Node/Hapi.js - How to stream/append result set from database via hapi.js?

Question

I'm trying to create REST service that returns data from database as a response via hapi.js.

I'm using tedious to execute SQL queries and I want to format results as JSON or XML and return them as a response of hapi request. Note that this is not tedious-specific, I can have the same problem with any database. Tedious has a callback that is invoked each time it receives a new row from the result set:

sqlRequest.on('row', function (columns) {
        fnOutput(columns[0].value);
});

This is the simplest example with one column output. fnOutput is a custom function that accepts text that should be returned. It can concatenate results and format them as JSON that will be returned to client.

I'm getting row-by-row and I want to concatenate values in rows and return them to the client via hapi. How to continuously send partial results to the response?

I don't want to concatenate all rows in this callback and then push entire formatted JSON when the query is finished. I don't know how many records I will have and I want to avoid big strings that will be accumulated.
If I try to call reply(columns[0].value) in fnOutput each time I get new row, it fails when second row is returned with: "reply interface called twice"

Is there some way to continuously append results in this callback to hapi.js output stream each time I get new row in callback function?

Does the database driver you are using support streaming results? — arb
– arb, Commented Jan 22, 2016 at 20:27
tedious is event based so it run callback every time it receives a new row. I have found some requests to support streaming but it seems that it is not implemented. — Jovan MSFT
– Jovan MSFT, Commented Jan 23, 2016 at 22:22
I believe that I'm looking for something like response.write method from express stackoverflow.com/questions/18857693/… . Is there an equivalent or anything similar in hapijs. — Jovan MSFT
– Jovan MSFT, Commented Jan 23, 2016 at 23:03

mikefrey · Accepted Answer · 2016-01-24 20:09:04Z

1

You may be able to write the data to the raw response using request.raw.res.write()

request.raw.res is the raw ServerResponse object, and you can find the documentation for the write method here: https://nodejs.org/dist/latest-v4.x/docs/api/http.html#http_response_write_chunk_encoding_callback

Once you are done writing data, you'll need to tell hapi that you are done handling the request manually by calling reply.close()

Something similar to this (untested):

sqlRequest.on('row', function (columns) {
    request.raw.res.write(columns[0].value);
});

sqlRequest.on('done', function () {
    reply.continue();
});

edited Jan 24, 2016 at 20:09

answered Jan 24, 2016 at 19:52

mikefrey

4,7013 gold badges32 silver badges41 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Jovan MSFT Over a year ago

You are right, this solved the problem. Instead of reply.continue() I have used request.raw.res.end() because I have passed entire reply.raw.res object to my function. If works great.

Collectives™ on Stack Overflow

Node/Hapi.js - How to stream/append result set from database via hapi.js?

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related