duplex stream getting changed in callback:node js

Question

I have a code where I am getting a duplex stream and in that function I call a callback which return me the values from redis.

      function (index, arr, null, callback) {
      const streamObject = stream;
      const Id = arr[index].split(':')[0];
      const Version = arr[index].split(':')[1];


      console.log("STREAM RECEIVED IN SECOND 1");
      console.log(streamObject);//printing for the first time
      var response = this.ts.service(Id, Version, streamObject, (fn, type) => {
        console.log("STREAM RECEIVED IN SECOND 2");
        console.log(streamObject);
}

here when I print the stream object for the first time I get the stream object as follows

STREAM RECEIVED IN SECOND 1
Stream {
  domain: 
   Domain {
     domain: null,
     _events: { error: [Function] },
     _eventsCount: 1,
     _maxListeners: undefined,
     members: [] },
  _events: 
   { end: [Function],
     data: [Function],
     drain: [Function: ondrain],
     error: [Function: onerror],
     close: [Function: cleanup] },
  _eventsCount: 5,
  _maxListeners: undefined,
  writable: true,
  readable: true,
  paused: false,
  autoDestroy: true,
  write: [Function],
  push: [Function],
  queue: [Function],
  end: [Function],
  destroy: [Function],
  pause: [Function],
  resume: [Function] }

and in the second time I get

STREAM RECEIVED IN SECOND 2

Stream {
  domain: 
   Domain {
     domain: null,
     _events: { error: [Function] },
     _eventsCount: 1,
     _maxListeners: undefined,
     members: [] },
  _events: { end: [Function], data: [Function] },
  _eventsCount: 2,
  _maxListeners: undefined,
  writable: false,
  readable: false,
  paused: false,
  autoDestroy: true,
  write: [Function],
  push: [Function],
  queue: [Function],
  end: [Function],
  destroy: [Function],
  pause: [Function],
  resume: [Function],
  root: null }

so stream is getting modified I am not sure why is it happening, I am not doing anything with the stream in the function called.

this is how my service method look which I am calling

service(id, vn, requestObject, callback) {
    log.info("entering transformer service");
    var transformerCombinedKey = id + vn;

    if (!_.isString(transformerId)) {
      throw new TypeError("Expected a string for transformerId");
    }

    if (!(transformerCombinedKey in this.functionRepositoryStore)) {
      //FIXME: after using cache as a implementation should ret
      var persistenceClientPromise = this.persistenceClient.getTransformerByIdAndVersion(transformerId, versionNumber)

      persistenceClientPromise.then(
        (aJSONStringifiedTransformer) => {
          if (!aJSONStringifiedTransformer) {
            callback(new Error("The given transformerId, " + transformerId + ", was not found."));
            return;
          }

          this.functionRepositoryStore[transformerCombinedKey] = JSON.parse(aJSONStringifiedTransformer).transformerFunction;
          this.transformerTypeRepository[transformerCombinedKey] = JSON.parse(aJSONStringifiedTransformer).transformerType;

          const code = "var _ = require('lodash'); console.log('runnig VM1'); module.exports = " + this.functionRepositoryStore[transformerCombinedKey] + ';';
          var transformerFunction = vm.runInNewContext(code, sandbox);
          console.log("Calling callback inside the transformer service===1 ");
          console.log(JSON.stringify(transformerFunction));
          callback(transformerFunction, this.transformerTypeRepository[transformerCombinedKey]);
          return
        },
        (error) => {
          log.error("Error while getting transformer for Id " + transformerId + " and versionNumber " + versionNumber);
          callback(error, null);
        });


    } else {

      const code = "var _ = require('lodash'); console.log('runnig VM2'); module.exports = " + this.functionRepositoryStore[transformerCombinedKey] + '; ';
      var transformerFunction = vm.runInNewContext(code, sandbox);
      console.log("Calling callback inside the transformer service=== ");
      console.log(JSON.stringify(transformerFunction));
      callback(transformerFunction, this.transformerTypeRepository[transformerCombinedKey]);
    }
  }

}

this issue I see when I hit my app for the first time, when I hit it again without restarting the app, It works fine stream remain duplex also. and also if I remove my call to redis this method , then stream doesn't change it works fine.

I am using waterfall and this is the second function of my waterfall model like

async.waterfall([func1,func2], function (err, result) {
        if (err) {
          console.log(err);
          reject(err);
        } else {
          fulfill(result);
        }

      });

this first function also do the same thing but it works fine, the output of first is passed to the second. this is how I create my stream

   let streamParser = JSONStream.parse('*');
                streamParser.on('data', fn);

                let toPassStreamObject = streamObject.pipe(JSONStream.stringify())
                  .pipe(streamParser)

streamObject is the stream which I get from my DB.

fn (data) {
      data['Date'] = data["month"];
      delete data['month'];
    }

I stuck on this for some time.how to prevent stream from changing.

this is reference to my previous post

duplex stream getting changed in callback:node js

0 Answers0