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Finish first draft

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Bradlee Speice 2019-09-28 00:18:20 -04:00
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_posts/2019-09-01-binary-format-shootout.md
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---
layout: post
title: "Binary Format Shootout"
description: "Making sense of binary streams"
description: "Cap'n Proto vs. Flatbuffers vs. SBE"
category:
tags: [rust]
---
@ -161,11 +161,40 @@ message to indicate the size. Not specifically a problem, but I would've rather
Ultimately, I enjoyed using Flatbuffers, and had to do significantly less work to make it perform well.
# Final Results
# Part 3: Simple Binary Encoding
NOTE: Need to expand on this, but numbers reported below are from the IEX's 2019-09-03 data, took average over 10 runs.
Support for SBE was added by the author of one of my favorite
[Rust blog posts](https://web.archive.org/web/20190427124806/https://polysync.io/blog/session-types-for-hearty-codecs/).
I've [talked previously]({% post_url 2019-06-31-high-performance-systems %}) about how important variance is in
high-performance systems, so it was encouraging to read about a format that
[directly addressed](https://github.com/real-logic/simple-binary-encoding/wiki/Why-Low-Latency) my concerns. SBE has by far
the simplest binary format, but it does make some tradeoffs.
Serialization
Both Cap'n Proto and Flatbuffers use [pointers in their messages](https://capnproto.org/encoding.html#structs) to handle
variable-length data, [unions](https://capnproto.org/language.html#unions), and a couple other features. In contrast,
messages in SBE are essentially [primitive structs](https://github.com/real-logic/simple-binary-encoding/blob/master/sbe-samples/src/main/resources/example-schema.xml);
variable-length data is supported, but there's no union type.
As mentioned in the beginning, the Rust port of SBE is certainly usable, but is essentially unmaintained. However, if you
don't need union types, and can accept that schemas are XML documents, it's still worth using.
# Results
After building a test harness [for](https://github.com/bspeice/speice.io-md_shootout/blob/master/src/capnp_runner.rs)
[each](https://github.com/bspeice/speice.io-md_shootout/blob/master/src/flatbuffers_runner.rs)
[protocol](https://github.com/bspeice/speice.io-md_shootout/blob/master/src/sbe_runner.rs),
it was time to actually take them for a spin. I used
[this script](https://github.com/bspeice/speice.io-md_shootout/blob/master/run_shootout.sh) to manage the test process,
and the raw results are [here](https://github.com/bspeice/speice.io-md_shootout/blob/master/shootout.csv). All data
reported below is the average of 10 runs over a single day of IEX data. Data checks were implemented to make sure
that each format achieved the same results.
## Serialization
Serialization measures on a
[per-message basis](https://github.com/bspeice/speice.io-md_shootout/blob/master/src/main.rs#L268-L272)
how long it takes to convert the pre-parsed IEX message into the desired format
and write to a pre-allocated buffer.
| Schema | Median | 99th Pctl | 99.9th Pctl | Total |
|:---------------------|:-------|:----------|:------------|:-------|
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| Flatbuffers | 355ns | 2185ns | 3497ns | 14.31s |
| SBE | 91ns | 1535ns | 2423ns | 3.91s |
Deserialization
## Deserialization
Deserialization measures on a
[per-message basis](https://github.com/bspeice/speice.io-md_shootout/blob/master/src/main.rs#L294-L298)
how long it takes to read the message encoded during deserialization and
perform some basic aggregation. The aggregation code is the same for each format,
so any performance differences are due solely to the format implementation.
| Schema | Median | 99th Pctl | 99.9th Pctl | Total |
|:---------------------|:-------|:----------|:------------|:-------|
@ -182,3 +217,12 @@ Deserialization
| Cap'n Proto Unpacked | 366ns | 737ns | 1583ns | 12.32s |
| Flatbuffers | 173ns | 421ns | 1007ns | 6.00s |
| SBE | 116ns | 286ns | 659ns | 4.05s |
# Conclusion
Building a benchmark turned out to be incredibly helpful in making a decision; because a
"union" type isn't important to me, I'll be using SBE for my personal projects.
And while SBE was the fastest in terms of both median and worst-case performance, its worst case
performance was proportionately far higher than any other format. Further research is necessary
to figure out why this is the case. But that's for another time.