Green ELEPHPANT

How to create sustainable PHP applications

Carsten Windler

vs.

Carsten Windler

Principal Backend Engineer

Worldwide greenhouse gas emissions

Information and communications technology

OUR PROBLEM

Solutions(?)

Compensation

CCS

Renewables

https://www.pexels.com/photo/green-pine-trees-1179229/
https://www.boell.de/en/2015/11/10/carbon-capture-and-storage-problems-depth
https://www.pexels.com/photo/alternative-energy-blade-blue-clouds-414928/

...but...

https://unsplash.com/photos/iy8h-Cl8MLc
https://www.pexels.com/photo/man-in-white-coat-doing-an-experiment-8326464/
https://www.coursehero.com/study-guides/physics/15-5-applications-of-thermodynamics-heat-pumps-and-refrigerators/

Green IT

GREEN SOFTWARE ENGINEERING

SHIFT

RETHINK

REDUCE

GREEN SOFTWARE ENGINEERING

SHIFT

RETHINK

REDUCE

CPU usage =

Power consumption =

Carbon emissions

How to reduce emissions?

Network usage =

Power consumption =

Carbon emissions

How to reduce emissions?

Storage usage =

Power consumption =

Carbon emissions

How to reduce emissions?

2 Bytes

1,900 Bytes

vs.

200,000 Bytes

Lean software =

Less waste =

Less emissions

Embodied 83%

Network and

data centres
15%

Electricity use 2%

Embodied carbon

≈ 500 kgCO2e

How do we achieve that with PHP?

?

Algorithms

How to chose the right algorithm
Big O Notation:
O(1), O(N), O(N²), O(2^N), O(log N)

👉 Use native functions, since compiled

👉 Use the right function for the job

Performance Measurement

class StringPositionBench
{
    #[Bench\Revs(1000)]
    #[Bench\Iterations(5)]
    public function benchStrContains()
    {
        str_contains('string contains PHP', 'PHP');
    }

    #[Bench\Revs(1000)]
    #[Bench\Iterations(5)]
    public function benchPregMatch()
    {
        preg_match("/php/i", 'string contains PHP');
    }
}

https://github.com/phpbench/phpbench

Performance Measurement

Debugging & Profiling

Performance Improvements

Caching
- In-Memory-Caching (i.e. storing values in variables)
- Redis, Memcached
- ....
Optimize code execution
- Avoid costly operation
- Move costly operations out of the loop
- Order of conditions in if clauses
- ....

Danger zone: Packages

Are packages always necessary?

Danger zone: Packages

class DateFormatBench
{
    public function benchDate()
    {
        date('D M d Y H:m:s');
    }

    public function benchDateTime()
    {
        (new \DateTime())->format('D M d Y H:m:s');
    }

    public function benchCarbon()
    {
        (new Carbon\Carbon())->format('D M d Y H:m:s');
    }
}

Database

Use the right tool for the job
- SQL for logging or unstructured data?
Learn about performance tweaks
- Indexes!!!1
- Slow query log
- EXPLAIN statement
- ...
Use large test data locally
- Spot problems early

Danger zone: ORM

PerformanceTest::where('some_flag', '=', 1)->get();
// Time: 2.10s
// Memory Peak: 372.92 MB


DB::select(
  'SELECT * FROM performance_tests WHERE some_flag = 1'
);
// Time: 0.95s (=> 0.45x)
// Memory Peak: 246.06 MB

Test setup:

performance_tests with 500.000 rows
half of them have some_flag = 1
PerformanceTest model

Danger zone: ORM

PerformanceTest::where('some_flag', '=', 1)->cursor();
// Time: 2.640s (=> 1.25x)
// Memory Peak: 81.64 MB


DB::cursor(
  'SELECT * FROM performance_tests WHERE some_flag = 1'
);
// Time: 0.70s (=> 0.38x)
// Memory Peak: 85.88 MB

Danger zone: ORM

PerformanceTest::get()->where('some_flag', '=', 1);
// Time: 5.05s
// Memory Peak: 701.77 MB 

PerformanceTest::where('some_flag', '=', 1)->get();
// Time: 2.10s
// Memory Peak: 372.92 MB

Danger zone: ORM

DB::cursor(
   'SELECT id, first_name, last_name 
   FROM performance_tests WHERE some_flag = 1'
);
// Time: 0.60s
// Memory Peak: 66.49 MB

https://www.pexels.com/photo/stopwatch-on-smartphone-4114778/

APIs

Source: Cloudflare

APIs

Reduce amount of data transferred
Split up endpoints
- GET /users/12
- GET /users/34/address
Specify fields
- GET /users/56?fields=id,last_name
Caching
- Client- and server-side
GraphQL

Storage

Log only what is necessary
Data retention
Compression / file formats
Garbage collectors

https://www.pexels.com/photo/black-trash-bin-with-full-of-trash-3806764/

We can only optimize code so much.

What else can we do?

?

GREEN SOFTWARE ENGINEERING

SHIFT

RETHINK

REDUCE

gCO2eq/kWh

Let's become CARBON AWARE

!

Temporal Shifting

Do things WHEN carbon intensity is LOW

!

Temporal Shifting

...but how do we know?

Temporal Shifting

use GreenElephpant\CarbonAware\Connector\Co2Signal;
use GreenElephpant\CarbonAware\CarbonAwareService;

$co2SignalConnector = new Co2Signal('my_apikey');
$carbonAwareService = new CarbonAwareService($co2SignalConnector);

if ($carbonAwareService->isLow()) {
    $schedule
        ->command('reports:generate')
        ->everyHour();
}

https://unsplash.com/photos/D0y9rNIN-IE

Carbon Forecast

Demand Shaping

Do LESS when the carbon intensity is HIGH

!

Demand Shaping

if ($carbonAwareService->isLow()) {
    $schedule
        ->command('dashboard:update')
        ->everyFiveMinutes();
} else {
    $schedule
        ->command('dashboard:update')
        ->everyTenMinutes();
}

Geospatial Shifting