How to configure Py4web for multi user applications

[raghavender goud]

Hi,

I'm a newbie to web application development, trying to build an app which will be used by multiple users concurrently. Right now I could see that Py4web processes the request in sequence. If there is an long running task other request are in queue and processed only after previous task completes.

One option i have is to create threads for long running tasks. I'm curious to know if py4web can be configured to process the request asynchronously? 

[Massimo DiPierro]

py4web handles requests concurrently. Problem is that you may be using SQLite which is single threads and blocks the database on writing. So db access may make your request serial. You should use postgresql. Also you many to execute any long term running task in a background process. Maybe use celery.

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[raghavender goud]

Hi Massimo,

We are using MySQL as the database, will Py4web process the requests concurrently with this database?

[Massimo DiPierro]

It should. It uses the tornado web server by default. If your requests block for some reason you may have to use a multi threaded web server like rocket or cherrypy or waitress. You can select them with command line options, if installed. You can also take advantage of multiple CPUs with gunicorn. Let me know and can send more details istructions.

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[raghavender goud]

Hi Massimo,

I do not use multiple workers option, start my application using the command "py4web run apps", let me know if using "-w" switch helps resolve my issue. 

Yes, by default is starts using "tornado". Let me know which server works best for my requirement, rocket or cherrypy or waitress. Any instructions on installation or usage will definitely help.

py4web run -h command lists following list of server options. 

  -s, --server [default|wsgiref|tornado|gunicorn|gevent|waitress|geventWebSocketServer|wsgirefThreadingServer|rocketServer]

This is my Py4web version: py4web: 1.20210328.2

Thank you.

[Massimo DiPierro]

If concuccercy is more important than speed pip import rocket3 and use -w=rocketServer

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[raghavender goud]

Have tried using rocket server,  this is throwing up database exceptions. Where ever we try to update an integer value in database we observer this error. Though the value is not null we see this error. Same code works fine with default tornodo server. Any ideas why we are seeing these errors?

  File "/home/raghu/Documents/testRunner/testRunner/framework/apps/mate/controllers.py", line 89, in update_config_to_db

    db.current_executions.insert(

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/objects.py", line 890, in insert

    ret = self._db._adapter.insert(self, row.op_values())

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/adapters/base.py", line 539, in insert

    query = self._insert(table, fields)

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/adapters/base.py", line 534, in _insert

    ",".join(self.expand(v, f.type) for f, v in fields),

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/adapters/base.py", line 534, in <genexpr>

    ",".join(self.expand(v, f.type) for f, v in fields),

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/adapters/base.py", line 504, in _expand

    rv = self.represent(expression, field_type)

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/adapters/base.py", line 437, in represent

    return super(SQLAdapter, self).represent(obj, field_type)

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/adapters/base.py", line 391, in represent

    return self.representer.represent(obj, field_type)

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/representers/__init__.py", line 246, in represent

    rv = self.get_representer_for_type(field_type)(rv, field_type)

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/representers/__init__.py", line 138, in __call__

    return self.adapt(self.call(value, field_type))

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/representers/__init__.py", line 135, in _call

    return self.inner_call(value)

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/representers/__init__.py", line 123, in _inner_call

    return self.obj.f(self.representer, value, **kwargs)

  File "/home/raghu/mypyenv/lib/python3.8/site-packages/pydal/representers/base.py", line 29, in _integer

    return str(long(value))

TypeError: int() argument must be a string, a bytes-like object or a number, not 'IS_EMPTY_OR'

[Massimo]

as mentioned in other tests. The problem is somewhere else. Not sure why it manifest itself only with rocket3