Add memcache memoize support

.gitattributes

@@ -7,6 +7,7 @@
 /.github            export-ignore
 /.gitattributes     export-ignore
 /.gitignore         export-ignore
+/.travis            export-ignore
 /.*.yml             export-ignore
 /phpcs.xml          export-ignore
 /phpunit.xml.dist   export-ignore

.travis.yml

@@ -7,11 +7,15 @@ php:
 env:
   - PREFER_LOWEST="--prefer-lowest --prefer-stable"
   - PREFER_LOWEST=""
+services:
+  - memcached
 matrix:
   fast_finish: true
   allow_failures:
     - php: nightly
 before_script:
+  - phpenv config-add .travis/memcached.ini
+  - phpenv config-add .travis/memcache.ini
   - composer update $PREFER_LOWEST
 script:
   - ./vendor/bin/phpunit --coverage-clover clover.xml

.travis/memcache.ini

@@ -0,0 +1 @@
+extension=memcache.so

.travis/memcached.ini

@@ -0,0 +1 @@
+extension=memcached.so

README.md

@@ -100,6 +100,28 @@ $compute = function() {
 $result = $memoize->memoizeCallable('myLongOperation', $compute, 3600);
 ```
 
+### Memcache
+The memcache provider uses the [memcache](https://www.php.net/manual/en/book.memcache.php) library to
+cache the results in Memcache.  It supports the `$cacheTime` parameter so that
+results can be recomputed after the time expires.
+
+This memoizer can be used in a way that makes it persistent between processes
+rather than only caching computation for the current process.
+
+#### Example
+```php
+$memcache = new Memcache;
+$memcacheInstance = $memcache->connect('127.0.0.1', 11211);
+$memoize = new \TraderInteractive\Memoize\Memcache($memcacheInstance);
+
+$compute = function() {
+    // Perform some long operation that you want to memoize
+};
+
+// Cache he results of $compute for 1 hour.
+$result = $memoize->memoizeCallable('myLongOperation', $compute, 3600);
+```
+
 ### Memory
 This is a standard in-memory memoizer.  It does not support `$cacheTime` at the
 moment and only keeps the results around as long as the memoizer is in memory.

composer.json

@@ -14,16 +14,21 @@
         "sort-packages": true
     },
     "require": {
-        "php": "^7.0 || ^8.0"
+        "php": "^7.0 || ^8.0",
+        "ext-json": "*"
     },
     "require-dev": {
         "php-coveralls/php-coveralls": "^1.0",
         "phpunit/phpunit": "^6.0 || ^7.0 || ^8.0 || ^9.0",
         "predis/predis": "^1.0",
-        "squizlabs/php_codesniffer": "^3.2"
+        "squizlabs/php_codesniffer": "^3.2",
+        "ext-memcache": "*",
+        "ext-memcached": "*"
     },
     "suggest": {
-        "predis/predis": "Allows for Redis-based memoization."
+        "predis/predis": "Allows for Redis-based memoization.",
+        "ext-memcache": "Allows for Memcache-based memoization.",
+        "ext-memcached": "Allows for Memcache-based memoization."
     },
     "autoload": {
         "psr-4": { "TraderInteractive\\Memoize\\": "src/" }

src/Memcache.php

@@ -0,0 +1,95 @@
+<?php
+
+namespace TraderInteractive\Memoize;
+
+/**
+ * A memoizer that caches the results in memcache.
+ */
+class Memcache implements Memoize
+{
+    /**
+     * The memcache client
+     *
+     * @var \Memcache
+     */
+    private $client;
+
+    /**
+     * Cache refresh
+     *
+     * @var boolean
+     */
+    private $refresh;
+
+    /**
+     * Sets the memcache client.
+     *
+     * @param \Memcache $client  The memcache client to use
+     * @param boolean         $refresh If true we will always overwrite cache even if it is already set
+     */
+    public function __construct(\Memcache $client, bool $refresh = false)
+    {
+        $this->client = $client;
+        $this->refresh = $refresh;
+    }
+
+    /**
+     * The value is stored in memcache as a json_encoded string,
+     * so make sure that the value you return from $compute is json-encode-able.
+     *
+     * @see Memoize::memoizeCallable
+     *
+     * @param string   $key
+     * @param callable $compute
+     * @param int|null $cacheTime
+     * @param bool     $refresh
+     *
+     * @return mixed
+     */
+    public function memoizeCallable(string $key, callable $compute, int $cacheTime = null, bool $refresh = false)
+    {
+        if (!$this->refresh && !$refresh) {
+            try {
+                $cached = $this->client->get($key, $flags, $flags);
+                if ($cached !== false && $cached != null) {
+                    $data = json_decode($cached, true);
+                    return $data['result'];
+                }
+            } catch (\Exception $e) {
+                return call_user_func($compute);
+            }
+        }
+
+        $result = call_user_func($compute);
+
+        // If the result is false/null/empty, then there is no point in storing it in cache.
+        if ($result === false || $result == null || empty($result)) {
+            return $result;
+        }
+
+        $this->cache($key, json_encode(['result' => $result]), $cacheTime);
+
+        return $result;
+    }
+
+    /**
+     * Caches the value into memcache with errors suppressed.
+     *
+     * @param string $key       The key.
+     * @param string $value     The value.
+     * @param int    $cacheTime The optional cache time
+     *
+     * @return void
+     */
+    private function cache(string $key, string $value, int $cacheTime = null)
+    {
+        try {
+            $this->client->set($key, $value, 0, $cacheTime);
+        } catch (\Exception $e) {
+            // We don't want exceptions in accessing the cache to break functionality.
+            // The cache should be as transparent as possible.
+            // If insight is needed into these exceptions,
+            // a better way would be by notifying an observer with the errors.
+        }
+    }
+}

tests/MemcacheTest.php

@@ -0,0 +1,134 @@
+<?php
+
+namespace TraderInteractive\Memoize;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @coversDefaultClass \TraderInteractive\Memoize\Memcache
+ * @covers ::<private>
+ */
+class MemcacheTest extends TestCase
+{
+    /**
+     * @test
+     * @covers ::__construct
+     * @covers ::memoizeCallable
+     */
+    public function memoizeCallableWithCachedValue()
+    {
+        $count = 0;
+        $key = 'foo';
+        $value = 'bar';
+        $cachedValue = json_encode(['result' => $value]);
+        $compute = function () use (&$count, $value) {
+            $count++;
+
+            return $value;
+        };
+
+
+        $client = $this->getMemcacheMock();
+        $client->expects(
+            $this->once()
+        )->method('get')->with($this->equalTo($key))->will($this->returnValue($cachedValue));
+
+        $memoizer = new Memcache($client);
+
+        $this->assertSame($value, $memoizer->memoizeCallable($key, $compute));
+        $this->assertSame(0, $count);
+    }
+
+    /**
+     * @test
+     * @covers ::__construct
+     * @covers ::memoizeCallable
+     */
+    public function memoizeCallableWithExceptionOnGet()
+    {
+        $count = 0;
+        $key = 'foo';
+        $value = 'bar';
+        $compute = function () use (&$count, $value) {
+            $count++;
+
+            return $value;
+        };
+
+        $client = $this->getMemcacheMock();
+        $client->expects(
+            $this->once()
+        )->method('get')->with($this->equalTo($key))->will($this->throwException(new \Exception()));
+
+        $memoizer = new Memcache($client);
+
+        $this->assertSame($value, $memoizer->memoizeCallable($key, $compute));
+        $this->assertSame(1, $count);
+    }
+
+    /**
+     * @test
+     * @covers ::__construct
+     * @covers ::memoizeCallable
+     */
+    public function memoizeCallableWithUncachedKey()
+    {
+        $count = 0;
+        $key = 'foo';
+        $value = 'bar';
+        $cachedValue = json_encode(['result' => $value]);
+        $cacheTime = 1234;
+        $compute = function () use (&$count, $value) {
+            $count++;
+
+            return $value;
+        };
+
+        $client = $this->getMemcacheMock();
+        $client->expects($this->once())->method('get')->with($this->equalTo($key))->will($this->returnValue(null));
+        $client->expects($this->once())->method('set')
+            ->with($this->equalTo($key), $this->equalTo($cachedValue), $this->equalTo(0), $this->equalTo($cacheTime));
+
+        $memoizer = new Memcache($client);
+
+        $this->assertSame($value, $memoizer->memoizeCallable($key, $compute, $cacheTime));
+        $this->assertSame(1, $count);
+    }
+
+    /**
+     * @test
+     * @covers ::__construct
+     * @covers ::memoizeCallable
+     */
+    public function memoizeCallableWithUncachedKeyWithExceptionOnSet()
+    {
+        $count = 0;
+        $key = 'foo';
+        $value = 'bar';
+        $cachedValue = json_encode(['result' => $value]);
+        $compute = function () use (&$count, $value) {
+            $count++;
+
+            return $value;
+        };
+
+        $client = $this->getMemcacheMock();
+        $client->expects(
+            $this->once()
+        )->method('get')->with($this->equalTo($key))->will($this->returnValue(null));
+        $setExpectation = $client->expects(
+            $this->once()
+        )->method('set')->with($this->equalTo($key), $this->equalTo($cachedValue));
+        $setExpectation->will($this->throwException(new \Exception()));
+
+        $memoizer = new Memcache($client);
+
+        $this->assertSame($value, $memoizer->memoizeCallable($key, $compute));
+        $this->assertSame(1, $count);
+    }
+
+    public function getMemcacheMock() : \Memcache
+    {
+        return $this->getMockBuilder('\Memcache')->setMethods(['get', 'set'])->getMock();
+    }
+}