middy-event-loop-tracer
v1.1.0
Published
Middy AWS Lambda event loop tracer middleware
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middy-event-loop-tracer
Middy middleware for dumping active tasks with their stacktraces in the event queue just before AWS Lambda function timeouts. So you can understand what was going on in the function when timeout happens.
A sample event loop dump will look like this:
START RequestId: 90dc31a4-10cf-4485-8c8e-914891b4cddb Version: $LATEST
2021-11-30T17:24:58.366Z 90dc31a4-10cf-4485-8c8e-914891b4cddb INFO About timeout! Dumping active tasks in the event loop ...
2021-11-30T17:24:58.366Z 90dc31a4-10cf-4485-8c8e-914891b4cddb INFO Task groups:
2021-11-30T17:24:58.366Z 90dc31a4-10cf-4485-8c8e-914891b4cddb INFO -
{
"id": "PROMISE@90dc31a4-10cf-4485-8c8e-914891b4cddb_1662448958",
"type": "PROMISE",
"awsRequestId": "90dc31a4-10cf-4485-8c8e-914891b4cddb",
"count": 1380,
"stackTrace": [
" at AsyncHook._initAsync (/var/task/src/middleware.js:95:11)",
" at PromiseWrap.emitInitNative (internal/async_hooks.js:195:43)",
" at new Promise (<anonymous>)",
" at Request.promise (/var/runtime/node_modules/aws-sdk/lib/request.js:783:12)",
" at myHandler (/var/task/src/index.js:31:46)",
" at runRequest (/var/task/node_modules/@middy/core/index.js:86:32)"
]
}
2021-11-30T17:24:58.366Z 90dc31a4-10cf-4485-8c8e-914891b4cddb INFO -
{
"id": "TCPWRAP@90dc31a4-10cf-4485-8c8e-914891b4cddb_842007963",
"type": "TCPWRAP",
"awsRequestId": "90dc31a4-10cf-4485-8c8e-914891b4cddb",
"count": 50,
"stackTrace": [
" at AsyncHook._initAsync (/var/task/src/middleware.js:95:11)",
" at TCP.emitInitNative (internal/async_hooks.js:195:43)",
" at TLSSocket._wrapHandle (_tls_wrap.js:592:7)",
" at new TLSSocket (_tls_wrap.js:499:18)",
" at Object.connect (_tls_wrap.js:1595:19)",
" at Agent.createConnection (https.js:132:22)",
" at Agent.createSocket (_http_agent.js:321:26)",
" at Agent.addRequest (_http_agent.js:275:10)",
" at new ClientRequest (_http_client.js:297:16)",
" at Object.request (https.js:316:10)"
]
}
2021-11-30T17:24:58.366Z 90dc31a4-10cf-4485-8c8e-914891b4cddb INFO -
{
"id": "HTTPCLIENTREQUEST@90dc31a4-10cf-4485-8c8e-914891b4cddb_2122473569",
"type": "HTTPCLIENTREQUEST",
"awsRequestId": "90dc31a4-10cf-4485-8c8e-914891b4cddb",
"count": 50,
"stackTrace": [
" at AsyncHook._initAsync (/var/task/src/middleware.js:95:11)",
" at HTTPClientAsyncResource.emitInitNative (internal/async_hooks.js:195:43)",
" at tickOnSocket (_http_client.js:679:10)",
" at onSocketNT (_http_client.js:750:5)",
" at processTicksAndRejections (internal/process/task_queues.js:84:21)"
]
}
END RequestId: 90dc31a4-10cf-4485-8c8e-914891b4cddb
REPORT RequestId: 90dc31a4-10cf-4485-8c8e-914891b4cddb Duration: 5005.41 ms Billed Duration: 5000 ms Memory Size: 1024 MB Max Memory Used: 139 MB Init Duration: 447.07 ms
2021-11-30T17:24:58.869Z 90dc31a4-10cf-4485-8c8e-914891b4cddb Task timed out after 5.01 seconds
Installation
To install the middleware, you can use NPM:
npm install --save middy-event-loop-tracer
Note: Requires @middy/core
version 2.0.0
+
Usage
- Register
middy-event-loop-tracer
middleware in your handler:
const middy = require('@middy/core');
const eventLoopTracer = require('middy-event-loop-tracer');
const handler = async(event, context) => {
// Do something meaningful
return {
statusCode: 200,
}
}
module.exports.handler = middy(handler).use(eventLoopTracer());
Optionally, you can configure timeout margin which is the minimum remaining time before the actual timeout happens to assume that invocation will timeout. So we take action and dump the active tasks in the event loop because when the timeout happens, the game is over and there is nothing to do. By default, timeout margin is
500
milliseconds and it can be configured by environment variable or options passed to middleware:- By environment variable:
Set
MIDDY_ELT_TIMEOUT_MARGIN
environment variable with the desired value for the timeout margin.
MIDDY_ELT_TIMEOUT_MARGIN=250
- By options: Pass the timeout margin through options.
const eventLoopTracer = require('middy-event-loop-tracer'); module.exports.handler = middy(handler).use(eventLoopTracer({timeoutMargin: 250}));
- By environment variable:
Set
Contributing
Everyone is very welcome to contribute to this repository. Feel free to raise issues or to submit Pull Requests.
License
Licensed under MIT License.