I want to make my app more responsive when there are problems with getting data from server.
Right now I am using Reachability library to check access to Internet but i think that it is not enough. Sometimes server can handle request for long time or even be down and not responding.
In cases when network requests take too much time I want to notify user that something went wrong, not showing endless activity indicators.
Where to start from? What are the best practices?
Set a custom timeout interval for the URLRequest. It should be ideally
depending on the amount of data you expect the server to send and the
internal queries the server does to fetch the data and finally dump
the same to the API you are using.
Try using postman to get an idea of server response time and the data you received. Based on that estimate a justified timeout interval for your request.
let request = NSMutableURLRequest()
request.setValue("application/json", forHTTPHeaderField: "Accept")
request.timeoutInterval = 20 // this is what you need to set.
You can then provide message or response to the user through some message. As far as connectivity is concerned, you could look at the YouTube app, try putting device on flight mode and you'll see the strip which shows connectivity status without intruding the user experience.
First i would suggest add a loading before checking internet, and dismiss the loading when you received anythings from the URLRequest.
Second, you can set your custom timeout interval for URLSessionConfiguration, so that it wont hang in there
fyi: https://developer.apple.com/documentation/foundation/urlsessionconfiguration/1408259-timeoutintervalforrequest
Related
Is there any configuration like android user-permission in iOS to control access to internet?
I think all new projects access to internet by default, is that correct?
When I send a request to the internet it returns 0 http-error code, it means I can't access to the internet.
yes, it is correct all the new ios project have access to the internet by default.
A status code of 0 in an NSHTTPURLResponse object generally means there was no response and can occur for various reasons. The server will never return a status of 0 as this is not a valid HTTP status code.
Any http request will first be processed by the operating system, and during that phase you can get an error. Getting an error means that your request never got a response from the server (and with the exception of https requests where certificates were not accepted, most likely didn't reach the server).
If this phase succeeds, then you get eventually a reply from the server. This may take time, you may have to wait 60 seconds. Which is why you do all your internet requests on a background thread. That reply will have a status code (status, not error). The status code is NEVER 0.
By default, iOS doesn't allow http requests, and doesn't allow https requests to unsave servers, so you better use only https unless you have a very good reason. You will need a very good reason to convince Apple to let your app on the app store if you want http requests to succeed. But if you get this wrong, you get an error quite early on.
A status of zero most likely means that a background request didn't finish by the time you read the status, a basic programming mistake. You need to learn how background threads and callbacks work. Without that, you won't be able to use http successfully.
Also google for "Reachability" which can tell you if your app currently has internet access (like when WiFi and Mobile Data are turned off, or in Airplane mode).
I'm experiencing slow response times for my first http POST request to my server.
This happens both in Android and iOS networking libraries. (Volley on Android, and Alamofire in iOS).
First response is roughly 0.7s-0.9s, whereas subsequent requests are 0.2s.
I'm guessing this is due to the session being kept-alive by the server, therefore eliminating the need for establishing a new session on each request.
I figure I can make a dummy request when the app starts to start the session, but it doesn't seem very elegant.
I also control the server side (Node.js) so if any configuration needs to be done there I can also try it.
Investigating a little further, I tried sending an https CONNECT request before issuing the first "real" POST request, and the behavior replicates.
After 30 seconds or so, the connection is dropped (probably at the iOS URLSession level, the load balancer is configured to keep connections as 60 seconds).
In theory this makes sense because setting up an https connection takes up several (12 total) packets and I'm on an inter continental connection.
So my solution is to send a CONNECT request when I expect the user to send a regular request.
I have an app that lets the user send messages with images. A user might hit send, then immediately close their phone or switch to another app.
We were running into an issue that if there's temporarily a bad network connection the message would fail to send. We switched to using NSURLSession backgroundConfigurationWithIdentifier so that backgrounding the app doesn't immediately time out the running request. We switched to using this for all our api requests, thinking that it wouldn't hurt for every request to able to continue in the background if the app were closed at the wrong time.
Fast forward a couple weeks we're noticing all requests seem slow. Using wireshark I just discovered that this background session seems to use a new http connection per request, meaning it requires setting up a TCP connection and new TLS handshake for every request, which was adding a ~500ms latency on every request in our app. This is a pretty big deal but I can't find this behavior documented anywhere, including the link above or Apple's background transfer considerations.
So my question is, is this behavior expected, or am I doing something wrong somewhere? Is there an easy way with NSURLSession to make an HTTP request that will use an existing keep-alive connection if there is one, but can fall back to the backgroundConfiguration if the app gets moved to the background?
NSURLSession is the recommended way to fulfill your use case. Have you tried setting backgroundSessionConfig.discretionary = true
iOS Reference
A Boolean value that determines whether background tasks can be
scheduled at the discretion of the system for optimal performance.
If that doesn't help, I recommend filing a bug with iOS.
I have an iOS application where I POST transactions to an API each time a transaction is completed. Once I get a 200 response code from the server I update an attribute on the transaction:
newTransaction.Synced = true
Incase the network connection ever drops I also POST every transaction where Synced = false when Reachability detects a network connection.
In perfect network conditions this works wells. However when I enable the Network Link Conditioner on my iPad and set packet loss to say 40% I start to see duplicated transactions on my server. What I assumed was happening is that it was taking longer than 30 seconds (the client side timeout on the request) to send my request and get the response from the server due to the high packet loss.
To confirm this, I made my API Sleep for 40 seconds for each web request and disabled Network Link Conditioner. As expected, the iOS app never set the Synced attribute to true as it was timing out before it got the response. However the server still created the entity for each POST request that was generated each time the iOS app launched or got network connectivity.
What's the best way to handle this situation so that duplicates never occur? I did think of adding a GUID to the transaction and then coding the API not to re-add the transaction if the GUID already exists. However the flip side is the iOS app would still never know the transaction has successfully synced. Is there a better way to handle this? Perhaps a timeout on the request which the server also adheres to?
Your Idea of assigning the GUID to transaction is good, but you might need to maintain a table on client side (browser memory) which will hold a record of all the calls you made to server and never heard back.
In the iOS Developers Guide for Parse, it states "By default, all connections have a timeout of 10 seconds." I am looking to change this for all requests made from the app, but am not finding any information on how to do so.
The reason we'd like to modify this is that it's taking a long time for requests to fail when the user doesn't have Wi-Fi or Cellular enabled. We want to reduce the amount of time it takes to receive said error message, just a little. We don't want to implement our own reachability tests, as it will result in duplicate popup error messages and we have many requests in various view controllers throughout the app.
Can the timeout be modified, or is there some other way to obtain a better user experience than waiting 10 seconds for an error message?
There is no information on this but certainly the request timeout limits are set by Parse and a developer will not be able to change them. I think they kept the timeouts to be long to avoid a user request being rejected if their connection becomes suddenly intermittent or they go in a tunnel, etc.
You can try to warp Parse queries around a timer which uses let say 5 seconds timeout, if the response does not come in that time you cancel your your query using PFQuery cancel function and show them a message.
If you want to avoid timing out, consider checking Reachability before making the call. You may want to show the user an alert if they're not connected and you need to do something.
A lot of people say you should just assume a connection and make the attempt without checking reachability; basically just let the connection fail and handle the error that way. I think as long as the failure isn't invisible to the user, so they don't blame your app vs their network you're good though.