Yeah it is working fine what I did was
step1. Unlinked existing symlink
Step2. Create new symlink
Step3. Managed permissions and shell context of files
Therefore no
reload or restart is needed.
But I have doubt up to how many mod_wsgi daemons we can efficiently without
any disturbance and up to what extent we can trust this deployment process
using mod_wsgi in daemon mode for production environment.
Thankyou,
RajKumar
On Thursday 25 July 2024 at 13:04:18 UTC+5:30 RajKumar Ambadipelli wrote:
> Sorry that uoadmin is actually admin.
>
> Ok I will try this one.
>
> Thankyou,
> RajKumar
>
> On Thursday 25 July 2024 at 12:59:13 UTC+5:30 Graham Dumpleton wrote:
>
>> You have two different directories which may complicate it a little, but
>> what you can do is have something like:
>>
>> Listen 9002 <VirtualHost *:9002>
>> ServerName test.myapp.com
>> ErrorLog /var/log/webservice_error.log
>> WSGIPassAuthorization On
>> WSGIDaemonProcess Tes9002
>> python-path=/home/uoadmin/releases/test/students:/home/admin/releases/test/shared
>>
>> display-name=%{GROUP}
>> WSGIProcessGroup Tes9002 WSGIApplicationGroup %{GLOBAL}
>> WSGIScriptAlias / /home/admin/releases/test/students/conf/wsgi.py
>> <Directory /home/admin/releases/test/students/conf>
>> <Files wsgi.py> Require all granted </Files>
>> </Directory>
>> </VirtualHost>
>>
>> <VirtualHost *:9002>
>> ServerName dev.myapp.com
>> ErrorLog /var/log/webservice_error.log
>> WSGIPassAuthorization On
>> WSGIDaemonProcess Dev9002
>> python-path=/home/uoadmin/releases/dev/students:/home/admin/releases/dev/shared
>>
>> display-name=%{GROUP}
>> WSGIProcessGroup Dev9002 WSGIApplicationGroup %{GLOBAL}
>> WSGIScriptAlias / /home/admin/releases/dev/students/conf/wsgi.py
>> <Directory /home/admin/releases/dev/students/conf>
>> <Files wsgi.py> Require all granted </Files>
>> </Directory>
>> </VirtualHost>
>>
>> In this case /home/admin/releases/dev would actually be a symlink to the
>> versioned directory.
>>
>> Not sure why have separate uoadmin directory, but also have
>> /home/uoadmin/releases/dev as symlink to the versioned directory.
>>
>> To change what is used, remove/recreate symlinks so point to the
>> directory for the new version.
>>
>> That the wsgi.py has changed should trigger a process restart if auto
>> reloading is on (default).
>>
>> Alternatively could disable auto reloading and manually send SIGUSR1 to
>> process to trigger a graceful reload after changing the symlink.
>>
>> That all said, I can't remember if you might have to configure Apache to
>> tell it to allow following symlinks (Options FollowSymLinks). If it were
>> static file handling would definitely be needed, but can't remember if
>> would be required in this case where is WSGI application handling things.
>>
>> Graham
>>
>> On 25 Jul 2024, at 5:21 PM, RajKumar Ambadipelli <[email protected]>
>> wrote:
>>
>> Ok, If I have only two virtualhosts all the time and I am going to change
>> only python-path will that work with the direct signal using SIGUSR1.
>>
>> If the above is possible then I think I have some kind of solution.
>>
>> Thankyou,
>> RajKumar
>>
>> On Thursday 25 July 2024 at 12:35:09 UTC+5:30 Graham Dumpleton wrote:
>>
>>> Are you always using the same two virtual host server names and just
>>> updating the version number in the paths?
>>>
>>> On 25 Jul 2024, at 4:21 PM, RajKumar Ambadipelli <[email protected]>
>>> wrote:
>>>
>>> Yes I am adding new virtual hosts when ever I want to release a new
>>> version of that services lets say initially my virtualhost config will be
>>> like
>>>
>>> #Students Webservice Config
>>> Listen 9002 <VirtualHost *:9002>
>>> ServerName test.myapp.com
>>> ErrorLog /var/log/webservice_error.log
>>> WSGIPassAuthorization On
>>> WSGIDaemonProcess Tes9002 python-path=/home/uoadmin/releases/1.0.0
>>> /students:/home/admin/releases/1.0.0/shared display-name=%{GROUP}
>>> WSGIProcessGroup Tes9002 WSGIApplicationGroup %{GLOBAL}
>>> WSGIScriptAlias / /home/admin/releases/1.0.0/students/conf/wsgi.py
>>> <Directory /home/admin/releases/1.0.0/students/conf>
>>> <Files wsgi.py> Require all granted </Files>
>>> </Directory>
>>> </VirtualHost>
>>>
>>> When i want to go for new releases the down part is appended to above
>>> part
>>>
>>> <VirtualHost *:9002>
>>> ServerName dev.myapp.com
>>> ErrorLog /var/log/webservice_error.log
>>> WSGIPassAuthorization On
>>> WSGIDaemonProcess Dev9002 python- path=/home/uoadmin/releases/1.1.0
>>> /students:/home/admin/releases/1.1.0/shared display-name=%{GROUP}
>>> WSGIProcessGroup Dev9002 WSGIApplicationGroup %{GLOBAL}
>>> WSGIScriptAlias / /home/admin/releases/1.1.0/students/conf/wsgi.py
>>> <Directory /home/admin/releases/1.1.0/students/conf>
>>> <Files wsgi.py> Require all granted </Files>
>>> </Directory>
>>> </VirtualHost>
>>>
>>>
>>> Now I am going to have two virtualhosts with two daemons 1st is already
>>> recognized by apache server where as second one is not yet recognized by
>>> apache server
>>>
>>> Thankyou,
>>> RajKumar
>>>
>>> On Thursday 25 July 2024 at 11:40:31 UTC+5:30 Graham Dumpleton wrote:
>>>
>>>> What is the reason for doing the graceful restart? Is it because you
>>>> are adding/removing virtual hosts, or making some other Apache config
>>>> change.
>>>>
>>>> You do not need to do a complete Apache restart if just want to force a
>>>> daemon process to restart, you can instead send the processes a signal
>>>> directly. From memory it is SIGUSR1 that triggers a graceful restart of
>>>> processes, but you will need to confirm that.
>>>>
>>>> On 25 Jul 2024, at 3:28 PM, RajKumar Ambadipelli <[email protected]>
>>>> wrote:
>>>>
>>>> When i have 260 microservices those all are light weight applications
>>>> using same python interpreter and with django rest api framework, and
>>>> currently each application hosted on apache server usign mod_wsgi daemon
>>>> mode and my main problem is while making changes to one of application
>>>> virtualhost other ongoing daemons are distured as i need to reload or
>>>> restart.
>>>> All those 260 services very light weight each listen to http request on
>>>> unique ports.
>>>>
>>>> ThankYou
>>>> RajKumar
>>>>
>>>> On Tuesday 23 July 2024 at 16:37:42 UTC+5:30 Graham Dumpleton wrote:
>>>>
>>>>> One can optimise embedded mode for better performance, but I would put
>>>>> a big caveat on that and say is only probably a good idea to tackle if
>>>>> you
>>>>> have the one web service.
>>>>>
>>>>> Running 260 micro services in one Apache httpd instance with mod_wsgi
>>>>> sounds rather scary either way.
>>>>>
>>>>> If you use mod_wsgi daemon mode where each micro service is in its own
>>>>> daemon process group (with a single process and small number of threads),
>>>>> then you might get away with it if these aren't high volume sites. That
>>>>> said, it is still a lot of managed daemon mode processes and not sure how
>>>>> well Apache will handle that, especially on restarts.
>>>>>
>>>>> Running them all in embedded mode would be a bad idea if each needs a
>>>>> separate Python interpreter context because the Apache worker process
>>>>> would
>>>>> be huge in size. If Apache httpd was configured for prefork MPM it would
>>>>> be
>>>>> even worse because you would have a potentially large number of worker
>>>>> processes since all are single thread. You also run a big risk with micro
>>>>> services interfering with each other in strange ways if running in
>>>>> different sub interpreter contexts of the one process due to how Python
>>>>> imports C extensions, and process wide environment variables work.
>>>>> Various
>>>>> third party Python packages with C extensions will not even work in
>>>>> Python
>>>>> sub interpreters (eg., anything related to numpy).
>>>>>
>>>>> You definitely want event or worker MPM, but even then, for 260 micro
>>>>> services, if they need separate Python interpreter context I can't really
>>>>> recommend it still because of size concerns for processes and potential
>>>>> cross sub interpreter interference.
>>>>>
>>>>> So the question is whether when you said 260 micro services you really
>>>>> mean independent web applications, or whether you just mean you have 260
>>>>> different unique HTTP handlers as part of the one application, and thus
>>>>> in
>>>>> the same Python interpreter context.
>>>>>
>>>>> When people talk about such large number of micro services, usually
>>>>> you would not be aiming to host them in a single Apache instance but
>>>>> would
>>>>> instead be looking at running something which can handle things at scale
>>>>> like Kubernetes and creating separate deployments for them in that,
>>>>> relying
>>>>> on the ingress routing Kubernetes provides to get traffic to the
>>>>> appropriate micro service.
>>>>>
>>>>> Graham
>>>>>
>>>>> On 23 Jul 2024, at 7:13 PM, RajKumar Ambadipelli <[email protected]>
>>>>> wrote:
>>>>>
>>>>> mod_wsgi in embeded mode allows graceful restart,
>>>>> What are the potential issues that I will face if I use mod_wsgi in
>>>>> embedded mode instead of daemon mode,
>>>>> I have to host around 260 python micro services.
>>>>>
>>>>> I have saw your blog on 'why are you using mod_wsgi in embedded mode?'
>>>>> But, I unable to understand it very well in that you mentioned if we
>>>>> configure mpm settings correctly then mod_wsgi in embedded mode is better
>>>>> than daemon mode but not mentioned any configurations.
>>>>>
>>>>> Thanking you,
>>>>> RajKumar
>>>>>
>>>>> On Tuesday 23 July 2024 at 13:04:50 UTC+5:30 Graham Dumpleton wrote:
>>>>>
>>>>>> On 23 Jul 2024, at 4:09 PM, RajKumar Ambadipelli <[email protected]>
>>>>>> wrote:
>>>>>>
>>>>>> I am using Apache Server with mod_wsgi for hosting my python django
>>>>>> applications. Versions: Python 3.9.18 Server version: Apache/2.4.57
>>>>>> mod-wsgi==4.7.1
>>>>>>
>>>>>> One of my application virtual host configuration with two different
>>>>>> versions:
>>>>>>
>>>>>> ...
>>>>>>
>>>>>> So, When the source code is modified I can referesh the wsgi daemon
>>>>>> using touch /home/uoadmin/releases/1.1.0/students/conf/wsgi.py touch
>>>>>> /home/uoadmin/releases/1.0.0/students/conf/wsgi.py But when I added new
>>>>>> virtualhost to the above configuration file or else when I modify above
>>>>>> file the apache server unable to recognize modifications made the
>>>>>> existing
>>>>>> virtualhost or newly added virtualhost until doing apachectl graceful
>>>>>> (or)
>>>>>> apachectl restart (or) systemctl reload httpd but all the commands above
>>>>>> killing the ongoing requests forcefully directly terminating them.
>>>>>>
>>>>>> How to handle above situation.
>>>>>>
>>>>>> I want to know how will apache server recognize modifications to
>>>>>> virtualhost or newly added virtual host without reloading or restarting.
>>>>>>
>>>>>> It can't, Apache httpd requires you to perform a restart (reload) in
>>>>>> order to read changes to the Apache configuration files. That is how it
>>>>>> works.
>>>>>>
>>>>>> If above is not possible then is there anyway for restarting or
>>>>>> reloading apache server gracefully that is without terminating or
>>>>>> killing
>>>>>> other ongoing requests or daemons while using apache server + mod_wsgi
>>>>>> for
>>>>>> serving python with django?
>>>>>>
>>>>>> Unfortunately not. The way Apache httpd manages the mod_wsgi daemon
>>>>>> processes it will force a restart of those as well and even though
>>>>>> Apache
>>>>>> has a concept of graceful restart for it's own worker child processes,
>>>>>> it
>>>>>> doesn't extend that to managed process like the mod_wsgi daemon process
>>>>>> and
>>>>>> always restarts them immediately even when it is a graceful restart.
>>>>>> There
>>>>>> is nothing that can be done about this.
>>>>>>
>>>>>> The only way you could handle it if you need to be able to freely
>>>>>> restart the main Apache server and have it not affect your Python web
>>>>>> applications, is to run the Python web applications in distinct
>>>>>> secondary
>>>>>> web server processes and use the main Apache server to only proxy
>>>>>> requests
>>>>>> through to the secondary web servers.
>>>>>>
>>>>>> For the second web servers you could use mod_wsgi-express to make
>>>>>> things easier, but you could also just not use mod_wsgi for the
>>>>>> secondary
>>>>>> web servers and use gunicorn or some other standalone Python
>>>>>> WSGI/asyncio
>>>>>> web server.
>>>>>>
>>>>>> Graham
>>>>>>
>>>>>>
>>>>>>
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