2d1ddcbb6a
We saw scylla hit user after free in repair with the following procedure during tests:
- n1 and n2 in the cluster
- n2 ran decommission
- n2 sent data to n1 using repair
- n2 was killed forcely
- n1 tried to remove repair_meta for n1
- n1 hit use after free on repair_meta object
This was what happened on n1:
1) data was received -> do_apply_rows was called -> yield before create_writer() was called
2) repair_meta::stop() was called -> wait_for_writer_done() / do_wait_for_writer_done was called
with _writer_done[node_idx] not engaged
3) step 1 resumed, create_writer() was called and _repair_writer object was referenced
4) repair_meta::stop() finished, repair_meta object and its member _repair_writer was destroyed
5) The fiber created by create_writer() at step 3 hit use after free on _repair_writer object
To fix, we should call wait_for_writer_done() after any pending
operations were done which were protected by repair_meta::_gate. This
prevents wait for writer done finishes before the writer is in the
process of being created.
Fixes: #6853
Fixes: #6868
Backports: 4.0, 4.1, 4.2
(cherry picked from commit e6f640441a)
Scylla
Quick-start
Scylla is fairly fussy about its build environment, requiring very recent versions of the C++20 compiler and of many libraries to build. The document HACKING.md includes detailed information on building and developing Scylla, but to get Scylla building quickly on (almost) any build machine, Scylla offers offers a frozen toolchain, This is a pre-configured Docker image which includes recent versions of all the required compilers, libraries and build tools. Using the frozen toolchain allows you to avoid changing anything in your build machine to meet Scylla's requirements - you just need to meet the frozen toolchain's prerequisites (mostly, Docker or Podman being available).
Building and running Scylla with the frozen toolchain is as easy as:
$ ./tools/toolchain/dbuild ./configure.py
$ ./tools/toolchain/dbuild ninja build/release/scylla
$ ./tools/toolchain/dbuild ./build/release/scylla --developer-mode 1
Running Scylla
- Run Scylla
./build/release/scylla
- run Scylla with one CPU and ./tmp as work directory
./build/release/scylla --workdir tmp --smp 1
- For more run options:
./build/release/scylla --help
Testing
See test.py manual.
Scylla APIs and compatibility
By default, Scylla is compatible with Apache Cassandra and its APIs - CQL and Thrift. There is also experimental support for the API of Amazon DynamoDB, but being experimental it needs to be explicitly enabled to be used. For more information on how to enable the experimental DynamoDB compatibility in Scylla, and the current limitations of this feature, see Alternator and Getting started with Alternator.
Documentation
Documentation can be found in ./docs and on the wiki. There is currently no clear definition of what goes where, so when looking for something be sure to check both. Seastar documentation can be found here. User documentation can be found here.
Training
Training material and online courses can be found at Scylla University. The courses are free, self-paced and include hands-on examples. They cover a variety of topics including Scylla data modeling, administration, architecture, basic NoSQL concepts, using drivers for application development, Scylla setup, failover, compactions, multi-datacenters and how Scylla integrates with third-party applications.
Building a CentOS-based Docker image
Build a Docker image with:
cd dist/docker/redhat
docker build -t <image-name> .
This build is based on executables downloaded from downloads.scylladb.com, not on the executables built in this source directory. See further instructions in dist/docker/redhat/README.md to build a docker image from your own executables.
Run the image with:
docker run -p $(hostname -i):9042:9042 -i -t <image name>