Kostiantyn Hantsov kgantsov

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

Transforming Code into Beautiful, Idiomatic Python

Notes from Raymond Hettinger's talk at pycon US 2013 video, slides.

The code examples and direct quotes are all from Raymond's talk. I've reproduced them here for my own edification and the hopes that others will find them as handy as I have!

Looping over a range of numbers

for i in [0, 1, 2, 3, 4, 5]:

	- What do Etcd, Consul, and Zookeeper do?
	- Service Registration:
	- Host, port number, and sometimes authentication credentials, protocols, versions
	numbers, and/or environment details.
	- Service Discovery:
	- Ability for client application to query the central registry to learn of service location.
	- Consistent and durable general-purpose K/V store across distributed system.
	- Some solutions support this better than others.
	- Based on Paxos or some derivative (i.e. Raft) algorithm to quickly converge to a consistent state.
	- Centralized locking can be based on this K/V store.

	rabbitmqctl add_user someuser somepass
	rabbitmqctl set_user_tags someuser administrator
	rabbitmqctl set_permissions -p / someuser "." "." ".*"

	Enable admin:
	rabbitmq-plugins enable rabbitmq_management

	rabbitmqadmin list queues