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<?php |
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/** |
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* Request-boundary write coalescing. |
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* |
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* @package WCPOS\WooCommercePOS\Sync |
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*/ |
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|
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namespace WCPOS\WooCommercePOS\Sync; |
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|
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/** |
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* Coalesce repeated saves into one write per record between flushes. |
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* |
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* WooCommerce saves records repeatedly within one request. Keep the last |
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* non-null payload per blog/type/id until the owner needs the settled write. |
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* A new record beyond capacity flushes first, bounding bulk-import queues; |
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* capacity one also preserves the journal's ordering across different orders. |
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* Entries retain their blog so multisite switches cannot redirect writes. |
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* |
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* Owners flush last on shutdown: WooCommerce saves the customer at priority |
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* 10 and the session at 20 (which can fire woocommerce_update_customer). |
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* The shutdown latch makes any later save write immediately, not wait for a |
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* flush that will never come. Draining before writes prevents replay after an |
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* exception and lets reentrant saves start a fresh queue. |
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*/ |
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final class Request_Write_Queue { |
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/** |
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* Maximum pending distinct records. |
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* |
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* @var int |
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*/ |
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private int $capacity; |
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|
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/** |
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* Writer receiving type, id and payload under the entry's blog. |
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* |
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* @var callable |
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*/ |
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private $write; |
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|
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/** |
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* Pending [blog, type, id, payload] entries. |
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* |
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* @var array<string, array> |
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*/ |
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private array $entries = array(); |
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|
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/** |
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* Whether the final request-boundary flush has begun. |
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* |
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* @var bool |
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*/ |
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private bool $shutdown_flushed = false; |
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|
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/** |
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* Bind a writer and its pending-record capacity. |
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* |
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* @param int $capacity Maximum pending distinct records. |
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* @param callable $write Writer receiving type, id and payload. |
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*/ |
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public function __construct( int $capacity, callable $write ) { |
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$this->capacity = $capacity; |
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$this->write = $write; |
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} |
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|
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/** |
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* Owe one write, or write immediately after shutdown. |
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* |
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* @param string $type Record type. |
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* @param int $id Record id. |
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* @param mixed $payload Optional write context; null retains existing context. |
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*/ |
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public function owe( string $type, int $id, $payload = null ): void { |
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if ( $this->shutdown_flushed ) { |
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( $this->write )( $type, $id, $payload ); |
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return; |
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} |
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$key = $this->key( $type, $id ); |
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// A capacity flush runs writers that may re-enter owe(), so the pending |
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// state is re-read after each flush: the key may now be pending (keep it, |
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// merge the payload) or the queue full again. One re-check is enough for |
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// any real writer; a pathological one that refills the queue on every |
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// flush is then allowed a bounded overflow rather than an endless loop. |
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for ( $attempt = 0; $attempt < 2; $attempt++ ) { |
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if ( isset( $this->entries[ $key ] ) ) { |
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// After a flush the pending payload came from a re-entered writer and |
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// is newer than this call's; only fill a gap then. |
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if ( null !== $payload && ( 0 === $attempt || null === $this->entries[ $key ][3] ) ) { |
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$this->entries[ $key ][3] = $payload; |
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} |
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return; |
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} |
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if ( count( $this->entries ) < $this->capacity ) { |
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break; |
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} |
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$this->flush(); |
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} |
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$this->entries[ $key ] = array( get_current_blog_id(), $type, $id, $payload ); |
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} |
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|
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/** |
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* Whether this blog owes a write for the record. |
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* |
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* @param string $type Record type. |
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* @param int $id Record id. |
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* @return bool |
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*/ |
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public function owes( string $type, int $id ): bool { |
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return isset( $this->entries[ $this->key( $type, $id ) ] ); |
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} |
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|
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/** |
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* Forget this blog's pending write without writing it. |
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* |
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* @param string $type Record type. |
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* @param int $id Record id. |
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*/ |
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public function drop( string $type, int $id ): void { |
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unset( $this->entries[ $this->key( $type, $id ) ] ); |
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} |
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|
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/** Drain before writing so exceptions and reentrant saves cannot replay entries. */ |
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public function flush(): void { |
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$entries = $this->entries; |
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$this->entries = array(); |
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foreach ( $entries as $entry ) { |
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list( $blog, $type, $id, $payload ) = $entry; |
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$switch = is_multisite() && get_current_blog_id() !== $blog; |
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if ( $switch ) { |
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switch_to_blog( $blog ); |
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} |
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try { |
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( $this->write )( $type, $id, $payload ); |
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} finally { |
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if ( $switch ) { |
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restore_current_blog(); |
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} |
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} |
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} |
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} |
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|
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/** Latch even an empty queue so subsequent saves write immediately. */ |
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public function flush_at_shutdown(): void { |
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$this->shutdown_flushed = true; |
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$this->flush(); |
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} |
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|
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/** Discard entries and the shutdown latch. Tests only. */ |
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public function reset(): void { |
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$this->entries = array(); |
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$this->shutdown_flushed = false; |
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} |
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|
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/** |
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* Scope a record to its current blog. |
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* |
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* @param string $type Record type. |
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* @param int $id Record id. |
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* @return string |
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*/ |
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private function key( string $type, int $id ): string { |
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return get_current_blog_id() . ':' . $type . ':' . $id; |
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} |
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} |
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|
