bootstrap: implement run-time user-land snapshots via --build-snapshot and --snapshot-blob #38905
Commits on Aug 2, 2022
-
-
bootstrap: implement --snapshot-blob and --build-snapshot
This patch introduces `--build-snapshot` and `--snapshot-blob` options for creating and using user land snapshots. For the initial iteration, user land CJS modules and ESM are not yet supported in the snapshot, so only one single file can be snapshotted (users can bundle their applications into a single script with their bundler of choice to build a snapshot though). A subset of builtins should already work, and support for more builtins are being added. This PR includes tests checking that the TypeScript compiler and the marked markdown renderer (and the builtins they use) can be snapshotted and deserialized. To generate a snapshot using `snapshot.js` as entry point and write the snapshot blob to `snapshot.blob`: ``` $ echo "globalThis.foo = 'I am from the snapshot'" > snapshot.js $ node --snapshot-blob snapshot.blob --build-snapshot snapshot.js ``` To restore application state from `snapshot.blob`, with `index.js` as the entry point script for the deserialized application: ``` $ echo "console.log(globalThis.foo)" > index.js $ node --snapshot-blob snapshot.blob index.js I am from the snapshot ``` Users can also use the `v8.startupSnapshot` API to specify an entry point at snapshot building time, thus avoiding the need of an additional entry script at deserialization time: ``` $ echo "require('v8').startupSnapshot.setDeserializeMainFunction(() => console.log('I am from the snapshot'))" > snapshot.js $ node --snapshot-blob snapshot.blob --build-snapshot snapshot.js $ node --snapshot-blob snapshot.blob I am from the snapshot ``` Note that this patch only adds functionality to the `node` executable for building run-time user-land snapshots, the generated snapshot is stored into a separate file on disk. Building a single binary with both Node.js and an embedded snapshot has already been possible with the `--node-snapshot-main` option to the `configure` script if the user compiles Node.js from source. It would be a different task to enable the `node` executable to produce a single binary that contains both Node.js and an embedded snapshot without building Node.js from source, which should be layered on top of the SEA (Single Executable Apps) initiative. Known limitations/bugs that are being fixed in the upstream: - V8 hits a DCHECK when deserializing certain mutated globals, e.g. `Error.stackTraceLimit` (it should work fine in the release build, however): https://chromium-review.googlesource.com/c/v8/v8/+/3319481 - Layout of V8's read-only heap can be inconsistent after deserialization, resulting in memory corruption: https://bugs.chromium.org/p/v8/issues/detail?id=12921 PR-URL: nodejs#38905 Refs: nodejs#35711 Reviewed-By: Chengzhong Wu <legendecas@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> -
bootstrap: clean up warning setup during serialization
PR-URL: nodejs#38905 Refs: nodejs#35711 Reviewed-By: Chengzhong Wu <legendecas@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
-
test: add UMD module test with marked
PR-URL: nodejs#38905 Refs: nodejs#35711 Reviewed-By: Chengzhong Wu <legendecas@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
-
test: test snapshotting TypeScript compiler
PR-URL: nodejs#38905 Refs: nodejs#35711 Reviewed-By: Chengzhong Wu <legendecas@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.