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Uniqueness of MOIDs

August 16th, 2011 8 comments

A question was recently posted at the open source VI Java API forum regarding the uniqueness of MOIDs. The developer who raised the question wanted to build a caching on the client side so as to avoid getting back to the server for the name of a virtual machine with its MOID. If MOID doesn’t resonate with you, you may want to read this post before reading on.

Cloud Bursting: Is It Ready For Enterprises?

August 15th, 2011 4 comments

Cloud bursting means workload moves from one cloud to another on the fly. With differentiation of public cloud and private cloud, you can have 4 different permutations: private to public, private to private, public to public, and public to private.

What people talk about the most is the case of private to public cloud. Think about the case in which

Platform vs. Stairform

August 9th, 2011 No comments

It’s probably fair to say anyone working in software knows a term called platform. It’s a term borrowed from transportation industry, where a raised and flat space on which passengers trains in a station. In software, it means something you can leverage, either an environment for running your software or a development library for building your applications.

Like many things in software, platform has never had a clear definition. Different people basically have their own versions of definitions. That is not necessarily a bad thing – at least it helped

Programmable Data Centers: Next Big Thing in IT?

August 8th, 2011 No comments

As cloud computing gains momentum, more mega data centers are constructed or to be constructed. You can find cool videos on how companies like Google, Microsoft build and run their state-of-the-art data centers.

In these data centers, computers/storage/switches are packed and wired inside containers in factory before being shipped to a data center. After hooking up power, networking, and cooling, a container of servers are ready to go. These advances have

Workaround: vSphere Java API with Java Web Start

August 2nd, 2011 No comments

If you are using, or intend to use, the open source vijava API with Java Web start, you want to read this article carefully.

A community user recently reported an issue in this scenario. His test application was launched via Web Start jnlp. “First, when run a single test thread everything is fine and the VM tasks operate normally.  However as soon as we kick off a second test thread while the first test thread

Filtering vSphere API Requests

August 1st, 2011 No comments

I got an interesting question on how to find out WSDL files are used by vSphere Web Services at the VI Java API forum. After some clarification, it turns out the questioner just wanted to know what methods are called, so that the proxy between client and vCenter server can decide whether it should be allowed to go through.

Although a rare use case, but it’s a valid and sophisticated one. In general, you can use vSphere built in feature for security, for example,

Categories: vSphere API Tags: , ,

Java SE 7 released, finally!

July 28th, 2011 1 comment

After Java 6.0 released in 2006, it’s been 5 years during which Sun Microsystem was sold to Oracle. Today the 7.0 is finally GAed. It includes quite a few changes including small language changes as well as new and improved APIs.

The language changes are mostly small and may not affect you, for example, the switch statement now works with strings. The new try-with-resource statement, which is similar to using statement in C#, helps you with cleaner code, see the difference shown in the following

Is Compression Supported in vSphere API?

July 26th, 2011 No comments

There was recently a question in VMware vSphere Web Service SDK forum regarding gzip compression in vSphere API. I understand where the user came from – some of the SOAP responses could be pretty big. If they can be compressed, performance could be improved and network bandwidth reduced.

The case can be a little tricky. On one hand, compressing big data definitely saves bandwidth; on the other hand,

Categories: vSphere API Tags: ,

How to Save With New vSphere 5 Licensing Model

July 25th, 2011 8 comments

Disclaimer: These are my personal thoughts, and strictly mine.

I missed the big launch of vSphere 5 on July 12 because I was having my vacation. When I came back, I found so many discussions around the vSphere 5 licensing change. It’s understandable that people don’t like changes, especially if the changes may have financial impacts.

Technically, the vRAM pooling simplifies the licensing model, as pointed out by Carter Shanklin. Money wise,

My Vacation in China

July 21st, 2011 2 comments

I recently spent two weeks on vacation in China. I’d heard dramatic changes there since my last trip several years ago. My trip definitely confirmed these.

The following are several photos I took while visiting different places:


The Shanghai high speed train station, the end of the world longest high speed railway from Beijing. It started operation on

Categories: Others Tags: ,

Success Story: Cisco Data Center Network Manager

July 20th, 2011 No comments

Today I got an email from Louis Jia who is a Sr. Development manager at Cisco. He told me that the product his team has been working on had been rebranded as Cisco Data Center Network Manager (DCNM) and is formally released. Congratulations to Louis and team!

I don’t normally cover products from vendors, be it an established company or a startup. But this one is different

Three Stages To Master Programmers

July 19th, 2011 No comments

While everyone can learn and practice programming, it’s hard to find a good software engineer, even harder to find a great one. My definition of a great software engineer is someone who can solve real world problems with software expertise, not someone who can only write code, or someone who can only talk about architecture on paper, or someone who complicates real world problems.

Yes, we can all learn programming related concepts, languages, tools, and etc. But how to use them effectively on a business problem is really a test stone for anyone. It’s important to study textbooks, learn from others; even more so to

Reflection on OOP: Inheritance or Generalization

July 11th, 2011 No comments

As software engineers, we most likely have learned the three key characteristics of object oriented programming: inheritance, encapsulation, and polymorphism. Over the years I study and practice OOP, I realized that inheritance is out of date and arguably misleading, therefore should be replaced.

In OOP, inheritance refers to a relationship between two classes in which a subclass inherits the properties and methods of its super class. The term inheritance is not really a good one because

How Many Programming Languages Are Enough?

July 4th, 2011 2 comments

During last 60 some years after computer was invented, there have been hundreds, if not thousands, programming languages. If we include domain specific language (DSLs), which accorinding to Martin Fowler may include regular expression, spreadsheet, etc, the number can be even bigger, not to mention more programming languages continue to emerge.

This would be a big burden if we have to learn all of them. Luckily, we don’t have to. In fact, most of us just need to learn several most popular ones. Even better, these popular languages may look very similar in syntax. As a result,

Why Virtual Machine Not Found?

June 30th, 2011 2 comments

I saw a new bug (Intermittent ManagedObjectNotFound on VirtualMachine.getConf) filed in the open source VI Java API project today:

It looks like sometimes VirtualMachine.getConfig() returns null, but other times it throws:
Caused by: java.lang.RuntimeException: com.vmware.vim25.ManagedObjectNotFound
at com.vmware.vim25.mo.ManagedObject.retrieveObjectProperties(ManagedObject.java:158)
at com.vmware.vim25.mo.ManagedObject.getCurrentProperty(ManagedObject.java:179)
at com.vmware.vim25.mo.VirtualMachine.getConfig(VirtualMachine.java:55)

As the vSphere API reference points out,

Moving Virtual Machine Back From Distributed Virtual Switch

June 29th, 2011 4 comments

After blogging about moving virtual machines from a standard virtual switch to a distributed virtual switch, I saw a new question in VI Java API forum on how to roll it back. Technically, I don’t see any reason why one should switch back because using distributed virtual switch gives you a lot of benefits. But the decision is not mine but yours. Whatever you want to do, we help do it easily.

The method involved is

Is serverGuid Attribute Really Needed in vSphere?

June 28th, 2011 No comments

If you have paid close attention to the SOAP messages recorded by Oynx, you may have noticed that there is an extra attribute called “serverGuid” in a ManagedObjectReference. The following is copied from my previous posting “Moving Virtual Machine to Distributed Virtual Switch”.

<_this xsi:type=”ManagedObjectReference” type=”VirtualMachine” serverGuid=”BA9CE658-75F7-4A99-ACE6-99EB1376B94A”>vm-134</_this>

Note that this SOAP request message is from a vSphere Client. In VIJava API or other language binding, there is no such an attribute. You may wonder,

Categories: vSphere API Tags: , ,

In Praise of Static Methods

June 27th, 2011 No comments

In object-oriented programming, static methods are the methods that are defined with static keyword. They don’t have access to non-static instance variables. This very limitation can be an easy cure for many programming pitfalls I’ve seen over the years.

  • A static methods prevents you from using instance variables for passing information around, for example, as parameters to or as result from it. As a general rule, you should not define an instance variable if it’s not an intrinsic property of a class or type. It may seem obvious,

ManagedObjectReference vs ManagedObject

June 23rd, 2011 20 comments

One of the most common confusions that a newcomer has while learning vSphere API is the ManagedObjectReference, a.k.a MOR. If you read the API Reference, you will find a lot of them. Recently there was a question poping in the open source VIJava API forum. So I think it is worth explaining it here.

There are two major types in the vSphere API: managed object types are for these objects on the server side only; and data object types for properties, parameters, and results, which can be send back and forth between client and server. The MOR is a data object type, but used to represent managed objects living on server side. If you are familiar with C/C++ programming, you can think of it as pointer in some sense. Even better,

Categories: vSphere API Tags: ,

Most Used API in vSphere

June 21st, 2011 1 comment

Yesterday I blogged about the least used API in VMware vSphere. This naturally leads to another question, “what is the most used API in vSphere?” It’s a harder question than the “least” one, because for the latter I can be very sure that zero is the lowest possible usage. If that API is not the least, it must be one of the least.

Before we try to figure out the answer, let’s clarify a bit the “most used.” Does it mean the one that is called the most times? Does it mean the one that is touched and used by most developers?