e853191c17
Summary: This patch fixes two issues in DBTest.ApproximateMemoryUsage: - It was possible that a flush happened between getting the two properties in Phase 1, resulting in different numbers for the properties and failing the assertion. This is fixed by waiting for the flush to finish before getting the properties. - There was a similar issue in Phase 2 and additionally there was an issue that rocksdb.size-all-mem-tables was not monotonically increasing because it was possible that a flush happened just after getting the properties and then another flush just before getting the properties in the next round. In this situation, the reported memory usage decreased. This is fixed by forcing a flush before getting the properties. Note: during testing, I found that kFlushesPerRound does not seem very accurate. I added a TODO for this and it would be great to get some input on what to do there. Test Plan: The first issue can be made more likely to trigger by inserting a `usleep(10000);` between the calls to GetIntProperty() in Phase 1. The second issue can be made more likely to trigger by inserting a `if (r != 0) usleep(10000);` before the calls to GetIntProperty() and a `usleep(10000);` after the calls. Then execute make db_test && ./db_test --gtest_filter=DBTest.ApproximateMemoryUsage Reviewers: rven, yhchiang, igor, sdong, anthony Reviewed By: anthony Subscribers: dhruba, leveldb Differential Revision: https://reviews.facebook.net/D45675
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it specially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/master/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Design discussions are conducted in https://www.facebook.com/groups/rocksdb.dev/