Node.js - Can I store writeable streams as JSON in Redis? - json

Question

I am still working on fully understanding streams in node.js. If I create a writable stream, would I be able able to store the stream object as JSON in Redis, and then access it later, and continue writing to it (after JSON.parse)?
example:
var fs = require( 'fs' );
var redis = require( 'redis' );
var streamName = fs.createWriteStream(upfilePath, streamopts);
streamName = JSON.stringify(streamName);
rclient.set('streamJSON', streamName);
....
var myNewdata = 'whatever';
rclient.get('streamJSON', function (err, streamJSON) {
var recoveredStream = JSON.parse(streamJSON);
recoveredStream.write(myNewdata, function (err, written, buffer) {
//write successful??
}
}

Answer 1

You can't store variable references on redis. You would only need to store the filename, then reopen the stream with the a flag which allows you to append data to it.
I thought this was pretty an interesting question and created this that allows you to save the state of a stream and then use it later. But I don't see the point if you can just use the a flag. Might be useful for ReadableStreams though.
var fs = require('fs');
exports.stringify = function(stream) {
var obj = {
path: stream.path
, writable: stream.writable
, fd: stream.fd
, options: {
encoding: stream.encoding
, mode: stream.mode
}
};
if (stream.writable) {
obj.bytesWritten = stream.bytesWritten;
} else {
obj.options.bufferSize = stream.bufferSize;
obj.bytesRead = stream.bytesRead;
}
return JSON.stringify(obj);
};
exports.parse = function(json, callback) {
var obj = JSON.parse(json);
var stream;
if (obj.writable) {
obj.options.flags = 'a';
stream = fs.createWriteStream(obj.path, obj.options);
stream.bytesWritten = obj.bytesWritten;
} else {
stream = fs.createReadStream(obj.path, obj.options);
stream.bytesRead = obj.bytesRead;
}
// if stream was already opened, wait until it is
if (obj.fd !== null) {
stream.on('open', function() {
callback(null, stream);
});
} else {
process.nextTick(function() {
callback(null, stream);
});
}
return stream;
};