lambdasim
GitHub本地模拟 AWS Lambda 和 CloudWatch Logs，用于 NLP 函数开发与调试。支持流式调用、错误注入（限流、404等）及 API 调用审计，无需真实 AWS 环境即可测试 Lambda 路径。
Trigger Scenarios
Install
npx skills add langwatch/langwatch --skill lambdasim -g -y
SKILL.md
Frontmatter
{
"name": "lambdasim",
"description": "Run the studio's per-project NLP Lambda path locally with lambdasim, haven's AWS Lambda stand-in: functions, invokes and response streams answered on this stack's nlpgo. Use when someone says 'haven lambda', 'lambdasim', 'haven up +lambda', 'haven sim lambda', 'NLP Lambda locally', 'per-project Lambda', 'LANGWATCH_NLP_LAMBDA_CONFIG in dev', 'test the Lambda path without AWS', 'force a Lambda throttle', or 'InvokeWithResponseStream locally'.",
"user-invocable": true
}
lambdasim
Answers the AWS Lambda and CloudWatch Logs calls the workflow module makes on its
per-project NLP Lambda fleet, and runs every invoke on this stack's nlpgo, framed the
way the image's Lambda Web Adapter frames it (AWS_LWA_INVOKE_MODE=RESPONSE_STREAM:
JSON prelude, eight zero bytes, body). Code: services/sims/lambdasim, console
apps/sims/src/lambda, spec specs/setup/haven-lambdasim.feature.
Run it
- Opt-in:
haven up +lambda(sticky; restarts the stack). Runs in thegolane by default (seesims). - The overlay sets
LANGWATCH_NLP_LAMBDA_CONFIGto a placeholder fleet and pointsAWS_ENDPOINT_URL_LAMBDAandAWS_ENDPOINT_URL_CLOUDWATCH_LOGSat lambdasim, so the workflow module takes the per-project path (studio streams and synchronous runs). A fleet.envnames wins, and then nothing is pointed at lambdasim. - Every invoke goes to
LAMBDASIM_TARGET, this stack's nlpgo. The function's own environment (LANGWATCH_ENDPOINT,CACHE_BUCKET, ...) is recorded, not applied. - Console:
https://lambda.<slug>.langwatch.localhost. Standalone:make service svc=lambdasim(:5594, nlpgo assumed at :5562).
What it fakes
GET|DELETE /2015-03-31/functions/{name} GetFunction, DeleteFunction
POST /2015-03-31/functions CreateFunction (409 when it exists)
PUT /2015-03-31/functions/{name}/code|configuration
GET /2015-03-31/functions ListFunctions (one page)
POST /2015-03-31/functions/{name}/invocations Invoke
POST /2021-11-15/functions/{name}/response-streaming-invocations event stream
POST / (X-Amz-Target Logs_20140328.*) log groups, retention, DescribeLogStreams
Functions live in memory. An invoke of an unknown name or ARN registers it rather than
404 (a cached ARN outlives a restart); force not-found to test the 404.
Force a failure
haven sim lambda fault <kind>, or the console's Forced error picker. Sticky until off.
| kind | answer |
|---|---|
throttled |
429 TooManyRequestsException (the invoke lane retries) |
not-found |
404 ResourceNotFoundException |
function-error |
200 + X-Amz-Function-Error: Unhandled; stream ends with InvokeComplete ErrorCode |
service |
500 ServiceException |
nlpgo unreachable is a function error too, naming the dial failure.
Inspect and assert
GET /_sim/api/info stack, nlpgo target, functions, forced error
GET /_sim/api/calls newest first (function, mode, method, path, status, ms)
GET /_sim/api/calls/{id} with the event received and nlpgo's answer
DELETE /_sim/api/calls reset; ids keep counting
GET|PUT /_sim/api/settings {"forcedError": ""|"throttled"|"not-found"|"function-error"|"service"}
Caps: LAMBDASIM_MAX_CALLS (500) and LAMBDASIM_MAX_BODY_BYTES (65536 per body kept).
From a terminal or agent
--json on reads; non-zero exit on failure; --stack <slug> reads another worktree.
haven sim lambda status | list | get <id> | clear
haven sim lambda fault <off|throttled|not-found|function-error|service>
Version History
- c0c14dc Current 2026-10-19 19:33
