The ImapClient is currently busy processing a command in another thread #613
Comments
|
I think you just got lucky with 1.22. The problem is that the ImapClient is not re-entrant. In other words, you cannot send another command while an existing command is currently being processed. In your case, the NOOP command is still being processed when the event is triggered. MailKit does not wait for the entire server response to be read before it begins parsing the response and emitting events. Instead, it processes the response as it receives it. The Good:
The Bad:
The Solution: In your event handlers, queue your next command(s) to be executed once the existing command completes. |
|
Ah, wait, the reason it worked in 1.22 was because 1.22 used Task.Run() and locked the SyncRoot itself in the Async() methods. Now that 2.0 is fully async, I can't easily do locking around the sync call like in 1.22. |
|
In other words, this is what 1.22 does: public Task<T> DoSomethingAsync ()
{
return Task.Run (() => {
lock (SyncRoot) {
return DoSomething ();
}
});
} |
|
I might have a solution... |
|
Nope, that won't work... :( |
|
I would love for this to work, but I don't think it's possible without moving the ImapEngine's runloop into another thread which I really don't want to do (because it makes things a lot more complex). |
|
Dang! So, my next update will need to be to Queue the commands that are being called during the Event Handler? I don't have a problem with doing this, I am just unsure about how to go about doing this. Any insight you can give me here? I am sorry I am just now seeing this. I don't think I got a notification. Thank you for your assistance! |
|
MailKit doesn't provide a command queue that you can use, you'll have to do that yourself. What you could do is have a |
|
Another option is to do something like this: void OnMessageFlagsChanged (object sender, MessageFlagsChangedEventArgs e)
{
this.flags_changed = true;
}And then, in your NOOP logic: await client.NoOpAsync ();
if (this.flags_changed) {
var query = SearchQuery.SubjectContains("New message").And(SearchQuery.NotSeen);
var uids = await folder.SearchAsync(query);
}That said, I'm not sure why you're using the MessageFlagsChanged event for checking for new mail... MessageFlagsChanged is only emitted when the flags on an existing message change. You want CountChanged if you expect it to mean the potential for new mail to have arrived. |
|
Thank you! I will give your second option a try. I feel like that will do what I need. I will let you know how that goes. :) 👍 |
|
It appears that this resolved my issue. And I apologize, I didn't see the last bit of your message. I am building a transcription service and I wanted the ability to mark an email as unread and for the email to act as normal. I don't actually care about how many messages are in the inbox or anything, just what happens to the new messages that come in or messages that I mark as unread. |
|
Ah, ok. FWIW, the MessageFlagsChangedEventArgs argument provides information about the index of the message (sadly not the UID since the server does not provide that info) as well as what the new flags for the message are. Using that info to keep track of state would be cheaper than doing a Search(). For example: class MyMessageInfo
{
public UniqueId UniqueId;
public MessageFlags Flags;
public MyMessageInfo (UniqueId uid, MessageFLags flags)
{
UniqueId = uid;
Flags = flags;
}
}// after connecting and opening the folder you are interested in tracking, connect to some events so we can track the state of the server:
folder.CountChanged += OnCountChanged;
folder.MessageExpunged += OnMessageExpunged;
folder.MessageFlagsChanged += OnMessageFlagsChanged;
// now collect the list of message UIDs and their associated Flags:
this.messages = folder.Fetch (0, -1, MessageSummaryItems.UniqueId | MessageSummaryItems.Flags | OtherItemsYouCareAbout).Select (x => new MyMessageInfo (x.UniqueId, x.Flags).ToList ();
// .. some time passes, invoke NoOp:
client.NoOp ();
if (this.new_messages) {
this.new_messages = false;
var new_messages = folder.Fetch (this.messages.Count, -1, MessageSummaryItems.UniqueId | MessageSummaryItems.Flags | OtherItemsYouCareAbout).Select (x => new MyMessageInfo (x.UniqueId, x.Flags);
this.messages.AddRange (new_messages);
}Then, in your event handlers, you might have code that looks like this: void OnMessageExpunged (object sender, MessageEventArgs e)
{
// update our list of messages by removing the index of the message that just got expunged
this.messages.RemoveAt (e.Index);
}
void OnMessageFLagsChanged (object sender, MessageFlagsChangedEventArgs e)
{
// update the flags for the message at the specified index
this.messages[e.Index].Flags = e.Flags;
}
void OnCountChanged (object sender, EventArgs e)
{
var folder = (ImapFolder) sender;
// folder.Count will either be exactly the same as this.messages.Count
// -or-
// it will be larger if new messages have arrived
this.new_messages = folder.Count > messages.Count;
}Now you can stay in sync with the server and not have to constantly re-Search. |
|
Hi, From time to time, while trying to disconnect the ImapClient, I get the following exception:
I apologize for missing the protocol details, since the problem occurs in the release version. Before trying to disconnect, we try to stop the idling thread. public void LogoutAndDisconnect()
{
try
{
if (IsAuthenticated)
StopIdling();
if (IsConnected)
_client.Disconnect(true);
_client = null;
_inboxFolder = _processedFolder = _unprocessedFolder = null;
}
catch (Exception ex)
{
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex, string.Format(UNEXPECTED_ERROR, MethodBase.GetCurrentMethod().Name, ChannelCode, InboxFolderName, ex.Message));
}
}
public void ConnectAndLogin()
{
if (_client == null)
{
#if DEBUG
_client = new ImapClient(new ProtocolLogger(Console.OpenStandardError()));
#else
_client = new ImapClient();
#endif
_client.ServerCertificateValidationCallback = delegate { return true; };
}
try
{
var ok = TryConnectAndLogin();
if (!ok)
{
EventLogManager.Instance.WriteEntry(EventLogType.Error, string.Format(LOGIN_FAILED, Username, ChannelCode));
LogoutAndDisconnect();
}
}
catch (Exception ex)
{
var err = string.Format(UNEXPECTED_ERROR, MethodBase.GetCurrentMethod().Name, ChannelCode, InboxFolderName, ex.Message);
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex, err);
LogoutAndDisconnect();
}
}
public void StopIdling()
{
lock (_syncRoot)
{
try
{
if (_isIdle && _done?.IsCancellationRequested != true)
{
_done.Cancel();
_done.Dispose();
}
// if the thread doesn't end in 30 seconds, then abort it
_thread?.Join(30 * 100);
if (_thread?.IsAlive == true)
_thread.Abort();
_thread = null;
}
catch (Exception ex)
{
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex, string.Format(UNEXPECTED_ERROR, MethodBase.GetCurrentMethod().Name, ChannelCode, InboxFolderName, ex.Message));
}
}
}
public void StartIdling(bool connectAndLogin = true)
{
lock (_syncRoot)
{
if (connectAndLogin)
ConnectAndLogin();
if (IsConnected && IsAuthenticated && !_isIdle)
{
if (InboxFolder == null) // we check the property here, not the field, in order to initialize it if necessary !
return;
if (!_inboxFolder.IsOpen)
{
_inboxFolder.CountChanged -= Folder_CountChanged;
_inboxFolder.Open(FolderAccess.ReadWrite);
_inboxFolder.CountChanged += Folder_CountChanged;
}
_done = new CancellationTokenSource();
_thread = new Thread(IdleLoop);
_thread.Start(new IdleState(_client, _done.Token));
// the server should answer with "IDLE accepted, awaiting DONE command", so we give it max 10 seconds for safety
SpinWait.SpinUntil(() => _isIdle, 10 * 1000);
}
}
}We use the IdleState and IdleLoop taken from your sample ImapIdle.sln: #region - IdleState and IdleLoop
private class IdleState
{
readonly object mutex = new object();
CancellationTokenSource timeout;
/// <summary>
/// Get the cancellation token.
/// </summary>
/// <remarks>
/// <para>The cancellation token is the brute-force approach to cancelling the IDLE and/or NOOP command.</para>
/// <para>Using the cancellation token will typically drop the connection to the server and so should
/// not be used unless the client is in the process of shutting down or otherwise needs to
/// immediately abort communication with the server.</para>
/// </remarks>
/// <value>The cancellation token.</value>
public CancellationToken CancellationToken { get; private set; }
/// <summary>
/// Get the done token.
/// </summary>
/// <remarks>
/// <para>The done token tells the <see cref="Program.IdleLoop"/> that the user has requested to end the loop.</para>
/// <para>When the done token is cancelled, the <see cref="Program.IdleLoop"/> will gracefully come to an end by
/// cancelling the timeout and then breaking out of the loop.</para>
/// </remarks>
/// <value>The done token.</value>
public CancellationToken DoneToken { get; private set; }
/// <summary>
/// Get the IMAP client.
/// </summary>
/// <value>The IMAP client.</value>
public ImapClient Client { get; private set; }
/// <summary>
/// Check whether or not either of the CancellationToken's have been cancelled.
/// </summary>
/// <value><c>true</c> if cancellation was requested; otherwise, <c>false</c>.</value>
public bool IsCancellationRequested
{
get
{
return CancellationToken.IsCancellationRequested || DoneToken.IsCancellationRequested;
}
}
/// <summary>
/// Initializes a new instance of the <see cref="IdleState"/> class.
/// </summary>
/// <param name="client">The IMAP client.</param>
/// <param name="doneToken">The user-controlled 'done' token.</param>
/// <param name="cancellationToken">The brute-force cancellation token.</param>
public IdleState(ImapClient client, CancellationToken doneToken, CancellationToken cancellationToken = default(CancellationToken))
{
CancellationToken = cancellationToken;
DoneToken = doneToken;
Client = client;
// When the user hits a key, end the current timeout as well
doneToken.Register(CancelTimeout);
}
/// <summary>
/// Cancel the timeout token source, forcing ImapClient.Idle() to gracefully exit.
/// </summary>
void CancelTimeout()
{
lock (mutex)
{
if (timeout != null)
timeout.Cancel();
}
}
/// <summary>
/// Set the timeout source.
/// </summary>
/// <param name="source">The timeout source.</param>
public void SetTimeoutSource(CancellationTokenSource source)
{
lock (mutex)
{
timeout = source;
if (timeout != null && IsCancellationRequested)
timeout.Cancel();
}
}
}
private static void IdleLoop(object state)
{
var idle = (IdleState)state;
lock (idle.Client.SyncRoot)
{
// Note: since the IMAP server will drop the connection after 30 minutes, we must loop sending IDLE commands that
// last ~29 minutes or until the user has requested that they do not want to IDLE anymore.
//
// For GMail, we use a 9 minute interval because they do not seem to keep the connection alive for more than ~10 minutes.
while (!idle.IsCancellationRequested)
{
using (var timeout = new CancellationTokenSource(new TimeSpan(0, 0, CustomerEmailsConfig.NoopIssueTimeout)))
{
try
{
// We set the timeout source so that if the idle.DoneToken is cancelled, it can cancel the timeout
idle.SetTimeoutSource(timeout);
if (idle.Client.Capabilities.HasFlag(ImapCapabilities.Idle))
{
// The Idle() method will not return until the timeout has elapsed or idle.CancellationToken is cancelled
idle.Client.Idle(timeout.Token, idle.CancellationToken);
}
else
{
// The IMAP server does not support IDLE, so send a NOOP command instead
idle.Client.NoOp(idle.CancellationToken);
// Wait for the timeout to elapse or the cancellation token to be cancelled
WaitHandle.WaitAny(new[] { timeout.Token.WaitHandle, idle.CancellationToken.WaitHandle });
}
}
catch (OperationCanceledException ex)
{
// This means that idle.CancellationToken was cancelled, not the DoneToken nor the timeout.
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex);
break;
}
catch (ImapProtocolException ex)
{
// The IMAP server sent garbage in a response and the ImapClient was unable to deal with it.
// This should never happen in practice, but it's probably still a good idea to handle it.
//
// Note: an ImapProtocolException almost always results in the ImapClient getting disconnected.
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex);
break;
}
catch (ImapCommandException ex)
{
// The IMAP server responded with "NO" or "BAD" to either the IDLE command or the NOOP command.
// This should never happen... but again, we're catching it for the sake of completeness.
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex);
break;
}
catch (IOException ex)
{
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex);
break;
}
catch (Exception ex)
{
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex);
break;
}
finally
{
// We're about to Dispose() the timeout source, so set it to null.
idle.SetTimeoutSource(null);
}
}
}
}
}
#endregionI suspect that sometimes the idle thread cannot be terminated so that the Disconnect fails to be done. Please advise. |
|
The Idle/IdleAsync methods take 2 CancellationToken arguments: What I would do is, after cancelling This may still fail currently, but I've been working toward making cancel even more solid. I've made changes to SmtpClient so far and once I know that approach works for sure, I'll be adding it to ImapClient and Pop3Client. |
|
Hi Jstedfast, public void StopIdling()
{
lock (_syncRoot)
{
try
{
if (_isIdle && _done?.IsCancellationRequested != true)
{
_done.Cancel();
_done.Dispose();
}
// if the thread doesn't end in 30 seconds, then use the cancelation token
_thread?.Join(30 * 1000);
if (_thread?.IsAlive == true)
{
_cancel?.Cancel();
_thread?.Join(30 * 1000);
// if the thread doesn't end in 30 seconds, then abort it
if (_thread?.IsAlive == true)
_thread.Abort();
}
_thread = null;
}
catch (Exception ex)
{
EventLogManager.Instance.WriteEntry(EventLogType.Error, ex, string.Format(UNEXPECTED_ERROR, MethodBase.GetCurrentMethod().Name, ChannelCode, InboxFolderName, ex.Message));
}
}
}
public void StartIdling(bool connectAndLogin = true)
{
lock (_syncRoot)
{
if (connectAndLogin)
ConnectAndLogin();
if (IsConnected && IsAuthenticated && !_isIdle)
{
if (InboxFolder == null) // we check the property here, not the field, in order to initialize it if necessary !
return;
if (!_inboxFolder.IsOpen)
{
_inboxFolder.CountChanged -= Folder_CountChanged;
_inboxFolder.Open(FolderAccess.ReadWrite);
_inboxFolder.CountChanged += Folder_CountChanged;
}
_done = new CancellationTokenSource();
_cancel = new CancellationTokenSource();
_thread = new Thread(IdleLoop);
_thread.Start(new IdleState(_client, _done.Token, _cancel.Token));
// the server should answer with "IDLE accepted, awaiting DONE command", so we give it max 10 seconds for safety
SpinWait.SpinUntil(() => _isIdle, 10 * 1000);
}
}
}Additionally, do you recommend to do something in the catch block or to add a finally block? (in the StopIdling method). For example to abort the _thread if still alive. |
|
Also, do you think it's better to declare the IdleLoop method as instance method (instead of static)? |
|
Your new StopIdling() method looks exactly how I was recommending. As far as adding a finally goes, I've got a few thoughts:
That leaves your The only potential problem I see in your StopIdling method right now is that } finally {
if (_done != null)
_done.Dispose ();
}As far as making IdleLoop an instance vs static, I'm not sure it really matters. |
|
Hi Jstedfast, thank you so much for the useful suggestions !!! I just reproduced a scenario that might be the cause of the problems: The StartIdling method is called on every minute, and as you can see its code from above, based on the _idle flag value it renews the tokens and starts the new _thread. So it seems to be a concurrency issue, when the IdleLoop's timeout just expired (i.e. at 5 min) and at the same time the StartIdling was called. |
|
I would probably recommend avoiding the use of a boolean variable for this and use a ManualResentEvent instead. |
|
Hi Jeffrey, I continue on this thread, even if it is not on the same subject.
I know that you fixed similar issues in past. Please advise. |
|
That log doesn't contain the word The exception you are getting is because the IMAP response parser is encountering the word |
|
Hi Jeffrey, |
|
No, there's no way to do that. |
|
Ok, thank you! Maybe in future versions :). |
|
Actually... what you could do is write your own IProtocolLogger implementation that only writes the first line of the command and drops the rest of it. |
|
Interesting idea, but what do you think if derive from MailKit.ProtocolLogger and override the |
|
That won't work because MailKit will chunk the command to the logger, so the buffer does not necessarily contain the full command. |
|
Hi Jeffrey, The existing MailKit.ProtocolLogger code seems quite complex and I'm afraid to adjust it right now. |
|
All you need to do is buffer the data before it gets pushed to the underlying log stream: When LogClient() gets called, append it to the client buffer. When LogServer() gets called, you know the client buffer is complete and then you can print just the first and last lines. When LogServer() gets called, append it to the client buffer. When LogClient() gets called, you know the server buffer is complete and then you can print just the first and last lines. |
|
Hi Jeffrey,
Thank you. |
|
Not using the one provided by MailKit, but you could write your own that does. |
What were you trying to do?
Previously in 1.22.0, I was successfully able to listen for notifications without using IDLE and just NoOp. When an event is triggered, I would search the Inbox for any unseen items (if there were any) and if there were new items, it would parse the new messages.
What happened?
After updating to 2.0.0
When attempting to Fetch the items in the Inbox, I am getting the following message
This message occurs at the following commands under the EventHandler.
Oddly enough, I downgraded back to 1.22.0, and my issue went away, and everything works as I had expected.
Please let me know if there is anything more that I need to provide. I have no problem providing my code through email preferably.
The text was updated successfully, but these errors were encountered: