49 lines
1.7 KiB
Go
49 lines
1.7 KiB
Go
package cache
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import (
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"time"
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)
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// Type implements the logic to fetch certain types of data.
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type Type interface {
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// Fetch fetches a single unique item.
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//
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// The FetchOptions contain the index and timeouts for blocking queries.
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// The MinIndex value on the Request itself should NOT be used
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// as the blocking index since a request may be reused multiple times
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// as part of Refresh behavior.
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//
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// The return value is a FetchResult which contains information about
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// the fetch. If an error is given, the FetchResult is ignored. The
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// cache does not support backends that return partial values.
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//
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// On timeout, FetchResult can behave one of two ways. First, it can
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// return the last known value. This is the default behavior of blocking
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// RPC calls in Consul so this allows cache types to be implemented with
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// no extra logic. Second, FetchResult can return an unset value and index.
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// In this case, the cache will reuse the last value automatically.
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Fetch(FetchOptions, Request) (FetchResult, error)
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}
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// FetchOptions are various settable options when a Fetch is called.
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type FetchOptions struct {
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// MinIndex is the minimum index to be used for blocking queries.
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// If blocking queries aren't supported for data being returned,
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// this value can be ignored.
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MinIndex uint64
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// Timeout is the maximum time for the query. This must be implemented
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// in the Fetch itself.
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Timeout time.Duration
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}
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// FetchResult is the result of a Type Fetch operation and contains the
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// data along with metadata gathered from that operation.
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type FetchResult struct {
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// Value is the result of the fetch.
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Value interface{}
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// Index is the corresponding index value for this data.
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Index uint64
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}
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