Add vif: OCaml 5 web framework with Miou multicore scheduler#85
Add vif: OCaml 5 web framework with Miou multicore scheduler#85BennyFranciscus wants to merge 5 commits intoMDA2AV:mainfrom
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vif is built on httpcats and the Miou cooperative/preemptive scheduler, taking advantage of OCaml 5 domains for multicore HTTP serving. Key highlights: - Pure OCaml stack (TLS, crypto, compression all in OCaml) - Typed routing checked at compile time - httpcats engine for HTTP/1.1 parsing and connection management - Gzip compression via decompress (pure OCaml zlib implementation) Endpoints: baseline, pipelined, json, compression, upload, db, noisy, mixed References: - https://github.com/robur-coop/vif - https://github.com/robur-coop/httpcats - Tutorial: https://robur-coop.github.io/vif/
…POST content The routing DSL has two 'any' values: - Uri.any: wildcard for query parameters (used with /??) - Type.any: wildcard for content types (used with post) Opening Type shadowed Uri.any, causing a type mismatch on query routes. Fix: remove 'open Type', qualify post content-type as Type.any, and use nil for routes that don't need query params.
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Good catch, yeah that's dumb — the small dataset is static too so there's zero reason to recompute it per request. I'll cache the processed result at startup like |
json_endpoint was calling process_items on every request while the dataset is static. Cache the processed result at startup, matching what large_payload already does for the compression endpoint. Co-authored-by: jerrythetruckdriver
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Fixed in 0b60e6e — |
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/benchmark |
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🚀 Benchmark run triggered for |
Benchmark ResultsFramework: Full log |
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Nice, thanks for running the benchmarks! Results are roughly where I expected for a first OCaml 5 entry. The pipelined numbers are the standout — 25K req/s at 512c shows Miou's multicore scheduler handles connection multiplexing well. The drop-off to 9.3K at 16384c is steep though, might be worth looking at how httpcats handles fd pressure at that scale. Baseline sits around 3-4.5K which is modest, but honestly not bad for a beta framework that's doing OCaml effects-based scheduling under the hood. The upload endpoint is broken though — 0 req/s, memory ballooned to 3.8GiB and it just stopped responding after a handful of requests. Looking at the logs it seems like the streaming body read is accumulating in memory instead of being processed incrementally. I'll dig into the vif upload handler — probably need to handle the body chunks differently with the Miou scheduler to avoid buffering everything. Will push a fix for upload and we can re-run. |
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@BennyFranciscus cpu usage is very low, are we doing async or parallel properly? |
- Set domains = Domain.recommended_domain_count() - 1 in Vif.config (was defaulting to 1 domain = single core, explaining ~550% CPU instead of ~8000% on the benchmark machine) - Replace Flux.Stream-based body reading with direct Source pull loop to fix upload OOM (memory was ballooning to 3.8GiB then timing out at 0 req/s)
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Good catch — the low CPU usage was because I wasn't setting the Fixed in dce05bf: now uses Also fixed the upload endpoint in the same commit — replaced the Should be ready for a re-benchmark whenever — expecting a significant jump in the numbers with proper parallelism. 🤞 |
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Oops — the upload streaming fix I pushed in dce05bf had a typo: Still waiting on the re-benchmark with multicore domains enabled — the first run was only using 1 core (~550% CPU). With the |
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CI is green now ✅ — both detect and validate passing. The benchmark at 09:56 ran on the old code (single-core default, broken upload). Since then:
Ready for a re-benchmark whenever — expecting a solid jump in throughput with all cores active. 🤞 |
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/benchmark |
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🚀 Benchmark run triggered for |
Benchmark ResultsFramework: Full log |
Benchmark Results AnalysisThanks for the re-benchmark! The non-upload numbers with multicore enabled look solid:
The upload profile is the problem — 6 req/s at 64c, 0 req/s at 256c with memory ballooning to 11.9GB. Root causeOur
This is a framework-level behavior — there's no application-level workaround. It would need changes in vif's HTTP parser to expose a true streaming body API that yields chunks as they arrive from the socket. @dinosaure — is there a way to configure vif to not buffer the full request body? Or would that need a change in the framework itself? The upload benchmark sends 20MB POST bodies at high concurrency, so streaming from the socket is pretty important here. Other notes
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Firstly, the recent benchmarks carried out with Vif are based on a pre-release version that I can release in the coming days if necessary. Furthermore, these are the $ opam pin add httpcats git+https://github.com/robur-coop/httpcats.git#0883aebb68c6bc58eb36c787e1a54090f508ae29
$ opam pin add vif https://github.com/robur-coop/vif.git#8c6ac3fb97cb9a31bf6ad8ec63c942336dcfd03eNext, from what I can see, |
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Thanks for looking into this @dinosaure! You're right — looking at So the bottleneck might be elsewhere. A couple of theories:
ReproducingThe benchmark tool sends concurrent 20MB POST requests to # Generate a 20MB file
dd if=/dev/urandom of=/tmp/testfile bs=1M count=20
# Low concurrency (should work fine)
wrk -t4 -c64 -d10s -s post.lua http://localhost:8080/upload
# post.lua: wrk.method = "POST"; wrk.body = io.open("/tmp/testfile"):read("*a")
# High concurrency (this is where it breaks)
wrk -t4 -c256 -d10s -s post.lua http://localhost:8080/uploadAt 64c we saw ~6 req/s with memory climbing to 3GB. At 256c it hit 11.9GB and effectively stalled (0 req/s). For reference, other frameworks doing the same streaming-count pattern handle 256c at 300-500+ req/s with stable memory. If the pre-release versions you mentioned have changes that could help here, happy to pin to those and re-test! |
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@BennyFranciscus I'll try fix this locally, stay standby on this PR |
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With the upstream versions (and 8 cores), I get these results and can confirm (via the logs) that > taskset -c 16-27 wrk -t4 -c256 -d10s -s post.lua http://localhost:8080/upload
Running 10s test @ http://localhost:8080/upload
4 threads and 256 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 0.00us 0.00us 0.00us -nan%
Req/Sec 17.13 17.48 90.00 84.16%
248 requests in 10.09s, 20.59KB read
Socket errors: connect 0, read 0, write 0, timeout 248
Requests/sec: 24.58
Transfer/sec: 2.04KB
> taskset -c 16-27 wrk -t4 -c64 -d10s -s post.lua http://localhost:8080/upload
Running 10s test @ http://localhost:8080/upload
4 threads and 64 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 1.17s 322.22ms 1.80s 61.09%
Req/Sec 15.99 11.01 50.00 74.82%
514 requests in 10.09s, 42.67KB read
Requests/sec: 50.94
Transfer/sec: 4.23KBYou can change the size of the buffers used via |
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Thanks for testing this on your end @dinosaure — really helpful to have the framework author's perspective here! So if vif isn't buffering, that narrows it down. Your numbers actually confirm what we're seeing though — even on your machine with 8 cores:
For 20MB uploads those numbers are in the same ballpark as our benchmark results, so at least we're seeing the same behavior. Good call on the @MDA2AV heads up — dinosaure suggests pinning to the upstream versions and tweaking |
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Replaces #84 (closed due to branch protection blocking fixes).
What
Adds vif — an OCaml 5 web framework built on the Miou multicore scheduler, replacing the Dream entry per discussion on PR #25.
Stack
~compression:\Gzip`)Changes from #84
Uri.anyfor query wildcards vsType.anyfor POST content-type matchingnilfor routes that don't accept query parameters (pipeline, json, compression, upload)Endpoints
All 8 standard HttpArena endpoints implemented:
/pipeline— simple text response/baseline11GET/POST — query param sum + body/baseline2— query param sum/json— dataset processing/compression— gzip compressed response/upload— streaming body read with byte counting/db— SQLite query with parameterized range