jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

tototoshi

-- http://stackoverflow.com/questions/1124603/grouped-limit-in-postgresql-show-the-first-n-rows-for-each-group
-- http://www.postgresql.jp/document/9.2/html/tutorial-window.html

CREATE TABLE empsalary (
  depname varchar(10) not null
  , empno integer not null
  , salary integer not null
);

INSERT INTO empsalary (depname, empno, salary) VALUES ('develop', 11, 5200);

qwo

xxx,

Thanks again for taking the time to speak with me and for sending me your information.  I'm excited to tell you that we would like to move forward in the process!

One of our coordinators will be emailing you within the next week from an @google.com domain with the date and time of your phone interview.  In the meantime, I've included some preparation materials (below.)

Please note this will be a technical interview that will last for approximately 45 minutes. Google takes an academic approach to the interviewing process. This means that we are interested in your thought process, your approach to problem solving as well as your coding abilities. You may be asked questions that relate to technical knowledge, algorithms, coding, performance, how to test solutions, and perhaps your interest in Google products. The best advice that I can give you is to treat the interview like a conversation, talk through the problems, and please feel free to ask the interviewer if you are not clear with any of the questio

rkaneko

Installing zsh on CentOS

$ sudo yum install ncurses-devel

$ cd /usr/local/src

$ sudo curl -L http://sourceforge.net/projects/zsh/files/zsh/5.0.7/zsh-5.0.7.tar.gz/download -o zsh-5.0.7.tar.gz

jbeda

$ gsutil ls -R gs://kubernetes-release/release/v0.5.4 | sed 's|gs://kubernetes-release|https://storage.googleapis.com/kubernetes-release|; /^.*:$/d; /^$/d'
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/kubernetes-client-darwin-386.tar.gz
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/kubernetes-client-darwin-amd64.tar.gz
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/kubernetes-client-linux-386.tar.gz
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/kubernetes-client-linux-amd64.tar.gz
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/kubernetes-client-linux-arm.tar.gz
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/kubernetes-salt.tar.gz
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/kubernetes-server-linux-amd64.tar.gz
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/kubernetes.tar.gz
https://storage.googleapis.com/kubernetes-release/release/v0.5.4/bin/darwin/386/kubecfg

logrusorgru

-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
--                                                                            --
--                                  mysql                                     --
--                                                                            --
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

--
-- mysql <http://sqlfiddle.com/#!9/91afb5/2>
--        note: sqlfiddle is very stupid

ursuad

Kafka Topics

List existing topics

bin/kafka-topics.sh --zookeeper localhost:2181 --list

Describe a topic

bin/kafka-topics.sh --zookeeper localhost:2181 --describe --topic mytopic

Purge a topic

bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic mytopic --config retention.ms=1000

... wait a minute ...

simonw

How to recover lost Python source code if it's still resident in-memory

I screwed up using git ("git checkout --" on the wrong file) and managed to delete the code I had just written... but it was still running in a process in a docker container. Here's how I got it back, using https://pypi.python.org/pypi/pyrasite/ and https://pypi.python.org/pypi/uncompyle6

Attach a shell to the docker container

Install GDB (needed by pyrasite)

apt-get update && apt-get install gdb

polvi

Easiest HDFS cluster in the world with kubernetes.

Inspiration from kimoonkim/kubernetes-HDFS

kubectl create -f namenode.yaml
kubectl create -f datanode.yaml

Setup a port-forward to so you can see it is alive:

djspiewak

Quick Tips for Fast Code on the JVM

I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.

This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea