felixge

{
  "flameExplain": "Go to flame-explain.com and paste this JSON in the Input tab.",
  "input": {
    "plan": "[\n  {\n    \"Plan\": {\n      \"Node Type\": \"Function Scan\",\n      \"Parallel Aware\": false,\n      \"Function Name\": \"generate_series\",\n      \"Schema\": \"pg_catalog\",\n      \"Alias\": \"generate_series\",\n      \"Startup Cost\": 0.00,\n      \"Total Cost\": 10.00,\n      \"Plan Rows\": 1000,\n      \"Plan Width\": 4,\n      \"Actual Startup Time\": 194.503,\n      \"Actual Total Time\": 331.185,\n      \"Actual Rows\": 1500000,\n      \"Actual Loops\": 1,\n      \"Output\": [\"generate_series\"],\n      \"Function Call\": \"generate_series(1, 1500000)\",\n      \"Shared Hit Blocks\": 0,\n      \"Shared Read Blocks\": 0,\n      \"Shared Dirtied Blocks\": 0,\n      \"Shared Written Blocks\": 0,\n      \"Local Hit Blocks\": 0,\n      \"Local Read Blocks\": 0,\n      \"Local Dirtied Blocks\": 0,\n      \"Local Written Blocks\": 0,\n      \"Temp Read Blocks\": 0,\n      \"Temp Written Bloc

felixge

// Example program showing that signal delivery from setitimer ends up in
// "random" threads of the executing program.

#include <sys/time.h>
#include <unistd.h>
#include <signal.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

felixge

// Package multiwrap implements support for wrapping multiple errors into a
// single error value that supports the Go 1.13 Unwrap(), Is() and As()
// interface. It's similar to go-multierror [1].
//
// This is a proof of concept and I'm looking for feedback! Maybe somebody has
// already done a nicer version of this idea?
//
// [1] https://godoc.org/github.com/hashicorp/go-multierror
package multiwrap

felixge

# Here a few bash one-liners that helped me analyze / fight a weak DOS attack against debuggable.com. Mostly for future reference.
# The attacker was opening lots of tcp connections without sending data, I believe it's called a SYN flood, see: http://tools.ietf.org/html/rfc4987#section-3.2

# Step 0: Check what is going on at port 80
$ netstat -tan | grep ':80 ' | awk '{print $6}' | sort | uniq -c

# Step 1: Increase the number of available fds
$ ulimit -n 32000

# Step 2: Restart your webserver, for me:

felixge

  global  main
  extern  printf

  section .text
main:
  sub     rdi, 1  ; argc includes program name, so substract 1 to get arg count
  cmp     rdi, 1  ; check if we got exactly 1 arg
  jne     bad_arg_count ; if not, jump to bad_arg_count
  mov     r15, [rsi+8] ; main's argv[1]
  mov     r14, 0 ; index (also byte count)

felixge

let last = new Date();
setInterval(function () {
  delta = new Date() - last;
  if (delta > 2) {
    console.log(delta);
  }
  last = new Date();
}, 1);

setInterval(function () {

felixge

$ time wc test.txt
 16500000 49252094 2059004431 test.txt

real	0m5.930s
user	0m5.491s
sys	0m0.374s

$ go build wc.go && time ./wc test.txt
16500000 49252094 2059004431

felixge

[
  {
    "Plan": {
      "Node Type": "Nested Loop",
      "Parallel Aware": false,
      "Join Type": "Inner",
      "Startup Cost": 0.01,
      "Total Cost": 17402710335540.01,
      "Plan Rows": 1000000000000000,
      "Plan Width": 20,

felixge

[
  {
    "Plan": {
      "Node Type": "Nested Loop",
      "Parallel Aware": false,
      "Join Type": "Inner",
      "Startup Cost": 0.01,
      "Total Cost": 12522520.01,
      "Plan Rows": 1000000000,
      "Plan Width": 12,

felixge

[
  {
    "Plan": {
      "Node Type": "Seq Scan",
      "Parallel Aware": false,
      "Relation Name": "congrats_on_loading_your_first_gist",
      "Alias": "congrats_on_loading_your_first_gist",
      "Startup Cost": 0.00,
      "Total Cost": 35.50,
      "Plan Rows": 2550,