SlotCache

Reading and writing a slot’s rendered content to the shared cache.

Two things here are not a plain get/set.

The key has to change whenever anything the render depended on changes, so it folds in the module, action, output type, a digest of the slot’s arguments, and — when the action declares cache tags — the current version of each tag’s namespace. Bumping a tag’s version therefore invalidates every slot carrying it without touching the cache itself.

The payload carries its own monotonic expiry stamp, checked independently of the backend’s wall-clock expiry, so a cache whose clock disagrees with this process cannot serve content the slot already considers stale.

A cache that cannot be read or written is a miss, never an error: the page is still correct, only slower, and that is not worth failing a request over. It is reported, because a cache silently doing nothing is a performance cliff nobody notices.

Synopsis

final readonly class SlotCache

Source	Execution/Slot/SlotCache.php

Constructor

__construct()

public function __construct(CategoryLogger $logger, string $slotKey, RandomnessInterface $randomness = new SystemRandomness(…)): mixed

Parameter	Type	Description
$logger	CategoryLogger
$slotKey	string
$randomness	RandomnessInterface

Returns mixed

Methods

Method	Description
decode(mixed $cached): ?string	Unwraps a stored payload, or null when it is a miss or has expired.
encode(string $content, ?int $ttl): string	Wraps content with its expiry stamp when an explicit TTL is given.
keyFor(string $module, string $action, string $outputType, array<string, mixed> $parameters, array<int, mixed> $tags): string	Composes the cache key for one slot render.
read(string $cacheKey): ?string	The cached content, or null on a miss, an expired stamp, or an unreadable cache.
write(string $cacheKey, string $content, ?int $ttl): void	Stores the rendered content.

decode()

public function decode(mixed $cached): ?string

Unwraps a stored payload, or null when it is a miss or has expired.

An unwrapped string is always a hit: it was stored without a TTL, so its freshness is the backend’s business.

Parameter	Type	Description
$cached	mixed

Returns ?``string

encode()

public function encode(string $content, ?int $ttl): string

Wraps content with its expiry stamp when an explicit TTL is given.

Without one the backend’s own default expiry governs and the content is stored raw. Content that will not survive json_encode is also stored raw rather than dropped: losing the entry is worse than losing its stamp.

Parameter	Type	Description
$content	string
$ttl	?``int

Returns string

keyFor()

public function keyFor(string $module, string $action, string $outputType, array<string, mixed> $parameters, array<int, mixed> $tags): string

Composes the cache key for one slot render.

Parameter	Type	Description
$module	string
$action	string
$outputType	string
$parameters	array``<``string``, ``mixed``>
$tags	array``<``int``, ``mixed``>

Returns string

read()

public function read(string $cacheKey): ?string

The cached content, or null on a miss, an expired stamp, or an unreadable cache.

Parameter	Type	Description
$cacheKey	string

Returns ?``string

write()

public function write(string $cacheKey, string $content, ?int $ttl): void

Stores the rendered content.

A failure leaves the page correct and only slower.

Parameter	Type	Description
$cacheKey	string
$content	string
$ttl	?``int