Jenkins Installation

Today am going to discuss about Jenkins installation.
Jenkins can be installed on both unix and windows, i recently installed on my windows 7 laptop and thought of sharing the process in detail with screenshots. 
First we need to download jenkins from website -

https://jenkins.io/download/

Select relevant option from the below, i selected windows:

Once downloaded jenkin.msi needs to be run 

you will need to select installation location , i chose the default one :


 

Click on next to proceed:

few clicks our installation is completed 

In next step jenkins will start it's configuration 

In next step jenkins installation need a password stored in a file as per the screenshot, navigate to the file and enter the password.

Copy the password and enter, post the jenkins configuration will proceed further:

In next step jenkins with download , install plugins to create new jenkins jobs

Once above is completed , create new user page will appear

Fill in above details and next page will give default URL:Port of jenkins. We can change the below as per the requirement.

Finally our configuration is completed 

MongoDB

I have worked on MongoDB for sometime and wanted to share some knowledge gathered during this time.

Shell script to execute mysql query

We can run mysql queries via shell scripts, since this is required at times .

Say  a query is to be scheduled via crontab and shell script.

Here is a simple shell script example, as an example:

vi testscript.sh

-----------------------------------------------------------------------
#!/usr/bin/bash

DBUSER='username'
DBPASSWD='Password'

Query='show databases'   -- example query

mysql -u $DBUSER -p $DBPASSWD  <


$Query

EOF

----------------------------------------------------------------------

The above is a simple script to show databases and is executed with shell script..

# sh testscript.sh

We can schedule the above in crontab to run at a designated time.

Many such scripts can be written to automate daily tasks - backups etc..

Executing mysql commands from unix command prompt

We can also run mysql queries from unix command prompt. This is useful in many cases, say i want to check status of db cluster or check running processes etc.

I am sharing a basic example here:

mysql -u username -p -e "show databases;"

The above command will ask for password and share output of current databases.

This is a quick way to get required information.

Maridb Galera Cluster

So after working on Oracle RAC, SQL Server Always-On and DB2 HADR now finally i have got a chance to get hands-on Mariadb Galera Cluster and i am amazed. The Galera cluster is an Active-Active cluster , what that means you can write on any node and data is available on all nodes, changes are getting replicated quickly across all nodes and it's just so simple to install while Oracle and other clusters take too much time..

Here i will list done a few commands to monitor Galera cluster status :

MariaDB > Show status like 'wsrep%';

+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| wsrep_protocol_version |       |
| wsrep_last_committed   |       |
| ...                    | ...   |
| wsrep_thread_count   

You will see a list of variables related to galera in the output displaying about Number of Nodes in the cluster, their ip addresses, Current status..etc..

Will write more about these in my next post related to Galera.

Select Into OUTFILE Mariadb/MYSQL to export data in csv format

At  times where we need to export Data into csv format in mariadb/mysql,

SELECT INTO OUTFILE will write resulting rows from a query into a file - csv..

Below is a simple example on this :

select * from table INTO OUTFILE  '/path/test.csv'
FIELDS TERMINATED BY ','
ENCLOSED BY ' " '
ESCAPED BY '\\'
LINES TERMINATED BY '\n';

Handling Null values -

Another thing we will notice is having /N in output where we have Null values in table, in few cases requirement is to have blank Fields instead of /N in output. in these cases we need to use IFNULL function in the query

example,

Select name, IFNULL (Date, ' ') from table INTO OUTFILE  '/path/test.csv'
FIELDS TERMINATED BY ','
ENCLOSED BY ' " '
ESCAPED BY '\\'
LINES TERMINATED BY '\n';

With the above we replaced Null with blank in the csv output.