112 lines
3.2 KiB
JavaScript
112 lines
3.2 KiB
JavaScript
// tile cache policies
|
|
// it exports two cache types:
|
|
// 'nocache' implements a pass-troguth cache
|
|
// 'lru' implements a LRU cache
|
|
|
|
var LRUCache = require('./lru'),
|
|
CacheValidator = require('./cache_validator')
|
|
|
|
module.exports.NoCache = function() {
|
|
|
|
var me = {}
|
|
|
|
me.beforeTileRender = function(req, res, callback) {
|
|
callback(null);
|
|
}
|
|
|
|
me.afterTileRender = function(req, res, tile, headers, callback) {
|
|
callback(null, tile, headers);
|
|
}
|
|
|
|
return me;
|
|
|
|
}
|
|
|
|
module.exports.LRUcache = function(max_items, redis_opts) {
|
|
var cache_validator = CacheValidator(redis_opts);
|
|
return GenericCache(new LRUCache(max_items), cache_validator);
|
|
}
|
|
|
|
// implements a generic cache for tile
|
|
// cache_policy should implement set and get methods and optionally getStats
|
|
function GenericCache (cache_policy, cache_validator) {
|
|
|
|
var me = {
|
|
cache: cache_policy,
|
|
cache_validator: cache_validator,
|
|
cache_hits: 0,
|
|
cache_misses: 0,
|
|
current_items: 0,
|
|
cache_invalidated: 0,
|
|
max_items: 0
|
|
}
|
|
|
|
function cache_key(req) {
|
|
return req.url;
|
|
}
|
|
|
|
function update_items(n) {
|
|
me.current_items = n;
|
|
if(n > me.max_items) {
|
|
me.max_items = n;
|
|
}
|
|
}
|
|
|
|
me.beforeTileRender = function(req, res, callback) {
|
|
var key = cache_key(req);
|
|
var tile = me.cache.get(key);
|
|
if(tile) {
|
|
// validate the cache
|
|
me.cache_validator.getTimestamp(req.params.dbname, req.params.table, function(err, t) {
|
|
if(t != null && tile.timestamp < t) {
|
|
me.cache_misses++;
|
|
me.cache_invalidated++;
|
|
callback(null);
|
|
} else {
|
|
me.cache_hits++;
|
|
res.header('X-Cache-hit', 'true');
|
|
res.send(tile.tile, tile.headers, 200);
|
|
}
|
|
});
|
|
} else {
|
|
me.cache_misses++;
|
|
callback(null);
|
|
}
|
|
}
|
|
|
|
me.afterTileRender = function(req, res, tile, headers, callback) {
|
|
var timestamp = new Date().getTime()/1000.0;
|
|
me.cache.put(cache_key(req), { tile: tile, headers: headers, timestamp: timestamp});
|
|
update_items(me.cache.size || 0);
|
|
callback(null, tile, headers);
|
|
}
|
|
|
|
me.afterStateChange = function(req, data, callback) {
|
|
console.log("invalidating", req.params.dbname,", ", req.params.table);
|
|
me.cache_validator.setTimestamp(req.params.dbname, req.params.table, new Date().getTime()/1000.0, function(err, t) {
|
|
callback(err, data);
|
|
});
|
|
}
|
|
|
|
me.getStats = function() {
|
|
var total = me.cache_hits + me.cache_misses;
|
|
var mem = 0;
|
|
me.cache.forEach(function(key, value) {
|
|
if(value.tile.length !== undefined) {
|
|
mem += value.tile.length;
|
|
}
|
|
});
|
|
return {
|
|
cache_hits: me.cache_hits,
|
|
cache_misses: me.cache_misses,
|
|
current_items: me.current_items,
|
|
max_items: me.max_items,
|
|
memory: mem,
|
|
memory_per_item: total ? mem/total: 0,
|
|
ratio: total ? me.cache_hits/total: 0
|
|
};
|
|
}
|
|
|
|
return me;
|
|
}
|