Talk about CacheFilter of dubbo

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This article mainly studies dubbo’s 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 implements the Filter interface. Its invoke method will first determine whether cacheFactory is not null and the URL of invoker contains ca che parameters. If the condition holds, it will obtain cache from cacheFactory and then obtain value from cache. If the value is not null, it returns asyncrpresult. newdefaultasyncrypult. if the value is null, it is cached in cache after the invocation succeeds.

Example

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);
    }
}
  • Here, the parameterless method, the method with parameters, the method of throwing exceptions and the scenario with null value are verified respectively

Summary

CacheFilter implements the Filter interface. Its invoke method will first determine whether cacheFactory is not null and the URL of invoker contains cache parameters. If the condition holds, it will obtain cache from cacheFactory and then obtain value from cache. If the value is not null, it returns asyncrpresult. newdefaultasyncrypult. if the value is null, it is cached in cache after the invocation succeeds.

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