mirror of
https://github.com/tailscale/tailscale.git
synced 2024-12-04 23:45:34 +00:00
b8a2aedccd
Fixes tailscale/corp#15850 Co-authored-by: Adrian Dewhurst <adrian@tailscale.com> Signed-off-by: Claire Wang <claire@tailscale.com>
99 lines
2.7 KiB
Go
99 lines
2.7 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
|
|
// SPDX-License-Identifier: BSD-3-Clause
|
|
|
|
package syspolicy
|
|
|
|
import (
|
|
"errors"
|
|
"sync"
|
|
)
|
|
|
|
// CachingHandler is a handler that reads policies from an underlying handler the first time each key is requested
|
|
// and permanently caches the result unless there is an error. If there is an ErrNoSuchKey error, that result is cached,
|
|
// otherwise the actual error is returned and the next read for that key will retry using the handler.
|
|
type CachingHandler struct {
|
|
mu sync.Mutex
|
|
strings map[string]string
|
|
uint64s map[string]uint64
|
|
bools map[string]bool
|
|
notFound map[string]bool
|
|
handler Handler
|
|
}
|
|
|
|
// NewCachingHandler creates a CachingHandler given a handler.
|
|
func NewCachingHandler(handler Handler) *CachingHandler {
|
|
return &CachingHandler{
|
|
handler: handler,
|
|
strings: make(map[string]string),
|
|
uint64s: make(map[string]uint64),
|
|
bools: make(map[string]bool),
|
|
notFound: make(map[string]bool),
|
|
}
|
|
}
|
|
|
|
// ReadString reads the policy settings value string given the key.
|
|
// ReadString first reads from the handler's cache before resorting to using the handler.
|
|
func (ch *CachingHandler) ReadString(key string) (string, error) {
|
|
ch.mu.Lock()
|
|
defer ch.mu.Unlock()
|
|
if val, ok := ch.strings[key]; ok {
|
|
return val, nil
|
|
}
|
|
if notFound := ch.notFound[key]; notFound {
|
|
return "", ErrNoSuchKey
|
|
}
|
|
val, err := ch.handler.ReadString(key)
|
|
if errors.Is(err, ErrNoSuchKey) {
|
|
ch.notFound[key] = true
|
|
return "", err
|
|
} else if err != nil {
|
|
return "", err
|
|
}
|
|
ch.strings[key] = val
|
|
return val, nil
|
|
}
|
|
|
|
// ReadUInt64 reads the policy settings uint64 value given the key.
|
|
// ReadUInt64 first reads from the handler's cache before resorting to using the handler.
|
|
func (ch *CachingHandler) ReadUInt64(key string) (uint64, error) {
|
|
ch.mu.Lock()
|
|
defer ch.mu.Unlock()
|
|
if val, ok := ch.uint64s[key]; ok {
|
|
return val, nil
|
|
}
|
|
if notFound := ch.notFound[key]; notFound {
|
|
return 0, ErrNoSuchKey
|
|
}
|
|
val, err := ch.handler.ReadUInt64(key)
|
|
if errors.Is(err, ErrNoSuchKey) {
|
|
ch.notFound[key] = true
|
|
return 0, err
|
|
} else if err != nil {
|
|
return 0, err
|
|
}
|
|
ch.uint64s[key] = val
|
|
return val, nil
|
|
}
|
|
|
|
// ReadBoolean reads the policy settings boolean value given the key.
|
|
// ReadBoolean first reads from the handler's cache before resorting to using the handler.
|
|
func (ch *CachingHandler) ReadBoolean(key string) (bool, error) {
|
|
ch.mu.Lock()
|
|
defer ch.mu.Unlock()
|
|
if val, ok := ch.bools[key]; ok {
|
|
return val, nil
|
|
}
|
|
if notFound := ch.notFound[key]; notFound {
|
|
return false, ErrNoSuchKey
|
|
}
|
|
val, err := ch.handler.ReadBoolean(key)
|
|
if errors.Is(err, ErrNoSuchKey) {
|
|
ch.notFound[key] = true
|
|
return false, err
|
|
} else if err != nil {
|
|
return false, err
|
|
}
|
|
ch.bools[key] = val
|
|
return val, nil
|
|
}
|