+	max, err := d.Get(maxKey)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -83,3 +86,33 @@ func TestConfigStore(t *testing.T) {
 		t.Errorf("Body = %q, want %q", got, want)
 	}
 }
+
+func TestConfigStoreConcurrently(t *testing.T) {
+	d, err := configstore.Open("configstore")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var wg sync.WaitGroup
+	wg.Add(5)
+	var keys [5]string
+	var values [5][]byte
+	for i := 0; i < 5; i++ {
+		go func(i int) {
+			defer wg.Done()
+			var err error
+			keys[i] = "concurrent " + strconv.Itoa(i)
+			values[i], err = d.GetBytes(keys[i])
+			if err != nil {
+				t.Errorf("%d: GetBytes() error: %v", i, err)
+			}
+		}(i)
+	}
+	wg.Wait()
+	for i := 0; i < 5; i++ {
+		got := values[i]
+		want := bytes.Repeat([]byte{'0' + byte(i)}, i+1)
+		if !bytes.Equal(got, want) {
+			t.Errorf("%d: got: %q want: %q", i, got, want)
+		}
+	}
+}
diff --git a/internal/abi/fastly/hostcalls_guest.go b/internal/abi/fastly/hostcalls_guest.go
@@ -11,6 +11,7 @@ import (
 	"math"
 	"net"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/fastly/compute-sdk-go/internal/abi/prim"
@@ -2441,10 +2442,22 @@ func fastlyDictionaryOpen(
 // allows us to use valueBuf scratch space between the guest and host to avoid
 // allocations any larger than necessary, without locking.
 type Dictionary struct {
-	h        dictionaryHandle
-	valueBuf [dictionaryValueMaxLen]byte
+	h dictionaryHandle
+
+	mu       sync.Mutex // protects valueBuf
+	valueBuf [dictionaryMaxValueLen]byte
 }
 
+// Dictionaries are subject to very specific limitations: 255 character keys and 8000 character values, utf-8 encoded.
+// The current storage collation limits utf-8 representations to 3 bytes in length.
+// https://docs.fastly.com/en/guides/about-edge-dictionaries#limitations-and-considerations
+// https://dev.mysql.com/doc/refman/8.4/en/charset-unicode-utf8mb3.html
+// https://en.wikipedia.org/wiki/UTF-8#Encoding
+const (
+	dictionaryMaxKeyLen   = 255 * 3  // known maximum size for config store keys: 755 bytes, for 255 3-byte utf-8 encoded characters
+	dictionaryMaxValueLen = 8000 * 3 // known maximum size for config store values: 24,000 bytes, for 8000 3-byte utf-8 encoded characters
+)
+
 // OpenDictionary returns a reference to the named dictionary, if it exists.
 func OpenDictionary(name string) (*Dictionary, error) {
 	var d Dictionary
@@ -2481,13 +2494,18 @@ func fastlyDictionaryGet(
 	nWritten prim.Pointer[prim.Usize],
 ) FastlyStatus
 
-// Get the value for key, as a byte slice, if it exists.
-func (d *Dictionary) GetBytes(key string) ([]byte, error) {
-	keyBuffer := prim.NewReadBufferFromString(key).Wstring()
-	buf := prim.NewWriteBufferFromBytes(d.valueBuf[:])
+// Get the value for key, if it exists. The returned slice's backing array is
+// shared between multiple calls to getBytesUnlocked.
+func (d *Dictionary) getBytesUnlocked(key string) ([]byte, error) {
+	keyBuffer := prim.NewReadBufferFromString(key)
+	if keyBuffer.Len() > dictionaryMaxKeyLen {
+		return nil, FastlyStatusInval.toError()
+	}
+	buf := prim.NewWriteBufferFromBytes(d.valueBuf[:]) // fresh slice of backing array
+	keyStr := keyBuffer.Wstring()
 	status := fastlyDictionaryGet(
 		d.h,
-		keyBuffer.Data, keyBuffer.Len,
+		keyStr.Data, keyStr.Len,
 		prim.ToPointer(buf.Char8Pointer()), buf.Cap(),
 		prim.ToPointer(buf.NPointer()),
 	)
@@ -2497,17 +2515,21 @@ func (d *Dictionary) GetBytes(key string) ([]byte, error) {
 	return buf.AsBytes(), nil
 }
 
-// Get the value for key, if it exists.
-func (d *Dictionary) Get(key string) (string, error) {
-	buf, err := d.GetBytes(key)
+// GetBytes returns a slice of newly-allocated memory for the value
+// corresponding to key.
+func (d *Dictionary) GetBytes(key string) ([]byte, error) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	v, err := d.getBytesUnlocked(key)
 	if err != nil {
-		return "", err
+		return nil, err
 	}
-
-	return string(buf), nil
+	p := make([]byte, len(v))
+	copy(p, v)
+	return p, nil
 }
 
-// Has returns whether a value exists.
+// Has returns true if key is found.
 func (d *Dictionary) Has(key string) (bool, error) {
 	keyBuffer := prim.NewReadBufferFromString(key).Wstring()
 	var npointer prim.Usize = 0
diff --git a/internal/abi/fastly/types.go b/internal/abi/fastly/types.go
@@ -188,15 +188,6 @@ const (
 	ipBufLen  = 16  // known size for IP address buffers
 	dnsBufLen = 256 // known size for "DNS" values, enough to hold the longest possible hostname or domain name
 
-	// Dictionaries are subject to very specific limitations: 255 character keys and 8000 character values, utf-8 encoded.
-	// The current storage collation limits utf-8 representations to 3 bytes in length.
-	// https://docs.fastly.com/en/guides/about-edge-dictionaries#limitations-and-considerations
-	// https://dev.mysql.com/doc/refman/8.4/en/charset-unicode-utf8mb3.html
-	// https://en.wikipedia.org/wiki/UTF-8#Encoding
-	dictionaryMaxKeyLen        = 255 * 3  // known maximum size for config store keys: 755 bytes, for 255 3-byte utf-8 encoded characters
-	dictionaryValueASCIIMaxLen = 8000     // known for 8000 ASCII-range utf-8 encoded characters
-	dictionaryValueMaxLen      = 8000 * 3 // known maximum size for config store values: 24,000 bytes, for 8000 3-byte utf-8 encoded characters
-
 	DefaultSmallBufLen  = 128  // default size for "typically-small" values with variable sizes: HTTP methods, header names, tls protocol names, cipher suites
 	DefaultMediumBufLen = 1024 // default size for values between small and large, with variable sizes
 	DefaultLargeBufLen  = 8192 // default size for "typically-large" values with variable sizes; header values, URLs.

Original file line number	Diff line number	Diff line change
`@@ -61,8 +61,8 @@ func Open(name string) (*Store, error) {`
`61`	`61`	`return &Store{d}, nil`
`62`	`62`	`}`
`63`	`63`
`64`		`-// Has checks to see if the item exists in the config store, without allocating`
`65`		`-// any space to read it.`
	`64`	`+// Has returns true if the key exists in the config store, without allocating`
	`65`	`+// space to read a value.`
`66`	`66`	`func (s *Store) Has(key string) (bool, error) {`
`67`	`67`	`if s == nil {`
`68`	`68`	`return false, ErrKeyNotFound`
`@@ -86,7 +86,7 @@ func (s *Store) Has(key string) (bool, error) {`
`86`	`86`	`return v, nil`
`87`	`87`	`}`
`88`	`88`
`89`		`-// GetBytes returns the item in the config store with the given key, as a byte slice.`
	`89`	`+// GetBytes returns the value in the config store for the given key, if it exists, as a byte slice.`
`90`	`90`	`func (s *Store) GetBytes(key string) ([]byte, error) {`
`91`	`91`	`if s == nil {`
`92`	`92`	`return nil, ErrKeyNotFound`
`@@ -106,17 +106,14 @@ func (s *Store) GetBytes(key string) ([]byte, error) {`
`106`	`106`	`return nil, err`
`107`	`107`	`}`
`108`	`108`	`}`
`109`		`- p := make([]byte, len(v))`
`110`		`- copy(p, v)`
`111`		`- return p, nil`
	`109`	`+ return v, nil`
`112`	`110`	`}`
`113`	`111`
`114`		`-// Get returns the item in the config store with the given key.`
	`112`	`+// Get returns the value in the config store with the given key, if it exists.`
`115`	`113`	`func (s *Store) Get(key string) (string, error) {`
`116`	`114`	`buf, err := s.GetBytes(key)`
`117`	`115`	`if err != nil {`
`118`	`116`	`return "", err`
`119`	`117`	`}`
`120`		`-`
`121`	`118`	`return string(buf), nil`
`122`	`119`	`}`