From time to time the Progress & Performance page may show that zero items are imported in the last 10 minutes, but the hourly figures still rise. The speedometers may show zero throughputs.
In addition, if the Import log files are examined they may show high overall CPU usage, and problems or slowness transmitting results to Core.
The log files, for reference, may show:
2015-01-26 16:23:36Z|4796|114| INFO| TransferSuccessItems|Transferring  successful items to core in chunks of  items
The ‘transferring’ command should accumulate a large backlog of items to transmit back to Core when it is operating normally.
The statistics from the module may show:
2015-01-26 16:23:25Z|4796| 73| INFO| OnPerformanceTimerElapsedImpl|Last 2 minute(s) statistics: Count:  | Items/s: [39.48] | kb/s:  | ACPU:  | MaxCPU:  | MinCPU:  | TSize: [1447042 kb] | ASize: [305 kb] | MaxSize: [25032 kb] | | MinSize (kb):  | ATime: [1754 ms] | MaxTime: [288045 ms] | MinTime: [81 ms] 2015-01-26 16:23:25Z|4796| 7| INFO| OnPerformanceTimerElapsedImpl|Last 2 minute(s) statistics: Free memory: [3815 MB] | Avg Free Memory: [3653 MB] | Process Memory: [6122 MB] | Avg Process Memory: [6273 MB] | APCPU: [57 %] | PCPU: [43 %]
This type of issue is particularly relevant to the Exchange and Office 365 Ingest Modules.
The solution for this is that either the parallelism for the module should be lowered, or additional CPU resources should be allocated (which is the easiest option when the machine running the module is virtual)