72 lines
2.9 KiB
Go
72 lines
2.9 KiB
Go
package cache
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import (
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"time"
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)
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// Request is a cacheable request.
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//
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// This interface is typically implemented by request structures in
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// the agent/structs package.
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type Request interface {
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// CacheInfo returns information used for caching this request.
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CacheInfo() RequestInfo
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}
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// RequestInfo represents cache information for a request. The caching
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// framework uses this to control the behavior of caching and to determine
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// cacheability.
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//
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// TODO(peering): finish ensuring everything that sets a Datacenter sets or doesn't set PeerName.
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// TODO(peering): also make sure the peer name is present in the cache key likely in lieu of the datacenter somehow.
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type RequestInfo struct {
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// Key is a unique cache key for this request. This key should
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// be globally unique to identify this request, since any conflicting
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// cache keys could result in invalid data being returned from the cache.
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// The Key does not need to include ACL or DC information, since the
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// cache already partitions by these values prior to using this key.
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Key string
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// Token is the ACL token associated with this request.
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//
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// Datacenter is the datacenter that the request is targeting.
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//
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// PeerName is the peer that the request is targeting.
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//
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// All of these values are used to partition the cache. The cache framework
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// today partitions data on these values to simplify behavior: by
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// partitioning ACL tokens, the cache doesn't need to be smart about
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// filtering results. By filtering datacenter/peer results, the cache can
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// service the multi-DC/multi-peer nature of Consul. This comes at the expense of
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// working set size, but in general the effect is minimal.
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Token string
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Datacenter string
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PeerName string
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// MinIndex is the minimum index being queried. This is used to
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// determine if we already have data satisfying the query or if we need
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// to block until new data is available. If no index is available, the
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// default value (zero) is acceptable.
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MinIndex uint64
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// Timeout is the timeout for waiting on a blocking query. When the
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// timeout is reached, the last known value is returned (or maybe nil
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// if there was no prior value). This "last known value" behavior matches
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// normal Consul blocking queries.
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Timeout time.Duration
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// MaxAge if set limits how stale a cache entry can be. If it is non-zero and
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// there is an entry in cache that is older than specified, it is treated as a
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// cache miss and re-fetched. It is ignored for cachetypes with Refresh =
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// true.
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MaxAge time.Duration
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// MustRevalidate forces a new lookup of the cache even if there is an
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// existing one that has not expired. It is implied by HTTP requests with
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// `Cache-Control: max-age=0` but we can't distinguish that case from the
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// unset case for MaxAge. Later we may support revalidating the index without
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// a full re-fetch but for now the only option is to refetch. It is ignored
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// for cachetypes with Refresh = true.
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MustRevalidate bool
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}
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