Learning Apache Cassandra-Part-5-Getting Familiar With Nodetool

Manish Jha

In last post of this series we learnt about how to add nodes in a cassandra cluster. If you have missed earlier posts of this series

then you can read them from below links:

1: Introduction to Cassandra

2: Understanding Cassandra Read/Write Mechanism

3: Installing Cassandra on RHEL6

4: Adding Node To Cassandra Cluster

In this post we will explore nodetool and will see how we can manage a cassandra cluster using nodetool utility.

What is nodetool?

The nodetool utility is a command line interface for managing a cluster. It provides a simple command line interface to expose operations and attributes available with cassandra.

There are hundreds of options available with nodetool utility and in this post I will cover only those which ae used more often.

Note: This post is suitable for those admins who are not sevrice owners of cassandra nodes/cluster but have to interact with cassandra day in day out in their infrastructure.… Read More

Learning Apache Cassandra-Part-4-Adding Node To Cassandra Cluster

Manish Jha

In last post of this series we learnt how to install cassandra on Rhel 6. In this post we will look into additional configuration parameter that is needed to configure in order to facilitate other nodes to join the cassandra cluster.

If you have missed earlier posts of this series then you can read them from below links:

1: Introduction to Cassandra

2: Understanding Cassandra Read/Write Mechanism

3: Installing Cassandra on RHEL6

At the moment we have one node cassandra cluster. Before going ahead and installing cassandra on other nodes, we will first perform following configuration changes in cassandra.yaml file.

Navigate to cassandra.yaml file which is located in cassandra_install_dir/conf folder. Open the file in editor of your choice and look for following options:

  • Listen_address: Address where gossip will be listening to. This address can’t be localhost or 0.0.0.0, because the rest of nodes will try to connect to this address.
… Read More

Learning Apache Cassandra-Part-3-Installing Cassandra on RHEL6

Manish Jha

In last 2 posts of this series we learnt about Cassandra architecture and understood the cassandra Read/Write process.

If you have missed earlier posts of this series then you can read them from below links:

1:Introduction to cassandra

2: Understanding Cassandra Read/Write Mechanism

In this post we will learn about installing cassandra on Redhat Linux.

Before jumping into lab and start with installation, I want to touch down on few concepts first which will help in understanding installation process.

Bootstrapping

Bootstrapping is the process in which a newly-joining node gets the required data from the neighbors in the ring, so it can join the ring with the required data. Typically, a bootstrapping node joins the ring without any state or token and understands the ring structure after starting the gossip with the seed nodes; the second step is to choose a token to bootstrap.

During the bootstrap, the bootstrapping node will receive writes for the range that it will be responsible for after the bootstrap is completed.… Read More

Learning Apache Cassandra-Part-2:Understanding Cassandra Read/Write Mechanism

Manish Jha

In first post of this series we discussed about what is cassandra, what are the benefits of using cassandra. We also discussed a little bit about from where cassandra came and finally we looked at the architecture of cassandra and discussed some important terms like snitch, gossip, data replication, partitioner etc.

In this post we will see how cassandra Read/Write mechanism works.

Let’s discuss about some key components of cassandra first before discussing about Read/Write. Important components of cassandra can be summarized as below:

1: Node – This is the most basic component of cassandra and it is the place where data is stored.

2: Data Center – In simplest term a datacenter is nothing but a collection of nodes. A datacenter can be a physical datacenter or virtual datacenter.

3: Cluster – Collection of many data centers is termed as cluster.

4: Commit Log – Every write operation is written to Commit Log.… Read More

Learning Apache Cassandra-Part-1:Introduction

Manish Jha

Cassandra was very new to me when I joined the vCloud Air operations team back in 2015. Over last 1.5 years I have got a bit of understanding about cassandra now and it provoked me to learn this wonderful database technology.

To start my journey with Cassandra, I am following training course from Infinite-Skills and youtube videos along with documentation available from datastax.

As my journey will progress, I will keep writing and sharing my experience of learning about cassandra.

This is very first post of learning cassandra series where I will try to touch down few basic things about cassandra.

What is cassandra?

cassandra is a NoSQL database technology. NoSQL is referred as not only SQL and it means an alternative to traditional relational database technologies like MySQL, Oracle, MSSQL. Apache cassandra is a distributed database. With cassandra database do not lives only on one server but is spread across multiple servers.… Read More

Find Snapshot Creation Date of a vCloud Director VM

Manish Jha

Last month while working on a customer ticket, I came across a request from customer where he wanted to know snapshot creation date for one of his VM as he can not find this detail from vCD UI.

To confirm this, I logged into vCD and navigated to my test lab to see what are the information available.

On navigating through vCD I found that vCD only tells that whether or not snapshot exists for a vApp/VM.

You can see in below screenshot in top right corner that there is no option for selection snapshot creation date.

snap-1.PNG

On drilling down to VM level also, I did not found any option for checking snapshot creation date.

snap-2.PNG

After banging my head for 20 minutes or so, I decided to use API calls as many times I have found some info which is not visible in vCD GUI. And the trick worked for me.… Read More

Exploring vSphere 6.5 API-Part 3: Esxi Host

Manish Jha

In last 2 post of this series, we learn about digging out info about datacenter,cluster and virtual machines.

In this post we will learn about API options available for Esxi hosts.

If you have missed earlier posts of this series, you can read them from here:

1: Exploring vSphere 6.5 API-Datacenter & Cluster

2: Exploring vSphere 6.5 API-Virtual Machines

Let’s get started with fetching info about esxi hosts.

1: List all hosts present in a vCenter

Following query will list all esxi hosts that are present across all cluster/datacenter which are there in a vcenter.

# curl -sik -H ‘Accept: application/json’ -H ‘vmware-api-session-id: 7c639fb1e988b4c59dd77adef4c5d06c’ -X GET https://vcentersrv01.alex.local/rest/vcenter/host

Output
[code]
{“host”:”host-28″,”name”:”esxi01.alex.local”,”connection_state”:”CONNECTED”,”power_state”:”POWERED_ON”}

{“host”:”host-31″,”name”:”esxi02.alex.local”,”connection_state”:”CONNECTED”,”power_state”:”POWERED_ON”}

{“host”:”host-33″,”name”:”esxi03.alex.local”,”connection_state”:”CONNECTED”,”power_state”:”POWERED_ON”}

{“host”:”host-35″,”name”:”esxi04.alex.local”,”connection_state”:”CONNECTED”,”power_state”:”POWERED_ON”}

[/code]

 

2: List all host in a specific datacenter

You can limit search of esxi host to specific datacenter by using filter.datacenters option

# curl -sik -H ‘Accept: application/json’ -H ‘vmware-api-session-id: 7c639fb1e988b4c59dd77adef4c5d06c’ -X GET
https://vcentersrv01.alex.local/rest/vcenter/host?filter.datacenters=datacenter-2

3: List all hosts in a specific cluster

# curl -sik -H ‘Accept: application/json’ -H ‘vmware-api-session-id: 7c639fb1e988b4c59dd77adef4c5d06c’ -X GET https://vcentersrv01.alex.local/rest/vcenter/host?filter.clusters=domain-c7… Read More

Storage Migrate a vCloud Director VM using Rest API

Manish Jha

If you are using vCloud Director in your environment and if you have ever tried doing a Storage vMotion of a VM from vSphere directly, you will notice a warning saying that its not recommended to modify the entity since its managed by VCD.

sv-1

This is because of the the fact that with VCD, the management layer lies with itself and not with vSphere. All changes to the entities should be made via vCD and not vSphere.

Although doing a storage migration will not break anything but as a best practice we should avoid that.

So what to do if one of your backend LUN is full and you need to evacuate that by migrating some vm’s to another datastore which have enough free space. The answer is by using “Rest API”.

About the VMware vCloud API

The VMware vCloud API provides support for developers who are building interactive clients of VMware vCloud Director using a RESTful application development style.… Read More

Exploring vSphere 6.5 API-Part 2: Virtual Machines

Manish Jha

In last post of this series we looked into some basic Rest API’s to fetch info about datacenter and cluster.

In this post we will explore API options for virtual machines. Out of all the components like host, cluster etc, max number of available API options are for virtual machines.

Let’s start with figuring out available options:

To start exploring the different API options available for virtual machine, you can use below query:

1: List all VM’s in all datacenter

Output of above query will give you VM ID, cpu/memory stats, VM name and their power status.

all-vm

2: List Powered off VM’s

You can list all powered off VM’s in datacenter using the filter power_states in above query.… Read More

Exploring vSphere 6.5 API-Part 1: Datacenter & Cluster

Manish Jha

I am using API for quite a bit now in our prod environment which is based on vCloud Director and many times API’s had proved a handy way to troubleshoot issues where GUI was not providing a way to proceed.

Inspired by vCD API’s, i decided to test that in my vSphere 6.5 lab and in this post I will try to demonstrate few queries which can be helpful in fetching info in your infrastructure.

In my lab I am exploring REST API’s using a linux tool called curl.

1: You can browse list of API’s by browsing https://vcenter-fqdn/ and clicking on “Browse vSphere Rest API’s”

api-url

 

2: To start with you can use below query to see what are the different options available

# curl -sik -H ‘Accept:application/json’ -u “vc-user” -X GET https://vcenter-fqdn/rest/

You will see below URL’s in output:

3: You can list the available components which can be explored via REST API by using below query

# curl -sik -H ‘Accept:application/json’ -u “vcadmin@alex” -X GET https://vcentersrv03.alex.local/rest/com/vmware/vapi/rest/navigation/component… Read More