after filling 13 refactoring issues against the Java Client code[1], I started 
to dig into the server site code to understand the last issues with the Netty 
I feel bad. It's this feeling of "I don't wanna hurt you, but...". ZooKeeper 
is quite an important piece of the Hadoop ecosystem containing some of the 
most complicated pieces of code. And it'll only get more complex with more 

I'd propose to have a word about quality assurance. Is there already a 
strategy to ensure the ongoing maintainability of ZK? Is there a code style 
guide, a list of Dos-And-Donts (where I'd like to add some points)?

Should PMD be added to Hudson? What is the level of FindBugs? Should it be 

Some of the points I'd like to add to a style guide:

- Don't write methods longer then 20-40 lines of code

- Are you sure you want to use inner classes?

- If there is a new operator in a method? Could the method maybe already 
receive the object as a parameter?

- Are you sure you want to use system properties? They are like global 
variables and the IDE does not know about them

- Are you sure you want to extend a class? Often an aggregation is more 

- Don't nest ifs and loops deeper then 2 or 3 levels. If you do so, you should 
better break your code into more methods.

- Use Enums or constants instead of plain status integers

- please document your intentions in code comments. You don't need to comment 
the what? but the why?.

Do you agree with me, that there is a need for better code quality in 
ZooKeeper? If so, it's not really scalable if a manic like me fights like Don 
Quichotte to clean up the code. All developers would need to establish a sense 
for clean code and constantly improve the code.

[1] https://issues.apache.org/jira/browse/ZOOKEEPER-835

Best regards,

Thomas Koch, http://www.koch.ro

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