Add minor precompile workload

[rikhuijzer]

Just like my attempt in #738, I'm on a mission to reduce the time to first HTTP.get. Precompile a bigger part of the workload seems like low hanging fruit compared to the rewrite in that PR.

As a proof-of-concept, I've only added HTTP.get for now.

Demo

I've run @time using HTTP; @time HTTP.get("http://example.com") twice on master and precompile with Julia 1.7-beta3.0:

rik@nixos ~/g/HTTP.jl (master)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]
  2.374460 seconds (1.87 M allocations: 102.031 MiB, 0.87% gc time, 1.02% compilation time)
  3.711768 seconds (7.92 M allocations: 418.646 MiB, 6.11% gc time)

rik@nixos ~/g/HTTP.jl (precompile)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]
  4.184486 seconds (1.99 M allocations: 109.878 MiB, 0.51% gc time, 0.58% compilation time)
  3.053110 seconds (4.49 M allocations: 239.125 MiB, 1.89% gc time)

rik@nixos ~/g/HTTP.jl (master)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]
  2.416790 seconds (1.87 M allocations: 102.046 MiB, 0.88% gc time, 1.02% compilation time)
  3.486002 seconds (7.92 M allocations: 418.657 MiB, 4.36% gc time)

rik@nixos ~/g/HTTP.jl (precompile)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]
  4.140951 seconds (1.99 M allocations: 109.938 MiB, 0.48% gc time, 0.59% compilation time)
  3.161522 seconds (4.49 M allocations: 239.152 MiB, 1.82% gc time)

As you can see, precompilation takes 2 seconds longer on precompile. However, the first HTTP.get is sped up by 0.3-0.7 seconds (allocations are reduced by 180 MiB).

@timholy, could you take a quick look to see whether I've implemented it correctly?

[rikhuijzer]

I don't know why the tests fail. The tests pass locally on Julia 1.6.1 and Julia 1.7-beta3.0.

[rikhuijzer]

Updated demo

With Julia 1.6.2:

rik@nixos ~/g/HTTP.jl (master)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]
  2.603166 seconds (2.05 M allocations: 121.065 MiB, 1.15% gc time, 22.43% compilation time)
  3.317185 seconds (7.53 M allocations: 431.373 MiB, 6.20% gc time, 1.45% compilation time)

rik@nixos ~/g/HTTP.jl (master)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
  0.537877 seconds (606.13 k allocations: 36.799 MiB)
  3.214055 seconds (7.53 M allocations: 431.381 MiB, 5.26% gc time, 1.42% compilation time)



rik@nixos ~/g/HTTP.jl (precompile)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]
  4.123068 seconds (2.16 M allocations: 128.386 MiB, 0.55% gc time, 13.66% compilation time)
  2.650265 seconds (4.22 M allocations: 244.392 MiB, 2.28% gc time, 95.24% compilation time)

rik@nixos ~/g/HTTP.jl (precompile)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
  0.604902 seconds (715.10 k allocations: 44.111 MiB, 1.62% gc time)
  2.792045 seconds (4.22 M allocations: 244.404 MiB, 1.58% gc time, 91.93% compilation time)



rik@nixos ~/g/HTTP.jl (master)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]
  2.612097 seconds (2.05 M allocations: 121.121 MiB, 1.18% gc time, 24.54% compilation time)
  3.233083 seconds (7.53 M allocations: 431.332 MiB, 5.80% gc time, 1.39% compilation time)

rik@nixos ~/g/HTTP.jl (master)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
  0.559991 seconds (606.08 k allocations: 36.856 MiB)
  3.239811 seconds (7.53 M allocations: 431.340 MiB, 4.34% gc time, 1.46% compilation time)



rik@nixos ~/g/HTTP.jl (precompile)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]
  4.284226 seconds (2.16 M allocations: 128.239 MiB, 0.66% gc time, 13.38% compilation time)
  2.751134 seconds (4.22 M allocations: 244.407 MiB, 1.93% gc time, 95.25% compilation time)

rik@nixos ~/g/HTTP.jl (precompile)> julia --project -ie '@time using HTTP; @time HTTP.get("http://example.com")'
  0.609435 seconds (712.96 k allocations: 43.971 MiB, 1.55% gc time)
  2.675962 seconds (4.22 M allocations: 244.419 MiB, 2.00% gc time, 95.28% compilation time)

So, this gives the following means and means differences over two runs:

Stage	master-branch time (allocations)	precompile-branch time (allocations)	difference time (allocations)
using HTTP.jl with precompilation (2 datapoints)	2.6 seconds (2.05 MiB)	4.2 seconds (2.16 MiB)	+62% (+5%)
using HTTP.jl (2 datapoints)	0.54 seconds (36.75 MiB)	0.6 seconds (43.5 MiB)	+11% (+19%)
HTTP.get (4 datapoints)	3.2 seconds (431 MiB)	2.7 seconds (244 MiB)	-15% (-43%)

EDIT: I leave it up to you to decide whether this tradeoff is worth it. I think that saving about 0.5 seconds per use is worth it, but I might be biased.

[rikhuijzer]

Is it possible that the tests fail due to a missing API key? In one of the test failures, I see "{\"error\":\"Missing apiKey\"}". Locally, the tests pass.

[quinnj]

Is it possible that the tests fail due to a missing API key? In one of the test failures, I see "{\"error\":\"Missing apiKey\"}". Locally, the tests pass.

Yes, it's a current known issue for PRs coming from forks.

[fredrikekre]

Personally I think it is a bit strange that HTTP.jl would do a HTTP request during precompilation. What if there is a server listening on this port?

Isn't this simple enough to handle via PackageCompiler?

[timholy]

PackageCompiler should be our past, not our future 😄. The future should be nice compiled code cached with each package, each upgradable independently.

[rikhuijzer]

Yes, I'm aware that the implementation isn't perfect yet and am definitely open to better ideas