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Switch pager to return whether the result was paginated

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Kubernetes-commit: 5dcf08c1993718e94cf6537af50e0a411dd2878c
This commit is contained in:
wojtekt
2020-01-28 09:39:27 +01:00
committed by Kubernetes Publisher
parent 5534e24283
commit 0e2dbbf70a
4 changed files with 144 additions and 52 deletions
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57
tools/cache/reflector.go vendored
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@@ -75,6 +75,9 @@ type Reflector struct {
ShouldResync func() bool
// clock allows tests to manipulate time
clock clock.Clock
// paginatedResult defines whether pagination should be forced for list calls.
// It is set based on the result of the initial list call.
paginatedResult bool
// lastSyncResourceVersion is the resource version token last
// observed when doing a sync with the underlying store
// it is thread safe, but not synchronized with the underlying store
@@ -209,6 +212,7 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
initTrace := trace.New("Reflector ListAndWatch", trace.Field{"name", r.name})
defer initTrace.LogIfLong(10 * time.Second)
var list runtime.Object
var paginatedResult bool
var err error
listCh := make(chan struct{}, 1)
panicCh := make(chan interface{}, 1)
@@ -223,26 +227,30 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
pager := pager.New(pager.SimplePageFunc(func(opts metav1.ListOptions) (runtime.Object, error) {
return r.listerWatcher.List(opts)
}))
if r.WatchListPageSize != 0 {
switch {
case r.WatchListPageSize != 0:
pager.PageSize = r.WatchListPageSize
} else {
case r.paginatedResult:
// We got a paginated result initially. Assume this resource and server honor
// paging requests (i.e. watch cache is probably disabled) and leave the default
// pager size set.
case options.ResourceVersion != "" && options.ResourceVersion != "0":
// User didn't explicitly request pagination.
if options.ResourceVersion != "" && options.ResourceVersion != "0" {
// We also don't turn off pagination for ResourceVersion="0", since watch cache
// is ignoring Limit in that case anyway, and if watchcache is not enabled we
// don't introduce regression.
// With ResourceVersion != "", we have a possibility to list from watch cache,
// but we do that (for ResourceVersion != "0") only if Limit is unset.
// To avoid thundering herd on etcd (e.g. on master upgrades), we explicitly
// switch off pagination to force listing from watch cache (if enabled).
// With the existing semantic of RV (result is at least as fresh as provided RV),
// this is correct and doesn't lead to going back in time.
pager.PageSize = 0
}
//
// With ResourceVersion != "", we have a possibility to list from watch cache,
// but we do that (for ResourceVersion != "0") only if Limit is unset.
// To avoid thundering herd on etcd (e.g. on master upgrades), we explicitly
// switch off pagination to force listing from watch cache (if enabled).
// With the existing semantic of RV (result is at least as fresh as provided RV),
// this is correct and doesn't lead to going back in time.
//
// We also don't turn off pagination for ResourceVersion="0", since watch cache
// is ignoring Limit in that case anyway, and if watch cache is not enabled
// we don't introduce regression.
pager.PageSize = 0
}
list, err = pager.List(context.Background(), options)
list, paginatedResult, err = pager.List(context.Background(), options)
if isExpiredError(err) {
r.setIsLastSyncResourceVersionExpired(true)
// Retry immediately if the resource version used to list is expired.
@@ -250,7 +258,7 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
// continuation pages, but the pager might not be enabled, or the full list might fail because the
// resource version it is listing at is expired, so we need to fallback to resourceVersion="" in all
// to recover and ensure the reflector makes forward progress.
list, err = pager.List(context.Background(), metav1.ListOptions{ResourceVersion: r.relistResourceVersion()})
list, paginatedResult, err = pager.List(context.Background(), metav1.ListOptions{ResourceVersion: r.relistResourceVersion()})
}
close(listCh)
}()
@@ -264,6 +272,21 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
if err != nil {
return fmt.Errorf("%s: Failed to list %v: %v", r.name, r.expectedTypeName, err)
}
// We check if the list was paginated and if so set the paginatedResult based on that.
// However, we want to do that only for the initial list (which is the only case
// when we set ResourceVersion="0"). The reasoning behind it is that later, in some
// situations we may force listing directly from etcd (by setting ResourceVersion="")
// which will return paginated result, even if watch cache is enabled. However, in
// that case, we still want to prefer sending requests to watch cache if possible.
//
// Paginated result returned for request with ResourceVersion="0" mean that watch
// cache is disabled and there are a lot of objects of a given type. In such case,
// there is no need to prefer listing from watch cache.
if options.ResourceVersion == "0" && paginatedResult {
r.paginatedResult = true
}
r.setIsLastSyncResourceVersionExpired(false) // list was successful
initTrace.Step("Objects listed")
listMetaInterface, err := meta.ListAccessor(list)