Improve Lambda Layer cold start time #2 #171
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mxiamxia
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Mar 21, 2025
ezhang6811
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*Issue #, if available:* *Description of changes:* #171 introduced a bug where the Lambda server span was no longer produced in trace map for ESM-based handlers. This PR fixes the bug and now bundles the lambda layer directly instead of the autoinstrumentation package. The size of the bundled layer is now ~920KB, a nearly 94% reduction in size from the original 14.5MB. The following files were copied from upstream to support Lambda layer bundling with minor changes: `webpack.config.js`, `tsconfig.webpack.json`, `tsconfig.esm.json`, and`install-externals.sh`. Trace Map for CJS handler:  Trace Map for ESM handler:  Trace Map for ESM handler prior to fix (with bug):  By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.
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Description of changes:
This PR is a rehash of #163 with some minor changes reverted after several autoinstrumentation package dependencies were upgraded in #168. The changes suggested by the unaddressed comments in the previous PR are addressed here.
The primary change made to reduce the cold start time was to bundle the ADOT autoinstrumentation package with webpack instead of using the TS compiler. Using the same build targets as the upstream (see this PR), the cold start performance of the layer was improved by about 50%, from ~765ms to ~385ms.
By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.