Hello
We're using the CachingHttpClient and are seeing a spike in CPU usage when
it is enabled. We've profiled our application and see that most of the time
is being spent parsing dates. Specifically, it is trying to get the age of
a cache entry on a cache hit by parsing the "Date" header on the
HttpCacheEntry. I had a couple questions:
1) Why can't this use the responseDate value that lives on HttpCacheEntry?
(This would avoid the overhead of parsing)
2) If it needs to parse, is it possible to remember the result on the
HttpCacheEntry so it doesn't need to be parsed every time?
We are using version 4.2
thanks for any advice
sam
ps - Here is the full backtrace we are seeing:
org.apache.http.impl.cookie.DateUtils.parseDate(String)
org.apache.http.impl.client.cache.CacheValidityPolicy.getDateValue(HttpCacheEntry)
org.apache.http.impl.client.cache.CacheValidityPolicy.getApparentAgeSecs(HttpCacheEntry)
org.apache.http.impl.client.cache.CacheValidityPolicy.getCorrectedReceivedAgeSecs(HttpCacheEntry)
org.apache.http.impl.client.cache.CacheValidityPolicy.getCorrectedInitialAgeSecs(HttpCacheEntry)
org.apache.http.impl.client.cache.CacheValidityPolicy.getCurrentAgeSecs(HttpCacheEntry,
Date)
There are a couple callers to "getCorrectedAgeSecs":
CacheValidityPolicy.isResponseFresh(HttpCacheEntry, Date)
CachedResponseSuitabilityChecker.isFreshEnough(HttpCacheEntry,
HttpRequest, Date)
CachedResponseSuitabilityChecker.canCachedResponseBeUsed(HttpHost,
HttpRequest, HttpCacheEntry, Date)
CachingHttpClient.handleCacheHit(HttpHost, HttpRequest, HttpContext,
HttpCacheEntry)
CachedHttpResponseGenerator.generateResponse(HttpCacheEntry)
CachingHttpClient.generateCachedResponse(HttpRequest, HttpContext,
HttpCacheEntry, Date)
CachingHttpClient.handleCacheHit(HttpHost, HttpRequest, HttpContext,
HttpCacheEntry)
Looking at the code, it looks like this section from
CachingHttpClient.handleCacheHit will result in parsing the date twice
(apologies if I'm misreading this)
if (suitabilityChecker.canCachedResponseBeUsed(target, request,
entry, now)) {
return generateCachedResponse(request, context, entry, now);
}
Both the call to "canCachedResponseBeUsed" and the call to
"generatedCachedResponse" will ultimately call "getCurrentAgeSecs" and
parse the Date header.
