Python script to start mondod

[Yaroslav Kyrpych]

Hello!

I am writing script to start mondod instance from Python. I want to use subprocess.call from Python library. But I am not entirely clear what needs to be passed as arguments. I realize that there should be port specified. Anything else, like path? Any example would be extremely helpful.

Thank you,

Yaroslav

[Asya Kamsky]

Do you mean something like this: http://stackoverflow.com/questions/15368156/how-to-start-mongodb-daemon-in-python ?

Asya

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[Bernie Hackett]

Feel free to steal ideas from here:

https://github.com/mongodb/mongo-python-driver/blob/master/test/high_availability/ha_tools.py

[Yaroslav Kyrpych]

Thank you! That's much more than I needed. At this point I am not trying to have HA. If I were to simplify your code, does the following make sense:

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

import os
import random
import shutil
import signal
import socket
import subprocess
import sys
import time


from stat import S_IRUSR


import pymongo
import pymongo.errors
from pymongo.read_preferences import ReadPreference

home = os.environ.get('HOME')
default_dbpath = os.path.join(home, 'data', 'pymongo_high_availability')
dbpath = os.environ.get('DBPATH', default_dbpath)
default_logpath = os.path.join(home, 'log', 'pymongo_high_availability')
logpath = os.environ.get('LOGPATH', default_logpath)
hostname = os.environ.get('HOSTNAME', socket.gethostname())
port = int(os.environ.get('DBPORT', 27017))
mongod = os.environ.get('MONGOD', 'mongod')
mongos = os.environ.get('MONGOS', 'mongos')

try:
    from subprocess import DEVNULL  # Python 3.
except ImportError:

    DEVNULL = open(os.devnull, 'wb')

def wait_for(proc, port_num):
    trys = 0

    while proc.poll() is None and trys < 160:
        trys += 1

        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            try:
                s.connect((hostname, port_num))
                return True

            except (IOError, socket.error):
                time.sleep(0.25)
        finally:
            s.close()

def start_subprocess(cmd):
    """Run cmd (a list of strings) and return a Popen instance."""

    return subprocess.Popen(cmd, stdout=DEVNULL, stderr=DEVNULL)
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Do I need to use any other functions? I am confused about cmd, I could not find good explanation online of what goes there.


Thank you a lot for helping!


Yaroslav

[Yaroslav Kyrpych]

I found the following that I am trying to re-use:

http://stackoverflow.com/questions/17031268/how-to-best-way-to-wait-for-mongod-instance-to-start-before-proceeding

However, I am confused about arguments used in call. 

[Yaroslav Kyrpych]

I am getting error message - no module pymongo.errors and from pymongo.read_preferences import ReadPreference.

On Sat, Feb 22, 2014 at 8:46 PM, Bernie Hackett <ber...@mongodb.com> wrote:

[Stephen Steneker]

On Monday, 24 February 2014 10:34:40 UTC+11, Yaroslav Kyrpych wrote:

I am getting error message - no module pymongo.errors and from pymongo.read_preferences import ReadPreference.

Hi Yaroslav,

What version of PyMongo are you using? I believe pymongo.read_preferences was added in 2.3, but pymongo.errors has been around for much longer.

The current production version of PyMongo is 2.6.3, so you may need to update.

Regards,

Stephen

[Yaroslav Kyrpych]

I am using 2.4.6 on Win 64. So, it should be there.

--

[Yaroslav Kyrpych]

Another question I have - What do I pass as proc in wait_for function? Also port_num is not defined anywhere, do I pass 27017?

[Yaroslav Kyrpych]

There variable port that has 27017, is it just typo when later there is reference to port_num?

[Yaroslav Kyrpych]

One more question - Is this sufficient for cmd?

cmd=[mongod,'--dbpath','C:\mongodb\bin','--port',str(27017)]?

[Asya Kamsky]

It would be sufficient, but I find it very unusual that your data
files are in c:\mongodb\bin - are you sure that's what you intended?
Port 27017 is the default so you shouldn't need to specify it
explicitly.

Asya


On Sun, Feb 23, 2014 at 4:20 PM, Yaroslav Kyrpych

[Yaroslav Kyrpych]

Sorry, I was tired and not thinking straight. The data is in the following folder: C:\RCI\data. Thanks for pointing out mistake!

I am still wondering why I am having issues with pymongo.errors and pymongo.read_preferences. Any ideas/suggestions?

[A. Jesse Jiryu Davis]

Could you please open the Python interpreter? Just type "Python" at the command prompt. Do:

>>> import pymongo

>>> print pymongo.version

>>> import pymongo.errors
>>> pymongo.read_preferences

Let us know what the output is. Thanks.

[Yaroslav Kyrpych]

Typing "Python" gives error: NameError: name "Python" is not defined

print pymongo.version - wrong syntax, in python print has (), if I try it, getting AttributeError.

import pymongo.errors - ImportError: no module

pymongo.read_preferences - AttributeError, no attribute read_preferences.

[Yaroslav Kyrpych]

I am going to re-install mongodb - hope this helps.

[Jorge Puente Sarrín]

Hi Yaroslav,

In order to verify whatever MongoDB is successfully installed in your localhost, just run the mongo shell.

I don't understand why you have problems importing pymongo module. If your goal is run a MongoDB instance using Python's subprocess module, you don't need to use nor to install pymongo. Maybe... do you want to try connect to MongoDB after call to subprocess using the PyMongo driver?

Best regards.

Jorge Puente Sarrín.

[Yaroslav Kyrpych]

Hi Jorge,

Mongo shell works find - I created manually database and inserted data there, and then used find() to display it. 

Yes, I would like to connect to MongoDB using PyMongo driver once the instance is up and running.

Thank you,

Yaroslav

[Jorge Puente Sarrín]

Could you provide a snippet of your script?

I think you just need create an instance of MongoClient class.

[Yaroslav Kyrpych]

Please see below straw-man (there are things that are wrong there) that I have at this time:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

import os

import random

import shutil

import signal

import socket

import subprocess

import sys

import time

from stat import S_IRUSR

import pymongo

#import pymongo.errors

#from pymongo.read_preferences import ReadPreference

dbpath="C:\mongodb\bin"

default_logpath="C:\RCI\log"

hostname=os.environ.get('HOSTNAME',socket.gethostname())

port=int(os.environ.get('DBPORT',27017))

mongod=os.environ.get('MONGOD','mongod')

try:

from subprocess import DEVNULL

except ImportError:

DEVNULL=open(os.devnull,'wb')

def wait_for(proc,port_num):

trys=0

while proc.poll() is None and trys<160:

trys=+1

s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:

try:

s.connect((hostname,port_num))

return True

except (IOError,socket.error):

time.sleep(0.25)

finally:

s.close()

def start_subprocess(cmd):

return subprocess.Popen(cmd,stdout=DEVNULL,stderr=DEVNULL)

cmd=[mongod,'--dbpath','C:\mongodb\bin','--port',str(27017)]

proc=subprocess.Popen(cmd,stdout=DEVNULL,stderr=DEVNULL)

port_num="27017"

wait_for(proc,port_num)

[Yaroslav Kyrpych]

I tried to run the code after cleaning it a bit. However, got error from Python:

File "C:\Python33\lib\subprocess.py", line 1112, in _execute_child

    startupinfo)

FileNotFoundError: [WinError 2] The system cannot find the file specified

Any ideas/suggestions are much appreciated. It looks like I don't have subprocess module?

[Yaroslav Kyrpych]

I just checked Python installation - I do have subprocess.py at the specified path.