We have an application based on Quarkus (2.4.2), and its mailsender is Vert.x Mailer. Config used: The issue we are having is that 60 seconds after a mail is sent the following is logged: Based on this stacktrace it looks like it is smtp.office365.com that do Connection reset, timeout handling in Vert.x' SMTPConnection should close gracefully. Does anyone have any

Connection Reset for Vert.x mailsender on keep alive timeout

We have an application based on Quarkus (2.4.2), and its mailsender is Vert.x Mailer. Config used:

quarkus.mailer.host=smtp.office365.com
quarkus.mailer.keep-alive-timeout=PT60S
quarkus.mailer.keep-alive=true

The issue we are having is that 60 seconds after a mail is sent the following is logged:

2021-11-25T09:48:58.477+0100 ERROR [vert.x-eventloop-thread-2] io.vertx.ext.mail.impl.SMTPConnection Connection reset: java.net.SocketException: Connection reset
        at java.base/sun.nio.ch.SocketChannelImpl.throwConnectionReset(SocketChannelImpl.java:367)
        at java.base/sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:398)
        at io.netty.buffer.PooledByteBuf.setBytes(PooledByteBuf.java:253)
        at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:1132)
        at io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:350)
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:151)
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:719)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986)
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
        at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
        at java.base/java.lang.Thread.run(Thread.java:832)
: java.net.SocketException: Connection reset
        at java.base/sun.nio.ch.SocketChannelImpl.throwConnectionReset(SocketChannelImpl.java:367)
        at java.base/sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:398)
        at io.netty.buffer.PooledByteBuf.setBytes(PooledByteBuf.java:253)
        at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:1132)
        at io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:350)
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:151)
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:719)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986)
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
        at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
        at java.base/java.lang.Thread.run(Thread.java:832)

Based on this stacktrace it looks like it is smtp.office365.com that do Connection reset, timeout handling in Vert.x’ SMTPConnection should close gracefully.

Does anyone have any experiences like this?

Silencing logging for SMTPConnection is an option, but that does not seem right.

Answer

My interpretation after stepping through the code is that SMTPConnection.quitCloseConnection is missing a call for closing the actuall connection.

So QUIT is sent, then the smtp-server sends connection reset since the connection is not closed.

I created an issue in vert.x mail client.

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Answer