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(Selenium) Running many firefox browser with less performance [duplicate]

I am using selenium with Firefox to automate some tasks on Instagram. It basically goes back and forth between user profiles and notifications page and does tasks based on what it finds.
It has one infinite loop that makes sure that the task keeps on going. I have sleep() function every few steps but the memory usage keeps increasing. I have something like this in Python:
while(True):
expected_conditions()
...doTask()
driver.back()
expected_conditions()
...doAnotherTask()
driver.forward()
expected_conditions()
I never close the driver because that will slow down the program by a lot as it has a lot of queries to process. Is there any way to keep the memory usage from increasing overtime without closing or quitting the driver?
EDIT: Added explicit conditions but that did not help either. I am using headless mode of Firefox.

Well, This the serious problem I've been going through for some days. But I have found the solution. You can add some flags to optimize your memory usage.
options = Options()
options.add_argument("start-maximized")
options.add_argument("disable-infobars")
options.add_argument("--disable-extensions")
options.add_argument('--no-sandbox')
options.add_argument('--disable-application-cache')
options.add_argument('--disable-gpu')
options.add_argument("--disable-dev-shm-usage")
These are the flags I added. Before I added the flags RAM usage kept increasing after it crosses 4GB (8GB my machine) my machine stuck. after I added these flags memory usage didn't cross 500MB. And as DebanjanB answers, if you running for loop or while loop tries to put some seconds sleep after each execution it will give some time to kill the unused thread.

To start with Selenium have very little control over the amount of RAM used by Firefox. As you mentioned the Browser Client i.e. Mozilla goes back and forth between user profiles and notifications page on Instagram and does tasks based on what it finds is too broad as a single usecase. So, the first and foremost task would be to break up the infinite loop pertaining to your usecase into smaller Tests.
time.sleep()
Inducing time.sleep() virtually puts a blanket over the underlying issue. However while using Selenium and WebDriver to execute tests through your Automation Framework, using time.sleep() without any specific condition defeats the purpose of automation and should be avoided at any cost. As per the documentation:
time.sleep(secs) suspends the execution of the current thread for the given number of seconds. The argument may be a floating point number to indicate a more precise sleep time. The actual suspension time may be less than that requested because any caught signal will terminate the sleep() following execution of that signal’s catching routine. Also, the suspension time may be longer than requested by an arbitrary amount because of the scheduling of other activity in the system.
You can find a detailed discussion in How to sleep webdriver in python for milliseconds
Analysis
There were previous instances when Firefox consumed about 80% of the RAM.
However as per this discussion some of the users feels that the more memory is used the better because it means you don't have RAM wasted. Firefox uses RAM to make its processes faster since application data is transferred much faster in RAM.
Solution
You can implement either/all of the generic/specific steps as follows:
Upgrade Selenium to current levels Version 3.141.59.
Upgrade GeckoDriver to GeckoDriver v0.24.0 level.
Upgrade Firefox version to Firefox v65.0.2 levels.
Clean your Project Workspace through your IDE and Rebuild your project with required dependencies only.
If your base Web Client version is too old, then uninstall it and install a recent GA and released version of Web Client.
Some extensions allow you to block such unnecessary content, as an example:
uBlock Origin allows you to hide ads on websites.
NoScript allows you to selectively enable and disable all scripts running on websites.
To open the Firefox client with an extension you can download the extension i.e. the XPI file from https://addons.mozilla.org and use the add_extension(extension='webdriver.xpi') method to add the extension in a FirefoxProfile as follows:
from selenium import webdriver
profile = webdriver.FirefoxProfile()
profile.add_extension(extension='extension_name.xpi')
driver = webdriver.Firefox(firefox_profile=profile, executable_path=r'C:\path\to\geckodriver.exe')
If your Tests doesn't requires the CSS you can disable the CSS following the this discussion.

Use Explicit Waits or Implicit Waits.
Use driver.quit() to close all
the browser windows and terminate the WebDriver session because if
you do not use quit() at the end of the program, the WebDriver
session will not be closed properly and the files will not be cleared
off memory. And this may result in memory leak errors.

Creating new firefox profile and use it every time while running test cases in Firefox shall eventually increase the performance of execution as without doing so always new profile would be created and caching information would be done there and if driver.quit does not get called somehow before failure then in this case, every time we end up having new profiles created with some cached information which would be consuming memory.
// ------------ Creating a new firefox profile -------------------
1. If Firefox is open, close Firefox.
2. Press Windows +R on the keyboard. A Run dialog will open.
3. In the Run dialog box, type in firefox.exe -P
Note: You can use -P or -ProfileManager(either one should work).
4. Click OK.
5. Create a new profile and sets its location to the RAM Drive.
// ----------- Associating Firefox profile -------------------
ProfilesIni profile = new ProfilesIni();
FirefoxProfile myprofile = profile.getProfile("automation_profile");
WebDriver driver = new FirefoxDriver(myprofile);
Please share execution performance with community if you plan to implement this way.

There is no fix for that as of now.
I suggest you use driver.close() approach.
I was also struggling with the RAM issue and what i did was i counted the number of loops and when the loop count reached to a certain number( for me it was 200) i called driver.close() and then start the driver back again and also reset the count.
This way i did not need to close the driver every time the loop is executed and has less effect on the performance too.
Try this. Maybe it will help in your case too.

At which point should I place delete_all_cookies

I need to use delete_all_cookies in my code. I have some concerns:
Do I need to place before opening the url
or before quit
Can anyone clarify the same? A lot of cache has been created during my test runs. My main objective is to clear cache in test server machine.

This depends to some degree on the browser you're using. If you are using a current version of Chrome or Firefox, deleting all cookies before starting testing won't make sense, as every driver instance will start with a separate, temporary profile without any cookies anyway.
Deleting all cookies after running the tests is equally unnecessary in those browsers, as the next test will start up with a clean profile again anyway. There only real scenario where deleting cookies makes sense is if you do multiple things in the same test (i.e., with the same driver instance) where you know that at some point the app sets a cookie that you don't want to be there at a later stage in the test. That's more of an edge case, though.

Multi-threading in selenium python

I am working on a project which needs bit automation and web-scraping for which I am using Selenium and BeautifulSoup (python2.7).
I want to open only one instance of a web browser and login to a website, keeping that session, I am trying to open new tabs which will be independently controlled by threads, each thread controlling a tab and performing their own task. How should I do it? An example code would be nice. Well here's my code:
def threadFunc(driver, tabId):
if tabId == 1:
#open a new tab and do something in it
elif tabId == 2:
#open another new tab with some different link and perform some task
.... #other cases
class tabThreads(threading.Thread):
def __init__(self, driver, tabId):
threading.Thread.__init__(self)
self.tabID = tabId
self.driver = driver
def run(self):
print "Executing tab ", self.tabID
threadFunc(self.driver, self.tabID)
def func():
# Created a main window
driver = webdriver.Firefox()
driver.get("...someLink...")
# This is the part where i am stuck, whether to create threads and send
# them the same web-driver to stick with the current session by using the
# javascript call "window.open('')" or use a separate for each tab to
# operate on individual pages, but that will open a new browser instance
# everytime a driver is created
thread1 = tabThreads(driver, 1)
thread2 = tabThreads(driver, 2)
...... #other threads
I am open to suggestions for using any other module, if needed

My understanding is that Selenium drivers are not thread-safe. In the WebDriver spec, the Thread Safety section is empty...which I take to mean they have not addressed the topic at all. https://www.w3.org/TR/2012/WD-webdriver-20120710/#thread-safety
So while you could share the driver reference with multiple threads and make calls to the driver from multiple threads, there is no guarantee that the driver will be able to handle multiple asynchronous calls correctly.
Instead, you must either synchronize calls from multiple threads to ensure one is completed before the next starts, or you should have just one thread making Selenium API calls...potentially handling commands from a queue that is filled by multiple other threads.
Also, see Can Selenium use multi threading in one browser?

I you are using the script to automatically submit forms (simply said doing GET and POST requests), I would recommend you to look at requests. You can easily capture Post requests from your Browser (Network tab in Developer Pane on both Firefox and Chrome), and submit them. Something like:
session = requests.session()
response = session.get('https://stackoverflow.com/')
soup = BeautifulSoup(response.text)
and even POST data like:
postdata = {'username':'John','password':password}
response=session.post('example.com',data=postdata,allow_redirects=True)
It can be easily threaded, Multiple times faster than using selenium, the only problem is there is no JavaScript or Form support, so you need to do it the old fashioned way.
EDIT:
Also take a look at ThreadPoolExecutor

How to Speed up Test Execution Using Selenium Grid on single machine

I am selenium python and I would like to speed up my tests. let's say 5 tests simultaneously. How can I achieve that on the single machine with the help of selenium grid

You won't need a Selenium Grid for this. The Grid is used to distribute the test execution across multiple machines. Since you're only using one machine you don't need to use it.
You are running tests so I'm assuming you are using a test framework. You should do some research on how you can run tests in parallel using this framework.
There will probably also be a way to execute a function before test execution. In this function you can start the driver.
I'd be happy to give you a more detailed answer but your question is lacking the framework you are using to run the tests.

This is my base class:
class BaseTestCase(object):
_multiprocess_can_split_ = True
def setUp(self):
self.driver = webdriver.Firefox()
self.driver.get("https://login.com")
self.assertEqual("Authorization required", self.driver.title)
def tearDown(self):
if sys.exc_info()[0]:
test_method_name = self._testMethodName
self.driver.save_screenshot("users/desktop/ErrorScreenshots/" + test_method_name + ".png")
self.driver.quit()
When I try to achieve this with nose by typing nosetests --processes=2 in terminal. it opens all 30 browsers at the same time and all test fails

Changing execution speed of tests?

Updating with more context: Selenium 1 had a command called "setSpeed." This allowed the execution of each command to be slowed down by X milliseconds. The team behind Selenium 2 (Webdriver) decided to deprecate this command and now there is no way to slow down the tests to run at speeds where it's easy to visually monitor the App during execution. I've read the developers' explanation as to why they deprecated it, as well as the suggested workarounds like using implicit_waits, but that doesn't solve the issue for me (or the other people complaining about the deprecation). That said, I was hoping to work around this by setting a global execution speed that would be applicable to either each method in unittest, or the entire suite of tests.
Original Question: I have different unit tests that I'd like to execute using different delays between commands. I know that I can keep copying and pasting time.sleep between the commands, but surely there is a way to just set a universal sleep that will be run before each command in the specified method?
def test_x_test(self):
driver = self.driver
time.sleep(2)
print("running the First selenium command such as click button")
time.sleep(2)
print("running another Selenium command such as click link ")
time.sleep(2)
self.driver.quit()
if __name__ == '__main__':
unittest.main()

Ahh now the answer is so obvious.
Create a helper method that controls webdriver actions and before it executes the action put in a pause:
The below is going to be pseudocode-ish as I no longer have access to a Python IDE at work
#passing in Webdriver instance and the command we want to execute into our helper method
webdriverHelper(driver, command):
#this 2 second sleep will get run each time
time.sleep(2)
if command == "click":
driver.getElement.click()
elif command== "getText":
driver.getElement.getText()
etc...............