Add a Lettuce-based Redis singleton client.

service/src/test/java/org/whispersystems/textsecuregcm/redis/FaultTolerantRedisClientTest.java

@@ -0,0 +1,58 @@
+package org.whispersystems.textsecuregcm.redis;
+
+import io.github.resilience4j.circuitbreaker.CallNotPermittedException;
+import io.lettuce.core.RedisClient;
+import io.lettuce.core.RedisException;
+import io.lettuce.core.api.StatefulRedisConnection;
+import io.lettuce.core.api.sync.RedisCommands;
+import org.junit.Before;
+import org.junit.Test;
+import org.whispersystems.textsecuregcm.configuration.CircuitBreakerConfiguration;
+
+import java.time.Duration;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class FaultTolerantRedisClientTest {
+
+    private RedisCommands<String, String> commands;
+    private FaultTolerantRedisClient faultTolerantRedisClient;
+
+    @SuppressWarnings("unchecked")
+    @Before
+    public void setUp() {
+        final RedisClient redisClient                                   = mock(RedisClient.class);
+        final StatefulRedisConnection<String, String> clusterConnection = mock(StatefulRedisConnection.class);
+
+        commands = mock(RedisCommands.class);
+
+        when(redisClient.connect()).thenReturn(clusterConnection);
+        when(clusterConnection.sync()).thenReturn(commands);
+
+        final CircuitBreakerConfiguration breakerConfiguration = new CircuitBreakerConfiguration();
+        breakerConfiguration.setFailureRateThreshold(100);
+        breakerConfiguration.setRingBufferSizeInClosedState(1);
+        breakerConfiguration.setWaitDurationInOpenStateInSeconds(Integer.MAX_VALUE);
+
+        faultTolerantRedisClient = new FaultTolerantRedisClient("test", redisClient, Duration.ofSeconds(2), breakerConfiguration);
+    }
+
+    @Test
+    public void testBreaker() {
+        when(commands.get(anyString()))
+                     .thenReturn("value")
+                     .thenThrow(new io.lettuce.core.RedisException("Badness has ensued."));
+
+        assertEquals("value", faultTolerantRedisClient.withClient(connection -> connection.sync().get("key")));
+
+        assertThrows(RedisException.class,
+                () -> faultTolerantRedisClient.withClient(connection -> connection.sync().get("OH NO")));
+
+        assertThrows(CallNotPermittedException.class,
+                () -> faultTolerantRedisClient.withClient(connection -> connection.sync().get("OH NO")));
+    }
+}