Keep-alive connection not kept on 301 w/ host change

[MikeN123]

Redirect30xInterceptor tries to reuse a channel on a redirect if keep-alive is enabled, and tries to offer the channel to the pool if that is not possible due to a host change, see here:

async-http-client/client/src/main/java/org/asynchttpclient/netty/handler/intercept/Redirect30xInterceptor.java

Line 152 in 300a6c3

channelManager.drainChannelAndOffer(channel, future, initialConnectionKeepAlive, initialPartitionKey);

Unfortunately, that does not work, as NettyRequestSender.sendNextRequest() immediately clears the Channel attribute, which was a fix for another issue (#1059):

async-http-client/client/src/main/java/org/asynchttpclient/netty/request/NettyRequestSender.java

Line 473 in 300a6c3

Channels.setAttribute(channel, null);

Not sure about the correct fix, still trying to figure that out.

[slandelle]

Actually, your understanding is not correct. What's nulled out is the channel's attribute. The future's channel is still here.
Please provide a reproducer if you experience an issue.

[MikeN123]

Uhm, I don't think you get the issue. The problem is not the future's channel, the problem is the channel's attribute being nulled out.

I don't have a full reproduction available, but it is easily seen from the source. Working from Redirect30xInterceptor.

• The connection is redirected to a different host, hence sameBase = false
• channelManager.drainChannelAndOffer() is called, to drain the channel and send it to the pool (as expected, as the channel can still be used and is kept alive)
• drainChannelAndOffer() creates a new callback, using newDrainCallback(). This callback's task is simply to put the channel back in the pool when the remaining data has been received (i.e., when LastContent is received).
• This callback is set as the channel's attribute:

  async-http-client/client/src/main/java/org/asynchttpclient/netty/channel/ChannelManager.java

  Line 484 in 300a6c3

  Channels.setAttribute(channel, newDrainCallback(future, channel, keepAlive, partitionKey));

• The Redirect30xInterceptor then continues, calls NettyRequestSender.sendNextRequest(), which immediately clears the attribute. Hence the drain callback is gone.
• Somewhere in the future, the LastContent is received, we end up in AsyncHttpClientHandler. channelRead(), which reads the attribute, finds null, and ends up with a message about an orphan channel, and the channel is closed:

  async-http-client/client/src/main/java/org/asynchttpclient/netty/handler/AsyncHttpClientHandler.java

  Line 114 in 300a6c3

  logger.debug("Orphan channel {} with attribute {} received message {}, closing", channel, attribute, msg);

Hope that helps.

[slandelle]

Sorry, I didn't get your original "that does not work" :)
If think the buggy code is no longer necessary, I removed it.

Thanks for reporting!