I have a doubt in PWA and will be glad if someone helps me with that. In my PWA I don't have any problem with storing static files like HTML, JS & CSS. But am facing Issues on dynamic data. i.e : my self.addEventListener('fetch', function(e) { }) is not getting called, but other functionalities are working fine i.e: 'install' and 'active' event.
to be more particular, I am using #angular/service-worker which worked fine but I created another sw file called sw.js. In my sw-js I'm listening to the events like 'install' 'active' and 'fetch'. My sw.js fetch is not getting called whereas the other two methods work well. But while fetching the ngsw-worker.js's fetch method alone gets called.
The thing I need is to make CRUD Operations in PWA with angular.
Thanks in advance!
You can do the dynamic caching like below , the service worker will intercept every request and add in to the cache.
self.addEventListener("fetch", function (event) {
event.respondWith(
caches.open("dynamiccache").then(function (cache) {
return fetch(event.request).then(function (res) {
cache.put(event.request, res.clone());
return res;
})
})
)
}
Note : You can't cache POST Requests
Can service workers cache POST requests?
Related
I am working on PWA project. As per requirement, cached data is dynamic. Means, we are not using self.__WB_Manifest to cache the data. Instead of that, all the URL's sending over the API and storing those URL's under one cache.
Now issue is that, if certain html page, which is in same domain and same origin but not cached, in those case we want to show offline.html page.
Usually it will show if we use self.__WB_Manifest. But, as per requirement, we are not using it.
We do have offline.html page in cached data. Even it's present in folder structure, but it not triggering it.
Can anybody please help me guide on it, in case how to pickup the URL from cache and show as a offline page when app is in offline mode and particular page is not cached.
Currently using Workbox V6
addEventListener('fetch',async (event)=>{
console.log("add event listener fetch" + event);
event.respondWith(
caches.match(event.request).then(async (cachedResponse) =>{
console.log("inside cached response" + event.request.mode);
if (cachedResponse) {
console.log("fetch event if");
return cachedResponse;
}else if(!cachedResponse){
console.log("fetch event else");
return fetch(event.request);
}else{
const cache = await caches.open(OFFLINE_PAGES_RESPONSE);
return cache.match('/offline.html');
}
}).catch(async()=>{
console.log("inside cache");
const cache = await caches.open(OFFLINE_PAGES_RESPONSE);
return cache.match('/offline.html');
})
);
});
Overview
I've built an application with Vue, Express and MongoDB (mongoose ORM).
On loading the landing page, a series of GET requests are made for various bits of data. The loading times are extremely high, I've recorded some times as high as 22s for a particular route. It's lead me to believe that my requests are running sequentially, despite specifying in my logic that everything should run async
I've tried reducing the size of the objects being returned from the requests as well as using the .lean() method. These attempts shaved off a couple of seconds, but the overall issue is not remotely sorted. Times are still stupid high. To give an example:
From This:
// Method to find all users
var users = await User.find({});
To:
// Method to find all users
var users = await User.find({}, "username, uid").lean();
On the page in question, there are about 5 main components. Each component is making a get request. One of these is a Chat Column and the code for it is as follows:
ChatCol.vue
beforeMount () {
this.$store.dispatch('retrieve_chat')
}
Store.js (am using Vuex store)
retrieve_chat (context) {
return new Promise((resolve, reject) => {
axios({
url: api.dev + 'api/v1/chat',
method: 'GET',
})
.then(res => {
context.commit('set_chat', res.data)
resolve(res);
}).catch(err => {
// alert(err)
reject(err);
})
})
},
Requests in this format are being made on all the components. About 5 of them in the page in question.
Backend / Server Code
To give some context into the requests being made.
The client will hit the route 'http://localhost:3000/api/v1/chat'
and the code that makes the request on the server is the following:
var Chat = require("../models/ChatMessage");
module.exports = {
// LIMIT CHAT TO 100 MESSAGES
async get_chat(req, res) {
Chat.find({}, function(err, messages) {
if (err) {
return res.status(500).send({
message: "Interval Server Error",
type: "MONGO_CHAT_DOCUMENT_QUERY",
err: err,
})
}
if (!messages) {
return res.status(400).send({
message: "Resource not found",
type: "MONGO_CHAT_DOCUMENT_QUERY",
details: "!messages - no messages found",
})
}
messages.reverse();
return res.status(200).json({
messages,
});
}).sort({"_id": -1}).limit(30);
},
}
If I look at the network tab on the chrome dev tools, this is how the requests appear. Apologies for the long winded post, I literally have no idea what is causing this
Important Note:
It was mentioned to me that mongodb has this feature where it locks when mutating the data, and I thought that might be the case, but there are no mutations taking place. It's just 3/4 get requests happening in parallel, albeit pretty big requests, but they shouldn't be taking as long as they are
Screenshot of the network tab:
(ignore the failed req, and some of the duplicate named requests)
StackOverflow sempais please help. It's a very big application and I don't know what the issue is exactly, so If I've missed out any details - Apologies, I'll clarify anything that needs clarity.
Large amount of base64 encoded data from a previously abandoned and poorly implemented image upload feature was being stored in each chat message as well as other places, causing large amounts of data to be loaded in and ultimately lead to huge loading times.
Thank you Neil Lunn.
Just to make it clear, I'm using the MongoDB, Express, React and Node stack.
I'm trying to learn react.js right now. I got the basics right and I am able to code a simple react app with a router. I've also tried server-side rendering a simple react app and it also works perfectly. However, I'm kind of stuck now that I want to make a full app with a rest api and server-side rendering.
1) I don't know how I should go about separating the api and the react code in the server file. Would starting off by listing the api calls and then do the server-side rendering work?
Like so:
app.get('/api/whatever', function(req, res) {
//get whatever
});
app.get('*', function(req, res) {
//math routes and renderToString React
});
2) Also, the reason I couldn't even test the above, is that when I try to run the server with nodemon it throws an error because it doesn't understand the react code, how should I go about this? Should I somehow configure nodemon to read es6 or ignore it or configure webpack to run the express server ?
3) The final question that could clear this whole story quite easily. I've tried finding an answer but got many conflicting ones instead. Are the google crawlers capable of crawling a React app? I'm learning server-side rendering for SEO, is that all really necessary?
Sorry for the long question, looking forward to reading your answers.
I do it the same way you do in your code example in the project I'm currently working on – I match * and then use React Router to render different pages. I wrote a blog article about this, with code examples.
in the setup I have, I use webpack to compile my backend code, just like I do with the frontend code. I use the watch mechanism to listen for code changes and automatically restart the node server after recompiling. No need for nodemon.
#!/usr/bin/env node
const path = require('path');
const webpack = require('webpack');
const spawn = require('child_process').spawn;
const serverConfig = require('webpack.config.server');
const compiler = webpack(serverConfig);
const watchConfig = {
aggregateTimeout: 300,
poll: 1000,
ignored: '**/*.scss'
};
let serverControl;
compiler.watch(watchConfig, (err, stats) => {
if (err) {
console.error(err.stack || err);
if (err.details) {
console.error(err.details);
}
return;
}
const info = stats.toJson();
if (stats.hasErrors()) {
info.errors.forEach(message => console.log(message));
return;
}
if (stats.hasWarnings()) {
info.warnings.forEach(message => console.log(message));
}
if (serverControl) {
serverControl.kill();
}
serverControl = spawn('node', [path.resolve(__dirname, '../../dist/polly-server.js')]);
serverControl.stdout.on('data', data => console.log(`${new Date().toISOString()} [LOG] ${data}`));
serverControl.stderr.on('data', data => console.error(`${new Date().toISOString()} [ERROR] ${data}`));
});
yes, Google crawls client-side React code, but server-side rendering is still a good idea, because crawl results may be inconsistent, especially if you load parts of the page dynamically after Ajax calls
I am struggling to receive pubsub events in my client. The client store (reflux) gets the data from a project using its id. As I understand it this automatically subscribes the Sails socket for realtime events (from version 0.10), but I don't see it happening.
Here's my client store getting data from sails
(this is ES6 syntax)
onLoadProject(id) {
var url = '/api/projects/' + id;
io.socket.get(url, (p, jwres) => {
console.log('loaded project', id);
this.project = p;
this.trigger(p);
});
io.socket.on("project", function(event){
console.log('realtime event', event);
});
},
Then I created a test "touch" action in my project controller, just to have the modifiedAt field updated.
touch: function(req, res){
var id = req.param('id');
Project.findOne(id)
.then(function(project) {
if (!project) throw new Error('No project with id ' + id);
return Project.update({id: id}, {touched: project.touched+1});
})
.then(function(){
// this should not be required right?
return Project.publishUpdate(id);
})
.done(function() {
sails.log('touched ok');
res.ok();
}, function(e) {
sails.log("touch failed", e.message, e.stack);
res.serverError(e.message);
});
}
This doesn't trigger any realtime event in my client code. I also added a manual Project.publishUpdate(), but this shouldn't be required right?
What am I missing?
-------- edit ----------
There was a complication a result of my model touched attribute, since I set it to 'number' instead of 'integer' and the ORM exception wasn't caught by the promise error handling without a catch() part. So the code above works, hurray! But the realtime events are received for every instance of Project.
So let me rephrase my question:
How can I subscribe the client socket to an instance instead of a model? I could check the id on the client side and retrieve the updated instance data but that seems inefficient since every client receives a notification about every project even though they only should care about a single one.
----- edit again ------
So nevermind. The reason I was getting updates from every instance is simply because at the start of my application I triggered a findAll to get a list of available projects. As a result my socket got subscribed for all of them. The workaround would be to either initiate that call via plain http instead of a socket, or use a separate controller action for retrieving the list (therefor bypassing the blueprint route). I picked the second option because in my case it's silly to fetch all project data prior to picking one.
So to answer my own question. The reason I was getting updates from every instance is simply because at the start of my application I triggered a findAll to get a list of available projects. As a result my socket got subscribed for all of them.
The workaround would be to either initiate that call via plain http instead of a socket, or use a separate controller action for retrieving the list (therefor bypassing the blueprint route). I picked the second option because in my case it's silly to fetch all resources data prior to selecting one.
Here's the function I used to list all resources, where I filter part of the data which is not relevant for browsing the list initially.
list: function(req, res) {
Project.find()
.then(function(projects) {
var keys = [
'id',
'name',
'createdAt',
'updatedAt',
'author',
'description',
];
return projects.map(function(project){
return _.pick(project, keys);
});
})
.catch(function (e){
res.serverError(e.message);
})
.done(function(list){
res.json(list);
}, function(e) {
res.serverError(e.message);
});
},
Note that when the user loads a resource (project in my case) and then switches to another resource, the client is will be subscribed to both resources. I believe it requires a request to an action where you unsubscribe the socket explicitly to prevent this. In my case this isn't such a problem, but I plan to solve that later.
I hope this is helpful to someone.
I've got a node.js application that 'streams' tweets to users. At the moment, it just searches Twitter for a hard-coded string, but I'd like to allow users to configure this in the URL (eg. by visiting /?q=stackoverflow).
At the moment, my code looks a bit like this:
app.get('/', function (req, res) {
// page rendering skipped
io.sockets.on('connection', function (socket) {
twit.stream('user', {track: 'stackoverflow'}, function(stream) {
stream.on('data', function (data) {
socket.volatile.emit('tweet', data);
}
});
});
});
The question is, how do I make it so that each user can see a different stream of tweets simultaneously? At the moment, it works fine in a single browser tab, but it falls over as soon as a second one is opened - and the error is fairly deep down inside socket.io. Am I misusing it?
I haven't fully got my head around socket.io yet, so that could be the issue.
Thanks in advance!
Every time a new request comes in, you are redefining the connection callback with io.sockets.on - you should move that block of code outside of app.get, after your initialization statement of the io object.