51b24386e6
extensive testing has never found an instance where it reduced response size from the server
94 lines
3.4 KiB
JavaScript
94 lines
3.4 KiB
JavaScript
// MAP DATA CACHE ///////////////////////////////////
|
|
// cache for map data tiles.
|
|
|
|
window.DataCache = function() {
|
|
// stock site nemesis.dashboard.DataManager.CACHE_EXPIRY_MS_ = 18E4 - so should be 2 mins cache time
|
|
this.REQUEST_CACHE_FRESH_AGE = 120; // if younger than this, use data in the cache rather than fetching from the server
|
|
|
|
// stale cache entries can be updated (that's what the optional 'timestampMs' field in getThinnedEntnties is
|
|
// for, retrieving deltas) so use a long max age to take advantage of this
|
|
// however, ther must be an overall limit on the maximum age of data from the servers, otherwise the deletedEntity
|
|
// entries would grow indefinitely. an hour seems reasonable from experience with the data, so 55 mins max cache time
|
|
// this.REQUEST_CACHE_MAX_AGE = 55*60; // maximum cache age. entries are deleted from the cache after this time
|
|
//UPDATE: this timestampMs parameter doesn't work, so reduced max age to limit RAM usage
|
|
this.REQUEST_CACHE_MAX_AGE = 5*60; // maximum cache age. entries are deleted from the cache after this time
|
|
|
|
if (L.Browser.mobile) {
|
|
// on mobile devices, smaller cache size
|
|
this.REQUEST_CACHE_MAX_SIZE = 300; // if more than this many entries, expire early
|
|
} else {
|
|
// but on desktop, allow more
|
|
this.REQUEST_CACHE_MAX_SIZE = 1000; // if more than this many entries, expire early
|
|
}
|
|
|
|
this._cache = {};
|
|
this._interval = undefined;
|
|
|
|
}
|
|
|
|
window.DataCache.prototype.store = function(qk,data,date) {
|
|
// fixme? common behaviour for objects is that properties are kept in the order they're added
|
|
// this is handy, as it allows easy retrieval of the oldest entries for expiring
|
|
// however, this is not guaranteed by the standards, but all our supported browsers work this way
|
|
|
|
delete this._cache[qk];
|
|
|
|
if (date === undefined) date = new Date();
|
|
this._cache[qk] = { time: date.getTime(), data: data };
|
|
}
|
|
|
|
window.DataCache.prototype.get = function(qk) {
|
|
if (qk in this._cache) return this._cache[qk].data;
|
|
else return undefined;
|
|
}
|
|
|
|
window.DataCache.prototype.getTime = function(qk) {
|
|
if (qk in this._cache) return this._cache[qk].time;
|
|
else return 0;
|
|
}
|
|
|
|
window.DataCache.prototype.isFresh = function(qk) {
|
|
if (qk in this._cache) {
|
|
var d = new Date();
|
|
var t = d.getTime() - this.REQUEST_CACHE_FRESH_AGE*1000;
|
|
if (this._cache[qk].time >= t) return true;
|
|
else return false;
|
|
}
|
|
|
|
return undefined;
|
|
}
|
|
|
|
window.DataCache.prototype.startExpireInterval = function(period) {
|
|
if (this._interval === undefined) {
|
|
var savedContext = this;
|
|
this._interval = setInterval (function() { savedContext.runExpire(); }, period*1000);
|
|
}
|
|
}
|
|
|
|
window.DataCache.prototype.stopExpireInterval = function() {
|
|
if (this._interval !== undefined) {
|
|
stopInterval (this._interval);
|
|
this._interval = undefined;
|
|
}
|
|
}
|
|
|
|
|
|
|
|
window.DataCache.prototype.runExpire = function() {
|
|
var d = new Date();
|
|
var t = d.getTime()-this.REQUEST_CACHE_MAX_AGE*1000;
|
|
|
|
var cacheSize = Object.keys(this._cache).length;
|
|
|
|
for(var qk in this._cache) {
|
|
|
|
// fixme? our MAX_SIZE test here assumes we're processing the oldest first. this relies
|
|
// on looping over object properties in the order they were added. this is true in most browsers,
|
|
// but is not a requirement of the standards
|
|
if (cacheSize > this.REQUEST_CACHE_MAX_SIZE || this._cache[qk].time < t) {
|
|
delete this._cache[qk];
|
|
cacheSize--;
|
|
}
|
|
}
|
|
}
|