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{{/* 
    Flickr shortcode for Hugo
    Usage: {{< flickr photo_url="https://www.flickr.com/photos/username/1234567890" title="Photo title" >}}
    Parameters:
        photo_url: URL of the photo on Flickr
        title: Title of the photo
        caption: Caption of the photo (disables EXIF info)
        href: URL of the link (overrides photo_url)
    Output:
        <figure>

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Exiftool Examples

Following is a collection of real exiftool commands that I've used, along with explanations of what each does. exiftool is a command-line utility that provides very powerful EXIF reading, writing and searching capabilities.

I'm writing this down because I often spend a lot of time reading through exiftool documentation to find out how to get something done, just to forget it within hours. All of these examples work on a Unix shell environment like ZSH on MacOS or the various Linux shells.

Extracting EXIF Information

What does EXIF data look like? Let's try the following on an image file, DSC09535.JPG:

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package main

import (
	"fmt"
	"github.com/gomodule/redigo/redis"
	"sync"
	"time"
)

var rconns *redis.Pool

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package main

import (
	"fmt"
	"github.com/gomodule/redigo/redis"
	redsync "gopkg.in/redsync.v1"
	"sync"
	"sync/atomic"
	"time"
)

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// BEBOSchedule computes a Binary Exponential Back-Off schedule given the following:
// 	retries:  maximum number of retry attempts
// 	waittime: maximum number of seconds from the first attempt after which the operation is permanently failed
//
// The schedule is returned as a list of seconds since first attempt at which a retry must be made
// The schedule will have as many entries as the maximum number of attempts given

func BEBOSchedule(retries, waittime int) ([]uint, error) {
	if retries <= 0 || waittime <= 0 || waittime < 1<<uint(retries)-1 {
		return []uint{}, fmt.Errorf("Invalid retries or waittime")

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package main

import (
	"fmt"
	"math"
)

func max(l, r float64) float64 {
	if l > r {
		return l

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Error Handling 1-2-3

As we build infrastructure components that support a large user base, it becomes critical to be able to provide quick support to end users. A large chunk of support issues simply arise due to end users encountering an error that they are clueless about. E.g. an HTTP 500 error with a generic "failed to do " message leads the user to a dead end and causes frustration.

Apart from clear messaging to the end user, it's also important to provide maximum visibility into error logs, so that someone who is looking at the logs should be able to determine – even without being familiar with the system – whether the cause of the error is internal or external. This is extremely critical in high utilisation network applications because usually the source of error is an external failure rather than a code bug.

As an example of very poor logging, the other day I logged into a service backend hoping to find some trace of user reported issues in the error logs. After filtering out all

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package main

import (
	"context"
	"fmt"
	etcc "github.com/coreos/etcd/clientv3"
	etcsync "github.com/coreos/etcd/clientv3/concurrency"
	"time"
)

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package main

import (
	"context"
	"fmt"
	etcc "github.com/coreos/etcd/clientv3"
	"strconv"
	"time"
)

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package main

import (
	"bytes"
	"fmt"
	"sync"
	"strings"
)

// Stores the filesystem hierarchy, data node members and their capacity