聊聊dubbo的CacheFilter

序

本文主要研究一下dubbo的CacheFilter

CacheFilter

dubbo-2.7.2/dubbo-filter/dubbo-filter-cache/src/main/java/org/apache/dubbo/cache/filter/CacheFilter.java

@Activate(group = {CONSUMER, PROVIDER}, value = CACHE_KEY)
public class CacheFilter implements Filter {

    private CacheFactory cacheFactory;

    /**
     * Dubbo will populate and set the cache factory instance based on service/method/consumer/provider configured
     * cache attribute value. Dubbo will search for the class name implementing configured <b>cache</b> in file org.apache.dubbo.cache.CacheFactory
     * under META-INF sub folders.
     *
     * @param cacheFactory instance of CacheFactory based on <b>cache</b> type
     */
    public void setCacheFactory(CacheFactory cacheFactory) {
        this.cacheFactory = cacheFactory;
    }

    /**
     * If cache is configured, dubbo will invoke method on each method call. If cache value is returned by cache store
     * then it will return otherwise call the remote method and return value. If remote method's return valeu has error
     * then it will not cache the value.
     * @param invoker    service
     * @param invocation invocation.
     * @return Cache returned value if found by the underlying cache store. If cache miss it will call target method.
     * @throws RpcException
     */
    @Override
    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        if (cacheFactory != null && ConfigUtils.isNotEmpty(invoker.getUrl().getMethodParameter(invocation.getMethodName(), CACHE_KEY))) {
            Cache cache = cacheFactory.getCache(invoker.getUrl(), invocation);
            if (cache != null) {
                String key = StringUtils.toArgumentString(invocation.getArguments());
                Object value = cache.get(key);
                if (value != null) {
                    if (value instanceof ValueWrapper) {
                        return AsyncRpcResult.newDefaultAsyncResult(((ValueWrapper) value).get(), invocation);
                    } else {
                        return AsyncRpcResult.newDefaultAsyncResult(value, invocation);
                    }
                }
                Result result = invoker.invoke(invocation);
                if (!result.hasException()) {
                    cache.put(key, new ValueWrapper(result.getValue()));
                }
                return result;
            }
        }
        return invoker.invoke(invocation);
    }

    /**
     * Cache value wrapper.
     */
    static class ValueWrapper implements Serializable {

        private static final long serialVersionUID = -1777337318019193256L;

        private final Object value;

        public ValueWrapper (Object value) {
            this.value = value;
        }

        public Object get() {
            return this.value;
        }
    }
}

• CacheFilter實現了Filter接口，它的invoke方法會先判斷cacheFactory是否不爲null且invoker的URL中包含cache參數，若是該條件成立則從cacheFactory獲取cache，而後在從cache中獲取value，若是value不爲null則返回AsyncRpcResult.newDefaultAsyncResult，若是value爲null則執行invoke成功以後將該value緩存到cache中

實例

dubbo-2.7.2/dubbo-filter/dubbo-filter-cache/src/test/java/org/apache/dubbo/cache/filter/CacheFilterTest.java

public class CacheFilterTest {
    private RpcInvocation invocation;
    private CacheFilter cacheFilter = new CacheFilter();
    private Invoker<?> invoker = mock(Invoker.class);
    private Invoker<?> invoker1 = mock(Invoker.class);
    private Invoker<?> invoker2 = mock(Invoker.class);
    private Invoker<?> invoker3 = mock(Invoker.class);
    private Invoker<?> invoker4 = mock(Invoker.class);

    static Stream<Arguments> cacheFactories() {
        return Stream.of(
                Arguments.of("lru", new LruCacheFactory()),
                Arguments.of("jcache", new JCacheFactory()),
                Arguments.of("threadlocal", new ThreadLocalCacheFactory()),
                Arguments.of("expiring", new ExpiringCacheFactory())
        );
    }

    public void setUp(String cacheType, CacheFactory cacheFactory) {
        invocation = new RpcInvocation();
        cacheFilter.setCacheFactory(cacheFactory);

        URL url = URL.valueOf("test://test:11/test?cache=" + cacheType);

        given(invoker.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult("value", invocation));
        given(invoker.getUrl()).willReturn(url);

        given(invoker1.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult("value1", invocation));
        given(invoker1.getUrl()).willReturn(url);

        given(invoker2.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult("value2", invocation));
        given(invoker2.getUrl()).willReturn(url);

        given(invoker3.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult(new RuntimeException(), invocation));
        given(invoker3.getUrl()).willReturn(url);

        given(invoker4.invoke(invocation)).willReturn(AsyncRpcResult.newDefaultAsyncResult(invocation));
        given(invoker4.getUrl()).willReturn(url);
    }

    @ParameterizedTest
    @MethodSource("cacheFactories")
    public void testNonArgsMethod(String cacheType, CacheFactory cacheFactory) {
        setUp(cacheType, cacheFactory);
        invocation.setMethodName("echo");
        invocation.setParameterTypes(new Class<?>[]{});
        invocation.setArguments(new Object[]{});

        cacheFilter.invoke(invoker, invocation);
        Result rpcResult1 = cacheFilter.invoke(invoker1, invocation);
        Result rpcResult2 = cacheFilter.invoke(invoker2, invocation);
        Assertions.assertEquals(rpcResult1.getValue(), rpcResult2.getValue());
        Assertions.assertEquals(rpcResult1.getValue(), "value");
    }

    @ParameterizedTest
    @MethodSource("cacheFactories")
    public void testMethodWithArgs(String cacheType, CacheFactory cacheFactory) {
        setUp(cacheType, cacheFactory);
        invocation.setMethodName("echo1");
        invocation.setParameterTypes(new Class<?>[]{String.class});
        invocation.setArguments(new Object[]{"arg1"});

        cacheFilter.invoke(invoker, invocation);
        Result rpcResult1 = cacheFilter.invoke(invoker1, invocation);
        Result rpcResult2 = cacheFilter.invoke(invoker2, invocation);
        Assertions.assertEquals(rpcResult1.getValue(), rpcResult2.getValue());
        Assertions.assertEquals(rpcResult1.getValue(), "value");
    }

    @ParameterizedTest
    @MethodSource("cacheFactories")
    public void testException(String cacheType, CacheFactory cacheFactory) {
        setUp(cacheType, cacheFactory);
        invocation.setMethodName("echo1");
        invocation.setParameterTypes(new Class<?>[]{String.class});
        invocation.setArguments(new Object[]{"arg2"});

        cacheFilter.invoke(invoker3, invocation);
        Result rpcResult = cacheFilter.invoke(invoker2, invocation);
        Assertions.assertEquals(rpcResult.getValue(), "value2");
    }

    @ParameterizedTest
    @MethodSource("cacheFactories")
    public void testNull(String cacheType, CacheFactory cacheFactory) {
        setUp(cacheType, cacheFactory);
        invocation.setMethodName("echo1");
        invocation.setParameterTypes(new Class<?>[]{String.class});
        invocation.setArguments(new Object[]{"arg3"});

        cacheFilter.invoke(invoker4, invocation);
        Result result1 = cacheFilter.invoke(invoker1, invocation);
        Result result2 = cacheFilter.invoke(invoker2, invocation);
        Assertions.assertEquals(result1.getValue(), null);
        Assertions.assertEquals(result2.getValue(), null);
    }
}

• 這裏分別驗證了無參方法、帶參數方法、拋異常的方法、value爲null的場景

小結

CacheFilter實現了Filter接口，它的invoke方法會先判斷cacheFactory是否不爲null且invoker的URL中包含cache參數，若是該條件成立則從cacheFactory獲取cache，而後在從cache中獲取value，若是value不爲null則返回AsyncRpcResult.newDefaultAsyncResult，若是value爲null則執行invoke成功以後將該value緩存到cache中

doc

• CacheFilter