I'm trying to get plotly to stream data received by my server through a POST
request to http://localhost:3000/step
.
Building on the rest-example.js
in plotly-nodejs/examples, here's my server code (I've blurred out my username, apikey, and token):
'use strict';
var express = require('express');
var logger = require('morgan');
var bodyParser = require('body-parser');
var events = require('events');
var eventEmitter = new events.EventEmitter();
var app = express();
var server = require('http').Server(app);
var port = process.env.PORT || 3000;
server.listen(port);
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.post('/step', function(req, res) {
var data = req.body.data;
eventEmitter.emit('step', data);
res.end('ok');
});
var plotly = require('plotly')('username', 'apikey');
var token = 'token';
var dataInit = [{x:[], y:[], stream: { token: token, maxpoints: 10 } }];
var layout = {fileopt : "extend", filename : "REST-test"};
plotly.plot(dataInit, layout, function (err, msg) {
if(err) return console.error('step data error', err.stack);
var stream = plotly.stream(token, function() {});
eventEmitter.on('step', function(data) {
console.log('sending to plotly: ' + data + ' steps');
var streamObject = JSON.stringify({ x: getDateString(), y: data });
stream.write(streamObject+'\n');
});
});
function getDateString() {
var d = new Date();
return d.toLocaleString();
};
When I POST
data using cURL, for example curl http://localhost:3000/step --data "data=5"
, I can see that the data reaches the callback inside the plotly.plot
block, but plotly never starts up and streams the data.
In some slightly more complex server code I was working on earlier, I also get the error which may or may not be related and which always points to the beginning of the plotly.plot
block.
cb(null, body);
^
SyntaxError: Unexpected end of input
This is the full error stack:
/home/plotly-testing/node_modules/plotly/index.js:305
cb(null, body);
^
SyntaxError: Unexpected end of input
at Object.parse (native)
at /home/plotly-testing/node_modules/plotly/index.js:72:25
at IncomingMessage.<anonymous> (/home/plotly-testing/node_modules/plotly/index.js:305:9)
at IncomingMessage.emit (events.js:129:20)
at _stream_readable.js:908:16
at process._tickCallback (node.js:355:11)
---------------------------------------------
at IncomingMessage.Readable.on (_stream_readable.js:671:33)
at parseRes (/home/plotly-testing/node_modules/plotly/index.js:304:9)
at ClientRequest.<anonymous> (/home/plotly-testing/node_modules/plotly/index.js:71:9)
at ClientRequest.emit (events.js:107:17)
at HTTPParser.parserOnIncomingClient (_http_client.js:426:21)
at HTTPParser.parserOnHeadersComplete (_http_common.js:111:23)
at TLSSocket.socketOnData (_http_client.js:317:20)
---------------------------------------------
at new ClientRequest (_http_client.js:93:10)
at Object.exports.request (http.js:49:10)
at Object.exports.request (https.js:136:15)
at Plotly.plot (/home/plotly-testing/node_modules/plotly/index.js:70:21)
at Object.<anonymous> (/home/plotly-testing/index.js:175:8)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
Line 305 of plotly/index.js
points to the following method, which seems to indicate something was wrong in one of my callbacks, but I'm not sure.
// response parse helper fn
function parseRes (res, cb) {
var body = '';
if ('setEncoding' in res) res.setEncoding('utf-8');
res.on('data', function (data) {
body += data;
if (body.length > 1e10) {
// FLOOD ATTACK OR FAULTY CLIENT, NUKE REQ
res.connection.destroy();
res.writeHead(413, {'Content-Type': 'text/plain'});
res.end('req body too large');
return cb(new Error('body overflow'));
}
});
res.on('end', function () {
cb(null, body);
});
}
So I've modified the code to include a console.log
inside the Plotly.plot
callback.
See gist here: https://gist.github.com/alexander-daniel/b36f9be78abbbaa4847e#file-index-js-L33
And that way we can see that Plotly returned a graph URL that we can look at. https://gist.github.com/alexander-daniel/b36f9be78abbbaa4847e#file-console_output-L5
That should resolve the first issue.
As far as the second issue goes, it seems the problem is two fold: - JSON.parse
calls inside the library are not wrapped in try/catch, so it looks like if the stream-server returns anything that is not JSON, this will break.
We're looking into the streaming-server error returns, but I have opened this issue here re: the try/catch blocks in the API library.
github.com/plotly/plotly-nodejs/issues/37
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