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chore: patch jsii-pacmak to fix parallel packing bug (#16871)
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jsii-pacmak has a bug where modules are packed in parallel, rather than
sequentially. This causes packing failures on v2, where the alpha modules depend
on aws-cdk-lib, but may be packed first.

The jsii fix is aws/jsii#3045. However, to shortcut the
build+test+upgrade+merge+deploy cycle, creating this patch to speed up
verification.


----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*
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njlynch authored Oct 8, 2021
1 parent 97cf9dd commit 6f292e2
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20 changes: 7 additions & 13 deletions patches/README.md
Original file line number Diff line number Diff line change
Expand Up @@ -28,16 +28,10 @@ lerna success exec Executed command in 219 packages: "pwd"
1.11 real 0.99 user 0.82 sys
```

## jsii-rosetta+1.28.0.patch

jsii-rosetta uses multiple worker threads by default to speed up sample extraction.
It defaults to spawning workers equal to half the number of cores. On extremely
powerful build machines (e.g., CodeBuild X2_LARGE compute with 72 vCPUs),
the high number of workers (36) results in thrash and high memory usage due to
duplicate loads of source files. This was causing the v2 builds to fail with:
"FATAL ERROR: NewSpace::Rebalance Allocation failed - JavaScript heap out of memory"

The patch simply limits the top number of worker threads to an arbitrarily-chosen
maximum limit of 16. We could simply disable the worker threads, but this takes much
longer to process. With single-threading, rosetta takes ~35 minutes to extract samples
from the CDK; with 16 workers, it takes ~3.5 minutes.
## jsii-pacmak+1.38.0.patch

[email protected] has a bug that means all packages are packed in parallel for
several languages. This can cause issues on the v2 build, where the alpha modules
rely on aws-cdk-lib, but may be packed first. A fix will go out in 1.39.0, but in
the meantime, this patch allows us to more quickly verify the fix and get our
pipeline green again.
25 changes: 25 additions & 0 deletions patches/jsii-pacmak+1.38.0.patch
Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
diff --git a/node_modules/jsii-pacmak/lib/builder.js b/node_modules/jsii-pacmak/lib/builder.js
index 3d0f8b3..0d1e868 100644
--- a/node_modules/jsii-pacmak/lib/builder.js
+++ b/node_modules/jsii-pacmak/lib/builder.js
@@ -15,10 +15,16 @@ class OneByOneBuilder {
this.options = options;
}
async buildModules() {
- const promises = this.modules.map((module) => this.options.codeOnly
- ? this.generateModuleCode(module, this.options)
- : this.buildModule(module, this.options));
- await Promise.all(promises);
+ for (const module of this.modules) {
+ if (this.options.codeOnly) {
+ // eslint-disable-next-line no-await-in-loop
+ await this.generateModuleCode(module, this.options);
+ }
+ else {
+ // eslint-disable-next-line no-await-in-loop
+ await this.buildModule(module, this.options);
+ }
+ }
}
async generateModuleCode(module, options) {
const outputDir = this.finalOutputDir(module, options);

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