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package cache
import (
"context"
"errors"
"os"
"sync"
"time"
"gitlab.com/gitlab-org/gitlab-pages/internal/domain"
"gitlab.com/gitlab-org/gitlab-pages/internal/source/gitlab/api"
)
// Entry represents a cache object that can be retrieved asynchronously and
// holds a pointer to *api.Lookup when the domain lookup has been retrieved
// successfully
type Entry struct {
domain string
created time.Time
refreshedOriginalTimestamp time.Time
retrieve *sync.Once
refresh *sync.Once
mux *sync.RWMutex
retrieved chan struct{}
response *api.Lookup
refreshTimeout time.Duration
expirationTimeout time.Duration
retriever *Retriever
}
func newCacheEntry(domain string, refreshTimeout, entryExpirationTimeout time.Duration, retriever *Retriever) *Entry {
return &Entry{
domain: domain,
created: time.Now(),
retrieve: &sync.Once{},
refresh: &sync.Once{},
mux: &sync.RWMutex{},
retrieved: make(chan struct{}),
refreshTimeout: refreshTimeout,
expirationTimeout: entryExpirationTimeout,
retriever: retriever,
}
}
// IsUpToDate returns true if the entry has been resolved correctly and has not
// expired yet. False otherwise.
func (e *Entry) IsUpToDate() bool {
e.mux.RLock()
defer e.mux.RUnlock()
return e.isResolved() && !e.isOutdated()
}
// NeedsRefresh return true if the entry has been resolved correctly but it has
// expired since then.
func (e *Entry) NeedsRefresh() bool {
e.mux.RLock()
defer e.mux.RUnlock()
return e.isResolved() && e.isOutdated()
}
// Lookup returns a retriever Lookup response.
func (e *Entry) Lookup() *api.Lookup {
e.mux.RLock()
defer e.mux.RUnlock()
return e.response
}
// Retrieve perform a blocking retrieval of the cache entry response.
func (e *Entry) Retrieve(ctx context.Context) (lookup *api.Lookup) {
// We run the code within an additional func() to run both `e.setResponse`
// and `e.retrieve.Retrieve` asynchronously.
e.retrieve.Do(func() { go func() { e.setResponse(e.retriever.Retrieve(ctx, e.domain)) }() })
select {
case <-ctx.Done():
lookup = &api.Lookup{Name: e.domain, Error: errors.New("context done")}
case <-e.retrieved:
lookup = e.Lookup()
}
return lookup
}
// Refresh will update the entry in the store only when it gets resolved successfully.
// If an existing successful entry exists, it will only be replaced if the new resolved
// entry is successful too.
// Errored refreshed Entry responses will not replace the previously successful entry.response
// for a maximum time of e.expirationTimeout.
func (e *Entry) Refresh(store Store) {
e.refresh.Do(func() {
go e.refreshFunc(store)
})
}
func (e *Entry) refreshFunc(store Store) {
entry := newCacheEntry(e.domain, e.refreshTimeout, e.expirationTimeout, e.retriever)
entry.Retrieve(context.Background())
// do not replace existing Entry `e.response` when `entry.response` has an error
// and `e` has not expired. See https://gitlab.com/gitlab-org/gitlab-pages/-/issues/281.
if !e.isExpired() && entry.hasTemporaryError() {
entry.response = e.response
entry.refreshedOriginalTimestamp = e.created
}
store.ReplaceOrCreate(e.domain, entry)
}
func (e *Entry) setResponse(lookup api.Lookup) {
e.mux.Lock()
defer e.mux.Unlock()
e.response = &lookup
close(e.retrieved)
}
func (e *Entry) isOutdated() bool {
if !e.refreshedOriginalTimestamp.IsZero() {
return time.Since(e.refreshedOriginalTimestamp) > e.refreshTimeout
}
return time.Since(e.created) > e.refreshTimeout
}
func (e *Entry) isResolved() bool {
return e.response != nil
}
func (e *Entry) isExpired() bool {
if !e.refreshedOriginalTimestamp.IsZero() {
return time.Since(e.refreshedOriginalTimestamp) > e.expirationTimeout
}
return time.Since(e.created) > e.expirationTimeout
}
func (e *Entry) domainExists() bool {
return !errors.Is(e.response.Error, domain.ErrDomainDoesNotExist)
}
// hasTemporaryError checks currently refreshed entry for errors after resolving the lookup again
// and is different to domain.ErrDomainDoesNotExist (this is an edge case to prevent serving
// a page right after being deleted).
func (e *Entry) hasTemporaryError() bool {
if os.Getenv("FF_DISABLE_REFRESH_TEMPORARY_ERROR") == "true" {
return false
}
return e.response != nil &&
e.response.Error != nil &&
e.domainExists()
}
|
