| // Copyright 2016 The LUCI Authors. |
| // |
| // 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 bigtable |
| |
| import ( |
| "bytes" |
| "context" |
| "encoding/binary" |
| "time" |
| |
| "go.chromium.org/luci/logdog/common/storage" |
| "go.chromium.org/luci/logdog/common/types" |
| |
| log "go.chromium.org/luci/common/logging" |
| ) |
| |
| // cacheSchema represents the cache schema used by this version of the tail |
| // cache. If the underlying data format changes, this value must also be |
| // updated. |
| const cacheSchema = "v1" |
| |
| // lastTailIndexCacheDuration is the amount of time that the last tail index |
| // should be cached. |
| const lastTailIndexCacheDuration = 1 * time.Hour |
| |
| // getLastTailIndex will return the cached last tail index of a given stream. |
| // |
| // If there was an error, or if the item was not cached, 0 (first index) will be |
| // returned. |
| func getLastTailIndex(c context.Context, cache storage.Cache, project string, path types.StreamPath) int64 { |
| data, ok := cache.Get(c, mkLastTailKey(project, path)) |
| if !ok { |
| return 0 |
| } |
| |
| v, err := binary.ReadVarint(bytes.NewReader(data)) |
| if err != nil { |
| log.Fields{ |
| log.ErrorKey: err, |
| "project": project, |
| "path": path, |
| }.Warningf(c, "Could not decode last tail cache.") |
| return 0 |
| } |
| |
| log.Fields{ |
| "index": v, |
| }.Infof(c, "Using cached tail index.") |
| return v |
| } |
| |
| func putLastTailIndex(c context.Context, cache storage.Cache, project string, path types.StreamPath, v int64) { |
| buf := make([]byte, binary.MaxVarintLen64) |
| buf = buf[:binary.PutVarint(buf, v)] |
| |
| cache.Put(c, mkLastTailKey(project, path), buf, lastTailIndexCacheDuration) |
| } |
| |
| func mkLastTailKey(project string, path types.StreamPath) storage.CacheKey { |
| return storage.CacheKey{ |
| Schema: cacheSchema, |
| Type: "bt_tail_idx", |
| Key: storage.HashKey(project, string(path)), |
| } |
| } |