When joining a server with resource packs enabled, or having a server where the resourcepack switches depending on the area of the world you are in, the client hangs for up to a minute.
Upon looking at the logs, it seems the sound engine keeps rebooting for some unknown reason. https://gist.github.com/q220/8c3b2928585bae813b8157084219f744
Completely ignored arguments: [--nativeLauncherVersion, 307]
[03:19:36] [Client thread/INFO]: Setting user: [redacted]
[03:19:36] [Client thread/INFO]: LWJGL Version: 2.9.4
[03:19:37] [Client thread/INFO]: Reloading ResourceManager: Default
[03:19:37] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:38] [Thread-5/INFO]: Initializing LWJGL OpenAL
[03:19:38] [Thread-5/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:38] [Thread-5/INFO]: OpenAL initialized.
[03:19:38] [Sound Library Loader/INFO]: Sound engine started
[03:19:38] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:42] [Client thread/INFO]: Connecting to [redacted], 25565
[03:19:45] [Netty Client IO #1/INFO]: Found file F:\MinecraftGame\server-resource-packs\6670e96cab293739da3f8932815a00cf7ef8993c without verification hash
[03:19:45] [Client thread/INFO]: Reloading ResourceManager: Default
[03:19:45] [Netty Client IO #1/INFO]: Found file F:\MinecraftGame\server-resource-packs\6670e96cab293739da3f8932815a00cf7ef8993c without verification hash
[03:19:45] [Client thread/INFO]: SoundSystem shutting down...
[03:19:45] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:19:45] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:46] [Thread-9/INFO]: Initializing LWJGL OpenAL
[03:19:46] [Thread-9/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:46] [Thread-9/INFO]: OpenAL initialized.
[03:19:46] [Sound Library Loader/INFO]: Sound engine started
[03:19:46] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:46] [Client thread/INFO]: Reloading ResourceManager: Default, 6670e96cab293739da3f8932815a00cf7ef8993c
[03:19:47] [Client thread/INFO]: SoundSystem shutting down...
[03:19:47] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:19:47] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:48] [Thread-11/INFO]: Initializing LWJGL OpenAL
[03:19:48] [Thread-11/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:48] [Thread-11/INFO]: OpenAL initialized.
[03:19:48] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:48] [Sound Library Loader/INFO]: Sound engine started
[03:19:48] [Netty Client IO #1/INFO]: Found file F:\MinecraftGame\server-resource-packs\6670e96cab293739da3f8932815a00cf7ef8993c without verification hash
[03:19:48] [Client thread/INFO]: Reloading ResourceManager: Default
[03:19:49] [Netty Client IO #1/INFO]: Found file F:\MinecraftGame\server-resource-packs\6670e96cab293739da3f8932815a00cf7ef8993c without verification hash
[03:19:49] [Client thread/INFO]: SoundSystem shutting down...
[03:19:49] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:19:49] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:49] [Thread-13/INFO]: Initializing LWJGL OpenAL
[03:19:49] [Thread-13/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:49] [Thread-13/INFO]: OpenAL initialized.
[03:19:50] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:50] [Sound Library Loader/INFO]: Sound engine started
[03:19:50] [Client thread/INFO]: Reloading ResourceManager: Default, 6670e96cab293739da3f8932815a00cf7ef8993c
[03:19:51] [Client thread/INFO]: SoundSystem shutting down...
[03:19:51] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:19:51] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:51] [Thread-15/INFO]: Initializing LWJGL OpenAL
[03:19:51] [Thread-15/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:51] [Thread-15/INFO]: OpenAL initialized.
[03:19:52] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:52] [Sound Library Loader/INFO]: Sound engine started
[03:19:52] [Client thread/INFO]: Reloading ResourceManager: Default, 6670e96cab293739da3f8932815a00cf7ef8993c
[03:19:53] [Client thread/INFO]: SoundSystem shutting down...
[03:19:53] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:19:53] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:53] [Thread-17/INFO]: Initializing LWJGL OpenAL
[03:19:53] [Thread-17/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:53] [Thread-17/INFO]: OpenAL initialized.
[03:19:54] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:54] [Sound Library Loader/INFO]: Sound engine started
[03:19:54] [Client thread/INFO]: Reloading ResourceManager: Default, 6670e96cab293739da3f8932815a00cf7ef8993c
[03:19:55] [Client thread/INFO]: SoundSystem shutting down...
[03:19:55] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:19:55] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:55] [Thread-19/INFO]: Initializing LWJGL OpenAL
[03:19:55] [Thread-19/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:55] [Thread-19/INFO]: OpenAL initialized.
[03:19:55] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:55] [Sound Library Loader/INFO]: Sound engine started
[03:19:56] [Netty Client IO #1/INFO]: Found file F:\MinecraftGame\server-resource-packs\6670e96cab293739da3f8932815a00cf7ef8993c without verification hash
[03:19:56] [Client thread/INFO]: Reloading ResourceManager: Default
[03:19:56] [Netty Client IO #1/INFO]: Found file F:\MinecraftGame\server-resource-packs\6670e96cab293739da3f8932815a00cf7ef8993c without verification hash
[03:19:56] [Client thread/INFO]: SoundSystem shutting down...
[03:19:57] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:19:57] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:57] [Thread-21/INFO]: Initializing LWJGL OpenAL
[03:19:57] [Thread-21/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:57] [Thread-21/INFO]: OpenAL initialized.
[03:19:57] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:57] [Sound Library Loader/INFO]: Sound engine started
[03:19:58] [Client thread/INFO]: Reloading ResourceManager: Default, 6670e96cab293739da3f8932815a00cf7ef8993c
[03:19:58] [Client thread/INFO]: SoundSystem shutting down...
[03:19:58] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:19:58] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:19:59] [Thread-23/INFO]: Initializing LWJGL OpenAL
[03:19:59] [Thread-23/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:19:59] [Thread-23/INFO]: OpenAL initialized.
[03:19:59] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:19:59] [Sound Library Loader/INFO]: Sound engine started
[03:19:59] [Client thread/INFO]: Reloading ResourceManager: Default, 6670e96cab293739da3f8932815a00cf7ef8993c
[03:20:00] [Client thread/INFO]: SoundSystem shutting down...
[03:20:00] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:20:00] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:20:00] [Thread-25/INFO]: Initializing LWJGL OpenAL
[03:20:00] [Thread-25/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:20:00] [Thread-25/INFO]: OpenAL initialized.
[03:20:01] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:20:01] [Sound Library Loader/INFO]: Sound engine started
[03:20:01] [Client thread/INFO]: Reloading ResourceManager: Default, 6670e96cab293739da3f8932815a00cf7ef8993c
[03:20:02] [Client thread/INFO]: SoundSystem shutting down...
[03:20:02] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:20:02] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:20:02] [Thread-27/INFO]: Initializing LWJGL OpenAL
[03:20:02] [Thread-27/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:20:02] [Thread-27/INFO]: OpenAL initialized.
[03:20:02] [Client thread/INFO]: Created: 1024x512 textures-atlas
[03:20:03] [Sound Library Loader/INFO]: Sound engine started
[03:20:03] [Client thread/INFO]: Reloading ResourceManager: Default, 6670e96cab293739da3f8932815a00cf7ef8993c
[03:20:04] [Client thread/INFO]: SoundSystem shutting down...
[03:20:04] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
[03:20:04] [Sound Library Loader/INFO]: Starting up SoundSystem...
[03:20:04] [Thread-29/INFO]: Initializing LWJGL OpenAL
[03:20:04] [Thread-29/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[03:20:04] [Thread-29/INFO]: OpenAL initialized.
[03:20:05] [Sound Library Loader/INFO]: Sound engine started
[03:20:05] [Client thread/INFO]: Created: 1024x512 textures-atlas
Allright, I think this is not a Minecraft client bug. After we looked in the plugin that handled this 'texture switching based on region', we found multiple registered listeners in the plugin that caused duplicate texture changing packets being sent to the client.
After preventing multiple listeners from registering, the clients I tested on switched more quickly.