There is a new JSWASM approach that allows saving to SQLite (the fast OPFS way) in the browser via a javascript Worker. A sample is here that is (sort of) for a Chrome extension. Ideally, it would allow saving from the background.js, but it's unclear whether a worker can be called from there in MV3 based on this and this. Does anyone have a simple working example closer to my use case, which is saving content from the user's active tab to a SQLite database? Thanks.
The OPFS depends on the createSyncAccessHandle() method, which is exposed in Worker threads. The usual feature detection goes like this:
if (self instanceof WorkerGlobalScope && 'createSyncAccessHandle' in self.FileSystemFileHandle.prototype) {
// OPFS in `Worker` is supported!
}
Now an extension service worker (as currently implemented in Chrome) is an instance of ServiceWorkerGlobalScope, so the API is not supported there.
Unfortunately at the moment the only choice is to open an extension page and then run the OPFS code from there.
Related
Is there any difference in patch api in embedded and standard version of the server?
Is there a need to configure document store in some way to enable patch api?
I'm writing a test which use embedded raven. The code works correctly on the standard version but in test it doesn't. I'm constantly receiving patch result: DocumentDoesNotExists. I`ve checked with debugger and the document exists in the store - so it is not a problem with test.
Here you can find a repro of my issue: https://gist.github.com/pblachut/c2e0e227fa3beb51f4f9403505c292bb
I`ve reached the contact in the ravendb support and I have answer for my question.
There should be no difference between embedded and normal version of the server. The problem was that I did not passed explicitly for which database I want to invoke batch command. In the result I tried to patch document in system database.
var result = await documentStore.AsyncDatabaseCommands.ForDatabase("testDb).BatchAsync(new[] {command});
I assumed that database name will be taken from the session (beacuse I get documentStore from there). But the name of database should be always passed.
var documentStore = session.Advanced.DocumentStore;
I'm working on an Adobe AIR application which can upload files to a web server, which is running Apache and PHP. Several files can be uploaded at the same time and the application also calls the web server for various API requests.
The problem I'm having is that if I start two file uploads, while they are in progress any other HTTP requests will time out, which is causing a problem for the application and from a user point of view.
Are Adobe AIR applications limited to 2 HTTP connections, or is something else probably the issue?
From searching about this issue I've not found much but one article did indicated that it wasn't limited to just two connections.
The file uploads are performed by calling the File classes upload method, and the API calls are done using the HTTPService class. The development web server I am using is a WAMP server, however when the application is released it will be talking to a LAMP server.
Thanks,
Grant
Here is the code I'm using to upload the file:
protected function btnAddFile_clickHandler(event:MouseEvent):void
{
// Create a new File object and display the browse file dialog
var uploadFile:File = new File();
uploadFile.browseForOpen("Select File to Upload");
uploadFile.addEventListener(Event.SELECT, uploadFile_SelectedHandler);
}
private function uploadFile_SelectedHandler(event:Event):void
{
// Get the File object which was used to select the file
var uploadFile:File = event.target as File;
uploadFile.addEventListener(ProgressEvent.PROGRESS, file_progressHandler);
uploadFile.addEventListener(IOErrorEvent.IO_ERROR, file_ioErrorHandler);
uploadFile.addEventListener(Event.COMPLETE, file_completeHandler);
// Create the request URL based on the download URL
var requestURL:URLRequest = new URLRequest(AppEnvironment.instance.serverHostname + "upload.php");
requestURL.method = URLRequestMethod.POST;
// Set the post parameters
var params:URLVariables = new URLVariables();
params.name = "filename.ext";
requestURL.data = params;
// Start uploading the file to the server
uploadFile.upload(requestURL, "file");
}
Here is the code for the API calls:
private function sendHTTPPost(apiFile:String, postParams:Object, resultCallback:Function, initialCallerResultCallback:Function):void
{
var httpService:mx.rpc.http.HTTPService = new mx.rpc.http.HTTPService();
httpService.url = AppEnvironment.instance.serverHostname + apiFile;
httpService.method = "POST";
httpService.requestTimeout = 10;
httpService.resultFormat = HTTPService.RESULT_FORMAT_TEXT;
httpService.addEventListener("result", resultCallback);
httpService.addEventListener("fault", httpFault);
var token:AsyncToken = httpService.send(postParams);
// Add the initial caller's result callback function to the token
token.initialCallerResultCallback = initialCallerResultCallback;
}
If you are on a windows system, Adobe AIR is using Microsofts WinINet library to access the web. This library by default limits the number of concurrent connections to a single server to 2:
WinInet limits the number of simultaneous connections that it makes to a single HTTP server. If you exceed this limit, the requests block until one of the current connections has completed. This is by design and is in agreement with the HTTP specification and industry standards.
... Connections to a single HTTP 1.1 server are limited to two simultaneous connections
There is an API to change the value of this limit but I don't know if it is accessible from AIR.
Since this limit also affects page loading speed for web sites, some sites are using multiple DNS names for artifacts such as images, javascripts and stylesheets to allow a browser to open more parallel connections.
So if you are controlling the server part, a workaround could be to create DNS aliases like www.example.com for uploads and api.example.com for API requests.
So as I was looking into this, I came across this info about using File.upload() in the documentation:
Starts the upload of the file to a remote server. Although Flash Player has no restriction on the size of files you can upload or download, the player officially supports uploads or downloads of up to 100 MB. You must call the FileReference.browse() or FileReferenceList.browse() method before you call this method.
Listeners receive events to indicate the progress, success, or failure of the upload. Although you can use the FileReferenceList object to let users select multiple files for upload, you must upload the files one by one; to do so, iterate through the FileReferenceList.fileList array of FileReference objects.
The FileReference.upload() and FileReference.download() functions are
nonblocking. These functions return after they are called, before the
file transmission is complete. In addition, if the FileReference
object goes out of scope, any upload or download that is not yet
completed on that object is canceled upon leaving the scope. Be sure
that your FileReference object remains in scope for as long as the
upload or download is expected to continue.
I wonder if something there could be giving you issues with uploading multiple files. I see that you are using browserForOpen() instead of browse(). It seems like the probably do the same thing... but maybe not.
I also saw this in the File class documentation
Note that because of new functionality added to the Flash Player, when publishing to Flash Player 10, you can have only one of the following operations active at one time: FileReference.browse(), FileReference.upload(), FileReference.download(), FileReference.load(), FileReference.save(). Otherwise, Flash Player throws a runtime error (code 2174). Use FileReference.cancel() to stop an operation in progress. This restriction applies only to Flash Player 10. Previous versions of Flash Player are unaffected by this restriction on simultaneous multiple operations.
When you say that you let users upload multiple files, do you mean subsequent calls to browse() and upload() or do you mean one call that includes multiple files? It seems that if you are trying to do multiple separate calls that that may be an issue.
Anyway, I don't know if this is much help. It definitely seems that what you are trying to do should be possible. I can only guess that what is going wrong is perhaps a problem with implementation. Good luck :)
Reference: http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/net/FileReference.html#upload()
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/net/FileReference.html#browse()
Just because I was thinking about a very similar question because of an error in one of my actual apps, I decided to write down the answer I found.
I instantiated 11
HttpConnections
and was wondering why my Flex 4 Application stopped working and threw an HTTP-Error although it was working pretty good formerly with just 5 simultanious HttpConnections to the same server.
I tested this myself because I did not find anything regarding this in the Flex docs or on the internet.
I found that using more than 5 HTTPConnections was the reason for the Flex application to throw the runtime error.
I decided to instantiate the connections one after another as a temporally workaround: Load the next one after the other has received the data and so on.
Thats of course just temporally since one of the next steps will be to alter the responding server code in that way that it answers a request that contains the results of requests to more then one table in one respond. Of course the client application logic needs to be altered, too.
What's the standard way of storing user preferences in a Flex application for AIR? I need to store simple parameters like lists of recently opened files, window positions and sizes etc.
my favorite way to do it is to combine a VO with LSO (local shared object). If you have a LOT of settings, this doesn't work too well. The advantage is that you get a strongly typed settings object which is therfore bindable and has code introspection and completion.
The cool thing is it's only about 5 lines of code to manage an LSO. In addition, it's also pretty easy to manage a local encrypted store if you want to store any sensitive data.
registerClassAlias("SettingsVO",SettingsVO); //This lets us store a typed object in LSO
var settings:SettingsVO;
var settingsSO = SharedObject.getLocal("settings");
//Check to make sure settings exist... if not, create a new settings object
if( settingsSO.size && settingsSO.data && settingsSO.data.settings){
settings = settingsSO.data.settings as SettingsVO;
}else{
settings = new SettingsVO();
}
Now if you want to save settings you simply do
settings.someSetting = "newValue";
settingsSO.data.settings = settings;
settingsSO.flush();
And this solution works on BOTH AIR and Flex in any browser. Newer browsers will delete this data when clearing cookies, so beware of that.
I think the most flexible way is to use a local SQLite database. It gives you unlimited, structured storage and encryption if needed. See Peter Elst's introduction if you want to get more info.
There is no "Standard" way, but there are a lot of approaches, all which boil down to storing the user's preferences, then loading them up at runtime based on some uesr credentials, then changing the app based on those preferences.
You may store them in a server side database, such as SQL Server or MySQL; then have flex call a service which queries the database and returns the data.
You may store them as Shared Objects, which are the Flash version of browser cookies. (I believe they work on AIR applications too). This can get cumbersome with lots of data.
You may store them in an XML document and throw them on the server. Conceptually this is not much different than storing them in a server side database; but could get very tedious if you have a lot of users.
You could also store them, in an AIR app, locally using a SQLite database. SQLite is an embedded database used in Adobe AIR.
I don't bother with any of the fancy stuff. Just store it in an xml file in the application directory. Done.
Filestream does throw an error if you try to store it using File.applicationDirectory. I just trick the program...
var trickFile:File = File.applicationDirectory;
var file:File = new File(trickFile.nativePath + mySettings.xml);
Air falls for it every time.
I have an ASP.NET running in IIS 7.5 that creates files on the local file system and then attempts to delete after performing some logic in between creation and deletion. I'm running into a situation though where deletion is failing with a response such as "The process cannot access the file 'C:...\Uploads\c1fe593f-85de-4de1-b5d1-7239e1fc0648_Tulips.jpg' because it is being used by another process.'" The file appears to be locked by IIS and I can't delete it. Here's an example of the code for creating and deleteing:
// File.WriteAllBytes(path, rawData); // this seems to leave the file open!
using (var file = File.Create(path))
{
file.Write(rawData, 0, rawData.Length);
file.Close(); // should close when it goes out of scope, but just to be safe
}
Is there some special option I need to pass into File.Create? How do I get around this?
File.WriteAllBytes(path, rawData); should work fine assuming the path parameter you are passing is unique and that you don't have concurrent requests one writing and other trying to read at the same time. To ensure this you could use a ReaderWriterLockSlim to synchronize the access if this situation could potentially occur. Also make sure that there are no other parts of the code that might leak the file handle.
Take a look at SysInternals Process Explorer which could allow you to know exactly where this file handle is leaked.
The code has a runtime dependency which is not available in our development environment (and is available in test and prod). It's expensive to actually test for the dependency, and I want to test for the environment instead.
if (isDevEnvironment) {
// fake it
}
else {
// actually do it
}
Without using appSettings, what code/technique/test would you use to set isDevEnvironment?
Example answers:
check machine name (partial or full)
check for running instance of Visual Studio
check for environment variable
I'm hoping for a test I hadn't considered.
You should try to not test your environment in the code! That's why dependency inversion (and then injection) has been invented for.
Draw some inspiration from NewSpeak, where where the complete platform is abstracted in an object and passed as parameter down the chain of method calls.
The code you provided (if (isDevEnvironment) ..) smells with test code in production.
Without using appSettings, what code/technique/test would you use to set isDevEnvironment?
Generally, Dependency Injection.
But also the the possible Solution in the link provided.
You should not check the environment, instead you need to provide the environment.
You've hit upon the major techniques. At my current job, we use the Enviroment variable technique.
At a previous job, all servers had three NIC's, there was the public front end, the middle tier for server to server traffic, and the back end Network Operations would connect to.
There were on different IP subnets. It made it easy to detect where something was coming from, but also who where was it.
Example:
10.100.x.xxx - Production Subnet
10.100.1.xxx - Back
10.100.2.xxx - Middle
10.100.3.xxx - Front
10.0.1.x - Development Subnet
This required nothing to be installed special on the servers, just code detection and then caching.
I prefer to do this:
if(Properties.Settings.Default.TestEnvironment || HttpContext.Current.Request.ServerVariables["Server_Name"] == "localhost")
{
// do something
}