[IOTDB-125] [potential] a concurrency conflict may occur when a delete command and insertion command appears concurrently

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.10.0
• Labels: medium pull-request-available
• Assignee: Yuan Tian
• Reporter: xiangdong Huang
• Created: 02/Jul/19 13:30
• Updated: 25/Apr/20 08:26
• Resolved: 25/Apr/20 08:26

Description

• Hi, 

we find a potential bug,

Suppose client A calls a delete time series root.sg1.*, then  OverflowQPExecutor.java's operateMetadata() will be called.

 At the same time, client B calls a insertion command insert into root.sg1.d1.s1 ..., then the bug may appear:

1. B checks the schema and find sg1.d1.s1 is valid, then B is waiting for the write lock of related StorageGroupProcessor,

2. A removes the definition of time series in SG1,  all data files of SG1 and then return back;

3. B gets the write lock and write data successfully; finally, the data is flushed on disk.

Then, if client C calls `select * from root.sg1`, C gets nothing because there is no time series defined under the storage group.

Now client C creates sg1.d1.s1 again, and then executes `select * from root.sg1`, C will find the data that B wrote....

 

A solution is set a database-level read write lock. For all operations which will modify the schema, the write lock is needed; For all other operations (e.g., insertion), the read lock is needed.

(We need to consider the cost of calling the read lock for each insertion operation)

 

 

Issue Links

• links to: GitHub Pull Request #1088