How to add self-signed certificates to replica set nodes?

https://medium.com/@rossbulat/deploy-a-3-node-mongodb-3-6-replica-set-with-x-509-authentication-self-signed-certificates-d539fda94db4

#mongo #mongodb #ssl #self_signed #openssl

In order to see how much time your mongoDB slave is behind the primary node:

rs0:SECONDARY> db.printSlaveReplicationInfo()
 source: mongo.mongo.com:27017
     syncedTo: Mon Nov 12 2018 06:33:40 GMT+0000 (UTC)
     -4 secs (0 hrs) behind the primary

#mongodb #mongo #slave #printSlaveReplicationInfo #replica #replication

How to check MongoDB replication lag in Icinga2 and get notified when it is over 15 seconds?

We assume here that you have a replica set in place. First download the python script for our nagios plugin:

cd /usr/lib/nagios/plugins
 git clone git://github.com/mzupan/nagios-plugin-mongodb.git

Now the Icinga2 part. You first need to create a command for replication lag check:

cd /etc/icinga2/conf.d/commands

Create a new file replication_lag.conf:

object CheckCommand "check_replication_lag" {
     import "plugin-check-command"
     command = [ PluginDir + "/nagios-plugin-mongodb/check_mongodb.py", "-A", "replication_lag" ]
     arguments = {
         "-H" = "$mongo_host$"
         "-P" = "$mongo_port$"
     }
 }

Create a new file in services folder called replication_lag.conf:

apply Service for (display_name => config in host.vars.replication) {
     import "generic-service"
     check_command = "check_replication_lag"
     vars += config
     assign where host.vars.replication
 }

This service gets enabled where it finds replication in host config. Now in secondary mongoDB hosts configuration add the below part:

vars.replication["Secondary DB"] = {
     mongo_host = "slave.example.com"
     mongo_port = 27017
 }

#sysadmin #icinga2 #mongodb #replication #replication_lag #nagios_plugin

https://blog.shippable.com/why-we-moved-from-nosql-mongodb-to-postgressql

#mongoDB #posgreSQL

In MongoDB you can compare one field to another using $expr:

db.users.find({ $expr: { $eq: ["$created_at", "$updated_at"] } })

Here we get users that their updated_at field is equal to created_at field, here it means that user has not yet updated his profile.

#mongodb #mongo #expr #find

MongoDB server Load Average: 0.5 (It can reach 16)
Database Size: 100GB (It is compressed in MySQL it reaches 300 GB in size!)
Req/Sec: 500

Our server seems hungry for more requests and more data.

#mongodb #mongo #awesomeness

In MongoDB you can use $regex in order to find something based on a regex pattern:

my_col.find({'name': { $regex: '^ali.*' } })

It will find all users that their names start with ali. Now let's say you want to search users based on their phone country code which has a + in its number like +98901.... You need to escape the + character but escape it twice:

my_col.find({'phone': { $regex: '^\\+98.*' } })

#mongoDB #pymongo #regex

Is there a way to create ObjectID from an INT in MongoDB?

import bson

def object_id_from_int(n):
    s = str(n)
    s = '0' * (24 - len(s)) + s
    return bson.ObjectId(s)

def int_from_object_id(obj):
    return int(str(obj))

n = 12345
obj = object_id_from_int(n)
n = int_from_object_id(obj)
print(repr(obj))  # ObjectId('000000000000000000012345')
print(n)  # 12345

#mongodb #objectid #pymongo #python #bson #int

https://medium.com/@xoor/indexing-mongodb-with-elasticsearch-2c428b676343

#mongodb #elastic #elasticsearch #indexing #fulltext #fulltext_search #search #ngram #medium

Did you know you can use jsonSchema in MongoDB to search for documents?

Let's say you have users collection with data below:

{ "_id" : ObjectId("5f64bd1eca8806f2c04fcbe3"), "customer_id" : 100, "username" : "john" }
{ "_id" : ObjectId("5f64bd1eca8806f2c04fcbe5"), "customer_id" : 206, "username" : "new_customer" }
{ "_id" : ObjectId("60420df441558d6671cf54f2"), "customer_id" : "123", "username" : "Ali" }

Now let's say you want to find all documents that has a customer_id of type string instead of int.
In Mongo shell:

let ms = {required: ["customer_id"], properties: {customer_id: {bsonType: "string"}}}

This schema says look for documents that have customer_id field with string type. To search:

> db.customers.find({$jsonSchema: ms})
{ "_id" : ObjectId("60420df441558d6671cf54f2"), "customer_id" : "123", "username" : "Ali" }

Interesting, right? :)

#database #mongodb #jsonSchema #json_schema