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DB Access: OnChange cache (sonic-net#82)
* DB Access: OnChange cache 1) Introduced the OnChange cache in the DB object. Cache is maintained as map[string]db.Value, where map key is the redis key. OnChange cache is not enabled by default. DB instance should be inited with IsEnableOnChange=true option and caching should be enabled for specific tables by calling DB.RegisterTableForOnChangeCaching(). DB.OnChangeCacheUpdate() and DB.OnChangeCacheDelete() functions should be used to refresh the cache contents. 2) Enhanced DB.GetEntry() to return value from the OnChnage cahce if the key exists in the cache. Otherwise the value will be read from redis and cache will be updated. Signed-off-by: Arun Barboza <[email protected]> Signed-off-by: Sachin Holla <[email protected]> * Rename IsEnableOnChange option as IsOnChangeEnabled --------- Signed-off-by: Arun Barboza <[email protected]> Signed-off-by: Sachin Holla <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,123 @@ | ||
| //////////////////////////////////////////////////////////////////////////////// | ||
| // // | ||
| // Copyright 2021 Broadcom. The term Broadcom refers to Broadcom Inc. and/or // | ||
| // its subsidiaries. // | ||
| // // | ||
| // 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. // | ||
| // // | ||
| //////////////////////////////////////////////////////////////////////////////// | ||
|
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| package db | ||
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| import ( | ||
| "github.com/golang/glog" | ||
| ) | ||
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| //////////////////////////////////////////////////////////////////////////////// | ||
| // Internal Types // | ||
| //////////////////////////////////////////////////////////////////////////////// | ||
|
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| type dbOnChangeReg struct { | ||
| CacheTables map[string]bool // Only cache these tables. | ||
| } | ||
|
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| //////////////////////////////////////////////////////////////////////////////// | ||
| // Exported Functions // | ||
| //////////////////////////////////////////////////////////////////////////////// | ||
|
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| func (d *DB) RegisterTableForOnChangeCaching(ts *TableSpec) error { | ||
| if glog.V(3) { | ||
| glog.Info("RegisterTableForOnChange: ts:", ts) | ||
| } | ||
| if !d.IsOpen() { | ||
| return ConnectionClosed | ||
| } | ||
| if !d.Opts.IsOnChangeEnabled { | ||
| return OnChangeDisabled | ||
| } | ||
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| d.onCReg.CacheTables[ts.Name] = true | ||
| return nil | ||
| } | ||
|
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| // OnChangeCacheUpdate reads a db entry from redis and updates the on_change cache. | ||
| // Returns both previously cached Value and current Value. Previous Value will be | ||
| // empty if there was no such cache entry earlier. Returns an error if DB entry | ||
| // does not exists or could not be read. | ||
| func (d *DB) OnChangeCacheUpdate(ts *TableSpec, key Key) (Value, Value, error) { | ||
| if glog.V(3) { | ||
| glog.Info("OnChangeCacheUpdate: Begin: ", "ts: ", ts, " key: ", key) | ||
| } | ||
| if !d.IsOpen() { | ||
| return Value{}, Value{}, ConnectionClosed | ||
| } | ||
| if !d.Opts.IsOnChangeEnabled { | ||
| return Value{}, Value{}, OnChangeDisabled | ||
| } | ||
|
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| var valueOrig Value | ||
| if _, ok := d.cache.Tables[ts.Name]; ok { | ||
| valueOrig = d.cache.Tables[ts.Name].entry[d.key2redis(ts, key)] | ||
| } | ||
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| // Get New Value from the DB | ||
| value, e := d.getEntry(ts, key, true) | ||
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| return valueOrig, value, e | ||
| } | ||
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| // OnChangeCacheDelete deletes an entry from the on_change cache. | ||
| // Returns the previously cached Value object; or an empty Value if there was | ||
| // no such cache entry. | ||
| func (d *DB) OnChangeCacheDelete(ts *TableSpec, key Key) (Value, error) { | ||
| if glog.V(3) { | ||
| glog.Info("OnChangeCacheDelete: Begin: ", "ts:", ts, " key:", key) | ||
| } | ||
| if !d.IsOpen() { | ||
| return Value{}, ConnectionClosed | ||
| } | ||
| if !d.Opts.IsOnChangeEnabled { | ||
| return Value{}, OnChangeDisabled | ||
| } | ||
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| redisKey := d.key2redis(ts, key) | ||
| var valueOrig Value | ||
| _, ok := d.cache.Tables[ts.Name] | ||
| if ok { | ||
| valueOrig, ok = d.cache.Tables[ts.Name].entry[redisKey] | ||
| } | ||
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| if ok { | ||
| glog.V(2).Info("OnChangeCacheDelete: Delete ts:", ts, " key:", key) | ||
| delete(d.cache.Tables[ts.Name].entry, redisKey) | ||
| } else { | ||
| glog.V(2).Info("OnChangeCacheDelete: Not found; ts:", ts, " key:", key) | ||
| } | ||
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| return valueOrig, nil | ||
| } | ||
|
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| //////////////////////////////////////////////////////////////////////////////// | ||
| // Internal Functions // | ||
| //////////////////////////////////////////////////////////////////////////////// | ||
|
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| func init() { | ||
| } | ||
|
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| func (reg *dbOnChangeReg) isCacheTable(name string) bool { | ||
| return reg.CacheTables[name] | ||
| } | ||
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| func (reg *dbOnChangeReg) size() int { | ||
| return len(reg.CacheTables) | ||
| } |
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