Summary:
The problem
-------------
ComparatorOptions is AutoCloseable.
AbstractComparator does not hold a reference to its ComparatorOptions, but the native C++ ComparatorJniCallback holds a reference to the ComparatorOptions’ native C++ options structure. This gets deleted when the ComparatorOptions is closed, either explicitly, or as part of try-with-resources.
Later, the deleted C++ options structure gets used by the callback and the comparator options are effectively random.
The original bug report https://github.com/facebook/rocksdb/issues/8715 was caused by a GC-initiated finalization closing the still-in-use ComparatorOptions. As of 7.0, finalization of RocksDB objects no longer closes them, which worked round the reported bug, but still left ComparatorOptions with a potentially broken lifetime.
In any case, we encourage API clients to use the try-with-resources model, and so we need it to work. And if they don't use it, they leak resources.
The solution
-------------
The solution implemented here is to make a copy of the native C++ options object into the ComparatorJniCallback, rather than a reference. Then the deletion of the native object held by ComparatorOptions is *correctly* deleted when its scope is closed in try/finally.
Testing
-------
We added a regression unit test based on the original test for the reported ticket.
This checkin closes https://github.com/facebook/rocksdb/issues/8715
We expect that there are more instances of "lifecycle" bugs in the Java API. They are a major source of support time/cost, and we note that they could be addressed as a whole using the model proposed/prototyped in https://github.com/facebook/rocksdb/pull/10736
Pull Request resolved: https://github.com/facebook/rocksdb/pull/11176
Reviewed By: cbi42
Differential Revision: D43160885
Pulled By: pdillinger
fbshipit-source-id: 60b54215a02ad9abb17363319650328c00a9ad62
Summary:
Run format check for .h and .cc files to clean the format
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10851
Test Plan: Watch CI tests to pass
Reviewed By: ajkr
Differential Revision: D40649723
fbshipit-source-id: 62d32cead0b3b8e6540e86d25451bd72642109eb
Summary:
When dynamically linking two binaries together, different builds of RocksDB from two sources might cause errors. To provide a tool for user to solve the problem, the RocksDB namespace is changed to a flag which can be overridden in build time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6433
Test Plan: Build release, all and jtest. Try to build with ROCKSDB_NAMESPACE with another flag.
Differential Revision: D19977691
fbshipit-source-id: aa7f2d0972e1c31d75339ac48478f34f6cfcfb3e
Summary:
This is a redesign of the API for RocksJava comparators with the aim of improving performance. It also simplifies the class hierarchy.
**NOTE**: This breaks backwards compatibility for existing 3rd party Comparators implemented in Java... so we need to consider carefully which release branches this goes into.
Previously when implementing a comparator in Java the developer had a choice of subclassing either `DirectComparator` or `Comparator` which would use direct and non-direct byte-buffers resepectively (via `DirectSlice` and `Slice`).
In this redesign there we have eliminated the overhead of using the Java Slice classes, and just use `ByteBuffer`s. The `ComparatorOptions` supplied when constructing a Comparator allow you to choose between direct and non-direct byte buffers by setting `useDirect`.
In addition, the `ComparatorOptions` now allow you to choose whether a ByteBuffer is reused over multiple comparator calls, by setting `maxReusedBufferSize > 0`. When buffers are reused, ComparatorOptions provides a choice of mutex type by setting `useAdaptiveMutex`.
---
[JMH benchmarks previously indicated](https://github.com/facebook/rocksdb/pull/6241#issue-356398306) that the difference between C++ and Java for implementing a comparator was ~7x slowdown in Java.
With these changes, when reusing buffers and guarding access to them via mutexes the slowdown is approximately the same. However, these changes offer a new facility to not reuse mutextes, which reduces the slowdown to ~5.5x in Java. We also offer a `thread_local` mechanism for reusing buffers, which reduces slowdown to ~5.2x in Java (closes https://github.com/facebook/rocksdb/pull/4425).
These changes also form a good base for further optimisation work such as further JNI lookup caching, and JNI critical.
---
These numbers were captured without jemalloc. With jemalloc, the performance improves for all tests, and the Java slowdown reduces to between 4.8x and 5.x.
```
ComparatorBenchmarks.put native_bytewise thrpt 25 124483.795 ± 2032.443 ops/s
ComparatorBenchmarks.put native_reverse_bytewise thrpt 25 114414.536 ± 3486.156 ops/s
ComparatorBenchmarks.put java_bytewise_non-direct_reused-64_adaptive-mutex thrpt 25 17228.250 ± 1288.546 ops/s
ComparatorBenchmarks.put java_bytewise_non-direct_reused-64_non-adaptive-mutex thrpt 25 16035.865 ± 1248.099 ops/s
ComparatorBenchmarks.put java_bytewise_non-direct_reused-64_thread-local thrpt 25 21571.500 ± 871.521 ops/s
ComparatorBenchmarks.put java_bytewise_direct_reused-64_adaptive-mutex thrpt 25 23613.773 ± 8465.660 ops/s
ComparatorBenchmarks.put java_bytewise_direct_reused-64_non-adaptive-mutex thrpt 25 16768.172 ± 5618.489 ops/s
ComparatorBenchmarks.put java_bytewise_direct_reused-64_thread-local thrpt 25 23921.164 ± 8734.742 ops/s
ComparatorBenchmarks.put java_bytewise_non-direct_no-reuse thrpt 25 17899.684 ± 839.679 ops/s
ComparatorBenchmarks.put java_bytewise_direct_no-reuse thrpt 25 22148.316 ± 1215.527 ops/s
ComparatorBenchmarks.put java_reverse_bytewise_non-direct_reused-64_adaptive-mutex thrpt 25 11311.126 ± 820.602 ops/s
ComparatorBenchmarks.put java_reverse_bytewise_non-direct_reused-64_non-adaptive-mutex thrpt 25 11421.311 ± 807.210 ops/s
ComparatorBenchmarks.put java_reverse_bytewise_non-direct_reused-64_thread-local thrpt 25 11554.005 ± 960.556 ops/s
ComparatorBenchmarks.put java_reverse_bytewise_direct_reused-64_adaptive-mutex thrpt 25 22960.523 ± 1673.421 ops/s
ComparatorBenchmarks.put java_reverse_bytewise_direct_reused-64_non-adaptive-mutex thrpt 25 18293.317 ± 1434.601 ops/s
ComparatorBenchmarks.put java_reverse_bytewise_direct_reused-64_thread-local thrpt 25 24479.361 ± 2157.306 ops/s
ComparatorBenchmarks.put java_reverse_bytewise_non-direct_no-reuse thrpt 25 7942.286 ± 626.170 ops/s
ComparatorBenchmarks.put java_reverse_bytewise_direct_no-reuse thrpt 25 11781.955 ± 1019.843 ops/s
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6252
Differential Revision: D19331064
Pulled By: pdillinger
fbshipit-source-id: 1f3b794e6a14162b2c3ffb943e8c0e64a0c03738
Summary:
This PR also includes some cleanup, bugfixes and refactoring of the Java API. However these are really pre-cursors on the road to CompactionFilterFactory support.
Closes https://github.com/facebook/rocksdb/pull/1241
Differential Revision: D6012778
Pulled By: sagar0
fbshipit-source-id: 0774465940ee99001a78906e4fed4ef57068ad5c
Summary:
I have manually audited the entire RocksJava code base.
Sorry for the large pull-request, I have broken it down into many small atomic commits though.
My initial intention was to fix the warnings that appear when running RocksJava on Java 8 with `-Xcheck:jni`, for example when running `make jtest` you would see many errors similar to:
```
WARNING in native method: JNI call made without checking exceptions when required to from CallObjectMethod
WARNING in native method: JNI call made without checking exceptions when required to from CallVoidMethod
WARNING in native method: JNI call made without checking exceptions when required to from CallStaticVoidMethod
...
```
A few of those warnings still remain, however they seem to come directly from the JVM and are not directly related to RocksJava; I am in contact with the OpenJDK hostpot-dev mailing list about these - http://mail.openjdk.java.net/pipermail/hotspot-dev/2017-February/025981.html.
As a result of fixing these, I realised we were not r
Closes https://github.com/facebook/rocksdb/pull/1890
Differential Revision: D4591758
Pulled By: siying
fbshipit-source-id: 7f7fdf4
Alan Paxton