3 ms·

Haven’t watched the video either, so asking perhaps a naive question: Why is it faster? Is it algorithmic, or some neat trick, or just a much more efficient i

Haven’t watched the video either, so asking perhaps a naive question: Why is it faster? Is it algorithmic, or some neat trick, or just a much more efficient implementation? And are they closely equivalent? Would you use one or the other for the same thing, or do they make different CAP promises?

kreetx 5y ago
It appears to be a C++ rewrite of Cassandra (written in Java).
- jeffbee 5y ago
  Similar vibe to redpanda vs. kafka: take a reasonable idea and reimplement it so it isn't terrible. https://vectorized.io/blog/fast-and-safe/ https://vectorized.io/blog/fast-and-safe/
  - dieters 5y ago
    Yup, and redpanda happens to use Scylla's Seastar framework as well
hiyer 5y ago
> Why is it faster? Is it algorithmic, or some neat trick, or just a much more efficient implementation? Scylla is written in C++ (versus Java for Cassandra) and uses the high-performance Seastar[0] framework. > And are they closely equivalent? Would you use one or the other for the same thing, or do they make different CAP promises? Scylla claims to be a drop-in replacement for Cassandra. 0. http://seastar.io/ http://seastar.io/
- nivertech 5y ago
  BTW, there is a word play here: seastar -> sea star -> C* -> Cassandra ;)
jandrewrogers 5y ago
The use of C++ enables a couple architectural optimizations that would be difficult or impractical in Java, aside from C++ generally producing significantly faster runtimes. The important difference is that C++ is a systems language -- you could replace C++ with Rust, Zig, etc -- whereas Java is not. Scylla has a highly optimized low-level I/O path that largely bypasses high-level OS APIs and kernel services that Cassandra and other open source databases tend to use. This will typically generate an integer factor improvement in I/O performance if implemented well and makes a big difference for the kinds of write-heavy workloads Cassandra was built for. It requires taking strict control of low-level memory access and behavior, which (for better and worse) is the default case in C++. This code is intrinsically non-portable. Additionally, there are some important classes of throughput optimization that are incompatible with garbage collection. In principle you can abuse Java to effect these optimizations but it is much easier to implement these optimizations in languages that don't have a garbage collector. If absolute performance is the objective, like Scylla, it is easier to do the implementation in a language that won't fight your intent every step of the way. tl;dr: The performance isn't so much that it is written in C++ but that C++ makes critical optimizations relatively straightforward and economic to implement.
- gunnarmorling 5y ago
  > there are some important classes of throughput optimization that are incompatible with garbage collection Can you share some more details about these optimizations? I.e. what they are and why GC tends to go against them?
- _benedict 5y ago
  In part it's also simply a demonstration of different priorities. Scylla's USP is performance, so a lot of elbow grease is spent there. The Apache Cassandra community is focused primarily on operating at scale, as that's its USP. Performance is adequate for Cassandra, so the community has (for several years) primarily focused elsewhere. It will be a priority again in future, but in the meantime with many huge scale users out there the community has focused on guaranteeing correctness and stability at scale. For example, the Harry[1] toolkit for validating huge databases, and an adversarial cluster simulator[2] for exposing distributed and other complex bugs. Also a huge amount of behind-the-scenes work that isn't so easy to call out. The community is now focusing on expanding the utility of the database for these use cases. For example the recently proposed enhancement to bring state-of-the-art general purpose transactions[3] to Apache Cassandra. [1] https://github.com/apache/cassandra-harry https://github.com/apache/cassandra-harry [2] https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-10%3A+Cluster+and+Code+Simulations https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-10... [3] https://cwiki.apache.org/confluence/download/attachments/188744725/Accord.pdf https://cwiki.apache.org/confluence/download/attachments/188... [edit] disclaimer: I’m an Apache Cassandra contributor involved with some of the above work.

kreetx 5y ago

It appears to be a C++ rewrite of Cassandra (written in Java).

jeffbee 5y ago
Similar vibe to redpanda vs. kafka: take a reasonable idea and reimplement it so it isn't terrible. https://vectorized.io/blog/fast-and-safe/ https://vectorized.io/blog/fast-and-safe/
- dieters 5y ago
  Yup, and redpanda happens to use Scylla's Seastar framework as well

hiyer 5y ago

> Why is it faster? Is it algorithmic, or some neat trick, or just a much more efficient implementation? Scylla is written in C++ (versus Java for Cassandra) and uses the high-performance Seastar[0] framework. > And are they closely equivalent? Would you use one or the other for the same thing, or do they make different CAP promises? Scylla claims to be a drop-in replacement for Cassandra. 0. http://seastar.io/ http://seastar.io/

nivertech 5y ago
BTW, there is a word play here: seastar -> sea star -> C* -> Cassandra ;)

jandrewrogers 5y ago

The use of C++ enables a couple architectural optimizations that would be difficult or impractical in Java, aside from C++ generally producing significantly faster runtimes. The important difference is that C++ is a systems language -- you could replace C++ with Rust, Zig, etc -- whereas Java is not. Scylla has a highly optimized low-level I/O path that largely bypasses high-level OS APIs and kernel services that Cassandra and other open source databases tend to use. This will typically generate an integer factor improvement in I/O performance if implemented well and makes a big difference for the kinds of write-heavy workloads Cassandra was built for. It requires taking strict control of low-level memory access and behavior, which (for better and worse) is the default case in C++. This code is intrinsically non-portable. Additionally, there are some important classes of throughput optimization that are incompatible with garbage collection. In principle you can abuse Java to effect these optimizations but it is much easier to implement these optimizations in languages that don't have a garbage collector. If absolute performance is the objective, like Scylla, it is easier to do the implementation in a language that won't fight your intent every step of the way. tl;dr: The performance isn't so much that it is written in C++ but that C++ makes critical optimizations relatively straightforward and economic to implement.

gunnarmorling 5y ago
> there are some important classes of throughput optimization that are incompatible with garbage collection Can you share some more details about these optimizations? I.e. what they are and why GC tends to go against them?
_benedict 5y ago
In part it's also simply a demonstration of different priorities. Scylla's USP is performance, so a lot of elbow grease is spent there. The Apache Cassandra community is focused primarily on operating at scale, as that's its USP. Performance is adequate for Cassandra, so the community has (for several years) primarily focused elsewhere. It will be a priority again in future, but in the meantime with many huge scale users out there the community has focused on guaranteeing correctness and stability at scale. For example, the Harry[1] toolkit for validating huge databases, and an adversarial cluster simulator[2] for exposing distributed and other complex bugs. Also a huge amount of behind-the-scenes work that isn't so easy to call out. The community is now focusing on expanding the utility of the database for these use cases. For example the recently proposed enhancement to bring state-of-the-art general purpose transactions[3] to Apache Cassandra. [1] https://github.com/apache/cassandra-harry https://github.com/apache/cassandra-harry [2] https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-10%3A+Cluster+and+Code+Simulations https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-10... [3] https://cwiki.apache.org/confluence/download/attachments/188744725/Accord.pdf https://cwiki.apache.org/confluence/download/attachments/188... [edit] disclaimer: I’m an Apache Cassandra contributor involved with some of the above work.