JavaMail IdleManager throws "Folder is not using SocketChannels" exception after a while - scala

Question

I'm using IdleManager, in Scala, to listen to a Gmail folder.
I already have this props.setProperty("mail.imaps.usesocketchannels", "true")
The main part of my code is like this:
folder.addMessageCountListener(new MessageCountAdapter() {
override def messagesAdded(ev: MessageCountEvent) {
Logger.info("Got " + ev.getMessages.length + " new messages")
idleManager.watch(folder)
}
})
// timeLength = 20 minutes
system.scheduler.schedule(initialDelay = timeLength, interval = timeLength) {
try {
folder.asInstanceOf[IMAPFolder].doCommand(new IMAPFolder.ProtocolCommand() {
def doCommand(p: IMAPProtocol) = {
p.simpleCommand("NOOP", null)
null
}
})
Logger.debug("Continue after sending NOOP")
idleManager.watch(folder)
} catch {
case e: Exception => Logger.error(s"MailHelper: ${e.getMessage}")
}
}
idleManager.watch(folder)
You can see that I let the idleManager continue watching the folder after I get new messages and after I send a NOOP command. A scheduler is created to periodically (currently, once in 20 minutes) send a NOOP command to the server, to keep the connection. My program worked fine, but just for a while.
14 hours after the first call idleManager.watch(folder) and about 12.5 hours after the last email received, I still got the log Continue after sending NOOP, but right after that is an error log MailHelper: Folder is not using SocketChannels.
Could you please help me with this?
Edited:
Thanks #BillShannon for your quick reply. I have updated from v1.5.2 to v1.5.6 and turned on the debug output. I'm sure the Properties object and the "store" instance (created from a Session with the "imaps" protocol) are unchanged.
The error has appeared again. After a call to idleManager.watch(folder), here is the log ([folder] is the imaps protocol string for my folder)
DEBUG IMAP: IdleManager watching [folder]
A385 IDLE
+ idling
DEBUG IMAP: startIdle: set to IDLE
DEBUG IMAP: startIdle: return true
DEBUG IMAP: IdleManager.watch startIdle succeeded for [folder]
DEBUG IMAP: IdleManager selected 0 channels
DEBUG IMAP: IdleManager adding [folder] to selector
DEBUG IMAP: IdleManager waiting...
DEBUG IMAP: IdleManager selected 1 channels
DEBUG IMAP: IdleManager selected folder: [folder]
DEBUG IMAP: handleIdle: set to RUNNING
DEBUG IMAP: IdleManager got exception for folder: [folder], THROW:
javax.mail.FolderClosedException: * BYE JavaMail Exception: java.io.IOException: Connection dropped by server?
at com.sun.mail.imap.IMAPFolder.handleIdle(IMAPFolder.java:3199)
at com.sun.mail.imap.IdleManager.processKeys(IdleManager.java:370)
at com.sun.mail.imap.IdleManager.select(IdleManager.java:281)
at com.sun.mail.imap.IdleManager.access$200(IdleManager.java:137)
at com.sun.mail.imap.IdleManager$1.run(IdleManager.java:164)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
DEBUG IMAP: IdleManager waiting...
20 minutes later, the program sent another "NOOP", the status returned was "OK". And the program called idleManager.watch(folder) once again, here the error log reappeared Folder is not using SocketChannels.
Do you need anything else? Is this an issue with the library?