Http Headers related error with code pulled.

[madkid66]

We pulled parse-server code from master yesterday and while using that code, we notice the following stack trace in log for all the cloud calls being made. Anyone else seeing this? Also, any suggestions, tips for resolving this are appreciated. Thank you.

Error: Can't set headers after they are sent.
    at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11)
    at /var/app/current/node_modules/express/lib/application.js:153:9
    at /var/app/current/node_modules/express/lib/router/index.js:137:5
    at /var/app/current/node_modules/express/lib/router/index.js:250:10
    at next (/var/app/current/node_modules/express/lib/router/index.js:160:14)
    at next (/var/app/current/node_modules/express/lib/router/index.js:176:38)
    at Immediate.<anonymous> (/var/app/current/node_modules/express/lib/application.js:190:9)
    at Immediate.<anonymous> (/var/app/current/node_modules/parse-server/node_modules/express/lib/router/index.js:618:15)
    at Immediate.immediate._onImmediate (timers.js:435:18)
    at processImmediate [as _immediateCallback] (timers.js:383:17)

[sprabs]

I'm noticing this, too. I had done a pull on master branch on 7/12. That had been working fine. When I pulled yesterday and deployed the newer parse server code, I started seeing this error. I suspect it must have been a commit that was introduced between 7/12 and 7/21.

@flovilmart Have you noticed this error, too?

[flovilmart]

I haven't noticed it, not sure what would generate it.

[flovilmart]

It doesn't seem to happen when using parse-server from the CLI, how did you configure/run it?
Can you provide more info about the code?

We recently added next handlers (#2338) this is maybe because your setup has a middleware that write the headers after they are written from parse-server

[madkid66]

Thank you for the reply Florent.

We are running it on AWS Elastic Beanstalk on a t2.medium and seeing this error in the nodejs logs. The configuration of our environment has not changed over the last 3 weeks and we are running it with verbose set to true. The only thing we changed was we pulled the lasted parse-server code from master.

The error seems to happen any time a cloud code method is invoked. We use promises in our methods. It definitely seems to have been caused by the changes you pointed me to in PromiseRouter.js. Once I removed those changes in my local branch and redeployed, the errors went away. What is the purpose of those changes? Is that something that can be reverted? Or Is there something that our cloud-code needs to do to avoid seeing this error? Please share your thoughts on this.

[tillifywebb]

We are running on node chef, Our code is also now breaking. The issue appears that if we make any database queries from server code, cloud function or from express we get the fore mentioned error.

If we call queries from JS client - all works find. If we do anything server side we get the error. We have tried removing our app.js require so that our express set-up is removed, this did not fix the issue.

Can anybody help with this?

at Layer.handle as handle_request
at jsonParser (/bundle/node_modules/parse-server/node_modules/body-parser/lib/types/json.js:94:7)
at next (/bundle/node_modules/express/lib/router/index.js:271:10)
at Function.process_params (/bundle/node_modules/express/lib/router/index.js:330:12)
at /bundle/node_modules/express/lib/router/index.js:280:7
at trim_prefix (/bundle/node_modules/express/lib/router/index.js:312:13)
at Layer.handle as handle_request
at allowCrossDomain (/bundle/index.js:439:9)
at ServerResponse.header (/bundle/node_modules/express/lib/response.js:719:10)
at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11)
Error: Can't set headers after they are sent.

[nitrag]

Seeing same error as well. AWS ElastBeanstalk, t2.micro, 64bit Amazon Linux 2016.03 v2.1.3, node version 4.4.6 (perhaps that's the issue?).

Errors are seen after running a cloud function, but my app still receives a valid response...

Parse.Cloud.define("getParks", function(request, response){

    if(!request.user){
        response.error();
        return;
    }

    var Parks = Parse.Object.extend("Park");
    var query = new Parse.Query(Parks);
    query.equalTo("Approved", true);

    query.find({useMasterKey: true}).then(function(results) {
        var parks = [];
        ..........
        return parks;
    }).then(function(parks) {
            response.success(parks);
        }, function(error) {
            response.error("Error: " + error.code + " " + error.message);
    });
});

[flovilmart]

The fix seem pretty trivial as it looks like it originates from one of our middleware that's run after the cloud functions. As you have the error, can any of you work on a fix?

[tillifywebb]

We have rolled back the last update which has fixed the error. Not sure how we fix it, seems any cloud function throws an error, but response is sent.

[flovilmart]

@madkid66 can you try #2381 's branch and let me know if it fixes?

[madkid66]

@flovilmart thank you for the reply. Will try that and update.

[sprabs]

@flovilmart Thanks for the suggestion. I tried that branch you pointed us to but am still getting this error:

Error: Can't set headers after they are sent.
at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11)
at /var/app/current/node_modules/express/lib/application.js:153:9
at /var/app/current/node_modules/express/lib/router/index.js:137:5
at /var/app/current/node_modules/express/lib/router/index.js:250:10
at next (/var/app/current/node_modules/express/lib/router/index.js:160:14)
at next (/var/app/current/node_modules/express/lib/router/index.js:176:38)
at Immediate. (/var/app/current/node_modules/express/lib/application.js:190:9)
at Immediate. (/var/app/current/node_modules/parse-server/node_modules/express/lib/router/index.js:618:15)
at Immediate.immediate._onImmediate (timers.js:435:18)
at processImmediate as _immediateCallback

@tillifywebb @madkid66 Did it work for you both or are you still seeing the issue, too?

[madkid66]

@sprabs We have tried that suggestion but still seeing the issue. Thank you

@flovilmart anything else we can try? Thank you

[jeffjen]

This is related to middleware firing header indiscriminately even though a previous handler had already sent header.

[woodardj]

Why was #2338 merged? This seems like a pretty drastic change in behavior for those of us working on getting our self-hosted infrastructure set up.

It appears that now our /parse/classes/:className endpoint is continuing through (not surprising with the addition of a next() into our express app's auth code that's been working fine until 2.2.16 (or 2.2.17)

What's the recommendation here?

[blacha]

@woodardj it was a bug to not have it, You should always call next() in your express apps. It prevented actions after data was returned to the client. (Eg logging and analytics)

If you are having issues with this, there is more than likely something not quite right in the order of the app.use inside your express application.

The order is very important to app.use

app.use(function(req, res, next) {
    console.log('beforeParse');
    next();
});

app.use('/parse', ParseInstance);

app.use(function(req, res, next) {
    console.log('afterParse');
    next();
});