D.Phuong Nguyen phuongdnguyen

Introduction

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About
Usage
Installation

GROKKING NOTES

I liked the way Grokking the coding interview organized problems into learnable patterns. However, the course is expensive and the majority of the time the problems are copy-pasted from leetcode. As the explanations on leetcode are usually just as good, the course really boils down to being a glorified curated list of leetcode problems.

So below I made a list of leetcode problems that are as close to grokking problems as possible.

Pattern: Sliding Window

Overview

Geth (Go-Ethereum) as of July 2022 takes about 650 GiB of space on a fast/snap sync, and then grows by ~ 14 GiB/week with default cache, ~ 8 GiB/week with more cache.

This will fill a 1TB SSD in a few months, to the point where space usage should be brought down again with an offline prune.

There is an odd behavior with Geth 1.10.20 where initial DB size is large after sync until Geth has been restarted twice. This is expected to be fixed soon, possibly as soon as 1.10.21.

Happily, Geth 1.10.x introduces "snapshot offline prune", which brings it back down to about its original size. It takes roughly 4-6 hours to prune the Geth database, and this has to be done while Geth is not running.

Caveat that while several folx have used offline pruning successfully, there is risk associated with it. The two failure mode

Overview

Geth, and other execution clients such as Erigon, Nethermind, and Besu, take some time on shutdown to cleanly close their database. When not given that time, they will need to resync upon restart, often for hours. This gist describes the systemd service file parameter to give them up to 5 minutes of time for a clean shutdown.

Steps

Find your service file. It may be called /etc/systemd/system/geth.service or /etc/systemd/system/eth1.service.
Edit it using sudo nano FILENAME, and add TimeoutStopSec=300 to the [Service] section. Here is an example of a service file after the change:

	aws-profile() {
	read -r -d '' SCRIPT <<'EOF'
	import argparse
	from configparser import RawConfigParser
	import os
	import shutil
	import subprocess
	import sys
	from textwrap import dedent

	package main

	import (
	"fmt"

	pkgerr "github.com/pkg/errors"
	)

	func main() {
	if err := foo(); err != nil {

	package main

	import (
	"context"
	"fmt"
	"math/rand"
	"os"
	"time"
	)

	var x string
	var l int
	func same(i, l int, x string) bool {
	j = i - l
	for k := 0 ; k < l; k ++ {
	// rune
	if x[i-k] != x[j-k] {
	return false
	}
	}

	# one or the other, NOT both

	[url "https://github"]
	insteadOf = git://github

	# or

	[url "[email protected]:"]
	insteadOf = git://github

	#!/bin/bash

	# https://cloud.google.com/compute/docs/faq#find_ip_range
	# nslookup -q=TXT _cloud-netblocks.googleusercontent.com 8.8.8.8

	myarray=()
	for LINE in `dig txt _cloud-netblocks.googleusercontent.com +short \| tr " " "\n" \| grep include \| cut -f 2 -d :`
	do
	myarray+=($LINE)
	for LINE2 in `dig txt $LINE +short \| tr " " "\n" \| grep include \| cut -f 2 -d :`