Fault-tolerant work fl ow orchestration in PHP Sebastian Grodzicki @ PHPCon Poland 2024 

Sebastian Grodzicki • CTO @ • ex-Google/Elastic/SHOWROOM/GoldenLine • PHP developer for 20+ years • PHPCon speaker/attendee for 10+ years •  @sebgrodzicki phpinfo(); 

The Need for Fault Tolerance • Application failures and crashes • Network outages • Flaky endpoints • Long-running processes • …and more. 

Event-Driven Architectures 

SAGA & Distributed Transactions 

State Machines 

Batch Processing 

Scheduled Jobs & Cron 

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Why Temporal? • Reliable distributed applications • Productive development paradigms and code structure • Visible distributed application state 

Why Temporal? Temporal works with your preexisting choices for: • runtime, • test framework, • deployment, • continuous integration, • web frameworks, • …and more. 

Why Temporal? Temporal allows you to develop with durable execution in di ff erent languages and multiple languages can be used to build single services, enabling polyglot development. 

Why Temporal? Temporal is built in the open and released under the MIT license. It has been endorsed by some of the world's best companies and is loved by a growing, vibrant community. 

– Rob Zienert, Senior Software Engineer @ Net fl ix "Net fl ix engineers spend less time writing logic to maintain application consistency or guard against failures because Temporal does it for them. The Temporal platform is easy to operate and fi ts naturally in our development work fl ow." 

– Mitchell Hashimoto, Co-founder @ Hashicorp "Temporal's technology satis fi ed all of these requirements out of the box and allowed our developers to focus on business logic. Without Temporal's technology, we would've spent a signi fi cant amount of time rebuilding Temporal and would've very likely done a worse job." 

– Sebastian Grodzicki, CTO @ Levity "Temporal has been a game-changer for our team. By abstracting away the complexities of building scalable distributed systems, it has allowed us to focus on delivering value to our customers at a much faster pace." 

The Building Blocks • Work fl ow: your business logic, de fi ned in code, outlining each step in your process. • Activities: individual units of work in your Work fl ow. • SDK: everything needed to build Work fl ows, Activities, and various other Temporal features in a speci fi c programming language. • Temporal Service: a set of services and components on your own infrastructure (or Temporal Cloud). 

Building Work fl ows in PHP • PHP SDK: $ composer require temporal/sdk • Temporal CLI: $ brew install temporal (on macOS) $ temporal server start-dev 

Demo: Money Transfer #[WorkflowInterface] interface AccountTransferWorkflowInterface { #[WorkflowMethod(name: "MoneyTransfer")] public function transfer( string $fromAccountId, string $toAccountId, string $referenceId, int $amountCents ); } 

Demo: Money Transfer #[ActivityInterface(prefix: "MoneyTransfer.")] interface AccountInterface { public function deposit(string $accountId, string $referenceId, int $amountCents): void; public function withdraw(string $accountId, string $referenceId, int $amountCents): void; } 

Demo: Money Transfer class AccountTransferWorkflow implements AccountTransferWorkflowInterface { private AccountInterface $account; public function __construct() { $this->account = Workflow::newActivityStub( AccountInterface::class, ActivityOptions::new() ->withStartToCloseTimeout(CarbonInterval::seconds(5)) ->withRetryOptions(RetryOptions::new()->withMaximumAttempts(10)) ); } public function transfer(string $fromAccountId, string $toAccountId, string $referenceId, int $amountCents) { yield $this->account->withdraw($fromAccountId, $referenceId, $amountCents); yield $this->account->deposit($toAccountId, $referenceId, $amountCents); } } 

Demo: Money Transfer class AccountActivity implements AccountInterface { public function deposit(string $accountId, string $referenceId, int $amountCents): void { $this->log( "Withdraw to %s of %d cents requested. ReferenceId=%s\n", $accountId, $amountCents, $referenceId ); // throw new \RuntimeException("simulated"); // Uncomment to simulate failure } public function withdraw(string $accountId, string $referenceId, int $amountCents): void { $this->log( "Deposit to %s of %d cents requested. ReferenceId=%s\n", $accountId, $amountCents, $referenceId ); } } 

Demo: Money Transfer class ExecuteCommand extends Command { protected const NAME = 'money-transfer'; protected const DESCRIPTION = 'Execute MoneyTransferWorkflow'; public function execute(InputInterface $input, OutputInterface $output): int { $workflow = $this->workflowClient->newWorkflowStub(AccountTransferWorkflowInterface::class); $output->writeln("Starting MoneyTransferWorkflow... "); // runs in blocking mode $workflow->transfer( 'fromID', 'toID', 'refID', 1000 ); $output->writeln("Workflow complete"); return self::SUCCESS; } } 

Demo: Subscription #[WorkflowInterface] interface SubscriptionWorkflowInterface { #[WorkflowMethod] public function subscribe( string $userID ); } 

Demo: Subscription #[ActivityInterface(prefix: "Subscription.")] interface AccountActivityInterface { public function sendWelcomeEmail(string $userID): void; public function chargeMonthlyFee(string $userID): void; public function sendEndOfTrialEmail(string $userID): void; public function sendMonthlyChargeEmail(string $userID): void; public function sendSorryToSeeYouGoEmail(string $userID): void; public function processSubscriptionCancellation(string $userID): void; } 

Demo: Subscription class SubscriptionWorkflow implements SubscriptionWorkflowInterface { private $account; public function __construct() { $this->account = Workflow::newActivityStub( AccountActivityInterface::class, ActivityOptions::new() ->withScheduleToCloseTimeout(CarbonInterval::seconds(2)) ); } public function subscribe(string $userID){...} } 

Demo: Subscription class SubscriptionWorkflow implements SubscriptionWorkflowInterface { public function subscribe(string $userID) { yield $this->account->sendWelcomeEmail($userID); try { $trialPeriod = true; while (true) { // Lower period duration to observe workflow behaviour yield Workflow::timer(CarbonInterval::days(30)); if ($trialPeriod) { yield $this->account->sendEndOfTrialEmail($userID); $trialPeriod = false; continue; } yield $this->account->chargeMonthlyFee($userID); yield $this->account->sendMonthlyChargeEmail($userID); } } catch (CanceledFailure $e) { yield Workflow::asyncDetached( function () use ($userID) { yield $this->account->processSubscriptionCancellation($userID); yield $this->account->sendSorryToSeeYouGoEmail($userID); } ); } } } 

Demo: Subscription class SubscribeCommand extends Command { protected const NAME = 'subscribe:start'; protected const DESCRIPTION = 'Execute Subscription\SubscriptionWorkflow with custom user ID'; protected const ARGUMENTS = [ ['userID', InputArgument::REQUIRED, 'Unique user ID'] ]; public function execute(InputInterface $input, OutputInterface $output): int{...} } 

Demo: Subscription class SubscribeCommand extends Command { public function execute(InputInterface $input, OutputInterface $output): int { $userID = $input->getArgument('userID'); $workflow = $this->workflowClient->newWorkflowStub( SubscriptionWorkflowInterface::class, WorkflowOptions::new() ->withWorkflowId('subscription:' . $userID) ->withWorkflowIdReusePolicy(IdReusePolicy::POLICY_ALLOW_DUPLICATE) ); $output->writeln("Start SubscriptionWorkflow... "); try { $run = $this->workflowClient->start($workflow, $userID); } catch (WorkflowExecutionAlreadyStartedException $e) { $output->writeln('Already running'); return self::SUCCESS; } $output->writeln( sprintf( 'Started: WorkflowID=%s, RunID=%s', $run->getExecution()->getID(), $run->getExecution()->getRunID(), ) ); return self::SUCCESS; } } 

Demo: Subscription class CancelCommand extends Command { protected const NAME = 'subscribe:cancel'; protected const DESCRIPTION = 'Cancel Subscription\SubscriptionWorkflow for user ID'; protected const ARGUMENTS = [ ['userID', InputArgument::REQUIRED, 'Unique user ID'] ]; public function execute(InputInterface $input, OutputInterface $output): int { $userID = $input->getArgument('userID'); $workflow = $this->workflowClient->newUntypedRunningWorkflowStub('subscription:' . $userID); try { $workflow->cancel(); $output->writeln('Cancelled'); } catch (WorkflowNotFoundException $e) { $output->writeln('Already stopped'); } return self::SUCCESS; } } 

Event-Driven Architectures 

SAGA & Distributed Transactions 

State Machines 

Batch Processing 

Scheduled Jobs & Cron 

Resources • https://temporal.io • https://docs.temporal.io/develop/php/ • https://learn.temporal.io/ • https://github.com/temporalio/samples-php 

Questions? 

Thank you! 

joind.in/talk/56805