xiangdong Huang created IOTDB-106:
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Summary: How about add a new strategy to close data files in IoTDB
according to the memory usage
Key: IOTDB-106
URL: https://issues.apache.org/jira/browse/IOTDB-106
Project: Apache IoTDB
Issue Type: Wish
Reporter: xiangdong Huang
Different with other LSM-based systems, IoTDB will flush multiple memtable into
one TsFile file.
The TsFile can support append memtables one by one unless a "close file"
operation is called.
Suppose $n$ memtables are flushed into one un-closed TsFile (called unsealed
file in the source code), these memtables' metadata will be hold in memory,
which may lead to high cost of memory under some heavy workloads.
Now there are 3 strategies to trigger a "close" operation: (1) call the
operation per `period_time_for_flush_in_second` seconds (configured in
iotdb-engine.properties); (2) if the unsealed tsfile size reaches to
`bufferwrite_file_size_threshold` (also configured in the same setting file);
(3) user call `flush` in the iotdb-cli shell.
How about add a new strategy: only allow $max$ metadata in memory. If the
number in memory exceeds $max$, seal the file. In advance, $max$ can be
calculated according to the available memory.
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