45 lines
2.3 KiB
Markdown
45 lines
2.3 KiB
Markdown
# 3. Payload: the one comparison that needs no benchmark
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Previous: [2. Benchmarks](02-benchmarks.md) · Next: [4. Back-pressure](04-backpressure.md)
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---
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Five fields — a symbol, a sequence number, two doubles and a timestamp — encoded three
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ways ([`payload-sizes.txt`](output/payload-sizes.txt)):
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```
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protobuf : 35 bytes 0a044141504c102a197b14ae47e11a5940215c8fc2f5281c5940288080abb4fef39203
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JSON : 83 bytes {"symbol":"AAPL","seq":42,"bid":100.42,"ask":100.44,"epochMicros":1772000000000000}
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CBOR : 67 bytes bf6673796d626f6c644141504c63736571182a63626964fb40591ae147ae147b6361736bfb40591c28f5c28f5c6b65706f63684d6963726f731b00064b9fe68ac000ff
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JSON is 2.37x protobuf; CBOR is 1.91x protobuf
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```
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This is a property of the formats, not of a machine, so it is the one row of the comparison that
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transfers to your hardware unchanged.
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**Protobuf is 35 bytes because field names are integers.** `0a04 41 41 50 4c` is field 1, length
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4, `AAPL`. There is no `"symbol"` on the wire at all — the name lives in the `.proto` file
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that both sides compiled against. That is where the size comes from, and it is also the whole
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argument about schemas: the saving and the coupling are the same fact.
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**CBOR is 67 bytes and still writes the field names.** `6673796d626f6c` is a 6-character text
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string, `symbol`. CBOR is binary JSON, not a schema format: it saves the punctuation and encodes
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numbers compactly, and it keeps every key. So its advantage over JSON is real but modest, and it
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does not require the coupling.
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Concretely, on a stream of a million quotes: 35 MB, 67 MB, 83 MB. On a loopback
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that difference disappears into memory bandwidth — which is exactly why the benchmarks in
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[chapter 2](02-benchmarks.md) do not reward it and a real link would.
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Two practical notes:
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- **Spring's RSocket default is CBOR**, not JSON, which is why
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`spring-boot-starter-rsocket` brings `jackson-dataformat-cbor`. If you are debugging with
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`tcpdump` and expecting to read your payloads, that is why you cannot.
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- **You can put protobuf on RSocket.** The encoding and the protocol are independent choices;
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the row above is what each stack does *by default*, not what it is capable of.
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---
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Previous: [2. Benchmarks](02-benchmarks.md) · Next: [4. Back-pressure](04-backpressure.md)
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