Return-Path: X-Original-To: archive-asf-public-internal@cust-asf2.ponee.io Delivered-To: archive-asf-public-internal@cust-asf2.ponee.io Received: from cust-asf.ponee.io (cust-asf.ponee.io [163.172.22.183]) by cust-asf2.ponee.io (Postfix) with ESMTP id CC5A2200C73 for ; Wed, 10 May 2017 17:09:12 +0200 (CEST) Received: by cust-asf.ponee.io (Postfix) id CAF52160BA8; Wed, 10 May 2017 15:09:12 +0000 (UTC) Delivered-To: archive-asf-public@cust-asf.ponee.io Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by cust-asf.ponee.io (Postfix) with SMTP id EB776160B9C for ; Wed, 10 May 2017 17:09:11 +0200 (CEST) Received: (qmail 63296 invoked by uid 500); 10 May 2017 15:09:11 -0000 Mailing-List: contact commits-help@cassandra.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Delivered-To: mailing list commits@cassandra.apache.org Received: (qmail 63285 invoked by uid 99); 10 May 2017 15:09:11 -0000 Received: from pnap-us-west-generic-nat.apache.org (HELO spamd4-us-west.apache.org) (209.188.14.142) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 10 May 2017 15:09:11 +0000 Received: from localhost (localhost [127.0.0.1]) by spamd4-us-west.apache.org (ASF Mail Server at spamd4-us-west.apache.org) with ESMTP id A065FC0922 for ; Wed, 10 May 2017 15:09:10 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at spamd4-us-west.apache.org X-Spam-Flag: NO X-Spam-Score: -99.201 X-Spam-Level: X-Spam-Status: No, score=-99.201 tagged_above=-999 required=6.31 tests=[KAM_ASCII_DIVIDERS=0.8, RP_MATCHES_RCVD=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001, USER_IN_WHITELIST=-100] autolearn=disabled Received: from mx1-lw-eu.apache.org ([10.40.0.8]) by localhost (spamd4-us-west.apache.org [10.40.0.11]) (amavisd-new, port 10024) with ESMTP id A699JC7jvobO for ; Wed, 10 May 2017 15:09:08 +0000 (UTC) Received: from mailrelay1-us-west.apache.org (mailrelay1-us-west.apache.org [209.188.14.139]) by mx1-lw-eu.apache.org (ASF Mail Server at mx1-lw-eu.apache.org) with ESMTP id BC0D360EAD for ; Wed, 10 May 2017 15:09:07 +0000 (UTC) Received: from jira-lw-us.apache.org (unknown [207.244.88.139]) by mailrelay1-us-west.apache.org (ASF Mail Server at mailrelay1-us-west.apache.org) with ESMTP id 7F1B8E0D4D for ; Wed, 10 May 2017 15:09:06 +0000 (UTC) Received: from jira-lw-us.apache.org (localhost [127.0.0.1]) by jira-lw-us.apache.org (ASF Mail Server at jira-lw-us.apache.org) with ESMTP id 14F0A21E13 for ; Wed, 10 May 2017 15:09:05 +0000 (UTC) Date: Wed, 10 May 2017 15:09:05 +0000 (UTC) From: "Benjamin Lerer (JIRA)" To: commits@cassandra.apache.org Message-ID: In-Reply-To: References: Subject: [jira] [Updated] (CASSANDRA-13120) Trace and Histogram output misleading MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 archived-at: Wed, 10 May 2017 15:09:13 -0000 [ https://issues.apache.org/jira/browse/CASSANDRA-13120?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Benjamin Lerer updated CASSANDRA-13120: --------------------------------------- Status: Open (was: Patch Available) > Trace and Histogram output misleading > ------------------------------------- > > Key: CASSANDRA-13120 > URL: https://issues.apache.org/jira/browse/CASSANDRA-13120 > Project: Cassandra > Issue Type: Bug > Components: Core > Reporter: Adam Hattrell > Assignee: Benjamin Lerer > Priority: Minor > > If we look at the following output: > {noformat} > [centos@cassandra-c-3]$ nodetool getsstables -- keyspace table 60ea4399-6b9f-4419-9ccb-ff2e6742de10 > /mnt/cassandra/data/data/keyspace/table-62f30431acf411e69a4ed7dd11246f8a/mc-647146-big-Data.db > /mnt/cassandra/data/data/keyspace/table-62f30431acf411e69a4ed7dd11246f8a/mc-647147-big-Data.db > /mnt/cassandra/data/data/keyspace/table-62f30431acf411e69a4ed7dd11246f8a/mc-647145-big-Data.db > /mnt/cassandra/data/data/keyspace/table-62f30431acf411e69a4ed7dd11246f8a/mc-647152-big-Data.db > /mnt/cassandra/data/data/keyspace/table-62f30431acf411e69a4ed7dd11246f8a/mc-647157-big-Data.db > /mnt/cassandra/data/data/keyspace/table-62f30431acf411e69a4ed7dd11246f8a/mc-648137-big-Data.db > {noformat} > We can see that this key value appears in just 6 sstables. However, when we run a select against the table and key we get: > {noformat} > Tracing session: a6c81330-d670-11e6-b00b-c1d403fd6e84 > activity | timestamp | source | source_elapsed > -------------------------------------------------------------------------------------------------------------------+----------------------------+----------------+---------------- > Execute CQL3 query | 2017-01-09 13:36:40.419000 | 10.200.254.141 | 0 > Parsing SELECT * FROM keyspace.table WHERE id = 60ea4399-6b9f-4419-9ccb-ff2e6742de10; [SharedPool-Worker-2] | 2017-01-09 13:36:40.419000 | 10.200.254.141 | 104 > Preparing statement [SharedPool-Worker-2] | 2017-01-09 13:36:40.419000 | 10.200.254.141 | 220 > Executing single-partition query on table [SharedPool-Worker-1] | 2017-01-09 13:36:40.419000 | 10.200.254.141 | 450 > Acquiring sstable references [SharedPool-Worker-1] | 2017-01-09 13:36:40.419000 | 10.200.254.141 | 477 > Bloom filter allows skipping sstable 648146 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419000 | 10.200.254.141 | 496 > Bloom filter allows skipping sstable 648145 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 503 > Key cache hit for sstable 648140 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 513 > Bloom filter allows skipping sstable 648135 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 520 > Bloom filter allows skipping sstable 648130 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 526 > Bloom filter allows skipping sstable 648048 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 530 > Bloom filter allows skipping sstable 647749 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 535 > Bloom filter allows skipping sstable 647404 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 540 > Key cache hit for sstable 647145 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 548 > Key cache hit for sstable 647146 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419001 | 10.200.254.141 | 556 > Key cache hit for sstable 647147 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 564 > Bloom filter allows skipping sstable 647148 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 570 > Bloom filter allows skipping sstable 647149 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 575 > Bloom filter allows skipping sstable 647150 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 580 > Bloom filter allows skipping sstable 647151 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 585 > Key cache hit for sstable 647152 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 591 > Bloom filter allows skipping sstable 647153 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 597 > Bloom filter allows skipping sstable 647154 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 601 > Bloom filter allows skipping sstable 647155 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 606 > Bloom filter allows skipping sstable 647156 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 611 > Key cache hit for sstable 647157 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419002 | 10.200.254.141 | 617 > Bloom filter allows skipping sstable 647158 [SharedPool-Worker-1] | 2017-01-09 13:36:40.419003 | 10.200.254.141 | 623 > Skipped 0/22 non-slice-intersecting sstables, included 0 due to tombstones [SharedPool-Worker-1] | 2017-01-09 13:36:40.419003 | 10.200.254.141 | 644 > Merging data from memtables and 22 sstables [SharedPool-Worker-1] | 2017-01-09 13:36:40.419003 | 10.200.254.141 | 654 > Read 9 live and 0 tombstone cells [SharedPool-Worker-1] | 2017-01-09 13:36:40.419003 | 10.200.254.141 | 732 > Request complete | 2017-01-09 13:36:40.419808 | 10.200.254.141 | 808 > {noformat} > You'll note we claim not to have skipped any files due to bloom filters - even though we know the data is only in 6 files. > CFHistograms also report that we're hitting every sstables: > {noformat} > Percentile SSTables Write Latency Read Latency Partition Size Cell Count > (micros) (micros) (bytes) > 50% 24.00 14.24 182.79 103 1 > 75% 24.00 17.08 315.85 149 2 > 95% 24.00 20.50 7007.51 372 7 > 98% 24.00 24.60 10090.81 642 12 > 99% 24.00 29.52 12108.97 770 14 > Min 21.00 3.31 29.52 43 0 > Max 29.00 1358.10 62479.63 1597 35 > {noformat} > Code for the read is here: > https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/db/SinglePartitionReadCommand.java#L561 > We seem to iterate over all the sstables and increment the metric as part of that iteration. > Either the reporting is incorrect - or we should maybe check the bloom filters first and then iterate the tombstones after? > In this particular case we were using TWCS which makes the problem more apparent. TWCS guarantees that we'll keep more sstables in an un-merged state. With STCS we have to search them all, but most of them should be merged together if Compaction is keeping up. LCS the read path is restricted which will disguise the impact. -- This message was sent by Atlassian JIRA (v6.3.15#6346) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscribe@cassandra.apache.org For additional commands, e-mail: commits-help@cassandra.apache.org