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SOLR-7419: document intentional overflow in SolrQueryTimeoutImpl thread local 

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1674866 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Steven Rowe 2015-04-20 14:25:52 +00:00
parent da1cd63a22
commit 0bc9c7821d
1 changed files with 17 additions and 0 deletions
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17
solr/core/src/java/org/apache/solr/search/SolrQueryTimeoutImpl.java
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@ -33,6 +33,23 @@ public class SolrQueryTimeoutImpl implements QueryTimeout {
* The ThreadLocal variable to store the time beyond which, the processing should exit. * The ThreadLocal variable to store the time beyond which, the processing should exit.
*/ */
public static ThreadLocal<Long> timeoutAt = new ThreadLocal<Long>() { public static ThreadLocal<Long> timeoutAt = new ThreadLocal<Long>() {
/**
* {@inheritDoc}
* <p>
* By default, timeoutAt is set as far in the future as possible,
* so that it effectively never happens.
* <p>
* Since nanoTime() values can be anything from Long.MIN_VALUE to
* Long.MAX_VALUE, adding Long.MAX_VALUE can cause overflow. That's
* expected and works fine, since in that case the subtraction of a
* future nanoTime() value from timeoutAt (in
* {@link SolrQueryTimeoutImpl#shouldExit}) will result in underflow,
* and checking the sign of the result of that subtraction (via
* comparison to zero) will correctly indicate whether the future
* nanoTime() value has exceeded the timeoutAt value.
* <p>
* See {@link System#nanoTime}
*/
@Override @Override
protected Long initialValue() { protected Long initialValue() {
return nanoTime() + Long.MAX_VALUE; return nanoTime() + Long.MAX_VALUE;