mirror of
https://github.com/ceph/ceph-csi.git
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249 lines
6.7 KiB
Go
249 lines
6.7 KiB
Go
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/*
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Copyright 2022 The Ceph-CSI Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package reftracker
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import (
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goerrors "errors"
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"fmt"
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"github.com/ceph/ceph-csi/internal/util/reftracker/errors"
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"github.com/ceph/ceph-csi/internal/util/reftracker/radoswrapper"
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"github.com/ceph/ceph-csi/internal/util/reftracker/reftype"
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v1 "github.com/ceph/ceph-csi/internal/util/reftracker/v1"
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"github.com/ceph/ceph-csi/internal/util/reftracker/version"
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"github.com/ceph/go-ceph/rados"
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)
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// reftracker is key-based implementation of a reference counter.
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//
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// Unlike integer-based counter, reftracker counts references by tracking
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// unique keys. This allows accounting in situations where idempotency must be
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// preserved. It guarantees there will be no duplicit increments or decrements
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// of the counter.
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//
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// It is stored persistently as a RADOS object, and is safe to use with
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// multiple concurrent writers, and across different nodes of a cluster.
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//
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// Example:
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//
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// created, err := Add(
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// ioctx,
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// "my-reftracker",
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// map[string]struct{}{
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// "ref-key-1": {},
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// "ref-key-2": {},
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// },
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// )
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//
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// Since this is a new reftracker object, `created` is `true`.
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//
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// "my-reftracker" now holds:
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// ["ref-key-1":reftype.Normal, "ref-key-2":reftype.Normal]
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// The reference count is 2.
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//
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// created, err := Add(
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// ioctx,
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// "my-reftracker",
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// map[string]struct{}{
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// "ref-key-1": {},
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// "ref-key-2": {},
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// "ref-key-3": {},
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// },
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// )
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//
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// Reftracker named "my-reftracker" already exists, so `created` is now
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// `false`. Since "ref-key-1" and "ref-key-2" keys are already tracked,
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// only "ref-key-3" is added.
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//
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// "my-reftracker" now holds:
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// ["ref-key-1":reftype.Normal, "ref-key-2":reftype.Normal,
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// "ref-key-3":reftype.Normal]
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// The reference count is 3.
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//
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// deleted, err := Remove(
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// ioctx,
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// "my-reftracker",
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// map[string]reftype.RefType{
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// "ref-key-1": reftype.Normal,
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// "ref-key-2": reftype.Mask,
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// },
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// )
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//
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// "my-reftracker" now holds:
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// ["ref-key-2":reftype.Mask, "ref-key-3":reftype.Normal]
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// The reference count is 1.
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//
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// Since the reference count is greater than zero, `deleted` is `false`.
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// "ref-key-1" was removed, and so is not listed among tracked references.
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// "ref-key-2" was only masked, so it's been kept. However, masked references
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// don't contribute to overall reference count, so the resulting refcount
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// after this Remove() call is 1.
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//
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// created, err := Add(
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// ioctx,
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// "my-reftracker",
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// map[string]struct{}{
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// "ref-key-2": {},
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// },
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// )
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//
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// "my-reftracker" now holds:
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// ["ref-key-2":reftype.Mask, "ref-key-3":reftype.Normal]
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// The reference count is 1.
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//
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// "ref-key-2" is already tracked, so it will not be added again. Since it
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// remains masked, it won't contribute to the reference count.
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//
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// deleted, err := Remove(
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// ioctx,
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// "my-reftracker",
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// map[string]reftype.RefType{
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// "ref-key-3": reftype.Normal,
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// },
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// )
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//
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// "ref-key-3" was the only tracked key that contributed to reference count.
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// After this Remove() call it's now removed. As a result, the reference count
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// dropped down to zero, and the whole object has been deleted too.
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// `deleted` is `true`.
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// Add atomically adds references to `rtName` reference tracker.
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// If the reftracker object doesn't exist yet, it is created and `true` is
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// returned. If some keys in `refs` map are already tracked by this reftracker
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// object, they will not be added again.
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func Add(
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ioctx radoswrapper.IOContextW,
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rtName string,
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refs map[string]struct{},
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) (bool, error) {
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if err := validateAddInput(rtName, refs); err != nil {
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return false, err
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}
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// Read reftracker version.
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rtVer, err := version.Read(ioctx, rtName)
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if err != nil {
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if goerrors.Is(err, rados.ErrNotFound) {
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// This is a new reftracker. Initialize it with `refs`.
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if err = v1.Init(ioctx, rtName, refs); err != nil {
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return false, fmt.Errorf("failed to initialize reftracker: %w", err)
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}
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return true, nil
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}
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return false, fmt.Errorf("failed to read reftracker version: %w", err)
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}
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// Add references to reftracker object.
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gen, err := ioctx.GetLastVersion()
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if err != nil {
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return false, fmt.Errorf("failed to get RADOS object version: %w", err)
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}
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switch rtVer {
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case v1.Version:
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err = v1.Add(ioctx, rtName, gen, refs)
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if err != nil {
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err = fmt.Errorf("failed to add refs: %w", err)
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}
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default:
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err = errors.UnknownObjectVersion(rtVer)
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}
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return false, err
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}
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// Remove atomically removes references from `rtName` reference tracker.
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// If the reftracker object holds no references after this removal, the whole
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// object is deleted too, and `true` is returned. If the reftracker object
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// doesn't exist, (true, nil) is returned.
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func Remove(
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ioctx radoswrapper.IOContextW,
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rtName string,
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refs map[string]reftype.RefType,
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) (bool, error) {
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if err := validateRemoveInput(rtName, refs); err != nil {
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return false, err
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}
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// Read reftracker version.
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rtVer, err := version.Read(ioctx, rtName)
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if err != nil {
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if goerrors.Is(err, rados.ErrNotFound) {
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// This reftracker doesn't exist. Assume it was already deleted.
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return true, nil
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}
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return false, fmt.Errorf("failed to read reftracker version: %w", err)
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}
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// Remove references from reftracker.
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gen, err := ioctx.GetLastVersion()
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if err != nil {
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return false, fmt.Errorf("failed to get RADOS object version: %w", err)
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}
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var deleted bool
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switch rtVer {
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case v1.Version:
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deleted, err = v1.Remove(ioctx, rtName, gen, refs)
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if err != nil {
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err = fmt.Errorf("failed to remove refs: %w", err)
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}
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default:
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err = errors.UnknownObjectVersion(rtVer)
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}
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return deleted, err
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}
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var (
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errNoRTName = goerrors.New("missing reftracker name")
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errNoRefs = goerrors.New("missing refs")
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)
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func validateAddInput(rtName string, refs map[string]struct{}) error {
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if rtName == "" {
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return errNoRTName
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}
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if len(refs) == 0 {
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return errNoRefs
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}
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return nil
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}
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func validateRemoveInput(rtName string, refs map[string]reftype.RefType) error {
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if rtName == "" {
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return errNoRTName
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}
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if len(refs) == 0 {
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return errNoRefs
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}
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return nil
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}
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