Mercurial > gemma
view pkg/octree/cache.go @ 1234:1a5564655f2a
refac: Sidebar reorganized
In order to make context switches between administrative tasks
which are map related and those which are system related, we now have
a category "administration" and "systemadministration".
The Riverbedmorphology does nothing than display the map, so it is
renamed to that (map). In case the context of "systemadministration"
is chosen, the "map" brings you just back to the map.
author | Thomas Junk <thomas.junk@intevation.de> |
---|---|
date | Tue, 20 Nov 2018 09:54:53 +0100 |
parents | 19a04b150b6c |
children | d753ce6cf588 |
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// This is Free Software under GNU Affero General Public License v >= 3.0 // without warranty, see README.md and license for details. // // SPDX-License-Identifier: AGPL-3.0-or-later // License-Filename: LICENSES/AGPL-3.0.txt // // Copyright (C) 2018 by via donau // – Österreichische Wasserstraßen-Gesellschaft mbH // Software engineering by Intevation GmbH // // Author(s): // * Sascha L. Teichmann <sascha.teichmann@intevation.de> package octree import ( "context" "database/sql" "sync" "time" ) type ( cacheKey struct { date time.Time bottleneck string } cacheEntry struct { checksum string tree *Tree access time.Time } OctreeCache struct { sync.Mutex entries map[cacheKey]*cacheEntry } ) const ( cleanupCacheSleep = 6 * time.Minute maxCacheAge = 5 * time.Minute maxCacheEntries = 4 ) const ( fetchOctreeSQL = ` SELECT octree_checksum, octree_index FROM waterway.sounding_results WHERE bottleneck_id = $1 AND date_info = $2::date AND octree_checksum IS NOT NULL AND octree_index IS NOT NULL ` checkOctreeSQL = ` SELECT CASE WHEN octree_checksum = $3 THEN NULL ELSE octree_index END FROM waterway.sounding_results WHERE bottleneck_id = $1 AND date_info = $2::date AND octree_checksum IS NOT NULL AND octree_index IS NOT NULL ` ) var Cache = OctreeCache{ entries: map[cacheKey]*cacheEntry{}, } func init() { go Cache.background() } func (oc *OctreeCache) background() { for { time.Sleep(cleanupCacheSleep) oc.cleanup() } } func (oc *OctreeCache) cleanup() { oc.Lock() defer oc.Unlock() good := time.Now().Add(-maxCacheAge) for k, v := range oc.entries { if v.access.Before(good) { delete(oc.entries, k) } } } func (oc *OctreeCache) Get( bottleneck string, date time.Time, conn *sql.Conn, ctx context.Context, ) (*Tree, error) { oc.Lock() defer oc.Unlock() key := cacheKey{date, bottleneck} entry := oc.entries[key] var data []byte var checksum string if entry == nil { // fetch from database err := conn.QueryRowContext( ctx, fetchOctreeSQL, bottleneck, date).Scan(&checksum, &data) switch { case err == sql.ErrNoRows: return nil, nil case err != nil: return nil, err } } else { // check if we are not outdated. err := conn.QueryRowContext( ctx, checkOctreeSQL, bottleneck, date, entry.checksum).Scan(&data) switch { case err == sql.ErrNoRows: return nil, nil case err != nil: return nil, err } if data == nil { // we are still current entry.access = time.Now() return entry.tree, nil } } tree, err := Deserialize(data) if err != nil { return nil, err } now := time.Now() if entry != nil { entry.tree = tree entry.access = now return tree, nil } for len(oc.entries) >= maxCacheEntries { // Evict the entry that is accessed the longest time ago. var oldestKey cacheKey oldest := now for k, v := range oc.entries { if v.access.Before(oldest) { oldest = v.access oldestKey = k } } delete(oc.entries, oldestKey) } oc.entries[key] = &cacheEntry{ checksum: checksum, tree: tree, access: now, } return tree, nil }