Sending stream from controller

[MaheshkumarSundaram]

Hi @neonexus,

Could you please show me an example for sending a stream (due to the file size) from Sails controller to front-end in a proper way as we have custom responses?

For example, I need to send a PDF file read from disk to the front-end for displaying it in an iframe. Thank you.

const fs = require('fs');
const path = require('path');

module.exports = {
    friendlyName: 'Send PDF',

    description: 'Read a PDF from disk and send its content.',

    inputs: {
        filePath: {
            type: 'string',
            description: 'Path to the PDF file on disk.',
            required: true
        }
    },

    exits: {
        success: {
            responseType: 'ok'
        },
        notFound: {
            responseType: 'notFound'
        },
        serverError: {
            responseType: 'serverError'
        }
    },

    fn: async function (inputs, exits) {
        try {
            const filePath = inputs.filePath;

            // Check if the file exists
            if (!fs.existsSync(filePath)) {
                return exits.notFound(`File not found at ${filePath}`);
            }

            // Get the file name from the file path
            const fileName = path.basename(filePath);

            // Set the appropriate headers for the PDF response
            this.res.set({
                'Content-Type': 'application/pdf',
                'Content-Disposition': `inline; filename="${fileName}"`
            });

            // Create a readable stream from the PDF file
            const stream = fs.createReadStream(filePath);

            // Pipe the stream to the response object
            stream.pipe(this.res);

            // Handle the end of the stream
            stream.on('end', () => {
                return exits.success();
            });

            // Handle any errors that occur during streaming
            stream.on('error', (error) => {
                return exits.serverError(error.message);
            });
        } catch (error) {
            // Handle any other errors
            return exits.serverError(error.message);
        }
    }
};

is the above code optimal or any better to send such data from controller?

[MaheshkumarSundaram]

@neonexus,
But this.res.set throws error for me. Not sure what am I doing wrong!

[neonexus]

You can’t use old style ‘this.res’, you have to use the third parameter ‘env’.

See the login controller I believe for an example.

[neonexus]

Did you get this fixed @MaheshkumarSundaram ?

Also, I just pushed a new release. It has an update to the request logger I meant to put out a long time ago; something I'm sure you'll appreciate if you are still using the logger: v5.3.2...v5.3.3

[MaheshkumarSundaram]

@neonexus ,

Sorry for the late response. I was away for a few days.

Also, I just pushed a new release. It has an update to the request logger I meant to put out a long time ago; something I'm sure you'll appreciate if you are still using the logger: v5.3.2...v5.3.3

Thanks for the note. I'll check them out today.

Did you get this fixed @MaheshkumarSundaram ?

I am having an issue with headers for the response.

Controller Code

   const fs = require('fs');
const path = require('path');

module.exports = {
    friendlyName: 'Send PDF',

    description: 'Read a PDF from disk and send its content.',

    inputs: {
        filePath: {
            type: 'string',
            description: 'Path to the PDF file on disk.',
            required: true,
        },
    },

    exits: {
        success: {
            responseType: 'ok',
        },
        notFound: {
            responseType: 'notFound',
        },
        serverError: {
            responseType: 'serverError',
        },
    },

    fn: async function (inputs, exits, env) {
        try {
            const filePath = inputs.filePath;

            // Check if the file exists
            if (!fs.existsSync(filePath)) {
                return exits.notFound(`File not found at ${filePath}`);
            }

            // Get the file name from the file path
            const fileName = path.basename(filePath);

            // Set the appropriate headers for the PDF response
            env.res.set({
                'Content-Type': 'application/pdf',
                 'Content-Disposition': `inline; filename="${fileName}"`,
            });

            // Create a readable stream from the PDF file
            const stream = fs.createReadStream(filePath);

            // Pipe the stream to the response object
            stream.pipe(env.res);

            // Handle the end of the stream
            stream.on('end', () => {
                return exits.success();
            });

            // Handle any errors that occur during streaming
            stream.on('error', (error) => {
                return exits.serverError(error.message);
            });
        } catch (error) {
            // Handle any other errors
            return exits.serverError(error.message);
        }
    },
};

And I get this error:

node:internal/errors:496
    ErrorCaptureStackTrace(err);
    ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at new NodeError (node:internal/errors:405:5)
    at ServerResponse.setHeader (node:_http_outgoing:648:11)
    at ServerResponse.header (F:\my-app\node_modules\express\lib\response.js:776:10)
    at ServerResponse.json (F:\my-app\node_modules\express\lib\response.js:264:10)
    at Object.sendOK (F:\my-app\api\responses\ok.js:30:21)
    at F:\my-app\node_modules\machine-as-action\lib\machine-as-action.js:1109:19
    at afterwards (F:\my-app\node_modules\machine-as-action\lib\machine-as-action.js:1112:17)
    at _waitForSimulatedLatencyIfRelevant (F:\my-app\node_modules\machine-as-action\lib\machine-as-action.js:620:50)
    at Object.respondApropos [as success] (F:\my-app\node_modules\machine-as-action\lib\machine-as-action.js:622:11)
    at F:\my-app\node_modules\machine\lib\private\help-build-machine.js:1517:30
    at proceedToFinalAfterExecLC (F:\my-app\node_modules\parley\lib\private\Deferred.js:1157:14)
    at proceedToInterceptsAndChecks (F:\my-app\node_modules\parley\lib\private\Deferred.js:913:12)
    at proceedToAfterExecSpinlocks (F:\my-app\node_modules\parley\lib\private\Deferred.js:845:10)
    at F:\my-app\node_modules\parley\lib\private\Deferred.js:303:7
    at F:\my-app\node_modules\machine\lib\private\help-build-machine.js:953:53
    at handlerCbs.success (F:\my-app\node_modules\machine\lib\private\help-build-machine.js:814:26) {
  code: 'ERR_HTTP_HEADERS_SENT'
}

Could you please guide me on this? Thanks.

[neonexus]

@MaheshkumarSundaram This might have something to do with the custom response handlers. Because they default to using res.status(200).json(out);, and you aren't sending JSON.

You can create a custom response handler called something like pdf, and change the responseType to match.