Precompile never stops with v 2.0.0?

[colbec]

I see that there has been a major upgrade to 2.0.0. I'm on Julia 1.12.6 and HTTP takes an inordinately long time to precompile. No error messages are generated. I need to get an application up and running so I went back to julia 1.12.5 and HTTP 1.11 and everything is working so no problems.

Since the precompile process is quite silent, I wonder if there is a way to increase the verbosity of the process to verify that progress is actually under way? Admittedly this is a big jump and it might be that my application demands are getting too loud.

[colbec]

I discovered that pressing 'v' while the precompile is in progtess should provide feedback on the machine state as the precompile proceeds. However when I press 'v' no output is generated.

For further info I am running Fedora 44 fully updated.

[quinnj]

Thanks for the report! Precompile workload in 2.0 is much more extensive that previous versions. A couple of things to try/report on:

You can disable precompilation entirely by doing:

using Preferences
set_preferences!("HTTP", "precompile_workload" => false; force=true)

that can at least be an escape hatch for you and more precisely help us know that it is indeed the precompilation workload that is hanging.

Also, how long did you let it run? As I mentioned, it's definitely more extensive than previous versions, and possible it's hitting some extreme compiler case or something where it's technically working, but takes forever.

Can you share the result of versioninfo() and JULIA_NUM_THREADS please?

also if you know of any firewall, SELinux, or ipv6 restrictions or things that may affect localhost serving/callbacks?

[colbec]

Here is version info:

julia>` versioninfo()
Julia Version 1.12.6
Commit 15346901f00 (2026-04-09 19:20 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × Intel(R) Core(TM) i5-4460  CPU @ 3.20GHz
  WORD_SIZE: 64
  LLVM: libLLVM-18.1.7 (ORCJIT, haswell)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 4 virtual cores)

JULIA_NUM_THREADS was not defined for my first attempts, so default values.

The longest I let it run was about 20 minutes.

julia --threads=4
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.12.6 (2026-04-09)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org release
|__/                   |

julia> using Preferences
 │ Package Preferences not found, but a package named Preferences is available from a registry. 
 │ Install package?
 │   (@v1.12) pkg> add Preferences 
 └ (y/n/o) [y]: y
   Resolving package versions...
    Updating `~/.julia/environments/v1.12/Project.toml`
  [21216c6a] + Preferences v1.5.2
    Manifest No packages added to or removed from `~/.julia/environments/v1.12/Manifest.toml`

julia> set_preferences!("HTTP", "precompile_workload" => false; force=true)

(@v1.12) pkg> status HTTP
Status `~/.julia/environments/v1.12/Project.toml`
  [cd3eb016] HTTP v2.0.0

julia> using HTTP
[ Info: Precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3](cache misses: incompatible header (1), dep missing source (1))
Precompiling packages  ╺━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 0/1
(..spinner..) HTTP Being precompiled by another process (pid: 27395, pidfile: /home/colin/.julia/com…

Process 27395 looks entirely normal.
Processor: Intel® Core™ i5-4460 × 4

Still no response from 'v' at the keyboard to trigger progress report.

The spinner is still twiddling away after 15 minutes so I will let it run for a bit and post back with result.

===
Update:
Two hours later still no response. Giving up.

^C Interrupted: Exiting precompilation...
[ Info: Waiting for another process (pid: 27395) to finish precompiling HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3]. Pidfile: /home/colin/.julia/compiled/v1.12/HTTP/zXWya_Cc45j.ji.pidfile

[colbec]

Is there a straightforward way to test whether my localhost is set up according to the requirements in this case? I am not aware of anything which might block the process. My OS is fully up to datebut there might be something I need to install, but what might that be? Applications that require a secure connection don't seem to have a problem. However I am not aware of anything using ipv6 for example.

[zgornel]

I have the same issue, on julia v1.12.6, v1.14.0-DEV.2136 and v1.14.0-DEV.2265. Looks like precompilation hangs somewhere, no CPU being used by the process itself.

[colbec]

Just updated Julia packages and this time HTTP 2.0.0 compiled without complaint in about 5 seconds.

Closing my issue. Thanks.

[rozmanmg]

@colbec Interestingly, I am still experiencing the exact same problem as you described in your original post on two different Fedora 44 machines. Could you double-check that the improvement you observed isn't simply due to a leftover LocalPreferences.toml file created while testing the "escape hatch" suggested by @quinnj?

[colbec]

@rozmanmg Thanks for your comment. I found the LocalPreferences file you mention and renamed it, restarted Julia, removed HTTP and added it back as v2.0.0 and the problem is back as you suggested it might, with HTTP never finishing precompile. I am reopening this issue since it seems that we still have the same problem.

[philbit]

I think I am hitting the same problem on Ubuntu 22.04 LTS (natively, and I also tried it in a docker container julia:1 to be sure I am dealing with a clean environment). After waiting for over two hours, precompilation of HTTP.jl still hasn't completed. When interrupting the precompilation via Ctrl+C, I consistently get the following stack trace (on docker):

^C Interrupted: Exiting precompilation...
  ◓ HTTP
  1 dependency had output during precompilation:
┌ HTTP
│  [56092] signal 2: Interrupt
│  in expression starting at /home/philip/.julia/packages/HTTP/2cpJl/src/precompile.jl:345
│  epoll_wait at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
│  _backend_poll_once! at /home/philip/.julia/packages/Reseau/chanm/src/iopoll/epoll.jl:228
│  _poller_thread_main! at /home/philip/.julia/packages/Reseau/chanm/src/iopoll/runtime.jl:384
│  _poller_thread_entry at /home/philip/.julia/packages/Reseau/chanm/src/iopoll/runtime.jl:401
│  jlcapi__poller_thread_entry_18478 at /home/philip/.julia/compiled/v1.12/Reseau/vKBJ8_xora4.so (unknown line)
│  unknown function (ip: 0x7f515fa94ac2) at /lib/x86_64-linux-gnu/libc.so.6
│  unknown function (ip: 0x7f515fb268cf) at /lib/x86_64-linux-gnu/libc.so.6
│  unknown function (ip: (nil)) at (unknown file)
│  unknown function (ip: 0x7f515fa91115) at /lib/x86_64-linux-gnu/libc.so.6
│  pthread_cond_wait at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
│  uv_cond_wait at /workspace/srcdir/libuv/src/unix/thread.c:822
│  ijl_task_get_next at /cache/build/builder-amdci5-4/julialang/julia-release-1-dot-12/src/scheduler.c:523
└  

On the docker container, I get a slightly shorter stack trace, but I guess it's the same spot:

^C Interrupted: Exiting precompilation...
  ◒ HTTP
  1 dependency had output during precompilation:
┌ HTTP
│  [101] signal 2: Interrupt
│  in expression starting at /root/.julia/packages/HTTP/2cpJl/src/precompile.jl:345
│  unknown function (ip: 0x7688fd2c79ec) at /lib/x86_64-linux-gnu/libc.so.6
│  unknown function (ip: 0x7688fd2bc667) at /lib/x86_64-linux-gnu/libc.so.6
│  unknown function (ip: 0x7688fd2bcc8b) at /lib/x86_64-linux-gnu/libc.so.6
│  pthread_cond_wait at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
│  uv_cond_wait at /workspace/srcdir/libuv/src/unix/thread.c:822
│  ijl_task_get_next at /cache/build/builder-amdci5-4/julialang/julia-release-1-dot-12/src/scheduler.c:523
└  

I get this no matter how long I wait after attempting precompilation again. So I assume it's not even progressing very slowly, but indeed stuck. And if the line in precompile.jl is accurate, it's stuck at the _precompile_workload_enabled() check. If there's anything I can provide or try to narrow down the problem, I'll be happy to do it.

Currently, I am using the same Julia version as the OP:

Julia Version 1.12.6
Commit 15346901f00 (2026-04-09 19:20 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × Intel(R) Core(TM) i5-4690K CPU @ 3.50GHz
  WORD_SIZE: 64
  LLVM: libLLVM-18.1.7 (ORCJIT, haswell)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 4 virtual cores)

I also tried 1.11.9 and 1.10.11: Same problem with 1.11.9, but with 1.10.11, precompilation works.

[quinnj]

I just kicked off a new Reseau release (1.1.4) that hopefully includes a fix for cases reported here; if anyone wants to try and check it out immediately to test, that would be great; but the release should be out in 15-20 minutes more generally available (JuliaServices/Reseau.jl@5bb8aa7). I ended up pushing that fix through a little quickly in the hopes that it resolves the issue people are seeing here.

[colbec]

Unfortunately there is no change here for HTTP. I attempted to update Reseau and HTTP, Reseau succeeded at 1.1.4 but HTTP kept trying to compile for 6 minutes so I stopped it. One of the reasons I did not let it run longer was that the 'v' call for information as the precompile progresses still does not work. Perhaps this actually does work but is preempted by the progress meter which regularly overwrites any information presented at the CLI.

Running System Information as the precompile proceeds reveals CPU activity which is minimal on all four cores.

If there is anything else you would like me to try then I am up for it. In the meantime 1.11 is still good so no worries, mate.

[philbit]

Likewise here. Still gets stuck at exactly the same place with Reseau@1.1.4 for Julia 1.11 and 1.12. Using Julia 1.10, it takes pretty long (~45s), but eventually succeeds.

[colbec]

FWIW Reseau 1.1.4 currently fails test in Julia, see JuliaServices/Reseau.jl#119