insert to replica set, and catach errors

handle_update_failover.py

#!/usr/bin/env python
"""
Updates documents in a safe manner and catches expected errors.
"""

import pymongo
import time


# Previous code; left here for reference.
# for i in range(0,500):
#     for retry in range (3):
#         try:
#             things.update_one({'_id':i}, {'$inc':{'votes':1}})
#             print "Updated Document: " + str(i)
#             time.sleep(.1)
#             break
#         except pymongo.errors.AutoReconnect as e:
#             print "Exception ",type(e), e
#             print "Retrying.."
#             time.sleep(5)


def main():
    client = pymongo.MongoClient(host=["mongodb://localhost:27017",
                                       "mongodb://localhost:27018",
                                       "mongodb://localhost:27019"],
                                 replicaSet="m101")

    db = client.m101
    things = db.things

    for i in xrange(500):
        time.sleep(.1)  # Don't want this to go too fast.
        for retry in xrange(3):
            try:  # to read the doc up to 3 times.
                votes = things.find_one({'_id': i})["votes"] + 1
                break
            except pymongo.errors.AutoReconnect as e:  # failover!
                print ("Exception reading doc with _id = {_id}. " +
                       "{te}: {e}").format(_id=i, te=type(e), e=e)
                print "Retrying..."
                time.sleep(5)
        else: 
            print "Unable to read from the database. Aborting."
            exit()
        for retry in xrange(3):
            try:  # to read the doc up to 3 times.
                things.update_one({'_id': i}, {'$set': {'votes': votes}})
                print "Updated Document with _id = {_id}".format(_id=i)
                break
            except pymongo.errors.AutoReconnect as e:  # failover!
                print ("Exception writing doc with _id = {_id}. " +
                       "{te}: {e}").format(_id=i, te=type(e), e=e)
                print "Retrying..."
                time.sleep(5)
        else:  # If no break, we failed to write the document. Abort.
            print ("We have failed to increment the 'votes' field for " +
                   "the document with _id = {_id} to {votes}. Exiting."
                  ).format(_id=i, votes=votes)
            exit()


if __name__ == '__main__':
    main()

insert_robustly.py

import pymongo
import sys
import time

c = pymongo.MongoClient(host=["mongodb://localhost:27017",
                              "mongodb://localhost:27018",
                              "mongodb://localhost:27019"],
                        replicaSet="m101")

db = c.m101

things = db.things
things.delete_many({})   # remove all the docs in the collection


for i in range(0,500):
    for retry in range (3): # try 3 times, it is more robust but not gurantee
        try:
            things.insert_one({'_id':i})
            print "Inserted Document: " + str(i)
            time.sleep(.1)
            break
        except pymongo.errors.AutoReconnect as e:
            print "Exception ",type(e), e
            print "Retrying.."
            time.sleep(5)
        except pymongo.errors.DuplicateKeyError as e:
            print "duplicate..but it worked"
            break

                


    

insert_to_replica_set.py

import pymongo
import sys
import time

c = pymongo.MongoClient(host=["mongodb://localhost:27017",
                              "mongodb://localhost:27018",
                              "mongodb://localhost:27019"],
                        replicaSet="m101")

db = c.m101

things = db.things
things.delete_many({})   # remove all the docs in the collection


for i in range(0,500):
    try:
        things.insert_one({'_id':i})
        print "Inserted Document: " + str(i)
        time.sleep(.1)
    except Exception as e:
        print "Exception ",type(e), e


                


    

re-election.js

rs.stepDown() // re election new primary,

read robustly.py

import pymongo
import sys
import time

c = pymongo.MongoClient(host=["mongodb://localhost:27017",
                              "mongodb://localhost:27018",
                              "mongodb://localhost:27019"],
                        replicaSet="m101")

db = c.m101

things = db.things
things.delete_many({})   # remove all the docs in the collection


for i in range(0,500):
    for retry in range (3):
        try:
            things.insert_one({'_id':i})
            print "Inserted Document: " + str(i)
            time.sleep(.1)
            break
        except pymongo.errors.AutoReconnect as e:
            print "Exception ",type(e), e
            print "Retrying.."
            time.sleep(5)
        except pymongo.errors.DuplicateKeyError as e:
            print "duplicate..but it worked"
            break

                


    

read_from_secondary_example.py

import pymongo
import time

read_pref = pymongo.read_preferences.ReadPreference.SECONDARY

c = pymongo.MongoClient(host=["mongodb://localhost:27017",
                              "mongodb://localhost:27018",
                              "mongodb://localhost:27019"],
                              read_preference=read_pref)

db = c.m101
things = db.things

for i in range(1000):
    doc = things.find_one({'_id':i})
    print "Found doc ", doc
    time.sleep(.1)