Building software is a very important part of software development cycle. In the C/C++ age, we used make and continue to use it today. When it came to Java age, two important build tools emerged: Ant and Maven. The former is very similar to make, but instead of script it uses XML. Both make and Ant describe HOW to build software in steps. The Maven takes a quite different approach – it describes WHAT the built software is using XML, and leaves the how to the Maven and its plugins.
In one of my recent projects, I got into a “big data” issue. One of the open source components emits so many logs that it quickly fills a hard disk. After isolating problem, I found huge number of log entries by the “find” command in a single log file whose size exceeds 50G – too big data for most system to handle.
The following is an example log entry in the log file:
If you want to find out the information in the vCenter database, the VMware support bundle comes handy. For example, if you want to analyze the event history, task history, you can dig out these information from the support bundle. By default, the vCenter support bundle is collected as part of the VMware support bundle on standalone client, but not on the vSphere Web Client. So make sure to mark the check box if you want the vCenter info.
Although I don’t think vSphere Web Client is a good choice as main GUI for vSphere administration, it has done one thing right and well – it has a unique URL for almost everything you can browse the vSphere Web Client. The benefit is that you can bookmark a URL and open to the page without many clicks.
Last week was a pretty busy week with VMworld 2014 in San Franciso, followed by a long weekend during which some of us may be even busier. If you haven’t got chance to the conference, you can check out the recorded VMworld keynotes, and maybe later recorded break-out sessions.
While there were many announcements/news in the conference from VMware and other vendors. I think the following three are the most important ones.
Today is the first day of VMworld 2014 San Francisco. For the last 7 consecutive years, I have attended all the VMworld conferences in US, either as a speaker, booth duty staff, or normal attendee. This year is no exception. As always, I find the solution exchange is the best part of the conference, so I spent several hours in the reception party this afternoon. While enjoying the good food, I talked to quite a few vendors. When the party was over, I found I only finished two rows. So there are a lot more work tomorrow.
In my last article, I talked about how to use logrotate to manage logs. As everything else, there are some tricks that are only learned when using it. Here are a few tricks and tips I learned recently. Hope it can save you some time.
Stickiness of Logrotate Rules
Logging is an important for software development and operation. Over the time, the log files can grow fast to fill up the disk space. To avoid the problem, log files are rotated, compressed, and deprecated based on certain rules, for example, periodically, over certain size limit, and retention limit.
Most mordern logging frameworks can do log rotation and compression, but different applications may use different frameworks thus configure them differently. If you want to have a solution across different applications for consistent policies, the logrote (https://fedorahosted.org/logrotate/) is a good choice.
It’s pretty easy to create a new user using vSphere APIs in Java. If you want one or two lines of scripts, you can write a few line Python script using PyVimomi wrapped by a command line. Even easier is a solution discussed at PureVirtual.
The trick is really about how to access the adduser command, which is available but not accessible from console as it is. To use the command, you have to type the following command from ESXi console: (I assume there are a few more commands that can be used in the same way)
As @lamw documented in his blog, you can access the database in the vCenter software appliance (vCSA). In the first appliance of version 5.0, VMware included IBM DB2 Embedded and then switched to vPostgres right after. That’s because vPostgres is VMware’s own product based on the open source Postgres.
By default, the access to the vPostgress database is limited to local applications. In other words, if you want to access the database remotely, it will not work. After researching a little, I figured out how to configure the databse for remote access.
VMware has evaluation license for ESXi servers. After 60 days, it expires and you have to apply a paid or free license to continue. Technically, there is a trick to reset the evaluation key by deleting two files (/etc/vmware/vmware.lic and /etc/vmware/license.cfg) and rebooting the server. It’s of course not complying with VMwrae license terms. Under some circumstances like training lab, it may be OK. Make sure to consult VMware on this if you are not working for VMware. But wait – if you are working for VMware, do you need evaluation license? In his reply to my tweet, Duncan mentioned he never saw license expiration.
Although VMware ESXi supports common Linux commands, its implementation is based on busybox. Some of the commands are not supported, or functionalities are reduced. Setting time is one of the cases.
To find out the current time, you issue the following command:
~ # date Sun Jul 13 10:50:59 UTC 2014
Now if you want to use the same date command to change the time, it’s a different story. In fact, the help of the date command works as normal, but when you really type in full command, you’ll see it won’t work.
It’s not common to do something with Java source code programmatically, but I find the javaparser project is very handy if such a use case comes up. It’s a Java 1.5 parser with AST generation and visitor support. With the API, you can access various elements in the source code like class, methods, statements, javadoc, comments, etc.
During software development, we often add lots of logs that help debug and trace the code. When the log files grow bigger, it gets harder to locate the right information of interest. Even we restart the application, the old log remains and new info appends the end of the file unless we delete log file. It’s OK to delete a log file but it’s better to keep it in case for information of previous runs. Here is a trick that I use to make it easier for me to find right log of interest, and it may help you as well.
Once in a while, I got into issues that my build failed because the IDE could not clean certain folder or file. The root cause was that they were opened by another application/process. If the application is known, just closed it and the build worked well. Some times I had no clue which application held the file. To find out quickly without guessing, right tools are needed.
On Linux, it’s quite easy with a command called lsof as follows:
For a long time, VMware wanted to grow upward the stack but did not work out well. Instead, it took the horizontal strategy as I discussed in my blog article two years ago. So far, the new strategy has worked well.
During the last few months, I worked a lot with Cisco UCS Director on daily basis. As I wrote before, UCS Director is a powerful platform for you to manage and orchestrate infrastructures from VMware, Hyper-V, KVM, to the public clouds like Amazon, Azure.
Just like any other management platform, it abstracts the underlying infrastructure and operations using its own concepts and workflows. By exploring its Flex GUI, one can gradually get familiar with these concepts. It takes time to master a product, and no exception for UCS Director. Understanding key concepts and their relationships can help speed up the process significantly.
The JavaFX is not really a new feature, but it’s the first time for it to make into a major Java release. JavaFX has a pretty long history as the next big thing for building cross platform GUI applications. Initially it has its own scripting language and hasn’t made its way in the Java community. The reason is simple: although the JavaFX has richer features on graphics, it does not seem worth learning a new language for it. For a long time, I was wonder why Sun didn’t use the investment to improve its Swing library which has much bigger audience than JavaFX.
I haven’t written Java code to access relational database for a while. Over the years there have been lots of progresses, especially with various Object Relational Mapping (ORM) frameworks. With these frameworks, accessing relational databases becomes pretty easy. In some cases, you don’t have to know SQL at all. Of course understanding SQL is always an advantage.