We have an application written in Mono that needs to communicate with an Finder Sync App extension.
All is working fine until we tried our app on El Capitan instead of on Yosemite.
We use a shared SQLite database to tell what paths are in which state and use NSDistributedNotificationCenter for communication between the two.
The shared SQLite database is outside of the sandboxed env so we have putted an excepention in our entitlements com.apple.security.temporary-exception.files.home-relative-path.read-write
If we remove this exception from the app extension, the extension works (but obviously we can't read our db)
Then we tought of putting the SQLite DB into memory, but shared memory databases isn't possible over multiple processes.
I can't find how I can create a NSFileHandle for a Sqlite Connection.
We could send over all the info to the application extension, but then that has to keep it in memory (preferably in a SQLite, cause we need to do some querying.)
Does anyone has some pointers of what we could do?
Try to look in The Application Group Container Directory it might do in your case. Basically it allows you to have shared folder between apps/extension.
App group container directories. A sandboxed app can specify an entitlement that gives it access to one or more app group container directories, each of which is shared among all apps with that entitlement.
After some research on similar problem I found it's much easier to have simple TCP server in main app that responds to extension with file status. This way you can easily broadcast file status change to all extension instances etc.
Related
I have lately re-discovered embedded databases such as Sqlite (sql, relational) and LiteDb (noSql) and I like working with them for small web apps or mobile apps.
However, I cannot find any good answer to where to place them. Where to put them if:
The web app is likely to be containerized
The database can grow dynamically
Changes to the code and new deployments should not risk losing any change in database
1. Database file as part of solution (versioned in source control)
I've seen places where the *.db file is placed somewhere in the solution and it's versioned in source control.
I can see how this could be a problem as the database can be modified outside the context of development (i.e: when the app is up and running in production, the DB may change and in the next deployment the db may be overwritten if no backup/restore process in place)
Sometimes I have seen it inside wwwroot/App_Data. See this for instance. I assume App_Data is some kind of protected folder and its files cannot be server statically by the web server (is it?). Otherwise this is even worse.
2. Database file in binary folder
When testing, it's fine to have the database file generated somewhere in the bin folder, but this causes a similar problem as the previous one. What happens when a new software version is released and therefore the database file is overwritten in production?
So the questions are:
Is there any good practice regarding where to place embedded database files?
Is there any alternative to having backup/restore processes to avoid the described data-loss scenarios?
What happens when the app is contenierized and the database file grows once deployed? If the file is inside a container along with the running application, can it grow indefinitely? I don't recall specifying anything about a maximum size for containers anywhere when creating images..
Is having the DB in an external storage such a cloud blob store the alternative? I'm guessing the real benefit of embedded databases is gone if the file is in a different host.
Any good read about this would be appreciated.
PS:
I am asking for AspNet Core apps mainly because I see some projects using the wwwroot folder to place the embedded DB, but the question applies to any technology/framework.
This other question doesn't help either.
I evaluated JxBrowser a short while ago. The following questions came to mind:
Can I use Java URIs to "reroute" all temporary files from the underlaying Chromium engine through a custom FileSystemProvider like encFs4J?
The reason I want to that is to comply with data privacy laws. Since browsers can not be forced by a web application to clear their cache or store any temporary files in a safe manner, I thought I could use JxBrowser for this. If I can handle all files myself, I can do some crypto magic so that (almost) no one has access to the data besides my application.
There is an API to define the directories via BrowserContextParams.
However, only absolute paths are allowed. URIs are not accepted.
Instead of doing
BrowserContext context = new BrowserContext(new BrowserContextParams("C:\\Chromium\\Data"));
Browser browser1 = new Browser(context);
I would like to do something like
BrowserContext context = new BrowserContext(new BrowserContextParams(new URI("enc+file:///C:/Chromium/Data"));
Browser browser1 = new Browser(context);
Does anyone know of a way to tap into the file handling routines of a process like JxBrowser? Can I somehow add this functionality like a wrapper around it?
I considered using something like VeraCrypt for this. But this is no good in terms of usability since you have to install virtual harddrive drivers. This is overkill for a rather simple issue.
Underlying Chromium engine in JxBrowser does not use Java IO API to access files. There is only a path string to the data directory that is passed to Chromium engine and it decides by itself how to handle all IO operations.
There is a mode in Chromium called incognito. In that mode all the files, including cookies, cache, history are stored in memory, nothing is stored on the hard drive, so once you close the application, all the data will be cleared automatically. If this meets your requirements we could investigate how to enable incognito mode in JxBrowser.
I will accepting Artem's answer to the original question. Incognito / private browser sessions - as long as they do not store anything on hard disk - would be a perfect and simple solution.
Furthermore, I want to share my research on this topic. The following answer is not related to JxBrowser but to any 3rd party applications and libraries which do not support URI path or require additional safeguarding of (temporary) files.
Option 1: RamDisk
needed: kernel mode driver for ram disk
privileges: admin once (to install the driver)
usability: might be seemless, if application can handle ram disk by code (not researched)
Installing a RamdDisk which can "catch" the files. If the ram disk only persists while the application is running, it is already automatically cleaned up. (not researched for feasibility)
With an own ram disk implementation one could perform additional steps.
Option 2: Virtual File System, e.g. VeraCrypt
needed: VeraCrypt, kernel mode driver
privileges: admin once (to install the driver)
usability: user has to mount container manually before using the application
Due to usability issues this was not further researched.
Option 3: embedded SMB server with local share
needed: SMB server implementation (e.g. JVLAN for Java), creating a server and share in code
privileges: user (Ports 1445 can be used under Linux etc.)
usability: seemless for the user, but quite a complicated solution for a simple issue
Steps: start a SMB server by code, add a share and user authentication (optional), mount the share to a local drive (windows) or mount point (linux), use an absolute path to access the files on the locally mounted share. If the application crashes, then the volatile / in-memory key for the "real" file encryption of the SMB server is lost and the files are safe from other eyes.
This option also has more potential, like clearing files once they got read, controling the access to third party apps and many more - even freakier - ideas.
I am about to embark on the development of a line of business application using the Universal Windows Platform (Windows 10). One of the requirements of the application is the synchronisation of data from a server to a local SQLite database; this is required because the application needs to be usable where there is no network connectivity.
It is likely that multiple (windows domain) users will be accessing the application on the same device, sometimes simply by "swapping users", other times by logging off the first user and logging on as a new user.
I realise that UWP applications are installed at a user level, however I would like to be able to share the SQLite database between these users instead of forcing each user to download their own copy of the data.
Is this possible? I am struggling to find any reference to this kind of sharing within the Microsoft documentation - but of course that documentation is new and far from complete!
I guess at the end of the day I am looking for access to a folder that is accessible by any user running that application on the same device, such as the "x:\Users\Public" folders that are available from the desktop, but without having to ask the user to provide access to that folder via any picker control - instead simply being able to "open" it.
Thanks.
In case anyone runs across this, this functionality is now available as described in this blog post:
We introduced a new storage location Windows 10, ApplicationData.SharedLocalFolder, that allows multiple users of one app to share local data. Obviously this feature is only interesting with devices that will be used by more than one person. For such scenarios, for example in educational uses, it may make sense to place any large downloads in Shared Local. The benefits will be two-fold: any user can access these files without the need to re-download them, also there will be storage space savings
Keep in mind that Shared Local is only available if the machine has the right group policy, otherwise when you call ApplicationData.Current.SharedLocalFolder you will get back a null result.
In order to enable Shared Local the machine administrator should enable the corresponding policy.
Alternatively, the administrator could create a REG_DWORD value called AllowSharedLocalAppData with a value of 1 under HKLM\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\AppModel\StateManager
Note that data store in ShareLocal will only be persisted as long as the app is installed on the device and won’t be backed up by the system.
In Solution Explorer , Right click on Package.appxmanifest then click on ViewCode , end of this file in both projects add below code :
<Extensions>
<Extension Category="windows.publisherCacheFolders">
<PublisherCacheFolders>
<Folder Name="FolderName" />
</PublisherCacheFolders>
</Extension>
</Extensions>
After that in code you can access this folder with below line of code :
StorageFolder sharedDownloadsFolder = ApplicationData.Current.GetPublisherCacheFolder("FolderName");
It`s so important that the folder you will share between two these Apps depend on same publisher info at Certificate File [ProjectName]_TemporaryKey.pfx , if this Certificate File and publisher Info of app is same in both Projects , then you can access the same SharedFolder in both application and use it for create or use dataBase file(like SQLite Database file) or other files that need to be share in both applications.
Is there anyway to open and read a SQLite database file on GAE?
I am currently uploading dbs to blobstore as admin and serving them publicly to user clients. I just can't read them in the GAE admin interface.
You can use SQLITE on Google App Engine. The problem has nothing to do with the support of certain libraries. It has to do with read-only file system. There is, however, a writable /tmp directory. If your app on startup first copies the db.sqlite3 file to /tmp/db.sqlite3 and references this path as database path, it will work.
There are, however, drawbacks.
1. This is not a "real" directory i.e. it's stored im memory. If database is too large, one will get problems.
2. Each instance has its own copy of db.sqlite3 file. Does not scale well.
Here is a django example:
Using SQLITE for local Django development for Google App Engine?
Short answer, no it is not possible to use a SQLite database on a standard Google App Engine application as it is not currently supported. However, you can give a try at implementing your own configuration with the App Engine Flexible Environment that allows to take advantage of custom libraries through Infrastructure Customization.
In case you would want to experiment, here is a sample Django application designed to be run with its default SQLite database on the App Engine Flexible Environment. Still, make sure to read the database notice providing alternative data storage options and explaining that SQLite data does not persist upon instance restart.
I have developed an application win QT which uses SQLIte database. The copy of database is located on each site.
On one site let's say site 'BOB1' it works perfectly without any problem. But when we try to use it on another site lets say 'BOB2' it takes long time to open a database connection(approx 2000 milliseconds).
I thought that perhaps there is a network problem, So they tried to use the server of the site 'BOB1' as their server, which works fine. But when i tried to use the server of the site 'BOB2' from the site 'BOB1', I have the same problem. So i thought it may not be the network issue.
Another thing that came to my mind was that, perhaps there is a problem of DNS resolution. But when i tried to ping the server using IP and hostname, the response time is the same.
Any idea or pointer that what can be the problem.
PS: Server + database file path is specified in the setDatabasePath() fuinction using enviornment variables.
Consider copying the database to the local machine (eg temp folder if transient, or other suitable location if permanent). You can safely use either file copy, or consider using the qt backup API to ensure that the transfer happens successfully (plus you get the option of progress feedback)
https://sqlite.org/backup.html
You could even "backup" the file from the remote server to in-memory if the file is small and you say you're reading only?
You can see some sample code here on how to import an sqlite DB into a Qt QSqlDatabase. Note that when you do this, you want to make sure the version of sqlite native API that you're using is the same as that compiled into Qt, or you may get error messages from sqlite or Qt.