Scope: minimize the number of gets

.github/workflows/php.yml

@@ -26,7 +26,7 @@ jobs:
             compiler: jit
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
     - name: Install libmemcached
       run: sudo apt-get install -y libmemcached-dev
@@ -48,7 +48,7 @@ jobs:
 
     - name: Cache Composer packages
       id: composer-cache
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: vendor
         key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}

library/iFixit/Matryoshka/Scope.php

@@ -21,14 +21,20 @@ public function getPrefix() {
       return $this->scopePrefix ?: $this->getScopePrefix();
    }
 
-   public function getScopePrefix(bool $reset = false) {
+   public function getScopePrefix(bool $reset = false, bool $generateOnMiss = true) {
       if ($this->scopePrefix === null || $reset) {
-         $scopeValue = $this->backend->getAndSet($this->getScopeKey(),
-          function() {
-            return substr(md5(microtime() . $this->scopeName), 0, 16);
-         }, 0, $reset);
-
-         $this->scopePrefix = "{$scopeValue}-";
+         $scopeValue = $reset ? self::MISS : $this->backend->get($this->getScopeKey());
+         if ($scopeValue === self::MISS) {
+            if ($generateOnMiss) {
+               $scopeValue = substr(md5(microtime() . $this->scopeName), 0, 16);
+               $this->scopePrefix = "{$scopeValue}-";
+               $this->backend->set($this->getScopeKey(), $scopeValue);
+            } else {
+               return self::MISS;
+            }
+         } else {
+            $this->scopePrefix = "{$scopeValue}-";
+         }
       }
 
       return $this->scopePrefix;
@@ -52,4 +58,20 @@ public function deleteScope(): bool {
    private function getScopeKey() {
       return "scope-{$this->scopeName}";
    }
+
+   public function get($key) {
+      // If the scope prefix doesn't exist, all keys in this scope are a miss.
+      if (!$this->getScopePrefix(generateOnMiss: false)) {
+         return self::MISS;
+      }
+      return parent::get($key);
+   }
+
+   public function getMultiple(array $keys) {
+      // If the scope prefix doesn't exist, all keys in this scope are a miss.
+      if (!$this->getScopePrefix(generateOnMiss: false)) {
+         return [array_fill_keys(array_keys($keys), self::MISS), $keys];
+      }
+      return parent::getMultiple($keys);
+   }
 }

tests/ScopeTest.php

@@ -12,8 +12,7 @@ protected function getBackend() {
    public function testScope() {
       $memoryCache = new Matryoshka\Ephemeral();
       $scope = 'scope';
-      $scopedCache = new Matryoshka\Scope($memoryCache,
-       $scope);
+      $scopedCache = new Matryoshka\Scope($memoryCache, $scope);
       list($key1, $value1) = $this->getRandomKeyValue();
       list($key2, $value2) = $this->getRandomKeyValue();
 
@@ -41,6 +40,54 @@ public function testScope() {
       $this->assertTrue($scopedCache->set($key1, $value1));
 
       $this->assertSame($value1, $scopedCache->get($key1));
+
+      $scopedCache = new Matryoshka\Scope($memoryCache, $scope);
+      $this->assertSame($value1, $scopedCache->get($key1));
+   }
+
+   public function testScopeShortCircuitGet() {
+      $scope = 'scope';
+      $mockBackend = $this->getMockBuilder(Matryoshka\Ephemeral::class)
+            ->setMethods(['get'])
+            ->getMock();
+
+      // Assert get() is called only once because a missing scope value means
+      // that all underlying values are also missing.
+      $mockBackend->expects($this->once())
+         ->method('get')
+         ->with($this->stringContains($scope))
+         ->willReturn(Matryoshka\Backend::MISS);
+      $scopedCache = new Matryoshka\Scope($mockBackend, $scope);
+
+      $key = (string)rand(1, 100000);
+      $this->assertNull($scopedCache->get($key));
+   }
+
+   public function testScopeShortCircuitGetMultiple() {
+      $scope = 'scope';
+      $mockBackend = $this->getMockBuilder(Matryoshka\Ephemeral::class)
+            ->setMethods(['get', 'getMultiple'])
+            ->getMock();
+
+      // Assert get() is called only once because a missing scope value means
+      // that all underlying values are also missing.
+      $mockBackend->expects($this->once())
+         ->method('get')
+         ->with($this->stringContains($scope))
+         ->willReturn(Matryoshka\Backend::MISS);
+      // Assert getMultiple() is never called because a missi
+      // we don't need to check individual keys.
+      $mockBackend->expects($this->never())
+         ->method('getMultiple');
+
+      $scopedCache = new Matryoshka\Scope($mockBackend, $scope);
+
+      $key = (string)rand(1, 100000);
+      $keys = [$key => 'no matter'];
+      $this->assertSame(
+         [[$key => Matryoshka\Backend::MISS], $keys],
+         $scopedCache->getMultiple($keys)
+      );
    }
 
    public function testAbsoluteKey() {