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PingConnectionHandler will periodically send PING commands to Redis Server, and decide whether to reconnect based on whether it fails (the current strategy is to reconnect after three consecutive failures) This is essentially because KeepAlive that only relies on TCP is unreliable, for details, please refer to: #2082
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119 changes: 119 additions & 0 deletions
119
src/main/java/io/lettuce/core/PingConnectionHandler.java
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| package io.lettuce.core; | ||
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| import java.util.concurrent.CancellationException; | ||
| import java.util.concurrent.CompletableFuture; | ||
| import java.util.concurrent.CompletionException; | ||
| import java.util.concurrent.TimeUnit; | ||
| import java.util.concurrent.atomic.AtomicInteger; | ||
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| import io.lettuce.core.codec.StringCodec; | ||
| import io.lettuce.core.protocol.AsyncCommand; | ||
| import io.lettuce.core.protocol.Command; | ||
| import io.lettuce.core.resource.ClientResources; | ||
| import io.netty.channel.Channel; | ||
| import io.netty.channel.ChannelHandler; | ||
| import io.netty.channel.ChannelHandlerContext; | ||
| import io.netty.channel.ChannelInboundHandlerAdapter; | ||
| import io.netty.util.internal.logging.InternalLogger; | ||
| import io.netty.util.internal.logging.InternalLoggerFactory; | ||
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| /** | ||
| * A netty {@link ChannelHandler} responsible for monitoring (By periodically sending PING commands) Redis alive. | ||
| * | ||
| * @author Bodong Yang | ||
| * @date 2022/11/11 | ||
| */ | ||
| @ChannelHandler.Sharable | ||
| public class PingConnectionHandler extends ChannelInboundHandlerAdapter { | ||
| private static final InternalLogger logger = InternalLoggerFactory.getInstance(PingConnectionHandler.class); | ||
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| private final RedisCommandBuilder<String, String> commandBuilder = new RedisCommandBuilder<>(StringCodec.UTF8); | ||
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| private static final int MAX_PING_FAILED_TIMES = 3; | ||
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| private final AtomicInteger pingFailed = new AtomicInteger(0); | ||
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| private final ClientResources clientResources; | ||
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| private final ClientOptions clientOptions; | ||
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| public PingConnectionHandler(ClientResources clientResources, ClientOptions clientOptions) { | ||
| this.clientResources = clientResources; | ||
| this.clientOptions = clientOptions; | ||
| } | ||
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| @Override | ||
| public void channelActive(ChannelHandlerContext ctx) throws Exception { | ||
| sendPing(ctx); | ||
| ctx.fireChannelActive(); | ||
| } | ||
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| /** | ||
| * Periodically send the PING command, if it fails three times in a row, it will initiate a reconnection. | ||
| * Ignore exceptions returned by the following PING commands: {@link RedisLoadingException} | ||
| * {@link RedisBusyException} | ||
| * | ||
| * @param ctx the ctx | ||
| */ | ||
| private void sendPing(ChannelHandlerContext ctx) { | ||
| AsyncCommand<String, String, String> dispatch = dispatch(ctx.channel(), commandBuilder.ping()); | ||
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| clientResources.timer().newTimeout(timeout -> { | ||
| if (ctx.isRemoved() || !ctx.channel().isActive()) { | ||
| return; | ||
| } | ||
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| if (dispatch.cancel(false) || cause(dispatch) != null) { | ||
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| Throwable cause = cause(dispatch); | ||
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| if (!(cause instanceof RedisLoadingException | ||
| || cause instanceof RedisBusyException)) { | ||
| if (!dispatch.isCancelled()) { | ||
| logger.error("Unable to send PING command over channel: " + ctx.channel(), cause); | ||
| } | ||
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| if (pingFailed.incrementAndGet() == MAX_PING_FAILED_TIMES) { | ||
| logger.error("channel: {} closed due to {} consecutive PING response timeout set in {} ms", | ||
| ctx.channel(), MAX_PING_FAILED_TIMES, clientOptions.getPingConnectionInterval()); | ||
| pingFailed.set(0); | ||
| ctx.channel().close(); | ||
| } else { | ||
| sendPing(ctx); | ||
| } | ||
| } else { | ||
| pingFailed.set(0); | ||
| sendPing(ctx); | ||
| } | ||
| } else { | ||
| pingFailed.set(0); | ||
| sendPing(ctx); | ||
| } | ||
| }, clientOptions.getPingConnectionInterval(), TimeUnit.MILLISECONDS); | ||
| } | ||
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| private <T> AsyncCommand<String, String, T> dispatch(Channel channel, Command<String, String, T> command) { | ||
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| AsyncCommand<String, String, T> future = new AsyncCommand<>(command); | ||
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| channel.writeAndFlush(future).addListener(writeFuture -> { | ||
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| if (!writeFuture.isSuccess()) { | ||
| future.completeExceptionally(writeFuture.cause()); | ||
| } | ||
| }); | ||
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| return future; | ||
| } | ||
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| protected Throwable cause(CompletableFuture<?> future) { | ||
| try { | ||
| future.getNow(null); | ||
| return null; | ||
| } catch (CompletionException ex2) { | ||
| return ex2.getCause(); | ||
| } catch (CancellationException ex1) { | ||
| return ex1; | ||
| } | ||
| } | ||
| } |
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src/test/java/io/lettuce/examples/ConnectToRedisWithPingInterval.java
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,30 @@ | ||
| package io.lettuce.examples; | ||
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| import io.lettuce.core.ClientOptions; | ||
| import io.lettuce.core.RedisClient; | ||
| import io.lettuce.core.RedisURI; | ||
| import io.lettuce.core.api.StatefulRedisConnection; | ||
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| /** | ||
| * @author bodong.ybd | ||
| * @date 2022/11/11 | ||
| */ | ||
| public class ConnectToRedisWithPingInterval { | ||
| public static void main(String[] args) throws Exception { | ||
| RedisClient client = RedisClient.create(RedisURI.Builder.redis("localhost", 6379).build()); | ||
| client.setOptions(ClientOptions.builder().pingConnectionInterval(3000).build()); | ||
| StatefulRedisConnection<String, String> connection = client.connect(); | ||
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| for (int i = 0; i < 1000; i++) { | ||
| try { | ||
| Thread.sleep(1000); | ||
| System.out.printf("%d:%s\n", i, connection.sync().set("" + i, "" + i)); | ||
| } catch (Exception e) { | ||
| e.printStackTrace(); | ||
| } | ||
| } | ||
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| connection.close(); | ||
| client.shutdown(); | ||
| } | ||
| } |