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Support child_process in snapshot #50924
Description
Activity
I think at the very least we can register some of the child process methods. Some additional work may be done to ensure that users don't leave any ProcessWrap lingering when the snapshot is taken too.
@joyeecheung Is supposed for all unsupported modules to crash? I tried just
require('cluster'),require('http')and I got some error/strange message.(node:143236) Warning: built-in module cluster is not yet supported in user snapshots (Use `node --trace-warnings ...` to show where the warning was created) Unknown external reference 0xf0e510. <unresolved>(node:143589) Warning: built-in module http is not yet supported in user snapshots (Use `node --trace-warnings ...` to show where the warning was created) global handle not serialized: 0x43dc40a99f1: [[api object] 0] in OldSpace - map: 0x2a08a1ccfce9 <Map[40](HOLEY_ELEMENTS)> [FastProperties] - prototype: 0x25c423a8b9c1 <Object map = 0x3aa3b8ae20b9> - elements: 0x1c4597f00379 <FixedArray[0]> [HOLEY_ELEMENTS] - embedder fields: 2 - properties: 0x043dc40ae701 <PropertyArray[3]> - All own properties (excluding elements): { 0x25a483a72469: [String] in OldSpace: #methods: 0x25c423ab69e9 <JSArray[34]> (const data field 0), location: properties[0] 0x2a08a1cc9519: [String] in OldSpace: #HTTPParser: 0x2a08a1cced31 <JSFunction HTTPParser (sfi = 0x2a08a1ccecf1)> (const data field 1), location: properties[1] 0x2a08a1ccfcc9: [String] in OldSpace: #ConnectionsList: 0x2a08a1ccfc41 <JSFunction ConnectionsList (sfi = 0x2a08a1ccfc01)> (const data field 2), location: properties[2] } - embedder fields = { 0, aligned pointer: 0x6c9b322 0, aligned pointer: 0x6cea4b0 } # # Fatal error in , line 0 # CheckGlobalAndEternalHandles failed # # # #FailureMessage Object: 0x7ffcb8661ae0 1: 0xe5a541 [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] 2: 0x22c7291 V8_Fatal(char const*, ...) [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] 3: 0x169b14d v8::internal::SnapshotCreatorImpl::CreateBlob(v8::SnapshotCreator::FunctionCodeHandling, v8::base::Flags<v8::internal::Snapshot::SerializerFlag, int, int>) [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] 4: 0xe99fd5 node::SnapshotBuilder::CreateSnapshot(node::SnapshotData*, node::CommonEnvironmentSetup*, unsigned char) [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] 5: 0xe9a3c1 node::BuildSnapshotWithoutCodeCache(node::SnapshotData*, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&, std::optional<std::basic_string_view<char, std::char_traits<char> > >) [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] 6: 0xe9bbd5 node::SnapshotBuilder::Generate(node::SnapshotData*, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&, std::optional<std::basic_string_view<char, std::char_traits<char> > >) [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] 7: 0xd9a410 node::GenerateAndWriteSnapshotData(node::SnapshotData const**, node::InitializationResultImpl const*) [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] 8: 0xd9a948 node::Start(int, char**) [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] 9: 0x7f963d606083 __libc_start_main [/lib/x86_64-linux-gnu/libc.so.6] 10: 0xcf2c6e _start [/home/h4ad/.asdf/installs/nodejs/21.1.0/bin/node] [1] 143589 trace trap (core dumped) node --snapshot-blob snapshot.blob --build-snapshot empty-file.jsIs supposed for all unsupported modules to crash?
Not necessarily, they are crashing because they either have leftover wrapper objects that are not properly handled for the snapshot (could be a leak, even), or unregistered external references. Being unsupported means we haven't checked that they work in snapshot or make them to work in the snapshot, so they can fail in different ways, or work in some cases.
- changed the title
[-]core dumped on --build-snapshot with child_process[/-][+]Support child_process in snapshot[/+]on Nov 30, 2023 There has been no activity on this feature request for 5 months. To help maintain relevant open issues, please add the never-stale
Issues and PRs exempt from automated stale handling. label or close this issue if it should be closed. If not, the issue will be automatically closed 6 months after the last non-automated comment.
For more information on how the project manages feature requests, please consult the feature request management document.The synchronous methods are supported since #50943 so the snippet in the OP works now and I am closing this. Asynchronous method support would be a different beast (I think as long as the method finishes and resources are cleaned up before snapshot is taken it should work, haven't verified it yet though).
Reacted by Vinicius Lourenço
Version
21.1.0
Platform
Linux h4ad 5.15.0-89-generic #99~20.04.1-Ubuntu SMP Thu Nov 2 15:16:47 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Subsystem
child_process
What steps will reproduce the bug?
The following code:
Run with:
node --snapshot-blob snapshot.blob --build-snapshot file.jsHow often does it reproduce? Is there a required condition?
Always
What is the expected behavior? Why is that the expected behavior?
The snapshot being created without
core dumped.isWhat do you see instead?
Additional information
Found at https://github.com/mehulkar/bench-childprocess