I am having some issues trying to connect to a matrix server using the matrix-js-sdk in a react app.
I have provided a simple code example below, and made sure that credentials are valid (login works) and that the environment variable containing the URL for the matrix client is set. I have signed into element in a browser and created two rooms for testing purposes, and was expecting these two rooms would be returned from matrixClient.getRooms(). However, this simply returns an empty array. With some further testing it seems like the asynchronous functions provided for fetching room, member and group ID's only, works as expected.
According to https://matrix.org/docs/guides/usage-of-the-matrix-js-sd these should be valid steps for setting up the matrix-js-sdk, however the sync is never executed either.
const matrixClient = sdk.createClient(
process.env.REACT_APP_MATRIX_CLIENT_URL!
);
await matrixClient.long("m.login.password", credentials);
matrixClient.once('sync', () => {
debugger; // Never hit
}
for (const room of matrixClient.getRooms()) {
debugger; // Never hit
}
I did manage to use the roomId's returned from await matrixClient.roomInitialSync(roomId, limit, callback), however this lead me to another issue where I can't figure out how to decrypt messages, as the events containing the messages sent in the room seems to be of type 'm.room.encrypted' instead of 'm.room.message'.
Does anyone have any good examples of working implementations for the matrix-js-sdk, or any other good resources for properly understanding how to put this all together? I need to be able to load rooms, persons, messages etc. and display these respectively in a ReactJS application.
It turns out I simply forgot to run startClient on the matrix client, resulting in it not fetching any data.
Related
So I need to implement an "expensive" API endpoint. Basically, the user/client would need to be able to create a "group" of existing users.
So this "create group" API would need to check that each users fulfill the criteria, i.e. all users in the same group would need to be from the same region, same gender, within an age group etc. This operation can be quite expensive, especially since there are no limit on how many users in one group, so its possible that the client requests group of 1000 users for example.
My idea is that the endpoint will just create entry in database and mark the "group" as pending, while the checking process is still happening, then after its completed, it will update the group status to "completed" or "error" with error message, then the client would need to periodically fetch the status if its still pending.
My implementation idea is something along this line
const createGroup = async (req, res) => {
const { ownerUserId, userIds } = req.body;
// This will create database entry of group with "pending" status and return the primary key
const groupId = await insertGroup(ownerUserId, 'pending');
// This is an expensive function which will do checking over the network, and would take 0.5s per user id for example
// I would like this to keep running after this API endpoint send the response to client
checkUser(userIds)
.then((isUserIdsValid) => {
if (isUserIdsValid) {
updateGroup(groupId, 'success');
} else {
updateGroup(groupId, 'error');
}
})
.catch((err) => {
console.error(err);
updateGroup(groupId, 'error');
});
// The client will receive a groupId to check periodically whether its ready via separate API
res.status(200).json({ groupId });
};
My question is, is it a good idea to do this? Do I missing something important that I should consider?
Yes, this is the standard approach to long-running operations. Instead of offering a createGroup API that creates and returns a group, think of it as having an addGroupCreationJob API that creates and returns a job.
Instead of polling (periodically fetching the status to check whether it's still pending), you can use a notification API (events via websocket, SSE, webhooks etc) and even subscribe to the progress of processing. But sure, a check-status API (via GET request on the job identifier) is the lowest common denominator that all kinds of clients will be able to use.
Did I not consider something important?
Failure handling is getting much more complicated. Since you no longer create the group in a single transaction, you might find your application left in some intermediate state, e.g. when the service crashed (due to unrelated things) during the checkUser() call. You'll need something to ensure that there are no pending groups in your database for which no actual creation process is running. You'll need to give users the ability to retry a job - will insertGroup work if there already is a group with the same identifier in the error state? If you separate the group and the jobs into independent entities, do you need to ensure that no two pending jobs are trying to create the same group? Last but not least you might want to allow users to cancel a currently running job.
I've been trying out GunJs for a couple of days now and I'm really enjoying it. As a starter project I've followed the Fireship chat dapp video aimed at building your own chat.
Here's the issue, now that I've finished the tutorial I would like to create my own chat. However, for some reason if I get a 'chat' node within my own app it seems to pick up on the same 'chat' node as the tutorial one that is online.
onMount(() => {
// Get Messages in large chat
db.get('chat')
.map()
.once(async (data, id) => {
if (data) {
// key for E2E - to do: change for web3
const key = '#foo';
var message = {
//transform the data
who: await db.user(data).get('alias'),
what: (await SEA.decrypt(data.what, key)) + '',
when: GUN.state.is(data, 'what'),
};
if (message.what) {
messages = [...messages.slice(-100), message]
}
}
})
})
This is also the case if I change the encryption key (then the messages just become undefined). Multiple questions arise from this:
Are graph node names unique within the whole of GunDb?
How do you handle conflicts where two gun-based apps call on the same node name?
Is this problem generally solved through filtering using 'header' props?
How do I make it pick up on only my data?
Even if I've read most of the docs, there seems to be something I'm missing in my comprehension of how the graph is generally seperated between apps. Any insight on how this works would be much appreciated.
Are graph node names unique within the whole of GunDb?
Yes.
How do you handle conflicts where two gun-based apps call on the same node name?
You don't. The expected result will be, they will overwrite each other.
Is this problem generally solved through filtering using 'header' props?
I don't think it's the right way to do it.
How do I make it pick up on only my data?
Use your own relay server.
Conclusion :
gunDB doesn't really care about the who fetch / put the data. If you want to protect your data, use your own relay server (not a public one), and put data in your user space. user space is readonly to the public, but read/write for the owner.
I have an app where I spawn several BrowserWindows, with html forms, and I'd like to collect all the data (in order to save it, to be able to spawn them in the same state at a restart) at a press of a button.
At the moment, the only solution I found to do so, is to have each BrowserWindow do ipcRenderer.send every single time any variable changes (not too hard to do with Vuejs 'watchers'), but this seems demanding and inefficient.
I also thought of doing 'executeJavascript' to each window but that does not allow to capture the return value afaik.
I'd just like to be able to send a message from main when a request for saving is made, and wait for the windows to respond before saving all.
EDIT
I found a slightly better way, it looks like this
app.js
// wait for update reponses
ipc.on('update-response', (evt,args) => {
updates[evt.sender.id] = args;
if(Object.keys(updates).length == BrowserWindow.getAllWindows().length) {
// here I do what I need to save my settings, using what is stored in 'updates'
// ...
// and now reset updates for next time
updates = {}
}
});
// now send the requests for updates
BrowserWindow.getAllWindows().map(w => w.send('update'));
renderer.js
ipcRenderer.on('update', () => {
// collect the data
// var data = ...
ipcRenderer.send('update-response', data);
})
and obviously on the renderer side I am listening to these 'update' messages and sending data with 'udpate-response'.
But it seems a bit complicated and so I am sure there is a simpler way to achieve this using the framework.
EDIT 2
I realized that the above does not always work, because for some reason, the evt.sender.id do not match the ids obtained from BrowserWindows.getAllWindows(). I worked around that by sending ids in the request, and having the responder include it. But this is all so much fine for so very little...
I am trying to change the URL request on an already connected socket but I can't figure out how or if it is even possible.
I am working with the WebSocket API and CoinCap.
What I am doing right now is closing the connection and creating a new one with the new parameters.
// Create a new WS connection
const webSocketURL = `wss://ws.coincap.io/prices?assets=${loadedKeys}`
// loadedKeys could be a string of one coin (e.g. bitcoin) or an array
// or an array (e.g. bitcoin,ethereum,monero,litecoin), has to be dynamic.
pricesWs = new WebSocket(webSocketURL);
pricesWs.onopen = function () {
console.log(`conected: ${pricesWs.readyState}`)
}
pricesWs.onmessage = function (msg) {
handleUpdateCB(msg.data);
}
// then when I need to receive different coin prices
// I close the connection and reopen a new one.
anotherFunction() {
pricesWs.close();
pricesWs = new WebSocket(aNewWebSocketURL);
}
I tried sending parameters as messages with send() function without success, I keep receiving the same data, let's say I first connect asking for bitcoin and the I want to receive bitcoin and ethereum I tried this
pricesWs = new WebSocket(`wss://ws.coincap.io/prices?assets=bitcoin);
//then tried
pricesWs.send(bitcoin,ethereum)
this doesn't work, I also tried sending as JSON but I kept getting the same data just for the first query(bitcoin)
UPDATE:
This is the the Git for the app, if you are interested seeing the whole thing together.
Git
UPDATE 2:
I created this pen to make it easier to understand, note that the pen is made on VueJS, but that isn't important. The important part is on line 60 JS panel
Is there any reason why you want to switch the URL?
According to the coin cap documentation, you can request information about multiple crypto currency at once. Is it not an option for you?
Generally you should avoid opening and closing connections to a socket as there is slight latency albeit very insignificant. Leaving the connection open is better since you will be notified if price is changed for any of the currencies you are interested it.
The answer to your original question "Is it possible to change URL for a web socket connection?" is no! You can't change URL however you can create as many connections as you need. In your case you are closing the connection and opening it immediately but in the comments I noticed that you mentioned that it is based on user interaction. You can open connection just for the currencies you care about when user requests it and keep the connection opened until user switches the currency again because at that point you'll probably switch to another currency.
I also agree with #Taylor Spark, you can also just hide the dom for the currencies user don't care and render the ones they are interested in.
DATABASE:
SITUATION:
My website sells keys for a game.
A key is a randomly generated string of 20 characters whose uniqueness is guaranteed (not created by me).
When someone buys a key, NTWKeysLeft is read to find it's first element. That element is then copied, deleted from NTWKeysLeft and pasted to NTWUsedKeys.
Said key is then displayed on the buyer's screen.
PROBLEM:
How can I prevent the following problem :
1) 2 users buy the game at the exact same time.
2) They both get the same key read from NTWKeysLeft (first element in list)
3) And thus both get the same key
I know about Firebase Transactions already. I am looking for a pseudo-code/code answer that will point me in the right direction.
CURRENT CODE:
Would something like this work ? Can I put a transaction inside another transaction ?
var keyRef = admin.database().ref("NTWKeysLeft");
keyRef.limitToFirst(1).transaction(function (keySnapshot) {
keySnapshot.forEach(function(childKeySnapshot) {
// Key is read here:
var key = childKeySnapshot.val();
// How can I prevent two concurrent read requests from reading the same key ? Using a transaction to change a boolean could only happen after the read happens since I first need to read in order to know which key boolean to change.
var selectedKeyRef = admin.database().ref("NTWKeysLeft/"+key);
var usedKeyRef = admin.database().ref("NTWUsedKeys/"+key);
var keysLeftRef = admin.database().ref("keysLeft");
selectedKeyRef.remove();
usedKeyRef.set(true);
keysLeftRef.transaction(function (keysLeft) {
if (!keysLeft) {
keysLeft = 0;
}
keysLeft = keysLeft - 1;
return keysLeft;
});
res.render("bought", {key:key});
});
});
Just to be clear: keyRef.limitToFirst(1).transaction(function (keySnapshot) { does not work, but I would like to accomplish something to that effect.
Most depends on how you generate the keys, since that determines how likely collisions are. I recommend reading about Firebase's push IDs to get an idea how unique those are and compare that to your keys. If you can't statistically guarantee uniqueness of your keys or if statistical uniqueness isn't good enough, you'll have to use transactions to prevent conflicting updates.
The OP has changed the question a bit so, i will update the answer as follows: I will leave the bottom part about transactions as it was and will put the new update on top.
I can see two ways to proceed:
1) handle the lock system on your own and use JavaScript callbacks or other mechanisms for preventing simultaneous access to a portion of the code.
or
2) Use transactions/fireBase. On this case, i don't have the setup ready to share code other than sample/pseudo code provided at the bottom of this page.
With respect to option 1 above:
I have coded a use-case and put in on plunker. It uses JavaScript callbacks to queue users as they try to access the part of the code under lock.
I. user comes in and he is placed in queue
II. It then calls the callback function which pops users as
first come first out bases. I have the keys on top of the page to
be shared by the functions.
I have a button click event to this and when you click the button twice quickly, you will see keys assigned and they're different keys.
To read this code, click on the script.js file on the left and read starting from the bottom of the page where it calls the functions.
Here is the sample code in plunker. After clicking it, click on Run on top of the page and then click on the button on right hand side. Alert will pop up to show which key is given (note, there are two calls back to back to show two users coming in at same time)
https://plnkr.co/edit/GVFfvqQrlLeMaKlo5FCj?p=info
The fireBase transactions:
Use fireBase transactions to prevent concurrent read/write issues - below is the transaction() method signiture
transaction(dataToBeWritten, onComplete, applyLocally) returns fireBase.promise containing {
committed: boolean, nullable fireBase.database.snapshot }
Note, transaction needs writeOperation as first parameter and in your case looks like you’re removing a key upon success! hence the following function to be called in place of write
Try this pseudo code :
//first, get reference to your db
var selectedKeyRef = admin.database().ref("NTWKeysLeft/"+key);
// needed by transaction as first parameter
function writeOperation() {
selectedKeyRef.remove();
}
selectedKeyRef.transaction(function(writeOperation) , function(error,
committed, snapshot) {
if (error) {
console.log('Transaction failed abnormally!', error);
} else if (!committed) {
console.log('We aborted the transaction (because xyz).’);
} else {
console.log(‘keyRemoved!’);
}
console.log(“showKey: ", snapshot.val());
}); // end of the transaction() method call
Docs + to see parameters/return objects of the transaction() method see:
https://firebase.google.com/docs/reference/js/firebase.database.Reference#transaction
In the Docs.... If another client writes to the location before your new value is successfully written, your update function is called again with the new current value, and the write is retried.
https://firebase.google.com/docs/database/web/read-and-write#save_data_as_transactions
I don't think the problem you're worried about can happen. JavaScript, including Node, is single-threaded and can only do one thing at a time. If you had a big server infrastructure with more than one server running this code, then it would be possible, but for a single Node program, there's no problem.
Since none of the previous answers discussing the scope of Transactions worked out, I would suggest a different workaround.
Is it possible to trigger the unique code generation when someone buys a code? If yes, you could generate the unique string if the "buy" button is clicked, display the ID and save the ID to your database.
Later the user enters the key in your game, which checks if the ID is written in your database. This might probably also save a bit of data, since you do not need to keep track of the unique IDs before they get bought and you will also not run out of IDs, since they will always get generated when necessary.