Mongo db dhruba

MongoDB
(No SQL)
1Dhruba Mandal
Dhruba Mandal
Email : dhruvmandal@gmail.com

Introduction To MongoDB
MongoDB is an open-source, cross-platform, document-oriented database
written in C++ that provides high performance, high availability, and automatic
scaling.
It is developed and supported by a company named 10gen
MongoDB is available under General Public license for free, and it is also available under
Commercial license from the manufacturer.
2Dhruba Mandal

Document oriented database
MongoDB stores data as documents, so it is known as document oriented database
FirstName = "Dhruba",
Address = "New Delhi",
Spouse = [{Name: "abcde"}].
FirstName ="mandal",
Address = "saket"
There are two different documents (separated by ".")
Storing data in this manner is called as document oriented database.
Example : -
3Dhruba Mandal

Purpose of building MongoDB
All the modern applications require big data, fast features development, flexible
deployment, and the older database systems not competent enough, so the MongoDB
was needed.
The primary purpose of building MongoDB is:
• Scalability : Mongo Db has Scaling capacity from single server deployments to large,
complex multi-site architectures
• Performance
• High Availability
4Dhruba Mandal

Features of MongoDB
5Dhruba Mandal
1. Support ad hoc queries : An ad hoc query means query created to obtain information
as the need arises. In MongoDB, you can search by field, range query and it also
supports regular expression searches.
2. Indexing : We can index any field in a document. Indexes are created to improve the
performance of searches. The good thing is that any field in a MongoDB document can
be indexed with primary and secondary indices.
It enables the database engine to efficiently resolve queries which make it one of the
best key features of MongoDB. The database engine can use a predefined index, which
maps documents fields and can tell the engine which documents are compatible with
this query statement, hence improves performance.
3. Replication : MongoDB supports Master Slave replication , A master can perform Reads
and Writes and a Slave copies data from the master and can only be used for reads or
back up (not writes)
4. Duplication of data : MongoDB can run over multiple servers. The data is duplicated to
keep the system up and also keep its running condition in case of hardware failure.

Dhruba Mandal 6
5. Load balancing : It has an automatic load balancing configuration because of data
placed in shards.
Note : (Sharding is a type of database partitioning that separates very large databases
the into smaller, faster, more easily managed parts called data shards)
6 . Supports map reduce and aggregation tools.
Map reduce : - Map-reduce is a data processing paradigm (model) for condensing large
volumes of data into useful aggregated results. For map-reduce operations, MongoDB
provides the mapReduce database command. which collects and condenses(i.e make
more concentrated) the aggregated data.
Map() procedure performs filtering and sorting
Reduce() procedure performs a summary operation
db.collection.mapReduce()
Aggregation tools : Aggregations operations process data records and return computed
results. Aggregation operations group values from multiple documents together, and can
perform a variety of operations on the grouped data to return a single result.

Dhruba Mandal 7
9. Provides high performance : It uses BSON instead of JSON for storing data. BSON is
binary JSON. Being Binary it improves processing efficiency of the MongoDB
10. Stores files of any size easily without complicating your stack.
11 . Easy to administer in the case of failures.
12 . It also supports:
✓ JSON data model with dynamic schemas
✓ Auto-sharding for horizontal scalability
✓ Built in replication for high availability
8. It is a schema-less database written in C++ : MongoDB is a document database in
which one collection holds different documents. Number of fields, content and size of
the document can differ from one document to another.
7. Uses JavaScript instead of Procedures

MongoDB Known as NoSQL
Dhruba Mandal 8
We know that MongoDB is a NoSQL Database .
Generally Data Base are of 3 types
1. RDBMS (Relational Database Management System)
2. OLAP (Online Analytical Processing)
3. NoSQL (NON SQL )
NoSQL Database is used to refer a non-SQL or non relational database as It provides a
mechanism for storage and retrieval of data other than tabular relations model used in
relational databases .
It is generally used to store big data and real-time web applications.

concept of collection and document
Dhruba Mandal 9
Database :
• Database is a physical container for collections.
• Each database gets its own set of files on the file system.
• A single MongoDB server typically has multiple databases.
Collection
• Collection is a group of MongoDB documents.
• It is the equivalent of an RDBMS table .
• A collection exists within a single database
• Collections do not enforce a schema.
• Documents within a collection can have different fields
Document :
• A document is a set of key-value pairs.
• Documents have dynamic schema.
• Dynamic schema means that documents in the same collection do not need to have
the same set of fields or structure, and common fields in a collection's documents
may hold different types of data

Differences in Terminology
Dhruba Mandal 10
RDBMS MongoDB
Database Database
Table Collection
Tuple/Row Document
column Field
Table Join Embedded Documents
Primary Key
Primary Key (Default key _id provided by mongodb
itself)

Mongo DB Vs MySQL
Dhruba Mandal 11
MongoDB MySQL
MongoDB is an open-source database developed
by MongoDB, Inc
MySQL is a popular open-source relational
database management system (RDBMS) that is
developed by oracle Corporation
No Schema definition required Structured data with clear schema
In MongoDB, data represents in a collection of
JSON documents
In MySQL, data is in tables and rows
In MongoDB, each individual records are stored as
‘documents’.
In MySQL, each individual records are stored as
‘rows’ in a table.
MongoDB’s querying is object-oriented, which
means you pass MongoDB a document explaining
what you are querying
The query language is called Structured Query
Language i.e. you have to put a string in the query
language that the DB system parses
Mongo DB doesn’t support joints, it supports
multi-dimensional data types like other
documents and arrays.
MySQL support join operation
In MongoDB, if an index is not found, every
document within a collection must be scanned to
select the documents that provide a match to the
query statement
With MySQL, if an index is not defined, the
database engine must scan the entire table to find
all relevant rows.

MongoDB Advantages
Dhruba Mandal 12
❖ MongoDB is schema less. It is a document database in which one collection holds
different documents.
❖ There may be difference between number of fields, content and size of the
document from one to other.
❖ Structure of a single object is clear in MongoDB.
❖ There are no complex joins in MongoDB.
❖ MongoDB provides the facility of deep query because it supports a powerful dynamic
query on documents.
❖ It is very easy to scale.
❖ It uses internal memory for storing working sets and this is the reason of its fast
access.

MongoDB Data types
Dhruba Mandal 13
Data Types Description
Arrays This data type is used to store a list or multiple values into a single key.
Boolean This data type is used to store Boolean values. It just shows YES/NO values.
Date
This data type stores the current date or time in Unix time format. It makes
you Possible to specify your own date time by creating object of date and
pass the value of date, month, year into it.
Double Double data type stores floating point values.
Integer
Integer is used to store the numeric value. It can be 32 bit or 64 bit
depending on the server you are using.
Min/Max
Keys
This data type compare a value against the lowest and highest bson
elements.
Null It is used to store null values.
Object Object data type is used for embedded documents.
String
String is the most commonly used data type. A string must be UTF 8 valid in
mongodb.
Symbol It is generally used for languages that use a specific type.

Installing MongoDB
Dhruba Mandal 14
Step 1 – Adding the MongoDB Repository
sudo vi /etc/yum.repos.d/mongodb-org.repo
2. Inside mongodb-org.repo write the below configuration
[mongodb-org-3.4]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongod
b-org/3.4/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-3.4.asc
3. Save and Close File by !wq
4. Run command yum repolist
The above repolist command displays a list of enabled repositories:

Dhruba Mandal 15
5. Now installing MongoDB run below command
sudo yum install mongodb-org
There are two Is this ok [y/N]: prompts press Y
6. Next, start the MongoDB service with the systemctl utility:
sudo systemctl reload mongod
sudo systemctl start mongod
7 . check that the service started by viewing the end of the mongod.log file with
the tail command:
sudo tail /var/log/mongodb/mongod.log
. . .
[initandlisten] waiting for connections on port 27017
An output of waiting for a connection confirms that MongoDB has started successfully
and we can access the database server with the MongoDB Shell:
Output

Dhruba Mandal 16
8. To login into mongo db Type command
mongo
Note: When you launched the MongoDB Shell you may have seen a warning like this:
** WARNING: soft rlimits too low. rlimits set to 4096 processes, 64000 files. Number of
processes should be at least 32000 : 0.5 times number of files.
9. To resolve the warning, alter the processes soft rlimit value for mongod by editing
the 20-nproc.conf file:
sudo vi /etc/security/limits.d/20-nproc.conf
10. Add the following line to the end of file :
mongod soft nproc 32000
PTO

Dhruba Mandal 17
11 . For the new limit to be available to MongoDB, restart it using the systemctl utility:
sudo systemctl restart mongod
12 . Leave the mongod process running in the background, but quit the shell with
the exit command:
> exit
13 . Use the systemctl utility to check its startup status
systemctl is-enabled mongod; echo $?
Output
. . . enabled
0
An output of zero confirms an enabled daemon, which we want
14 . In the event of a disabled daemon, use the systemctl utility to enable it :
sudo systemctl enable mongod

Secure MongoDB with username and password
Dhruba Mandal 18
1. Connect to the instance.
mongo
2. At the mongo command line, set the administrator:
use admin
db.createUser(
{
user: "admin",
pwd: "admin123",
roles: [ { role: "root", db: "admin" }]
}
)exit;
3. Authenticate user with below command
db.auth("admin", "password")
Exit the mongo shell, re-connect, authenticate as the user.
4. Access the MongoDB with below command
mongo -u admin -p myadminpassword 127.0.0.1/admin

Accessing MongoDB Remotely
Dhruba Mandal 19
Once MongoDB credentials is created and Authenticated it is now time to enable
MongoDB to start using these access controls To do so .
1. open the file mongod.conf by below command
sudo vim /etc/mongod.conf
2. In the file at last add the below line
security:
authorization: enabled
3. Also in same file change bind IP from 127.0.0.1 to 0.0.0.0 for all or you can
give the IP of servers you want . 0.0.0.0. means for all
# network interfaces
net:
port: 27017
bindIp: 0.0.0.0 #default value is 127.0.0.1
4. Restart the MongoDB using below command
sudo service mongod restart

Dhruba Mandal 20
5. On client machine or machine from which we want to access MongoDB Install the
MongoDB- Client .
Steps :
1. Create the repository by command
sudo vim/etc/yum.repos.d/mongodb.repo
2. Inside mongodb-org.repo write the below configuration
[mongodb-org-3.4]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodborg/3.4/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-3.4.asc
3. Update the repository index by below command
sudo yum update -y

Dhruba Mandal 21
4. Install the MongoDB Shell Client with below command
sudo yum install mongodb-org-shell -y
5. Now you can connect your mongo DB from client or remote machine by below
command
mongo -u <username> -p <password> <ip-address>:27017/<collection-name>
Example : In my case I am connecting my MongoDB on my Centos 7 machine
10.0.205.53 from my centos7 machine 10.0.205.50 : Output is as below :

Concepts of Data Modeling
Dhruba Mandal 22
• Data modeling is a representation of the data structures in a table for a company’s
database
• It is a very powerful expression of the company's business requirements.
• Data models are used for many purposes, from high-level conceptual models to physical
data models.
Three basic styles of data modeling are generally used in practice today.
a. Conceptual Data Models(CDMs): High-level, static business structures and concepts
b. Logical Data Models (LDMs): Entity types, data attributes and relationships between
entities
c. Physical Data Models (PDMs): The internal schema database design

Data Modeling in MongoDB
Dhruba Mandal 23
➢ Data in MongoDB has a flexible schema. documents in the same collection
➢ The main challenge in data modeling is balancing the need of the application, the
performance characteristics of the database engine, and the data retrieval patterns
Below are some considerations while designing Schema in MongoDB
✓Always design schema according to user requirements.
✓Combine objects into one document if you will use them together. Otherwise separate
them (but make sure there should not be need of joins)
✓Do join on write operations not on read operations.
✓Optimize your schema for most frequent use cases.
✓Do complex aggregation in the schema.
✓ Duplicate the data (but limited) because disk space is cheap as compare to compute
time

Database and It’s Command in MongoDB
Dhruba Mandal 24
Database is a physical container for collections , each database gets its own set of
files on the file system. A single MongoDB server typically has multiple databases
1. To create database use command : use Database_name
Note : (use database name will create the database if database already exist
it will switch to that database)
2. Switching to other database use command : use Database_name
3. To check your currently selected database, use the command : db
Note: (It will display your present DB)
4. to check your databases list, use the command : show dbs
5. To delete the database in MongoDB
If you want to delete the database
1.First go to that database by command : use Database_name then
2.use command db.dropDatabase()

Collection & It's Command in MongoDB
Dhruba Mandal 25
Collection is a group of MongoDB documents. It is the equivalent of an RDBMS table .
A collection exists within a single database it does not enforce schema so the
document with in collection can have different fields.
1. command to create collection
. Go to DB use admin and run below command
db.createCollection(“name”, “options”)
Parameter Type Description
Name String Name of the collection to be
created
Options Document (Optional) Specify options
about memory size and
indexing
Creating collection by name
mycollection

Dhruba Mandal 26
2. After creating Collection to see the collection use command
show collections
command show collection will show all the collection as below
If we are getting any error like
"errmsg" : "not authorized on DB_Name to execute command { create: "mycollection"
}",
Means the user is not authorized and in this case we need to authorize user by below
command
use admin; db.grantRolesToUser('admin', [{ role: 'root', db: 'admin' }])
Here in example user is admin but for any user we can do the same
Important Note

Dhruba Mandal 27
Optional parameter of collections
Field Type Description
capped Boolean
(Optional) If true, enables a capped collection. Capped collection is a fixed
size collection that automatically overwrites its oldest entries when it reaches
its maximum size. ( If you specify true, you need to specify size parameter
also.)
autoIndexId Boolean
(Optional) If true, automatically create index on _id fields Default value is
false.
size number
(Optional) Specifies a maximum size in bytes for a capped collection. If capped
is true, then you need to specify this field also.
max number
(Optional) Specifies the maximum number of documents allowed in the
capped collection.
Example below shows the syntax of createCollection() method with few important options
db.createCollection("mycol", { capped : true, autoIndexId : true, size : 6142800, max : 10000 } )
{ "ok" : 1 } >

Dhruba Mandal 28
2. Command to drop Collection
In MongoDB, db.collection.drop() method is used to drop a collection from a
database.
It completely removes a collection from the database and does not leave any
indexes associated with the dropped collections.
Basic syntax : db.COLLECTION_NAME.drop()
First check the already existing collections in your database. By command
use DB_name (name of the db from where u want to drop collection)
show collections
db.mycollection.drop() (mycollection = Name of collection you want to drop)
If successful it will give output as : true

Documents and It’s Command in MongoDB
Dhruba Mandal 29
A document is a set of key-value pairs. It has have dynamic schema , it means that
documents in the same collection do not need to have the same set of fields or
structure, and common fields in a collection's documents may hold different types
of data.
MongoDB insert documents : There are also two methods "db.collection.update()"
method and "db.collection.save()" method used for adding or inserting new documents
into a collection in your database
Syntax : The basic syntax of insert() command is as follows −
db.COLLECTION_NAME.insert(document)
> show collections
users
> db.users.insert({
...
... id: '1' ,
... loginId: 'mandal',
... userPass: 'mandal',
... userType: 'admin',
... active: '1',
...
... })

Inserting Multiple record
Dhruba Mandal 30
db.users.insert([
{id: '4' ,
loginId: 'rahul',
userPass: 'rahul',
userType: 'admin',
active: '1',
},
{
id: '5' ,
loginId: 'mohit',
userPass: 'mohit',
userType: 'admin',
active: '1',
}
])
Here users is
collection name
Also insert ([ at
beginning and
write
documents
inside { } for
other use ,

MongoDB - Query Document
Dhruba Mandal 31
To query data from MongoDB collection, you need to use MongoDB's find() method.
Syntax
The basic syntax of find() method is as follows −
>db.COLLECTION_NAME.find()
db.users.find() (In my case users is collection name)
To display the results in a formatted way, you can use pretty() method. (same as using
G in MySQL )
>db.COLLECTION_NAME.find().pretty()
>db.users.find({"loginId":"mandal"}) (like where condition in MySQL )

RDBMS Where Clause Equivalents in MongoDB
Dhruba Mandal 32
To query the document on the basis of some condition, you can use following
operations
Operation Syntax Example RDBMS Equivalent
Equality {<key>:<value>} db.mycol.find({"by":"mandal"}).pretty() where by = 'mandal'
Less Than {<key>:{$lt:<value>}} db.mycol.find({"likes":{$lt:50}}).pretty() where likes < 50
Less Than Equals {<key>:{$lte:<value>}} db.mycol.find({"likes":{$lte:50}}).pretty() where likes <= 50
Greater Than {<key>:{$gt:<value>}} db.mycol.find({"likes":{$gt:50}}).pretty() where likes > 50
Greater Than Equals {<key>:{$gte:<value>}} db.mycol.find({"likes":{$gte:50}}).pretty() where likes >= 50
Not Equals {<key>:{$ne:<value>}} db.mycol.find({"likes":{$ne:50}}).pretty() where likes != 50

AND in MongoDB
Dhruba Mandal 33
In the find() method, if you pass multiple keys by separating them by ',' then
MongoDB treats it as AND condition. Following is the basic syntax of AND −
>db.collectionname.find(
{ $and: [
{"id“: “1”}, {key2:value2}
]
}
).pretty()

OR in MongoDB
Dhruba Mandal 34
To query documents based on the OR condition, you need to use $or keyword.
Following is the basic syntax of OR −
>db.collectionname.find(
{
$or: [
{key1: value1}, {key2:value2}
]
}
).pretty()
We can also use AND and OR Together
db.mycol.find({"likes": {$gt:10}, $or: [{"key1: value1"}, {"title": "key2:
value2"}]}).pretty()

MongoDB - Projection
Dhruba Mandal 35
In MongoDB, projection means selecting only the necessary data rather than
selecting whole of the data of a document. If a document has 5 fields and you need
to show only 3, then select only 3 fields from them.
The basic syntax of find() method with projection is as follows −
>db.COLLECTION_NAME.find({},{KEY:1})
Example :
> db.users.find({},{"loginId":1,_id:0})
{ "loginId" : "Sumit" }
{ "loginId" : "harsh" }
{ "loginId" : "one97" }
{ "loginId" : "mohit" }
Please note _id field is always displayed while executing find() method, if you don't
want this field, then you need to set it as 0.

MongoDB - Update Document
Dhruba Mandal 36
MongoDB's update() and save() methods are used to update document into a
collection. The update() method updates the values in the existing document while
the save() method replaces the existing document with the document passed in
save() method.
MongoDB Update() Method
Syntax
>db.COLLECTION_NAME.update(SELECTION_CRITERIA,UPDATED_DATA)
example
> db.users.update({"loginId" : "rahul"},{$set:{"loginId" : "one97"}})
Result : WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
db.users.find() will display the changes

Dhruba Mandal 37
MongoDB Save() Method
The save() method replaces the existing document with the new document passed in
the save() method.
Syntax
>db.COLLECTION_NAME.save({_id:ObjectId(),NEW_DATA})
db.users.save(
{
"_id" : ObjectId("5d6ca5b13212ff16c9e6ef1a"), "userPass":"mandal",
"by":"mandal@123"
}
)
Update is better to use than save

MongoDB - Delete Document
Dhruba Mandal 38
MongoDB's remove() method is used to remove a document from the collection.
remove() method accepts two parameters. One is deletion criteria and second is just One
flag.
deletion criteria − (Optional) deletion criteria according to documents will be removed.
justOne − (Optional) if set to true or 1, then remove only one document.
Basic syntax of remove()
>db.COLLECTION_NAME.remove(DELLETION_CRITTERIA)
db.users.remove({ "userPass" : "mandal"})
Example

Dhruba Mandal 39
If there are multiple records and you want to delete only the first record, then set
justOne parameter in remove() method.
db.COLLECTION_NAME.remove(DELETION_CRITERIA,1)
(Note : Here 1 means only first which meets deletion criteria , if multiple
rows meet the same criteria only first row will be deleted )
Remove All Documents of that collection
>db.collectionmane.remove({})
(Note : This is equivalent of SQL's truncate command )

The Limit() and skip() Method
Dhruba Mandal 40
To limit the records in MongoDB, you need to use limit() method.
The basic syntax of limit() method is as follows −
>db.COLLECTION_NAME.find().limit(NUMBER)
> db.users.find().limit(2) will only display 2 rows
Apart from limit() method, there is one more method skip() which also accepts
number type argument and is used to skip the number of documents.
The basic syntax of skip() method is as follows
db.COLLECTION_NAME.find().limit(NUMBER).skip(NUMBER)
> db.users.find().limit(2).skip(1)
i.e. it will skip the number of rows and will show 2 value after that row

MongoDB - Sort Records
Dhruba Mandal 41
In MongoDB, sort() method is used to sort the documents in the collection.
This method accepts a document containing list of fields along with their sorting
order.
The sorting order is specified as 1 or -1.
1 is used for ascending order sorting.
-1 is used for descending order sorting.
Basic syntax for sort in as below
>db.COLLECTION_NAME.find().sort({KEY:1})
Example :
>db.users.find({},{"loginId":1,_id:0}).sort({"loginId" :-1})
>db.users.find({},{"loginId":1,_id:0}).sort({"loginId" : 1})

MongoDB - Indexing
Dhruba Mandal 42
Indexes are special data structures, that store a small portion of the data set in an easy-
to-traverse form.
The index stores the value of a specific field or set of fields, ordered by the value of the
field as specified in the index
To create an index you need to use ensureIndex() method of MongoDB.
Syntax
>db.COLLECTION_NAME.ensureIndex({KEY:1})
Here key is the name of the field on which you want to create index and 1 is for ascending
order-1 create index in descending order
db.users.ensureIndex({"loginId":1})
By using ensureIndex() method you can pass multiple fields, to create index on
multiple fields.
Syntax
db.mycol.ensureIndex({"title":1,"description":-1})
db.users.ensureIndex({"loginId":1,"id" :1 })

MongoDB - Aggregation
Dhruba Mandal 43
Aggregations operations process data records and return computed results
In SQL count(*) and with group by is an equivalent of MongoDB aggregation.
For the aggregation in MongoDB, you should use aggregate() method.
Basic syntax of aggregate() method is as follows −
db.COLLECTION_NAME.aggregate(AGGREGATE_OPERATION)
Example :
db.users.aggregate([{$group : {_id : "loginId", num_tutorial : {$sum : 1}}}])
Output :
{ "_id" : "by_loginId", "num_tutorial" : 4 }

Dhruba Mandal 44
list of available aggregation expressions.
Expression Description Example
$sum
Sums up the defined value from all documents in the
collection.
db.users.aggregate([{$group : {_id : "$by_user", num_tutorial :
{$sum : "$likes"}}}])
$avg
Calculates the average of all given values from all
documents in the collection.
{$avg : "$likes"}}}])
$min
Gets the minimum of the corresponding values from all
{$min : "$likes"}}}])
$max
Gets the maximum of the corresponding values from all
db.mycol.aggregate([{$group : {_id : "$by_user", num_tutorial :
{$max : "$likes"}}}])
$push Inserts the value to an array in the resulting document.
db.users.aggregate([{$group : {_id : "$by_user", url : {$push:
"$url"}}}])
$addToSet
Inserts the value to an array in the resulting document
but does not create duplicates.
db.users.aggregate([{$group : {_id : "$by_user", url :
{$addToSet : "$url"}}}])
$first
Gets the first document from the source documents
according to the grouping. Typically this makes only
sense together with some previously applied “$sort”-
stage.
db.users.aggregate([{$group : {_id : "$by_user", first_url : {$first
: "$url"}}}])
$last
Gets the last document from the source documents
according to the grouping. Typically this makes only
sense together with some previously applied “$sort”-
stage.
db.users.aggregate([{$group : {_id : "$by_user", last_url : {$last
: "$url"}}}])

MongoDB - Replication
Dhruba Mandal 45
Replication is the process of synchronizing data across multiple servers. It provides
redundancy and increases data availability with multiple copies of data on different
database servers
1. Issue the below command to generate your key file:
openssl rand -base64 756 > mongo-keyfile
2. Create the /opt/mongo directory to store your key file:
sudo mkdir /opt/mongo
3. Move your key file to /opt/mongo and assign it the correct permissions:
sudo mv ~/mongo-keyfile /opt/mongo
sudo chmod 400 /opt/mongo/mongo-keyfile
4. Update the ownership of your key
sudo chown mongod:mongod /opt/mongo/mongo-keyfile
5. Create an Administrative User on server which u choose as primary member of
your replication set

Dhruba Mandal 46
Create an Administrative User by below steps
5a. log in to the mongo shell by command
Mongo
5b. Connect to the admin database:
use admin
5c. Create an administrative user with root privileges. Replace “password” with a strong
password of your choice:
db.createUser({user: "mongo-admin", pwd: "password", roles:[{role: "root", db: "admin"}]})
6 . Open the configuration file of MongoDB on both server by command
sudo vim /etc/mongod.conf
7 In configuration file remove hash (#) from replication and add below lines
replSetName: "myreplica01“
( Important Note : Here myreplica01 is replication name, you can use any name but it should be same on both
server also there should be 2 space after replication: i.e. don’t write replSetName just below replication: use 2
space else it will show error )

Dhruba Mandal 47
8 . Once changes has been made restart the mongod service by command:
sudo systemctl restart mongod
9 . Connect via SSH to the node that you intend to use as your primary
mongo -u mongo-admin -p --authenticationDatabase admin
Example in my case : mongo -u admin -p admin123 127.0.0.1/admin
10 . From the mongo shell, initiate the replica set:
rs.initiate()
It will give output as some thing below
11. While still connected to the mongo shell, add the other hosts to the replica set:(any
number of set i.e. servers)
rs.add("mongod1.net:27017")
rs.add("mongod2.net:27017")
12 . Once all members have been added, check the configuration of your replica set:
rs.conf()
Do any changes on primary and it will replicate on secondary

MongoDB - Sharding
Dhruba Mandal 48
Sharding is a concept in MongoDB, which splits large data sets into small data sets
across multiple MongoDB instances.
Sometimes the data within MongoDB will be so huge, that queries against such big
data sets can cause a lot of CPU utilization on the server.
To tackle this situation, MongoDB has a concept of Sharding, which is basically the
splitting of data sets across multiple MongoDB instances.
Mongo DB Sharding uses horizontal scaling to solve the problems
Concept of Horizontal and Vertical Scaling
Horizontal scaling means that you scale by adding more machines into your pool of
resources whereas Vertical scaling means that you scale by adding more power
(CPU, RAM) to an existing machine.

How to Implement Sharding
Dhruba Mandal 49
Shards are implemented by using clusters which are nothing but a group of MongoDB
instances.
1. A Shard – This is a MongoDB instance which holds the subset of the data. In production
environments, all shards need to be part of replica sets
2. Config server – This is a MongoDB instance which holds metadata (i.e. a set of data that
describes and gives information about other data) about the cluster, basically information
about the various MongoDB instances which will hold the shard data.
3. A Router – This is a MongoDB instance which basically is responsible to re-directing
the commands send by the client to the right servers.

MongoDB Backup & Restore
Dhruba Mandal 50
All backup and restore command will run on node machine not on MongoDB
Backup Single Database
mongodump --db mydb --out /backup/db/
Ex: - mongodump --db VodaIdeapanel --out /backup/db/
(Here VodaIdeapanel is my db name and /backup/db/ is my path )
Backup All Databases
mongodump --out /backup/db/
Backup Single Collection
mongodump --collection mycollection --db mydb --out /backup/db/
Example : mongodump --collection user --db VodaIdeapanel --out /backup/db/
(Note here user is my collection name )
Remote database backup
specify host, port, username and password for remote databases connections backups like
below.
mongodump --host 10.0.1.7 --port 27017 --username admin --password some password --
db mydb --out /backup/db/

Dhruba Mandal 51
mongorestore is command line tool for restoring MongoDB database backup

Restore MongoDB Database
Dhruba Mandal 52
mongorestore is command line tool for restoring MongoDB database backup
mongorestore --db mydb --drop /backup/db/mydb
Example : mongorestore --db pannel --drop /backup/db/VodaIdeapanel
(Here /data/db/ is location of your MongoDB data directory and /backup/db is
location of backup directory.)
MongoDB Backup Shell Script
#!/bin/sh
TODAY=`date +%d%b%Y`
BACKUP_DIR=/backup/db
mkdir -p ${BACKUP_DIR}/${TODAY}
mongodump -h <DATABASE_HOST> -d <DATABASE_NAME> -u <USERNAME> -p
<PASSWRD> --out ${BACKUP_DIR}/${TODAY}/

When to use MangoDB /MySQL
Dhruba Mandal 53
MongoDB MySQL
High Availability : When you need high Availability
of data with automatic fast and instant data
recovery
Low Maintenance: When your just starting and
your database is not going to scale much, MySQL
will help you in easy and low maintenance set up
IN Built Sharding : In future, if you're going to grow
big as MangoDB has inbuilt Sharding solution
Limited Budget: if you want high performance in
limited budget
Unstable Schema: if you have an unstable schema
and you want to reduce your schema migration cost
Fixed Schema: If you have fixed schema and data
structure isn't going to change over the time like
Wikipedia
NO DBA : if you don't have Database Administrator
(required for larger)
High Transaction: If high transaction rate is going
to be your requirement (i.e. high insert or select)
Cloud Computing: If most of your services are
cloud-based , MongoDB is best suitable
Data Security: If data security is your top priority ,
MySQL is the most secure DBMS

References
Dhruba Mandal 54
https://www.tutorialsjar.com/key-features-of-mongodb/
https://www.quora.com/How-can-Mongo-db-provides-high-performance
https://www.mongodb.com/nosql-explained
https://www.digitalocean.com/community/tutorials/how-to-install-mongodb-on-centos-7
https://www.javatpoint.com/mongodb-tutorial
https://stackoverflow.com/questions/4881208/how-to-secure-mongodb-with-username-
and-password
https://stackoverflow.com/questions/23943651/mongodb-admin-user-not-authorized
https://www.linode.com/docs/databases/mongodb/create-a-mongodb-replica-set/
http://www.dba86.com/docs/mongo/2.4/reference/limits.html
https://www.howtoforge.com/tutorial/deploying-mongodb-sharded-cluster-on-centos-
7/#three-sharding-components
https://tecadmin.net/backup-and-restore-mongodb-database/

Mongo db dhruba

Recommended

More Related Content

What's hot (20)

Similar to Mongo db dhruba (20)

More from Dhrubaji Mandal ♛ (15)

Recently uploaded (20)

Mongo db dhruba