grpc莫名其妙报错，具体报错日志如下：
2021-03-13 21:51:18,623:INFO grpc-default-worker-ELG-8-1 (:) - Transport failed io.netty.handler.codec.http2.Http2Exception: HTTP/2 client preface string missing or corrupt. Hex dump for received bytes: 0a at io.netty.handler.codec.http2.Http2Exception.connectionError(Http2Exception.java:103) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.handler.codec.http2.Http2ConnectionHandler$PrefaceDecoder.readClientPrefaceString(Http2ConnectionHandler.java:306) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.handler.codec.http2.Http2ConnectionHandler$PrefaceDecoder.decode(Http2ConnectionHandler.java:239) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.handler.codec.http2.Http2ConnectionHandler.decode(Http2ConnectionHandler.java:438) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:498) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:437) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:276) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:377) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:363) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:355) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:377) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:363) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:792) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:475) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:378) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-all-4.1.45.Final.jar:4.1.45.Final] at java.lang.Thread.run(Thread.java:834) [?:?]
最终在 https://yidongnan.github.io/grpc-spring-boot-starter/en/trouble-shooting.html#transport-failed 找到：
spring配置文件增加
grpc.client.__name__.negotiationType=PLAINTEXT问题解决