[jira] [Updated] (CASSANDRA-6682) Loss of precision under concurrent access on o.a.c.utils.EstimatedHistogram methods
[ https://issues.apache.org/jira/browse/CASSANDRA-6682?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Paulo Gaspar updated CASSANDRA-6682: Attachment: 6682.txt The attached files contains all necessary changes. Loss of precision under concurrent access on o.a.c.utils.EstimatedHistogram methods --- Key: CASSANDRA-6682 URL: https://issues.apache.org/jira/browse/CASSANDRA-6682 Project: Cassandra Issue Type: Bug Reporter: Paulo Gaspar Priority: Minor Fix For: 1.2.16, 2.0.6 Attachments: 6682.txt On method getBuckets(), under concurrent use of an instance, the value of a buckets variable element might change between its access on the 1st for cycle and its access on the 2nd, when it is reset to 0. This means that, if one collects metrics by repeatedly calling estHist.getBuckets(true), (e.g.: to sum its values) it will miss counting some values added to buckets entries between that 1st and 2nd access. On method mean(), if the i-th entry of buckets changes value between the 1st and 2nd access inside the for cycle, than the elements and sum accumulators are not working with the same values for that entry. It is more precise (and faster) to use a local variable to read the value just once. Not an error but a semantic improvement: at my initial read of this class, I thought the buckets and bucketOffsets fields could change length. Such perception can be avoided by making the bucketOffsets field final. -- This message was sent by Atlassian JIRA (v6.1.5#6160)
[jira] [Updated] (CASSANDRA-6682) Loss of precision under concurrent access on o.a.c.utils.EstimatedHistogram methods
[ https://issues.apache.org/jira/browse/CASSANDRA-6682?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Jonathan Ellis updated CASSANDRA-6682: -- Reviewer: Jonathan Ellis Component/s: Core Fix Version/s: (was: 1.2.16) Assignee: Paulo Gaspar Loss of precision under concurrent access on o.a.c.utils.EstimatedHistogram methods --- Key: CASSANDRA-6682 URL: https://issues.apache.org/jira/browse/CASSANDRA-6682 Project: Cassandra Issue Type: Bug Components: Core Reporter: Paulo Gaspar Assignee: Paulo Gaspar Priority: Minor Fix For: 2.0.6 Attachments: 6682.txt On method getBuckets(), under concurrent use of an instance, the value of a buckets variable element might change between its access on the 1st for cycle and its access on the 2nd, when it is reset to 0. This means that, if one collects metrics by repeatedly calling estHist.getBuckets(true), (e.g.: to sum its values) it will miss counting some values added to buckets entries between that 1st and 2nd access. On method mean(), if the i-th entry of buckets changes value between the 1st and 2nd access inside the for cycle, than the elements and sum accumulators are not working with the same values for that entry. It is more precise (and faster) to use a local variable to read the value just once. Not an error but a semantic improvement: at my initial read of this class, I thought the buckets and bucketOffsets fields could change length. Such perception can be avoided by making the bucketOffsets field final. -- This message was sent by Atlassian JIRA (v6.1.5#6160)
