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Lambda runs init with close to a full vCPU and caps each invocation at the
memory's share (about 0.58 vCPU at 1024 MB), so the work a cold start's first
request does ran about 1.7x slower than it would during init.
- createWebinyApiHandler returns the handler with a warmUp() that sends one
internal { __typename } request (5 s cap, errors swallowed so init can
never fail because of it).
- warmUpLambdaHandler() picks the handler the function runs from _HANDLER,
so the stream function, which loads the same bundle, skips it.
- The api/graphql templates await it at the top level.
- ai-powerups loads @webiny/lexical-converter on first use. It brought
lexical, cheerio and undici into every cold start (main bundle 4.5 -> 3.0 MB),
and importing undici swapped the dispatcher behind the global fetch.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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🚓 Slop Cop ✅ Nothing worth flagging. The diff looks consistent with the PR's stated intent and the code-style rules. The PR is a coherent, well-scoped perf change (Lambda warm-up + lazy lexical-converter import) with matching tests; no integrity or style issues found. Automated, non-blocking heads-up from an LLM. It can be wrong — use your judgment. Regenerates on every push. |
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Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 4 remain after this review. 📝 WalkthroughWalkthroughThe Lexical parser now loads and caches its converter on first use. AWS API handlers gain warm-up support, which the DDB packages expose and the GraphQL templates call during module initialization. ChangesLexical parser loading
AWS Lambda handler warm-up
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Feature Sequence Diagram(s)sequenceDiagram
participant GraphQL entry point
participant warmUpLambdaHandler
participant Warmable handler
GraphQL entry point->>warmUpLambdaHandler: Pass exported handlers
warmUpLambdaHandler->>Warmable handler: Call warmUp for the selected handler
Warmable handler->>Warmable handler: Invoke handler with synthetic GraphQL request and context
Merge Risk: ⚪ Minimal · up to No material merge blocker is supported. The generic warm-up skips the streaming Lambda because its calling convention differs; the supplied context establishes no separate requirement to warm it. Architecture SummaryArchitecture risk: 🔵 Low · up to The change affects 5 systems. Changed systems: Architecture concerns Review detailsSystems and components
Before / after behavior
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Review comments at @packages/api-event-handler-aws/src/warmUp.ts:
- Line 67: Update warmUpLambdaHandler to start the handler invocation inside a
promise chain so synchronous throws reach the existing best-effort error
handling instead of rejecting initialization. Add a test using a handler that
throws synchronously.
- Line 62: Remove timer.unref() from the warm-up timeout flow so the five-second
deadline remains referenced while handler(event, context) is pending; retain the
existing finally block that clears the timer.
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packages/ai-powerups/__tests__/features/WbTranslatePage/LexicalParser.test.tspackages/ai-powerups/src/api/features/WbTranslatePage/LexicalParser.tspackages/api-event-handler-aws-ddb-os/src/index.tspackages/api-event-handler-aws-ddb/src/index.tspackages/api-event-handler-aws/__tests__/warmUp.test.tspackages/api-event-handler-aws/src/createWebinyApiHandler.tspackages/api-event-handler-aws/src/index.tspackages/api-event-handler-aws/src/warmUp.tspackages/project-aws/_templates/appTemplates/api/graphql/src/index.tspackages/project-aws/_templates/extensions/OpenSearch/api/graphql/src/index.ts
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- With the timer unreferenced, a warm-up request that stalls with nothing else holding the event loop let Node exit on the unsettled top-level await (exit code 13), which would fail Lambda init. Reproduced with a handler that never settles: it now continues after the 5 s cap. - A handler that throws before returning a promise rejected the warm-up and failed init. The call now starts inside the promise chain. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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how positive are you that this will not cause cross-request bleeds? didnt go much through the code, but first thing that comes to mind is that we created whole system basically on each request. now there is some "init" phase which loads i-dont-know-what. might be nothing, but i want to make sure we dont introduce that sort of issue again |
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Closing for now. |
2 participants
Why
Lambda runs a function's init phase with close to a full vCPU, then caps each invocation at the share that comes with its memory: about 0.58 vCPU at 1024 MB. I measured this on the dev stack with
process.cpuUsage()against wall time. Init ran at about 0.9 CPU seconds per second. The first request ran at about 0.57, with the event loop idle for only about 45 ms, so it was CPU-bound, not waiting on the network. Everything a cold start's first request does therefore runs about 1.7x slower than the same work during init: building the root and request containers, fetching the WCP license, opening the DynamoDB connection, building the GraphQL schema, and compiling the code on that path.What changed
createWebinyApiHandlernow returns the handler with awarmUp()method. It sends one internal{ __typename }API Gateway event through the full stack. It stops waiting after 5 seconds (init has a 10 second limit) and swallows errors, so init can never fail because of it. A fresh install, for example, has no tenant yet.warmUpLambdaHandler({ handler, streamHandler })warms up only the handler this function runs, read from Lambda's_HANDLER. Thegraphql-streamfunction loads the same bundle and skips it, since its handler has nowarmUp().api/graphqltemplates (DynamoDB and OpenSearch)awaitit at the top level, so it runs during init. Existing projects get it when their app workspace is regenerated.ai-powerupsloads@webiny/lexical-converteron first use. Only page translation needs it, but it pulledlexical,cheerioandcheerio's bundledundiciinto every cold start. The main bundle file drops from 4.5 MB to 3.0 MB. Importingundicialso replaced the dispatcher behind Node's built-infetchwith the bundled copy, wasm HTTP parser included.Results
1024 MB Lambda, forced cold starts, alternating builds, without
--enable-source-maps(production settings). Medians from each run.{ __typename }{ __typename }listFileslistFilesThe
{ __typename }rows are the best case, since the warm-up sends the same query. A different first request still finds the containers, connection, license and JIT already warm, and saves about 210 ms. Measured without the lazy converter, the warm-up alone gave 1698 ms against 1595 ms with both changes.The "before" numbers include #5899 (schema build). This PR doesn't depend on it.
Testing
__tests__/warmUp.test.ts(api-event-handler-aws) covers five cases: it calls only the handler named in_HANDLER, with a POST{ __typename }; it skips handlers withoutwarmUp(); it does nothing outside Lambda; it doesn't throw when the request fails; and it stops waiting for a request that hangs.__tests__/features/WbTranslatePage/LexicalParser.test.ts(ai-powerups) runs the real parser through the lazy import. The existing translation test mocks it.api-event-handler-awspasses 11 of 11, andai-powerupspasses 89 of 89 plus the new test.wd apiand checked both functions.graphqlserved an authenticatedlistFiles.graphql-stream, invoked directly with a Function URL event, returned{ __typename }with a normal init, so it skipped the warm-up.Workspace: wby-next4 · ✨ Event Van Handler 🎸
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