[ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client #3994
Description
Prerequisites
- I have written a descriptive issue title
- I have searched existing issues to ensure the regression has not already been reported
Last working version
3.29.0
Stopped working in version
4.0.0
Node.js version
18.2.0
Operating system
Linux
Operating system version (i.e. 20.04, 11.3, 10)
Node.js running in Docker in an continuous integration environment
💥 Regression Report
Since the update to fastify v4.0.0 we receive randomly:
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at onSendEnd (/builds/my/project/node_modules/fastify/lib/reply.js:493:7)
at onSendHook (/builds/my/project/node_modules/fastify/lib/reply.js:427:5)
at fallbackErrorHandler (/builds/my/project/node_modules/fastify/lib/error-handler.js:124:3)
at handleError (/builds/my/project/node_modules/fastify/lib/error-handler.js:54:5)
at onErrorHook (/builds/my/project/node_modules/fastify/lib/reply.js:594:5)
at _Reply.Reply.send (/builds/my/project/node_modules/fastify/lib/reply.js:119:5)
at defaultErrorHandler (/builds/my/project/node_modules/fastify/lib/error-handler.js:85:9)
at handleError (/builds/my/project/node_modules/fastify/lib/error-handler.js:58:18)
at onErrorHook (/builds/my/project/node_modules/fastify/lib/reply.js:594:5)
at _Reply.Reply.send (/builds/my/project/node_modules/fastify/lib/reply.js:119:5)
at /builds/my/project/node_modules/fastify/lib/wrapThenable.js:23:15Sometimes it works sometimes most of the time not so I guess this is some kind of timing issue or race condition. All of our route handlers looks like this
{
async handler(_request, reply) {
return reply.type('application/json').send({
foo: 'bar',
});
},
method: 'GET'
};or
{
async handler(request, reply) {
await delay(3000); // simulate slow responses
return reply.type('application/json').headers({ my: 'header' }).send({ foo: 'bar' });
},
method: 'GET'
}Steps to Reproduce
Unfortunately I don't have any steps or repository to reproduce the issue. Our CI jobs are failing mostly all the time because of this. Locally I cannot reproduce the issue (I guess because my machine has more power and is faster)
Expected Behavior
No response