I was just playing around with Buffers in Node and am trying to understand them. I'm not too sure what the reason is for this event:
Here is my code:
var test = new Buffer(16);
test.fill(0);
test.write("Hey");
res.send(test.toString());
res.send(test.toString());
The message Hey is only sent once. Can you explain this to me?
Also, If the two lines looked like so:
res.send(test.toString());
res.send(test);
It would say Hey, but not download the second Buffer. Can Buffers only be sent once?
What is the purpose of blocking a second sending? This is probably a dumb question but I am just curious.
Related
I set up the command handler for my bot using the Discord.js guide (I am relatively new to Discord.js, as well as JavaScript itself, I'd say). However, as all my commands are in different files, is there a way that I can share variables between the files? I've tried experimenting with exporting modules, but sadly could not get it to work.
For example (I think it's somewhat understandable, but still), to skip a song you must first check if there is actually any audio streaming (which is all done in the play file), then end the current stream and move on to the next one in the queue (the variable for which is also in the play file).
I have gotten a separate music bot up and running, but all the code is in one file, linked together by if/else if/else chains. Perhaps I could just copy this code into the main file for my other bot instead of using the command handler for those specific commands?
I assume that there is a way to do this that is quite obvious, and I apologize if I am wasting peoples' time.
Also, I don't believe code is required for this question but if I'm wrong, please let me know.
Thank you in advance.
EDIT:
I have also read this question multiple times beforehand and have tried the solution, although I haven't gotten it to work.
A simple way to "carry over" variables without exporting anything is to assign them to a property of your client. That way, wherever you have your client (or bot) variable, you also have access to the needed information without requiring a file.
For example...
ready.js (assuming you have an event handler; otherwise your ready event)
client.queue = {};
for (guild of client.guilds) client.queue[guild.id] = [];
play.js
const queue = client.queue[message.guild.id];
queue.push({ song: 'Old Town Road', requester: message.author.id });
queue.js
const queue = client.queue[message.guild.id];
message.channel.send(`**${queue.length}** song${queue.length !== 1 ? 's' : ''} queued.`)
.catch(console.error);
So far I've only been able to get text and links from what other people on my discord channel type, but I want to be able to save posted images/gifs. is there any way I can do this through the bot or is it impossible? I'm using discord.js.
Images in Discord.js come in the form of MessageAttachments via Message#attachments. By looping through the amount of attachments, we can retrieve the raw file via MessageAttachment#attachment and the file type using MessageAttachment#name. Then, we use node's FileSystem to write the file onto the system. Here's a quick example. This example assumes you already have the message event and the message variable.
const fs = require('fs');
msg.attachments.forEach(a => {
fs.writeFileSync(`./${a.name}`, a.file); // Write the file to the system synchronously.
});
Please note that in a real world scenario you should surround the synchronous function with a try/catch statement, for errors.
Also note that, according to the docs, the attachment can be a stream. I have yet to have this happen in the real world, but if it does it might be worth checking if a is typeof Stream, and then using fs.createWriteStream and piping the file into it.
I'm using Node as webserver and I want to log every request to it into a database. I also want the user to receive the response as quickly as possible, so I came up with this code:
// ... putting together the response_data
res.send(response_data);
// ... now log the request into the DB and maybe do additional stuff
It works and I like the idea of putting some of the (time) expensive stuff behind the send. But as I'm new to Node I'm asking if this is a common pattern?
On Stackoverflow I just find people having problems bc they try to send additional data after res.send - but I never heard anybody saying "yeah this is a great feature for your responsiveness" so I'm not sure if there's a major flaw with this solution I just don't see yet...
As long as you don't need to send anything back to the user as a result of the "additional" stuff then your approach is fine.
The problem most people come across is trying to send data down the response after the response has already been sent e.g.
res.send(response_data);
// do additional stuff
res.send(additional_data); // KABOOM!
So this is the setup I'm working with:
I am on an express server which must stream an archived binary payload to a browser (does not matter if it is zip, tar or tar.gz - although zip would be nice).
On this server, I have a websocket open that connects to another server which is sending me binary payloads of individual files in a directory. I get these payloads streamed, piece-by-piece, as buffers, and I'm doing this serially (that is - file-by-file - there aren't multiple websockets open at one time, and there is one websocket per file). This is the websocket library I'm using: https://github.com/einaros/ws
I would like to go through each file, open a websocket, and then append the buffers to an archiver as they come through the websockets. When data is appended to the archiver, it would be nice if I could stream the ouput of the archiver to the browser (via the response object with response.write). So, basically, as I'm getting the payload from the websocket, I would like that payload streamed through an archiver and then to the response. :-)
Some things I have looked into:
node-zipstream - This is nice because it gives me an output stream I can pipe directly to response.write. However, it doesn't appear to support nested files/folders, and, more importantly, it only accepts an input stream. I have looked at the source code (which is quite terse and readable), and it seems as though, if I were able to have access to the update function within ZipStream.prototype.addFile, I could just call that each time on the message event when I get a binary buffer from the websocket. This is quite messy/hacky though, and, given that this library already doesn't seem to support nested files/folders, I'm not sure I will be going with it.
node-archiver - This suffers from the same issue as node-zipstream (probably because it was inspired by it) where it allows me to pipe the output, but I cannot append multiple buffers for the same file within the archive (and then manually signal when the last buffer has been appended for a given file). However, it does allow me to have nested folders, which is a clear win over node-zipstream.
Is there something I'm not aware of, or is this just a really crazy thing that I want to do?
The only alternative I see at this point is to wait for the entire payload to be streamed through a websocket and then append with node-archiver, but I really would like to reap the benefit of true streaming/archiving on-the-fly.
I've also thought about the possibility of creating a read stream of sorts just to serve as a proxy object that I can pass into node-archiver and then just append the buffers I get from the websocket to this read stream. Looking at various read streams, I'm not sure how to do this though. The only way I could think of was creating a writestream, piping buffers to it, and having a readstream read from that writestream. Am I on the correct thought process here?
As always, thanks for any help/direction you can offer SO community.
EDIT:
Since I just opened this question, and I'm new to node, there may be a better answer than the one I provided. I will keep this question open and accept a better answer if one presents itself within a few days. As always, I will upvote any other answers, even if they're ridiculous, as long as they're correct and allow me to stream on-the-fly as mine does.
I figured out a way to get this working with node-archiver. :-)
It was based off my hunch of creating a temporary "proxy stream" of sorts, inspired by this SO question: How to create streams from string in Node.Js?
The basic gist is (coffeescript syntax):
archive = archiver 'zip'
archive.pipe response // where response is the http response
// and then for each file...
fileName = ... // known file name
fileSize = ... // known file size
ws = .... // create websocket
proxyStream = new Stream()
numBytesStreamed = 0
archive.append proxyStream, name: fileName
ws.on 'message', (dataBuffer) ->
numBytesStreamed += dataBuffer.length
proxyStream.emit 'data', dataBuffer
if numBytesStreamed is fileSize
proxyStream.emit 'end'
// function/indicator to do this for the next file in the folder
// and then when you're completely done...
archive.finalize (err, bytesOfArchive) ->
if err?
// do whatever
else
// unless you somehow knew this ahead of time
res.addTrailers
'Content-Length': bytesOfArchive
res.end()
Note that this is not the complete solution I implemented. There is still a lot of logic dealing with getting the files, their paths, etc. Not to mention error-handling.
EDIT:
Since I just opened this question, and I'm new to node, there may be a better answer. I will keep this question open and accept a better answer if one presents itself within a few days. As always, I will upvote any other answers, even if they're ridiculous, as long as they're correct and allow me to stream on-the-fly as mine does.
I am working on an AS3 project in FDT6. I am using the lastest FLEX 4.6 and AIR 3.7.
I have a worker.swf file that is embedded into the main application to do threading work with.
I am using the MessageChannel class to pass information between the two.
In my main class I have defined
private var mainToWorker:MessageChannel;
private var workerToMain:MessageChannel;
mainToWorker = Worker.current.createMessageChannel(worker);
workerToMain = worker.createMessageChannel(Worker.current);
on the mainToWorker I only ever send messages. In these messages I send a byte array of information. The information is an object that contains a 'command' property and a 'props' property. Basically acting like a function call. The command is a function name and the props is an object that contains data for that function.
mainToWorkerMutex.lock();
mainToWorker.send(ByteArrayUtils.ObjectToByteArray({command:"DoSomething", props:{propA:1,propB:7}}));
mainToWorkerMutex.unlock();
The same occurs for the workerToMain var except I only send byte data that contains the 'message' and 'props' parameters.
workerToMainMutex.lock();
workerToMain.send(ByteArrayUtils.ObjectToByteArray({command:"complete", props:{return:"result"}}));
workerToMainMutex.unlock();
As a sanity check I make sure that the message channels are getting what they should.
It is working fine when I build it in FDT, however when it is built using an ANT script through flash builder I am sometimes getting the 'command' events coming back through in the workerToMain channel.
I am sending quite a lot of data through the message channel. Is it possible that I am overloading it and causing a buffer overflow into the other message channel somehow? How could that only be happening in FB?
I have checked my code many times and I am sure there is nothing in my own code that is sending that message back.
I had similar issue. When sending many bytearrays using channels sometimes things i received was not things i've actually sended. I had 4 channels (message channel to worker, message channel to main, data channel to worker, data channel to main).
I've noticed that data channel to main was affecting message channel to worker. When i turned off data channel to main - message channel to worker stared working just fine :D...
They have a big issue there with sending byte arrays it seems.
But what helped me was using shareable (at first it was not shareable) bytearray for communication via channels, but only for communication, as soon as i am receiving such bytearray i'm copying it to another byte array and parsing a copy.
This removed the problem (made quite hard stress tests there)...
Cheers
P.S. I'm also using static functions (like your ByteArrayUtils) to create bytearray's used for communication, but it seems fine, even made tests using non static functions.
So, it looks like I have found the issue. Looks like it's the ByteArray that is doing it.
ByteArray.toString() is basically sometimes mangles your data meaning you can't really trust it.
http://www.actionscript.org/forums/showthread.php3?t=155067
If you read the comment by "Jim Freer" he mentions how strings sometimes do this.
My solution was to switch to using a JSON encoded string instead of ByteArray data in the message channel. The reason I was using bytearray data to begin with is because I wanted to preserve class definition information, which JSON doesn't do.