mirror of
https://github.com/featurebasedb/featurebase.git
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94 lines
2.7 KiB
Go
94 lines
2.7 KiB
Go
// Copyright 2017 Pilosa Corp.
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//
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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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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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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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package etcd
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import (
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"context"
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"sync"
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"time"
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"github.com/pilosa/pilosa/v2/topology"
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)
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// EtcdWithCache is a wrapper around the Etcd type which will return a
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// cached value when the number of requests come in below a configured
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// frequency. It also breaks the cache after a configured TTL.
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type EtcdWithCache struct {
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*Etcd
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peerMetadataMu sync.RWMutex
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peerMetadata map[string][]byte
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peersMu sync.Mutex // peer-list cache updates
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nodes []*topology.Node // unmarshalled Node data
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nodesTTL int // seconds
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nodesLastRequest time.Time // last time requested
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}
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// NewEtcdWithCache returns a new instance of Cache.
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func NewEtcdWithCache(opt Options, replicas int) *EtcdWithCache {
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return &EtcdWithCache{
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Etcd: NewEtcd(opt, replicas),
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nodesTTL: 6,
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peerMetadata: make(map[string][]byte),
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}
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}
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// Metadata is a cache wrapper around the Metadator.Metadata method.
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func (c *EtcdWithCache) Metadata(ctx context.Context, peerID string) ([]byte, error) {
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c.peerMetadataMu.RLock()
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v, ok := c.peerMetadata[peerID]
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c.peerMetadataMu.RUnlock()
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if ok {
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return v, nil
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}
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v, err := c.Etcd.Metadata(ctx, peerID)
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if err == nil {
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c.peerMetadataMu.Lock()
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c.peerMetadata[peerID] = v
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c.peerMetadataMu.Unlock()
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}
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return v, err
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}
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// Nodes caches the result of the underlying implementation's node list.
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func (c *EtcdWithCache) Nodes() []*topology.Node {
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c.peersMu.Lock()
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defer c.peersMu.Unlock()
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now := time.Now()
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if now.Sub(c.nodesLastRequest) > (time.Duration(c.nodesTTL) * time.Second) {
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c.nodes = c.Etcd.Nodes()
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c.nodesLastRequest = now
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}
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return c.nodes
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}
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// SetNodes implements the Noder interface as NOP
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// (because we can't force to set nodes for etcd).
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func (c *EtcdWithCache) SetNodes(nodes []*topology.Node) {}
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// AppendNode implements the Noder interface as NOP
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// (because resizer is responsible for adding new nodes).
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func (c *EtcdWithCache) AppendNode(node *topology.Node) {}
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// RemoveNode implements the Noder interface as NOP
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// (because resizer is responsible for removing existing nodes)
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func (c *EtcdWithCache) RemoveNode(nodeID string) bool {
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return false
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}
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