[sync] PING-SYNC storm

[Arjen de Korte]

Occasionally I see a significant battery drain on my mobile phone that  
syncs through ActiveSync. I enabled debugging and found that during  
such an event it continuously repeats the same PING-SYNC sycle.

When it PINGs the server, it will get a reply status of 2 and in the  
logs it mentions

2013-02-22T14:36:53+01:00 DEBUG: [29575] Initializing state for  
collection: Commercieel, synckey:  
{512745e0-365c-4a01-9e3f-4202c0a8010a}2
2013-02-22T14:36:53+01:00 DEBUG: [29575] Loading state for synckey  
{512745e0-365c-4a01-9e3f-4202c0a8010a}2
2013-02-22T14:36:53+01:00 DEBUG: [29575] Initializing message diff  
engine for Commercieel
2013-02-22T14:36:53+01:00 DEBUG: [29575]  
Horde_Core_ActiveSync_Driver::getServerChanges(Commercieel,  
1361528289, 1361540213, 0, 1)
2013-02-22T14:36:54+01:00 DEBUG: [29575] Found 1 message changes in  
Commercieel.
2013-02-22T14:36:54+01:00 DEBUG: [29575] No PIM changes present,  
returning all messages.

But when it subsequently attempts to SYNC that folder, no changes are found:

2013-02-22T14:36:56+01:00 DEBUG: [29598] Initializing state for  
collection: Commercieel, synckey:  
{512745e0-365c-4a01-9e3f-4202c0a8010a}2
2013-02-22T14:36:56+01:00 DEBUG: [29598] Loading state for synckey  
{512745e0-365c-4a01-9e3f-4202c0a8010a}2
2013-02-22T14:36:56+01:00 DEBUG: [29598] Initializing message diff  
engine for Commercieel
2013-02-22T14:36:56+01:00 DEBUG: [29598]  
Horde_Core_ActiveSync_Driver::getServerChanges(Commercieel,  
1361528289, 1361540216, 1359121016, 0)
2013-02-22T14:36:57+01:00 DEBUG: IMAP status: Array
(
     [uidnext] => 1349
     [uidvalidity] => 1108813680
     [highestmodseq] => 1506
)

2013-02-22T14:36:57+01:00 DEBUG: CONDSTORE and CHANGES
2013-02-22T14:36:57+01:00 DEBUG: [29598] Found 0 message changes in  
Commercieel.

This cycle repeats every few seconds until a new message arrives in  
that folder, after which the situation is back to normal. It looks  
like at times the cached state is out of sync with the IMAP server,  
which is only resolved if new messages arrive. Is there any way I can  
assist in debugging what is going on here?

Best regards, Arjen