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cache: Add a simple partitioned lazy cache

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bep committed May 25, 2017
1 parent a91c270 commit 87203139c38e0b992c96d7b8a23c7730649c68e5
Showing with 172 additions and 0 deletions.
  1. +80 −0 cache/partitioned_lazy_cache.go
  2. +92 −0 cache/partitioned_lazy_cache_test.go
@@ -0,0 +1,80 @@
// Copyright 2017-present The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cache
import (
"sync"
)
// Partition represents a cache partition where Load is the callback
// for when the partition is needed.
type Partition struct {
Key string
Load func() (map[string]interface{}, error)
}
type lazyPartition struct {
initSync sync.Once
cache map[string]interface{}
load func() (map[string]interface{}, error)
}
func (l *lazyPartition) init() error {
var err error
l.initSync.Do(func() {
var c map[string]interface{}
c, err = l.load()
l.cache = c
})
return err
}
// PartitionedLazyCache is a lazily loaded cache paritioned by a supplied string key.
type PartitionedLazyCache struct {
partitions map[string]*lazyPartition
}
// NewPartitionedLazyCache creates a new NewPartitionedLazyCache with the supplied
// partitions.
func NewPartitionedLazyCache(partitions ...Partition) *PartitionedLazyCache {
lazyPartitions := make(map[string]*lazyPartition, len(partitions))
for _, partition := range partitions {
lazyPartitions[partition.Key] = &lazyPartition{load: partition.Load}
}
cache := &PartitionedLazyCache{partitions: lazyPartitions}
return cache
}
// Get initializes the partition if not already done so, then looks up the given
// key in the given partition, returns nil if no value found.
func (c *PartitionedLazyCache) Get(partition, key string) (interface{}, error) {
p, found := c.partitions[partition]
if !found {
return nil, nil
}
if err := p.init(); err != nil {
return nil, err
}
if v, found := p.cache[key]; found {
return v, nil
}
return nil, nil
}
@@ -0,0 +1,92 @@
// Copyright 2017-present The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cache
import (
"errors"
"testing"
"github.com/stretchr/testify/require"
)
func TestNewPartitionedLazyCache(t *testing.T) {
t.Parallel()
assert := require.New(t)
p1 := Partition{
Key: "p1",
Load: func() (map[string]interface{}, error) {
return map[string]interface{}{
"p1_1": "p1v1",
"p1_2": "p1v2",
"p1_nil": nil,
}, nil
},
}
p2 := Partition{
Key: "p2",
Load: func() (map[string]interface{}, error) {
return map[string]interface{}{
"p2_1": "p2v1",
"p2_2": "p2v2",
"p2_3": "p2v3",
}, nil
},
}
cache := NewPartitionedLazyCache(p1, p2)
v, err := cache.Get("p1", "p1_1")
assert.NoError(err)
assert.Equal("p1v1", v)
v, err = cache.Get("p1", "p2_1")
assert.NoError(err)
assert.Nil(v)
v, err = cache.Get("p1", "p1_nil")
assert.NoError(err)
assert.Nil(v)
v, err = cache.Get("p2", "p2_3")
assert.NoError(err)
assert.Equal("p2v3", v)
v, err = cache.Get("doesnotexist", "p1_1")
assert.NoError(err)
assert.Nil(v)
v, err = cache.Get("p1", "doesnotexist")
assert.NoError(err)
assert.Nil(v)
errorP := Partition{
Key: "p3",
Load: func() (map[string]interface{}, error) {
return nil, errors.New("Failed")
},
}
cache = NewPartitionedLazyCache(errorP)
v, err = cache.Get("p1", "doesnotexist")
assert.NoError(err)
assert.Nil(v)
_, err = cache.Get("p3", "doesnotexist")
assert.Error(err)
}

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