Documentation
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Overview ¶
Package cache is a thin, nil-safe wrapper around a shared Redis/Valkey instance. It exists for the narrow case a dataset store is the wrong tool for: deciding, among several concurrent callers racing over the same key, which one goes first — something a MergeTree-backed store cannot answer quickly, because a row it was just asked to write is not guaranteed queryable back the instant the write call returns.
Every method is a safe no-op (a permanent miss) on a nil *Client, so a deployment that has not configured Redis keeps working exactly as it did before this package existed: callers fall through to their real source of truth every time.
Index ¶
- type Client
- func (c *Client) Claim(ctx context.Context, key, value string, ttl time.Duration) (claimed bool, current string, err error)
- func (c *Client) Close() error
- func (c *Client) Get(ctx context.Context, key string) (string, bool)
- func (c *Client) Set(ctx context.Context, key, value string, ttl time.Duration)
- func (c *Client) Touch(ctx context.Context, key string, ttl time.Duration)
- type Config
Constants ¶
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Variables ¶
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Functions ¶
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Types ¶
type Client ¶
type Client struct {
// contains filtered or unexported fields
}
func (*Client) Claim ¶
func (c *Client) Claim(ctx context.Context, key, value string, ttl time.Duration) (claimed bool, current string, err error)
Claim atomically sets key to value only if key does not already exist — the primitive a caller needs to pick exactly one winner among several concurrent, otherwise-identical attempts, which Get-then-Set cannot do because two callers can both Get a miss before either Sets.
claimed is true when this call is the one that set it. When it is false, current is whatever value is there now — either another concurrent caller's winning claim, or one set earlier by Set — and the caller should treat that as the answer rather than as a reason to claim again.
A nil Client always reports an unclaimed miss (claimed=false, current="", err=nil): without a real cache behind it there is no winner to pick, and the caller's ordinary fallback path is what decides instead.
func (*Client) Get ¶
Get returns the cached value and whether it was present. A nil Client, a connection error, and an actual miss all read the same to the caller: false — there is no real-time-vs-expired distinction a check-then-act caller needs to make, since all three mean "consult the real source of truth instead."
func (*Client) Set ¶
Set stores value under key for ttl. Best-effort: a write failure here just means the next Get falls through to the real source of truth again, same as if the key had never been set.
Source Files