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Improve IMAP reconnection and error handling in polling

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Refactored PollInboxAsync to better handle IMAP connection drops and protocol errors by reconnecting and resuming processing as needed. Switched from using a using statement to explicit disposal in a finally block. Now logs and recovers from transient IMAP issues, and ensures proper cancellation handling by rethrowing OperationCanceledException. This increases service robustness and reliability.
This commit is contained in:
Peter
2026-04-12 14:23:16 +01:00
parent 387c0dc155
commit 1c00512661
1 changed files with 68 additions and 46 deletions
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114
src/SpamGuard/Services/InboxMonitorService.cs
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@@ -90,62 +90,84 @@ public sealed partial class InboxMonitorService : BackgroundService
private async Task PollInboxAsync(CancellationToken ct)
{
using var client = await _imapFactory.CreateConnectedClientAsync(_imap, ct);
var inbox = client.Inbox;
await inbox.OpenAsync(FolderAccess.ReadWrite, ct);
var client = await _imapFactory.CreateConnectedClientAsync(_imap, ct);
try
{
var inbox = client.Inbox;
await inbox.OpenAsync(FolderAccess.ReadWrite, ct);
// Build search query: only fetch new messages
IList<UniqueId> uids;
if (_lastSeenUid > 0)
{
var range = new UniqueIdRange(new UniqueId(_lastSeenUid + 1), UniqueId.MaxValue);
uids = await inbox.SearchAsync(range, SearchQuery.All, ct);
}
else if (_processedUids.Count > 0)
{
// Resuming from persisted state -- scan recent messages only
uids = await inbox.SearchAsync(
SearchQuery.DeliveredAfter(DateTime.UtcNow.AddDays(-1)), ct);
}
else
{
// First ever run -- initial scan window
uids = await inbox.SearchAsync(
SearchQuery.DeliveredAfter(DateTime.UtcNow.AddDays(-_monitoring.InitialScanDays)), ct);
}
_logger.LogDebug("Found {Count} messages in inbox", uids.Count);
// Find the spam/junk folder
var spamFolder = await FindSpamFolderAsync(client, ct);
foreach (var uid in uids)
{
if (_processedUids.Contains(uid.Id))
// Build search query: only fetch new messages
IList<UniqueId> uids;
if (_lastSeenUid > 0)
{
if (uid.Id > _lastSeenUid) _lastSeenUid = uid.Id;
continue;
var range = new UniqueIdRange(new UniqueId(_lastSeenUid + 1), UniqueId.MaxValue);
uids = await inbox.SearchAsync(range, SearchQuery.All, ct);
}
try
else if (_processedUids.Count > 0)
{
await ProcessMessageAsync(inbox, uid, spamFolder, ct);
// Resuming from persisted state -- scan recent messages only
uids = await inbox.SearchAsync(
SearchQuery.DeliveredAfter(DateTime.UtcNow.AddDays(-1)), ct);
}
catch (Exception ex)
else
{
_logger.LogError(ex, "Error processing UID={Uid}", uid.Id);
_activityLog.Add(new ActivityEntry
// First ever run -- initial scan window
uids = await inbox.SearchAsync(
SearchQuery.DeliveredAfter(DateTime.UtcNow.AddDays(-_monitoring.InitialScanDays)), ct);
}
_logger.LogDebug("Found {Count} messages in inbox", uids.Count);
// Find the spam/junk folder
var spamFolder = await FindSpamFolderAsync(client, ct);
foreach (var uid in uids)
{
if (_processedUids.Contains(uid.Id))
{
Timestamp = DateTime.UtcNow, Sender = "", Subject = $"UID {uid.Id}",
Verdict = Verdict.Error, Reason = ex.Message,
Uid = uid.Id, AccountName = AccountName
});
_processedUids.Add(uid.Id);
if (uid.Id > _lastSeenUid) _lastSeenUid = uid.Id;
continue;
}
try
{
await ProcessMessageAsync(inbox, uid, spamFolder, ct);
}
catch (OperationCanceledException) when (ct.IsCancellationRequested)
{
throw;
}
catch (Exception ex)
{
_logger.LogError(ex, "Error processing UID={Uid}", uid.Id);
_activityLog.Add(new ActivityEntry
{
Timestamp = DateTime.UtcNow, Sender = "", Subject = $"UID {uid.Id}",
Verdict = Verdict.Error, Reason = ex.Message,
Uid = uid.Id, AccountName = AccountName
});
_processedUids.Add(uid.Id);
// Reconnect if the server dropped the connection (e.g. unexpected response after MoveToAsync)
if (!client.IsConnected || ex is MailKit.Net.Imap.ImapProtocolException)
{
_logger.LogWarning("IMAP connection lost for {Account}, reconnecting", AccountName);
try { client.Dispose(); } catch { }
client = await _imapFactory.CreateConnectedClientAsync(_imap, ct);
inbox = client.Inbox;
await inbox.OpenAsync(FolderAccess.ReadWrite, ct);
spamFolder = await FindSpamFolderAsync(client, ct);
}
}
if (uid.Id > _lastSeenUid) _lastSeenUid = uid.Id;
}
if (uid.Id > _lastSeenUid) _lastSeenUid = uid.Id;
await client.DisconnectAsync(true, ct);
}
finally
{
client.Dispose();
}
await client.DisconnectAsync(true, ct);
}
private async Task ProcessMessageAsync(