sea: snapshot support in single executable applications #46824

joyeecheung · 2023-02-24T18:28:13Z

This patch adds snapshot support to single executable applications.
To build a snapshot from the main script when preparing the
blob that will be injected into the single executable application,
add "useSnapshot": true to the configuration passed to
--experimental-sea-config. For example:

{
    "main": "snapshot.js",
    "output": "sea-prep.blob",
    "useSnapshot": true
}

The main script used to build the snapshot must invoke
v8.startupSnapshot.setDeserializeMainFunction() to configure the
entry point. The generated startup snapshot would be part of the
preparation blob and get injected into the final executable.

When the single executable application is launched, instead of running
the main script from scratch, Node.js would instead deserialize the
snapshot to get to the state initialized during build-time directly.

$ /path/to/node --experimental-sea-config sea-config.json
$ cp /path/to/node sea
$ postject sea NODE_SEA_BLOB sea-prep.blob --sentinel-fuse NODE_SEA_FUSE_fce680ab2cc467b6e072b8b5df1996b2
$ ./sea

nodejs-github-bot · 2023-02-24T18:28:18Z

Review requested:

@nodejs/startup

RaisinTen · 2023-02-27T13:11:34Z

Thanks for doing this!

add some tooling to process the inputs

I personally really like this approach. I've opened a discussion in nodejs/single-executable#58, so that we can have a decision on this.

joyeecheung · 2023-06-10T22:46:42Z

Rebased using the new SnapshotBuilder::Generate() overload added in #48242 and added a test. Will add more doc and tests next week but the implementation is there.

piranna · 2023-06-11T00:16:42Z

Rebased using the new SnapshotBuilder::Generate() overload added in #48242 and added a test. Will add more doc and tests next week but the implementation is there.

What's the difference between snapshot and code cache (bytenode)?

joyeecheung · 2023-06-14T13:13:22Z

What's the difference between snapshot and code cache (bytenode)?

If you have a bunch of top level code with a bunch of inner functions, usually when building the snapshot you run all the top level code and compile some of the inner functions, the snapshot contains the state of the heap after the top-level code is run and the bytecode of the inner functions that would be run again later. When deserializing the snapshot, you deserialize the state of an initialized heap (so there is no need to run the top-level code at all), and maybe later when the application invokes some of the inner functions, V8 deserialize the bytecode in the snapshot during the compilation of the function to speed things up. If there's just the code cache, what usually happens is that you have the bytecode of the top-level code and some inner functions. At runtime V8 deserializes the bytecode in the code cache to speed up compilation of the top-level code, but it still needs to run the top-level code to set up the heap.

nodejs-github-bot · 2023-06-14T14:04:00Z

CI: https://ci.nodejs.org/job/node-test-pull-request/52256/

joyeecheung · 2023-06-14T15:30:42Z

CI is almost green (with some flakes that look irrelevant). Can I have some reviews please? @nodejs/single-executable thanks!

piranna · 2023-06-14T16:08:07Z

If you have a bunch of top level code with a bunch of inner functions, usually when building the snapshot you run all the top level code and compile some of the inner functions, the snapshot contains the state of the heap after the top-level code is run and the bytecode of the inner functions that would be run again later. When deserializing the snapshot, you deserialize the state of an initialized heap (so there is no need to run the top-level code at all), and maybe later when the application invokes some of the inner functions, V8 deserialize the bytecode in the snapshot during the compilation of the function to speed things up. If there's just the code cache, what usually happens is that you have the bytecode of the top-level code and some inner functions. At runtime V8 deserializes the bytecode in the code cache to speed up compilation of the top-level code, but it still needs to run the top-level code to set up the heap.

Thank you @joyeecheung for your detailed explain :-) So, if I understood it correctly, a snapshoot is a combo of a module compiled and bytecode functions plus heap after executing the module top level code, while the code cache only have the bytecode of all the module code, isn't it?

joyeecheung · 2023-06-15T08:59:47Z

So, if I understood it correctly, a snapshoot is a combo of a module compiled and bytecode functions plus heap after executing the module top level code, while the code cache only have the bytecode of all the module code, isn't it?

Roughly yes. V8 does not always emit bytecode for all the code it encounters (e.g. inner-inner functions are usually just parsed for syntax checks, but no bytecode is generated until they actually get executed). In some cases snapshots may contain more bytecode if during the snapshot building cases these functions are invoked.

piranna · 2023-06-15T09:04:41Z

V8 does not always emit bytecode for all the code it encounters

Maybe bytenode is forcing its generation? Could it of our interest when generating the snapshots, so no Javascript code is included in it?

benjamingr

LGTM

benjamingr · 2023-06-15T16:55:07Z

@RaisenTen can you please confirm you are comfortable with this based on nodejs/single-executable#58 and nodejs/single-executable#58 (reply in thread) landing

joyeecheung · 2023-06-15T17:35:08Z

Could it of our interest when generating the snapshots, so no Javascript code is included in it?

I would say that's not always a win, you could also have a lot of dead code in that application, or code that never gets run in many use cases, then eagerly generating code may result in a memory/size overhead that's not always worth it. As a configurable thing that might be useful though.

RaisinTen · 2023-06-15T17:37:47Z

I can try to take a look day after tomorrow. (I'll be traveling pretty much the entire day tomorrow)

piranna · 2023-06-15T17:50:26Z

As a configurable thing that might be useful though.

Agree on that 👍🏻

nodejs-github-bot · 2023-07-20T18:44:40Z

CI: https://ci.nodejs.org/job/node-test-pull-request/52874/

nodejs-github-bot · 2023-07-20T20:28:42Z

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----------------------------------- PR info ------------------------------------
Title      sea: snapshot support in single executable applications (#46824)
Author     Joyee Cheung  (@joyeecheung)
Branch     joyeecheung:sea-snapshot -> nodejs:main
Labels     c++, lib / src, needs-ci, commit-queue-squash, single-executable
Commits    4
 - src: support snapshot in single executable applications
 - fixup! src: support snapshot in single executable applications
 - fixup! fixup! src: support snapshot in single executable applications
 - fixup! fixup! fixup! src: support snapshot in single executable appli…
Committers 1
 - Joyee Cheung 
PR-URL: https://github.com/nodejs/node/pull/46824
Refs: https://github.com/nodejs/single-executable/discussions/57
Reviewed-By: Benjamin Gruenbaum 
Reviewed-By: Darshan Sen 
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/46824
Refs: https://github.com/nodejs/single-executable/discussions/57
Reviewed-By: Benjamin Gruenbaum 
Reviewed-By: Darshan Sen 
--------------------------------------------------------------------------------
   ℹ  This PR was created on Fri, 24 Feb 2023 18:28:13 GMT
   ✔  Approvals: 2
   ✔  - Benjamin Gruenbaum (@benjamingr) (TSC): https://github.com/nodejs/node/pull/46824#pullrequestreview-1482036842
   ✔  - Darshan Sen (@RaisinTen) (TSC): https://github.com/nodejs/node/pull/46824#pullrequestreview-1538950503
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   ℹ  Last Full PR CI on 2023-07-20T18:44:40Z: https://ci.nodejs.org/job/node-test-pull-request/52874/
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nodejs-github-bot · 2023-07-20T22:57:03Z

Landed in ac34e75

piranna · 2023-07-20T23:10:32Z

doc/api/single-executable-applications.md

+### Startup snapshot support
+
+The `useSnapshot` field can be used to enable startup snapshot support. In this
+case the `main` script would not be when the final executable is launched.


It's missing a run: "would not be run"

This patch adds snapshot support to single executable applications. To build a snapshot from the main script when preparing the blob that will be injected into the single executable application, add `"useSnapshot": true` to the configuration passed to `--experimental-sea-config`. For example: ``` { "main": "snapshot.js", "output": "sea-prep.blob", "useSnapshot": true } ``` The main script used to build the snapshot must invoke `v8.startupSnapshot.setDeserializeMainFunction()` to configure the entry point. The generated startup snapshot would be part of the preparation blob and get injected into the final executable. When the single executable application is launched, instead of running the `main` script from scratch, Node.js would instead deserialize the snapshot to get to the state initialized during build-time directly. PR-URL: nodejs#46824 Refs: nodejs/single-executable#57 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Darshan Sen <[email protected]>

This patch adds snapshot support to single executable applications. To build a snapshot from the main script when preparing the blob that will be injected into the single executable application, add `"useSnapshot": true` to the configuration passed to `--experimental-sea-config`. For example: ``` { "main": "snapshot.js", "output": "sea-prep.blob", "useSnapshot": true } ``` The main script used to build the snapshot must invoke `v8.startupSnapshot.setDeserializeMainFunction()` to configure the entry point. The generated startup snapshot would be part of the preparation blob and get injected into the final executable. When the single executable application is launched, instead of running the `main` script from scratch, Node.js would instead deserialize the snapshot to get to the state initialized during build-time directly. PR-URL: #46824 Refs: nodejs/single-executable#57 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Darshan Sen <[email protected]>

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs related to general changes in the lib or src directory. needs-ci PRs that need a full CI run. labels Feb 24, 2023

joyeecheung mentioned this pull request Feb 27, 2023

src: share common code paths for SEA and embedder script #46825

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joyeecheung force-pushed the sea-snapshot branch from d830718 to e94ac97 Compare March 2, 2023 20:07

RaisinTen added the single-executable Issues and PRs related to single-executable applications label May 12, 2023

joyeecheung force-pushed the sea-snapshot branch from e94ac97 to 8dec8b7 Compare June 10, 2023 22:45

joyeecheung changed the title ~~POC: snapshot support in single executable applications~~ sea: snapshot support in single executable applications Jun 10, 2023

joyeecheung force-pushed the sea-snapshot branch from 8dec8b7 to eb703f7 Compare June 14, 2023 12:08

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Use built-in single executable application support in Node.js once it is released jonaschlegel/lgo-agisoft-converter#2

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v20.6.0 proposal #49185

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sea: snapshot support in single executable applications #46824

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