Koa SSE “write after end”
I have been trying to implement an SSE stream with Koa for hours now but got the following error when trying to send a message to my client after initializing the connection.
Error [ERR_STREAM_WRITE_AFTER_END]: write after end
Here's how I set up my SSE:
Client-side:
const source = new EventSource("http://localhost:8080/stream");
this.source.onmessage = (e) => {
console.log("---- RECEIVED MESSAGE: ", e.data);
};
// Catches errors
this.source.onerror = (e) => {
console.log("---- ERROR: ", e.data);
};
Server-side (Koa):
// Entry point to our SSE stream
router.get('/stream', ctx => {
// Set response status, type and headers
ctx.response.status = 200;
ctx.response.type = 'text/event-stream';
ctx.response.set({
'Cache-Control': 'no-cache',
Connection: 'keep-alive',
});
// Called when another route is reached
// Should send to the client the following
ctx.app.on('message', data => {
ctx.res.write(`event: Testn`);
ctx.res.write(`data: This is test datann`);
});
});
The error comes when we call ctx.res.write once a message is received.
Why is my stream ended although nothing explicitly is doing it?
How may I send a message through the stream with Koa?
server-sent-events koa
edited Nov 26 '18 at 15:31
Paul R
176k24298458
asked Nov 26 '18 at 14:43
ChristopherChristopher
692525
add a comment |
I have been trying to implement an SSE stream with Koa for hours now but got the following error when trying to send a message to my client after initializing the connection.
Error [ERR_STREAM_WRITE_AFTER_END]: write after end
Here's how I set up my SSE:
Client-side:
const source = new EventSource("http://localhost:8080/stream");
this.source.onmessage = (e) => {
console.log("---- RECEIVED MESSAGE: ", e.data);
};
// Catches errors
this.source.onerror = (e) => {
console.log("---- ERROR: ", e.data);
};
Server-side (Koa):
// Entry point to our SSE stream
router.get('/stream', ctx => {
// Set response status, type and headers
ctx.response.status = 200;
ctx.response.type = 'text/event-stream';
ctx.response.set({
'Cache-Control': 'no-cache',
Connection: 'keep-alive',
});
// Called when another route is reached
// Should send to the client the following
ctx.app.on('message', data => {
ctx.res.write(`event: Testn`);
ctx.res.write(`data: This is test datann`);
});
});
The error comes when we call ctx.res.write once a message is received.
Why is my stream ended although nothing explicitly is doing it?
How may I send a message through the stream with Koa?
server-sent-events koa
edited Nov 26 '18 at 15:31
Paul R
176k24298458
asked Nov 26 '18 at 14:43
ChristopherChristopher
692525
add a comment |
I have been trying to implement an SSE stream with Koa for hours now but got the following error when trying to send a message to my client after initializing the connection.
Error [ERR_STREAM_WRITE_AFTER_END]: write after end
Here's how I set up my SSE:
Client-side:
const source = new EventSource("http://localhost:8080/stream");
this.source.onmessage = (e) => {
console.log("---- RECEIVED MESSAGE: ", e.data);
};
// Catches errors
this.source.onerror = (e) => {
console.log("---- ERROR: ", e.data);
};
Server-side (Koa):
// Entry point to our SSE stream
router.get('/stream', ctx => {
// Set response status, type and headers
ctx.response.status = 200;
ctx.response.type = 'text/event-stream';
ctx.response.set({
'Cache-Control': 'no-cache',
Connection: 'keep-alive',
});
// Called when another route is reached
// Should send to the client the following
ctx.app.on('message', data => {
ctx.res.write(`event: Testn`);
ctx.res.write(`data: This is test datann`);
});
});
The error comes when we call ctx.res.write once a message is received.
Why is my stream ended although nothing explicitly is doing it?
How may I send a message through the stream with Koa?
server-sent-events koa
edited Nov 26 '18 at 15:31
Paul R
176k24298458
asked Nov 26 '18 at 14:43
ChristopherChristopher
692525
I have been trying to implement an SSE stream with Koa for hours now but got the following error when trying to send a message to my client after initializing the connection.
Error [ERR_STREAM_WRITE_AFTER_END]: write after end
Here's how I set up my SSE:
Client-side:
const source = new EventSource("http://localhost:8080/stream");
this.source.onmessage = (e) => {
console.log("---- RECEIVED MESSAGE: ", e.data);
};
// Catches errors
this.source.onerror = (e) => {
console.log("---- ERROR: ", e.data);
};
Server-side (Koa):
// Entry point to our SSE stream
router.get('/stream', ctx => {
// Set response status, type and headers
ctx.response.status = 200;
ctx.response.type = 'text/event-stream';
ctx.response.set({
'Cache-Control': 'no-cache',
Connection: 'keep-alive',
});
// Called when another route is reached
// Should send to the client the following
ctx.app.on('message', data => {
ctx.res.write(`event: Testn`);
ctx.res.write(`data: This is test datann`);
});
});
The error comes when we call ctx.res.write once a message is received.
Why is my stream ended although nothing explicitly is doing it?
How may I send a message through the stream with Koa?
server-sent-events koa
server-sent-events koa
edited Nov 26 '18 at 15:31
Paul R
176k24298458
asked Nov 26 '18 at 14:43
ChristopherChristopher
692525
edited Nov 26 '18 at 15:31
Paul R
176k24298458
asked Nov 26 '18 at 14:43
ChristopherChristopher
692525
edited Nov 26 '18 at 15:31
Paul R
176k24298458
edited Nov 26 '18 at 15:31
Paul R
176k24298458
edited Nov 26 '18 at 15:31
Paul R
176k24298458
176k24298458
asked Nov 26 '18 at 14:43
ChristopherChristopher
692525
asked Nov 26 '18 at 14:43
ChristopherChristopher
692525
asked Nov 26 '18 at 14:43
ChristopherChristopher
692525
692525
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Koa is entirely promise based and everything is a middleware.
Every middleware returns a promise (or nothing). The middleware chain is effectively 'awaited' and once the middleware returns, Koa knows the response is done and will end the stream.
To make sure that Koa doesn't do this, you have to make sure that the chain of middlewares don't end. To do this, you need to return a promise that only resolves when you're done streaming.
A quick hack to demonstrate would be to return a promise that doesn't resolve:
return new Promise( resolve => { }});
answered Nov 26 '18 at 17:34
EvertEvert
41.3k1570125
Thank you very much ! The middleware system of Koa is still rather obscure to me coming from Express. Especially when it comes to the execution flow.
– Christopher
Nov 27 '18 at 7:40
I guarantee that once you get the hang of it, you'll like it more!
– Evert
Nov 27 '18 at 15:16
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53483534%2fkoa-sse-write-after-end%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Koa is entirely promise based and everything is a middleware.
Every middleware returns a promise (or nothing). The middleware chain is effectively 'awaited' and once the middleware returns, Koa knows the response is done and will end the stream.
To make sure that Koa doesn't do this, you have to make sure that the chain of middlewares don't end. To do this, you need to return a promise that only resolves when you're done streaming.
A quick hack to demonstrate would be to return a promise that doesn't resolve:
return new Promise( resolve => { }});
answered Nov 26 '18 at 17:34
EvertEvert
41.3k1570125
Thank you very much ! The middleware system of Koa is still rather obscure to me coming from Express. Especially when it comes to the execution flow.
– Christopher
Nov 27 '18 at 7:40
I guarantee that once you get the hang of it, you'll like it more!
– Evert
Nov 27 '18 at 15:16
add a comment |
Koa is entirely promise based and everything is a middleware.
Every middleware returns a promise (or nothing). The middleware chain is effectively 'awaited' and once the middleware returns, Koa knows the response is done and will end the stream.
To make sure that Koa doesn't do this, you have to make sure that the chain of middlewares don't end. To do this, you need to return a promise that only resolves when you're done streaming.
A quick hack to demonstrate would be to return a promise that doesn't resolve:
return new Promise( resolve => { }});
answered Nov 26 '18 at 17:34
EvertEvert
41.3k1570125
Thank you very much ! The middleware system of Koa is still rather obscure to me coming from Express. Especially when it comes to the execution flow.
– Christopher
Nov 27 '18 at 7:40
I guarantee that once you get the hang of it, you'll like it more!
– Evert
Nov 27 '18 at 15:16
add a comment |
Koa is entirely promise based and everything is a middleware.
Every middleware returns a promise (or nothing). The middleware chain is effectively 'awaited' and once the middleware returns, Koa knows the response is done and will end the stream.
To make sure that Koa doesn't do this, you have to make sure that the chain of middlewares don't end. To do this, you need to return a promise that only resolves when you're done streaming.
A quick hack to demonstrate would be to return a promise that doesn't resolve:
return new Promise( resolve => { }});
answered Nov 26 '18 at 17:34
EvertEvert
41.3k1570125
Koa is entirely promise based and everything is a middleware.
Every middleware returns a promise (or nothing). The middleware chain is effectively 'awaited' and once the middleware returns, Koa knows the response is done and will end the stream.
To make sure that Koa doesn't do this, you have to make sure that the chain of middlewares don't end. To do this, you need to return a promise that only resolves when you're done streaming.
A quick hack to demonstrate would be to return a promise that doesn't resolve:
return new Promise( resolve => { }});
answered Nov 26 '18 at 17:34
EvertEvert
41.3k1570125
edited Nov 27 '18 at 15:16
answered Nov 26 '18 at 17:34
EvertEvert
41.3k1570125
answered Nov 26 '18 at 17:34
EvertEvert
41.3k1570125
answered Nov 26 '18 at 17:34
EvertEvert
41.3k1570125
41.3k1570125
Thank you very much ! The middleware system of Koa is still rather obscure to me coming from Express. Especially when it comes to the execution flow.
– Christopher
Nov 27 '18 at 7:40
I guarantee that once you get the hang of it, you'll like it more!
– Evert
Nov 27 '18 at 15:16
add a comment |
Thank you very much ! The middleware system of Koa is still rather obscure to me coming from Express. Especially when it comes to the execution flow.
– Christopher
Nov 27 '18 at 7:40
I guarantee that once you get the hang of it, you'll like it more!
– Evert
Nov 27 '18 at 15:16
Thank you very much ! The middleware system of Koa is still rather obscure to me coming from Express. Especially when it comes to the execution flow.
– Christopher
Nov 27 '18 at 7:40
Thank you very much ! The middleware system of Koa is still rather obscure to me coming from Express. Especially when it comes to the execution flow.
– Christopher
Nov 27 '18 at 7:40
I guarantee that once you get the hang of it, you'll like it more!
– Evert
Nov 27 '18 at 15:16
I guarantee that once you get the hang of it, you'll like it more!
– Evert
Nov 27 '18 at 15:16
add a comment |
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53483534%2fkoa-sse-write-after-end%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
