Mercurial > gemma
view pkg/octree/cache.go @ 3678:8f58851927c0
client: make layer factory only return new layer config for individual maps
instead of each time it is invoked. The purpose of the factory was to support multiple maps with individual layers.
But returning a new config each time it is invoked leads to bugs that rely on the layer's state. Now this factory
reuses the same objects it created before, per map.
author | Markus Kottlaender <markus@intevation.de> |
---|---|
date | Mon, 17 Jun 2019 17:31:35 +0200 |
parents | 86c7a023400e |
children | 49564382ffff |
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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 } // Cache holds Octrees for a defined amount of time in memory // before they are released. Cache 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 = Cache{ entries: map[cacheKey]*cacheEntry{}, } func init() { go cache.background() } func (c *Cache) background() { for { time.Sleep(cleanupCacheSleep) c.cleanup() } } func (c *Cache) cleanup() { c.Lock() defer c.Unlock() good := time.Now().Add(-maxCacheAge) for k, v := range c.entries { if v.access.Before(good) { delete(c.entries, k) } } } // FromCache fetches an Octree from the global Octree cache. func FromCache( ctx context.Context, conn *sql.Conn, bottleneck string, date time.Time, ) (*Tree, error) { return cache.get(ctx, conn, bottleneck, date) } func (c *Cache) get( ctx context.Context, conn *sql.Conn, bottleneck string, date time.Time, ) (*Tree, error) { c.Lock() defer c.Unlock() key := cacheKey{date, bottleneck} entry := c.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(c.entries) >= maxCacheEntries { // Evict the entry that is accessed the longest time ago. var oldestKey cacheKey oldest := now for k, v := range c.entries { if v.access.Before(oldest) { oldest = v.access oldestKey = k } } delete(c.entries, oldestKey) } c.entries[key] = &cacheEntry{ checksum: checksum, tree: tree, access: now, } return tree, nil }