Basically i'm developing an application in python where it listens to external sqlite database changes, so far i implemented update_hook()(from this example: SQLite Data Change Notification Callbacks in Python or Bash or CLI) it worked well when i launch SQL statements in the same process however when i use external database that has now relation with my process it doesn't work.
My question is how do i listen to database changes from an external process(A) that has no relation with process(B).
SQLite has no mechanism by which another process can be notified.
You have to implement some communication mechanism outside of SQLite.
Related
I would like to keep the django server running as I call some custom commands that will read / write to the sqlite DB. However I'm nervous that this may conflict due to the main server locking the database file.
Is this cause for concern ?
I can't use PostgreSQL or MySQL.
I tried this and it didn't throw any errors, however I would like to know if this is something that can occur.
I haven't been able to find any documentation regarding whether it's possible to access SQLITE3 (using Python) when the SQLITE database is hosted externally:
I have my SQLITE3 database hosted on my VPS (alongside some other stuff that doesn't really matter) - rather than having it as a local file with my Python program.
Therefore, is it possible for me to connect to the SQLITE database which is hosted on my VPS, or will the SQLITE DB have to be hosted locally for me to be able to do this?
The reason I want it to be accessible from my VPS is because I want to be able to run the program on multiple computers and them all have the same access to the database- if this isn't possible, are there any other options which would allow me to do this?
If you want to have a database server with external, possibly remote, applications interacting a client-server protocol switch to PostgreSQL, MariaDB, etc.
see: How to connect to SQLite3 database server?
We are developing a b2b application with django. For each client, we launch a new virtual server machine and a database. So each client has a separate installation of our application. (We do so because by the nature of our application, one client may require high use of resources at certain times, and we do not want one client's state to affect the others)
Each of these installations are binded to a central repository. If we update the application code, when we push to the master branch, all installations detect this, pull the latest version of the code and restart the application.
If we update the database schema on the other hand, currently, we need to run migrations manually by connecting to each db instance one by one (settings.py file reads the database settings from an external file which is not in the repo, we add this file manually upon installation).
Can we automate this process? i.e. given a list of databases, is it possible to run migrations on these databases with a single command?
If we update the application code, when we push to the master branch,
all installations detect this, pull the latest version of the code and
restart the application.
I assume that you have some sort of automation to pull the codes and restart the web server. You can just add the migration to this automation process. Each of the server's settings.py would read the database details from the external file and run the migration for you.
So the flow should be something like:
Pull the codes
Migrate
Collect Static
Restart the web server
First, I'd really look (very hard) for a way to launch a script that does as masnun suggests on the client side, really hard.
Second, if that does not work, then I'd try the following:
Configure on your local machine all client databases in the settings variable DATABASES
Make sure you can connect to all the client databases, this may need some fiddling
Then you run the "manage.py migrate" process with the extra flag --database=mydatabase (where "mydatabase" is the handle provided in the configuration) for EACH client database
I have not tried this, but I don't see why it wouldn't work ...
im working on python application that requiring database connections..I had developed my application with sqlite3 but it start showing the error(the database is locked).. so I decided to use MySQL database instead.. and it is pretty good with no error..
the only one problem is that I need to ask every user using my application to install MySQL server on his pc (appserv for example) ..
so can I make mysql to be like sqlite3 apart of python lib. so I can produce a python script can be converted into exe file by the tool pyInstaller.exe and no need to install mysql server by users???
update:
after reviewing the code I found opened connection not closed correctly and work fine with sqllite3 ..thank you every body
It depends (more "depends" in the answer).
If you need to share the data between the users of your application - you need a mysql database server somewhere setup, your application would need to have an access to it. And, the performance can really depend on the network - depends on how heavily would the application use the database. The application itself would only need to know how to "speak" with the database server - python mysql driver, like MySQLdb or pymysql.
If you don't need to share the data between users - then sqlite may be an option. Or may be not - depends on what do you want to store there, what for and what do you need to do with the data.
So, more questions than answers, probably it was more suitable for a comment. At least, think about what I've said.
Also see:
https://stackoverflow.com/questions/1009438/which-database-should-i-use-for-my-desktop-application
Python Desktop Application Database
Python Framework for Desktop Database Application
Hope that helps.
If your application is a stand-alone system such that each user maintains their own private database then you have no alternative to install MySQL on each system that is running the application. You cannot bundle MySQL into your application such that it does not require a separate installation.
There is an embedded version of MySQL that you can build into your application (thanks, Carsten, in the comments, for pointing this out). More information is here: http://mysql-python.blogspot.com/. It may take some effort to get this working (on Windows you apparently need to build it from source code) and will take some more work to get it packaged up when you generate your executable, but this might be a MySQL solution for you.
I've just finished updating a web application using SQLite which had begun reporting Database is locked errors as the usage scaled up. By rewriting the database code with care I was able to produce a system that can handle moderate to heavy usage (in the context of a 15 person company) reliably still using SQLite -- you have to be careful to keep your connections around for the minimum time necessary and always call .close() on them. If your application is really single-user you should have no problem supporting it using SQLite -- and that's doubly true if it's single-threaded.
Can I somehow work with remote databases (if they can do it) with the Django ORM?
It is understood that the sitting has spelled out the local database. And periodically to make connection to various external databases and perform any sort of commands such as load dump.
If you can connect to the database remotely, then you can simply specify its host/port in settings.py exactly as you would a local one.