Eric Hubert created HTTPCLIENT-1989:
---------------------------------------
Summary: NullPointerException CacheValidityPolicy#getAgeValue()
Key: HTTPCLIENT-1989
URL: https://issues.apache.org/jira/browse/HTTPCLIENT-1989
Project: HttpComponents HttpClient
Issue Type: Bug
Components: HttpCache
Affects Versions: 4.5.8
Reporter: Eric Hubert
While updating from HttpClient 4.4.1 to 4.5.8 we immediately faced an issue
where the following NPE was thrown.
{code:java}
Caused by: java.lang.NullPointerException
at
org.apache.http.impl.client.cache.CacheValidityPolicy.getAgeValue(CacheValidityPolicy.java:236)
at
org.apache.http.impl.client.cache.CacheValidityPolicy.getCorrectedReceivedAgeSecs(CacheValidityPolicy.java:253)
at
org.apache.http.impl.client.cache.CacheValidityPolicy.getCorrectedInitialAgeSecs(CacheValidityPolicy.java:263)
at
org.apache.http.impl.client.cache.CacheValidityPolicy.getCurrentAgeSecs(CacheValidityPolicy.java:54)
at
org.apache.http.impl.client.cache.CacheValidityPolicy.isResponseFresh(CacheValidityPolicy.java:77)
at
org.apache.http.impl.client.cache.CachedResponseSuitabilityChecker.isFreshEnough(CachedResponseSuitabilityChecker.java:76)
at
org.apache.http.impl.client.cache.CachedResponseSuitabilityChecker.canCachedResponseBeUsed(CachedResponseSuitabilityChecker.java:147)
at
org.apache.http.impl.client.cache.CachingExec.handleCacheHit(CachingExec.java:291)
at org.apache.http.impl.client.cache.CachingExec.execute(CachingExec.java:277)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
at
org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at
org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
at
org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108){code}
Determining the cause wasn't that obvious, at least not to me. Therefore I
thought it would be a good idea to file an issue for documentation purpose.
Maybe someone also has a good idea how to address it.
We use the HttpClient in conjunction with the HttpClient Caching module and
configured it to use the Memcached storage (MemcachedHttpCacheStorage). Our
memcached infrastructure systems are running all the time, also while we are
updating our applications using it. The memcached store serialized
representations of HttpCacheEntry. An HttpCacheEntry consists of a HeaderGroup
instance (from HttpCore).
It looks like this class received a change (between HttpCore 4.4.1 and 4.4.2)
which changed the serialization, although its serialVersionUID wasn't changed:
[https://github.com/apache/httpcomponents-core/commit/040af07704592c8acb98a5a47cbf6b90c17fe0e0#diff-5a11091c948c5a8abd9bcc6bb4f7bc0f]
effectively resulting in an NPE while accessing its new final member EMPTY
(which is NULL after deserializing an object created with HttpClient 4.4.1 with
a newer version).
{code:java}
private final Header[] EMPTY = new Header[] {};{code}
I have not yet had a chance to check what would have happened, if the
serialVersionUID were changed, but I expect the MemcachedHttpCacheStorage to
create some sort of SerializationException which may have handled even before
in a much more graceful manner. I will test this once I find the time.
For now we had to do a quick fallback to the old HttpClient version. Next I
need to look for a good solution as during rolling software upgrades we will
always have a time, were both HttpClient versions are in parallel usage and the
response caching seems to be essential (so simply turning off the cache usage
during the upgrade, flushing the cache and turning it on once all servers are
up with the new HttpClient version also does not seem to be a great option).
I'm looking forward for any ideas. Please also feel free to adjust/move this
ticket accordingly! It turned out not to be a bug in HttpClient Cache itself,
but I thought this would be a more logical place than HttpCore as it likely
only affects certain Cache usage scenarios.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
