Vinh v9n

There are three easy to make mistakes in go. I present them here in the way they are often found in the wild, not in the way that is easiest to understand.

All three of these mistakes have been made in Kubernetes code, getting past code review at least once each that I know of.

Loop variables are scoped outside the loop.

What do these lines do? Make predictions and then scroll down.

func print(pi *int) { fmt.Println(*pi) }

Git Cheat Sheet

Commands

Getting Started

git init

or

Hello!

This is a commentary and discussion from walking through what happens on startup in [https://github.com/circleci/frontend], looking at this SHA in December 2014: [https://github.com/circleci/frontend/commit/273558250040ce197e44e683d5528381f36c4eea].

The first part is a literal walkthrough, where I'm tracing my reading of how the code works. This is a way to check my understanding, since of course I don't have all of your context. And it's also a way to echo back to you how someone else might experience this code without that context. The second part is about asking questions, making suggestions, and exploring some paths for making it even more awesome. I also mixed in a few asides in the walkthrough part where I jump ahead a bit.

Doing this with colleagues has worked well for me as a way to do in-depth code reviews about more abstract design and architectural questions. The goal of the the first part is to clarify we're all looking at the same thing, which creates the space and shared understa

UPDATE a fork of this gist has been used as a starting point for a community-maintained "awesome" list: machine-learning-with-ruby Please look here for the most up-to-date info!

Resources for Machine Learning in Ruby

Gems

liblinear-ruby: Ruby interface to LIBLINEAR using SWIG

Combining two git repositories

Use case: You have repository A with remote location rA, and repository B (which may or may not have remote location rB). You want to do one of two things:

preserve all commits of both repositories, but replace everything from A with the contents of B, and use rA as your remote location
actually combine the two repositories, as if they are two branches that you want to merge, using rA as the remote location

NB: Check out git subtree/git submodule and this Stack Overflow question before going through the steps below. This gist is just a record of how I solved this problem on my own one day.

Before starting, make sure your local and remote repositories are up-to-date with all changes you need. The following steps use the general idea of changing the remote origin and renaming the local master branch of one of the repos in order to combine the two master branches.

Channels Are Not Enough

... or Why Pipelining Is Not That Easy

Golang Concurrency Patterns for brave and smart.

By @kachayev

Intro

Each of these commands will run an ad hoc http static server in your current (or specified) directory, available at http://localhost:8000. Use this power wisely.

Discussion on reddit.

Python 2.x

$ python -m SimpleHTTPServer 8000

Next Steps

Measure time spend on index, flush, refresh, merge, query, etc. (TD - done)
Take hot threads snapshots under read+write, read-only, write-only (TD - done)
Adjust refresh time to 10s (from 1s) and see how load changes (TD)
Measure time of a rolling restart doing disable_flush and disable_recovery (TD)
Specify routing on query -- make it choose same node for each shard each time (MD)
GC new generation size (TD)
Warmers

measure before/after of client query time with and without warmers (MD)


	location ~* ^/s3/(.*) {
	set $bucket '<REPLACE WITH YOUR S3 BUCKET NAME>';
	set $aws_access '<REPLACE WITH YOUR AWS ACCESS KEY>';
	set $aws_secret '<REPLACE WITH YOUR AWS SECRET KEY>';
	set $url_full "$1";
	set_by_lua $now "return ngx.cookie_time(ngx.time())";
	set $string_to_sign "$request_method\n\n\n\nx-amz-date:${now}\n/$bucket/$url_full";
	set_hmac_sha1 $aws_signature $aws_secret $string_to_sign;
	set_encode_base64 $aws_signature $aws_signature;

	App configuration in environment variables: for and against

	For (some of these as per the 12 factor principles)

	1) they are are easy to change between deploys without changing any code

	2) unlike config files, there is little chance of them being checked
	into the code repo accidentally

	3) unlike custom config files, or other config mechanisms such as Java