Knowledge Base
Category: Windows
Mac OS X
To manually start the Agent:
/usr/local/bin/datadog-agent start
To stop the Agent:
/usr/local/bin/datadog-agent stop
To restart the Agent
/usr/local/bin/datadog-agent restart
Linux
To manually start the Agent:
sudo /etc/init.d/datadog-agent start
To stop the Agent:
sudo /etc/init.d/datadog-agent stop
To restart the Agent
sudo /etc/init.d/datadog-agent restart
Windows
Step 1: Add your PC/Mac ssh key to your account.
1. If you are using Mac run following commands in Terminal window or if you are using Windows install GitBash command utility ( https://gitforwindows.github.io ) to run following commands.
Step 2. Create your SSH Keys:
2.1.Before generating an SSH key in your shell, check if your system already has
one by running the following command:
cat ~/.ssh/id_rsa.pub
2.2.if keys are not there then generate a new SSH key, use the following
command:
ssh keygen -t rsa -C"$your_email"
Note:This command will prompt you for a location and filename to store the
key pair and for a password. When prompted for the location and filename,
just press enter to use the default.
2.3. To copy your public key to the clipboard, use the code below. Depending on
your OS you’ll need to use a different command:
For Windows: clip < ~/.ssh/id_rsa.pub For Mac: pbcopy < ~/.ssh/id_rsa.pub
Step 3. Open Git repository from you credentials and Add your SSH Key
3.1. On the left side menu, click on “profile settings” and then click on “SSH Keys”:
3.2. Then click on the green button “Add SSH Key”
3.3. There, you should paste the SSH Key which you copied from command line.
Note:Now, you’ll be able to use Git over SSH
Step 1 ) Click on the settings icon that appears to the right of the address bar. In the newest versions of Chrome, this appears as three horizontal lines and in older versions will be a wrench icon .
Step 2) From the menu, select Tools > Clear browsing data….
Step 3) Check the following:
Select the beginning of time in the drop down box and click on the Clear browsing data button.
Step 1) Click Safari in the upper left hand side of your screen. In the menu that appears, click Preferences.
sudo service mosquitto stop cd /usr/local/bin
If you already Created a Password & want to change that then using below Command mosquitto_passwd -D /etc/mosquitto/passwd username
Below Command is for New Password Creation mosquitto_passwd -c /etc/mosquitto/passwd username Password Re-Enter
sudo nano /etc/mosquitto/mosquitto.conf allow anonymous false
#Default authentication and topic access control #password_file /etc/mosquitto/passwd sudo service mosqquitto start sudo service mosquitto status
Step 1) Choose Start→Control Panel. Click the System and Security link and then click Windows Firewall.
You see the main Windows Firewall control window.
Step 2) On the left, click the Advanced Settings link.
Step 3) On the left, click Inbound Rules. Then, on the right, under Actions, click the New Rule link.
Windows Firewall shows you the New Inbound Rule Wizard.
Step 4) Select the option marked Port and click Next.
The wizard asks you to specify which ports.
Step 5) In the Specific Local Ports box, type the ports you want to open, separated by commas, and then click Next.
For example, in this case, the TCP ports that need to be opened are 8081, 8082, 9001, and 9002. The wizard takes action and opens those ports to receive data.
Step 6) Choose Allow the Connection and click Next.
The New Inbound Rule Wizard wants to know whether it should apply this rule if you’re connected to a domain network, a private network, or a public network. The safest option is to make it only open on your home network.
Step 7)Check the boxes for Private or any other desired network type, and then click Next.
The wizard asks that you give the rule a name and, optionally, a description.
Step 8) Type a name (usually the name of whatever program required the opening). Click Finish
Your new rule appears in the Inbound Rules list. It takes effect immediately.
Let’s follow the given steps to create and configure the 3 nodes replica sets in MongoDB. The configuration should be as mentioned below:
The replica sets name is “Testing”.
Steps 1
You need to create three directories to store three mongod instances data separately.
On windows
Open command prompt and give the following command.
C:\>mkdir \data\rs1 \data\rs2 \data\rs3
On unix or mac
mkdir –p /data/rs1 /data/rs2 /data/rs3
Step 2
Now let’s start three mongod instances as follows.
On windows
C:\>start mongod --replSet Testing --logpath \data\rs1\1.log --dbpath \data\rs1 --port 27017 --smallfiles --oplogSize 64
C:\>start mongod --replSet Testing --logpath \data\rs1\2.log --dbpath \data\rs2 --port 27018 --smallfiles --oplogSize 64
C:\>start mongod --replSet Testing --logpath \data\rs1\3.log --dbpath \data\rs3 --port 27019 --smallfiles --oplogSize 64
On unix or mac
mongod --replSet Testing --logpath \data\rs1\1.log --dbpath /data/rs1 --port 27017 --smallfiles --oplogSize 64 --fork
mongod --replSet Testing --logpath \data\rs1\2.log --dbpath /data/rs2 --port 27018 --smallfiles --oplogSize 64 –fork
mongod --replSet Testing --logpath \data\rs1\3.log --dbpath /data/rs3 --port 27019 --smallfiles --oplogSize 64 --fork
Now three mongod servers are running but they are not configured or initialized yet to interconnect to work for replica sets.
Step 3
You need to interconnect all three nodes. You need to open a command prompt and write configuration code and finally you need to call rs.initiate(config) command to start the replica sets as expected. I am giving replica sets name as “acemyskillsrepsets” but you can give it any other name.
C:\>mongo --port 27017
MongoDB shell version: 3.0.3
connecting to: 127.0.0.1:27017/test
> config = {_id:"Testing", members: [
{_id: 0, host: "localhost:27017"},
{_id: 1, host: "localhost:27018"},
{_id: 2, host: "localhost:27019"}]
};
> rs.initiate(config);
{ "ok" : 1 }
Now replica sets with three nodes is setup and configured successfully. You can check the status of the replica sets withrs.status().
Testing:PRIMARY> rs.status();
{
"set" : "Testing",
"date" : ISODate("2015-09-13T10:14:03.474Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "localhost:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1855,
"optime" : Timestamp(1442138448, 1),
"optimeDate" : ISODate("2015-09-13T10:00:48Z"),
"electionTime" : Timestamp(1442138452, 1),
"electionDate" : ISODate("2015-09-13T10:00:52Z"),
"configVersion" : 1,
"self" : true
},
{
"_id" : 1,
"name" : "localhost:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 795,
"optime" : Timestamp(1442138448, 1),
"optimeDate" : ISODate("2015-09-13T10:00:48Z"),
"lastHeartbeat" : ISODate("2015-09-13T10:14:02.580Z"),
"lastHeartbeatRecv" : ISODate("2015-09-13T10:14:02.579Z"),
"pingMs" : 0,
"configVersion" : 1
},
{
"_id" : 2,
"name" : "localhost:27019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 795,
"optime" : Timestamp(1442138448, 1),
"optimeDate" : ISODate("2015-09-13T10:00:48Z"),
"lastHeartbeat" : ISODate("2015-09-13T10:14:02.580Z"),
"lastHeartbeatRecv" : ISODate("2015-09-13T10:14:02.580Z"),
"pingMs" : 0,
"configVersion" : 1
}
],
"ok" : 1
}
If you observe the above result set its clearly written that there are three nodes and localhost:27017 is the primary and rest two are secondary nodes. Congratulations!!! the replication system named as “Testing” is now ready to use.
Testing
Now we need to insert a document into the primary node and after insertion read the inserted document.
Testing:PRIMARY> db.movies.insert({name: "Up", releasedyear: "2009"});
WriteResult({ "nInserted" : 1 })
Testing:PRIMARY> db.movies.find();
{ "_id" : ObjectId("55f54f55524898bbac0e5792"), "name" : "Up", "releasedyear" : "2009" }
Now let’s connect with a secondary node and read the data inserted by the primary node. If we read the data in the secondary node means the secondary nodes are in sync with the primary node and primary node’s replication is available to all secondary nodes.
To connect with the localhost:27018 by opening another command prompt and connect with a secondary node localhost:27018. After connecting with localhost:27018 and once you try to read the data from the node, it gives you an error because by default you cannot read from the secondary node. To read data from the secondary node you need to give the command rs.slaveOk().
C:\>mongo --port 27018
MongoDB shell version: 3.0.3
connecting to: 127.0.0.1:27018/test
Testing:SECONDARY> db.movies.find();
Error: error: { "$err" : "not master and slaveOk=false", "code" : 13435 }
Testing:SECONDARY> rs.slaveOk();
Testing:SECONDARY> db.movies.find();
{ "_id" : ObjectId("55f54f55524898bbac0e5792"), "name" : "Up", "releasedyear" : "2009" }
You can only read data from the secondary nodes but cannot insert document to the secondary nodes. Try the following query which gives you error.
Testing:SECONDARY> db.movies.insert({name: "The Day After Tomorrow", releasedyear: 2004});
WriteResult({ "writeError" : { "code" : undefined, "errmsg" : "not master" } })
Replication Internals
To know how this replication is happening internally, you need to analyze the oplog.rs file in each nodes including primary and secondary.
Let’s connect to the primary node (localhost:27017) and switch to local database. You can use show collections command to see all the collections present in the local database. Finally, you can see the oplog.rs file by giving the query db.oplog.rs.find().pretty().
C:\>mongo --port 27017
MongoDB shell version: 3.0.3
connecting to: 127.0.0.1:27017/test
Testing:PRIMARY> use local
switched to db local
Testing:PRIMARY> show collections
me
oplog.rs
startup_log
system.indexes
system.replset
Testing:PRIMARY> db.oplog.rs.find().pretty();
{
"ts" : Timestamp(1442138448, 1),
"h" : NumberLong(0),
"v" : 2,
"op" : "n",
"ns" : "",
"o" : {
"msg" : "initiating set"
}
}
{
"ts" : Timestamp(1442139989, 1),
"h" : NumberLong("-5383414929107714031"),
"v" : 2,
"op" : "c",
"ns" : "test.$cmd",
"o" : {
"create" : "movies"
}
}
{
"ts" : Timestamp(1442139989, 2),
"h" : NumberLong("-3864814140778310651"),
"v" : 2,
"op" : "i",
"ns" : "test.movies",
"o" : {
"_id" : ObjectId("55f54f55524898bbac0e5792"),
"name" : "Up",
"releasedyear" : "2009"
}
In the above file you can see there are three operations creating replica sets, creating movies collection and inserting a movie “up” into the collection. You can find the similar oplog.rs file in all secondary nodes. This is the file which is synced between the nodes and replication is happened between the nodes.
Now let’s connect to a secondary node localhost:27018 to observe the oplog.rs but you will definitely see the similar file over there too.
C:\>mongo --port 27018
MongoDB shell version: 3.0.3
connecting to: 127.0.0.1:27018/test
Testing:SECONDARY> use local
switched to db local
Testing:SECONDARY> show collections
me
oplog.rs
replset.minvalid
startup_log
system.indexes
system.replset
Testing:SECONDARY> db.oplog.rs.find().pretty();
{
"ts" : Timestamp(1442138448, 1),
"h" : NumberLong(0),
"v" : 2,
"op" : "n",
"ns" : "",
"o" : {
"msg" : "initiating set"
}
}
{
"ts" : Timestamp(1442139989, 1),
"h" : NumberLong("-5383414929107714031"),
"v" : 2,
"op" : "c",
"ns" : "test.$cmd",
"o" : {
"create" : "movies"
}
}
{
"ts" : Timestamp(1442139989, 2),
"h" : NumberLong("-3864814140778310651"),
"v" : 2,
"op" : "i",
"ns" : "test.movies",
"o" : {
"_id" : ObjectId("55f54f55524898bbac0e5792"),
"name" : "Up",
"releasedyear" : "2009"
}
}
Failover in Replication
To see the failover situation in replica sets, let’s shutdown the primary node. It can be clearly seen in which node you are now in the command prompt. But if you want to check from command, you can give rs.isMaster(). If you are in the secondary node, you need to connect to localhost:27017 i.e. primary node. Once you are inside the primary node, we need to shutdown the primary node giving thedb.shutdownServer() command. Once the primary server is down there will be automatic election process to select the a new primary node which will take only a few milliseconds.
C:\>mongo --port 27017 MongoDB shell version: 3.0.3 connecting to: 127.0.0.1:27017/test Testing:PRIMARY> db.shutdownServer(); shutdown command only works with the admin database; try 'use admin' Testing:PRIMARY> use admin switched to db admin Testing:PRIMARY> db.shutdownServer(); 2015-09-13T17:11:16.247+0545 I NETWORK DBClientCursor::init call() failed server should be down... 2015-09-13T17:11:16.274+0545 I NETWORK trying reconnect to 127.0.0.1:27017 (127.0.0.1) failed 2015-09-13T17:11:16.275+0545 I NETWORK reconnect 127.0.0.1:27017 (127.0.0.1) ok 2015-09-13T17:11:17.031+0545 I NETWORK Socket recv() errno:10054 An existing connection was forcibly closed by the remote host. 127.0.0.1:27017 2015-09-13T17:11:17.032+0545 I NETWORK SocketException: remote: 127.0.0.1:27017 error: 9001 socket exception [RECV_ERROR] server [127.0.0.1:27017] 2015-09-13T17:11:17.032+0545 I NETWORK DBClientCursor::init call() failed 2015-09-13T17:11:17.036+0545 I NETWORK trying reconnect to 127.0.0.1:27017 (127.0.0.1) failed 2015-09-13T17:11:18.038+0545 W NETWORK Failed to connect to 127.0.0.1:27017, reason: errno:10061 No connection could be made because the target machine actively refused it. 2015-09-13T17:11:18.039+0545 I NETWORK reconnect 127.0.0.1:27017 (127.0.0.1) failed failed couldn't connect to server 127.0.0.1:27017 (127.0.0.1), connection attempt failed
Now let’s connect to localhost:27018 and give the rs.status() command . In the result set it can be seen that one of the two secondary nodes becomes primary. Whenever the previously shutdown node becomes up, it will be secondary.
C:\>mongo --port 27018
MongoDB shell version: 3.0.3
connecting to: 127.0.0.1:27018/test
Testing:PRIMARY> rs.status();
{
"set" : "Testing",
"date" : ISODate("2015-09-13T11:27:09.780Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "localhost:27017",
"health" : 0,
"state" : 8,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"optime" : Timestamp(0, 0),
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("2015-09-13T11:27:09.580Z"),
"lastHeartbeatRecv" : ISODate("2015-09-13T11:26:15.452Z"),
"pingMs" : 0,
"lastHeartbeatMessage" : "Failed attempt to connect to localhost:27017; couldn't connect to server localhost:27017 (127.0.0.1), connection attempt failed",
"configVersion" : -1
},
{
"_id" : 1,
"name" : "localhost:27018",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 6208,
"optime" : Timestamp(1442139989, 2),
"optimeDate" : ISODate("2015-09-13T10:26:29Z"),
"electionTime" : Timestamp(1442143577, 1),
"electionDate" : ISODate("2015-09-13T11:26:17Z"),
"configVersion" : 1,
"self" : true
},
{
"_id" : 2,
"name" : "localhost:27019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 5179,
"optime" : Timestamp(1442139989, 2),
"optimeDate" : ISODate("2015-09-13T10:26:29Z"),
"lastHeartbeat" : ISODate("2015-09-13T11:27:09.476Z"),
"lastHeartbeatRecv" : ISODate("2015-09-13T11:27:09.475Z"),
"pingMs" : 0,
"configVersion" : 1
}
],
"ok" : 1
}
To see what happens when the previous node is down but one document is inserted into the newly elected primary node. Its very simple, whenever the previously down server becomes up it becomes as secondary node and sync all the data (oplog.rs) that is in the new elected primary nodes. Let’s see this scenario in the following section.
Connect to the localhost:27017 (which was down before) and you can see all the documents including the inserted documents when it was down
C:\>mongo --port 27017
MongoDB shell version: 3.0.3
connecting to: 127.0.0.1:27017/test
Testing:SECONDARY> rs.slaveOk();
Testing:SECONDARY> db.movies.find();
{ "_id" : ObjectId("55f54f55524898bbac0e5792"), "name" : "Up", "releasedyear" : "2009" }
{ "_id" : ObjectId("55f55e78e57ac7df5b34d4cf"), "name" : "The Day After Tomorrow", "releasedyear"
Testing:SECONDARY> use local
switched to db local
Testing:SECONDARY> show collections
me
oplog.rs
replset.minvalid
startup_log
system.indexes
system.replset
Testing:SECONDARY> db.oplog.rs.find().pretty();
{
"ts" : Timestamp(1442138448, 1),
"h" : NumberLong(0),
"v" : 2,
"op" : "n",
"ns" : "",
"o" : {
"msg" : "initiating set"
}
}
{
"ts" : Timestamp(1442139989, 1),
"h" : NumberLong("-5383414929107714031"),
"v" : 2,
"op" : "c",
"ns" : "test.$cmd",
"o" : {
"create" : "movies"
}
}
{
"ts" : Timestamp(1442139989, 2),
"h" : NumberLong("-3864814140778310651"),
"v" : 2,
"op" : "i",
"ns" : "test.movies",
"o" : {
"_id" : ObjectId("55f54f55524898bbac0e5792"),
"name" : "Up",
"releasedyear" : "2009"
}
}
{
"ts" : Timestamp(1442143864, 1),
"h" : NumberLong("2305258910925694865"),
"v" : 2,
"op" : "i",
"ns" : "test.movies",
"o" : {
"_id" : ObjectId("55f55e78e57ac7df5b34d4cf"),
"name" : "The Day After Tomorrow",
"releasedyear" : 2004
}
}
That’s the end of this article. I believe you understand the basic set up and configuration of replica sets in MongoDB. After reading and exercising this article you can try replica sets with separate computer or if possible geographically separated servers that will reflect the real implementation of the replica sets but don’t forget to manage your firewall configuration in that case. Happy Coding!!! Cheers!!!
mongod --dbpath C:\mongodata
pThreads: ftp://sources.redhat.com/pub/pthreads-win32/dll-latest/dll/x86/
OpenSSL: http://slproweb.com/products/Win32OpenSSL.html
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