Default commitlog_sync_batch_window_in_ms changed to 2ms
patch by jbellis; reveiwed by bes for CASSANDRA-9504


Project: http://git-wip-us.apache.org/repos/asf/cassandra/repo
Commit: http://git-wip-us.apache.org/repos/asf/cassandra/commit/80ef2825
Tree: http://git-wip-us.apache.org/repos/asf/cassandra/tree/80ef2825
Diff: http://git-wip-us.apache.org/repos/asf/cassandra/diff/80ef2825

Branch: refs/heads/trunk
Commit: 80ef2825708dbb9d0e359a2aef8cac1061b52070
Parents: 66a48e7
Author: Jonathan Ellis <[email protected]>
Authored: Wed Jun 3 10:29:39 2015 -0700
Committer: Jonathan Ellis <[email protected]>
Committed: Wed Jun 3 10:29:39 2015 -0700

----------------------------------------------------------------------
 CHANGES.txt         |  1 +
 NEWS.txt            | 15 +++++++++++++++
 conf/cassandra.yaml | 11 +++++++----
 3 files changed, 23 insertions(+), 4 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/cassandra/blob/80ef2825/CHANGES.txt
----------------------------------------------------------------------
diff --git a/CHANGES.txt b/CHANGES.txt
index 4d38e1e..f5f9862 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 2.1.6
+ * Default commitlog_sync_batch_window_in_ms changed to 2ms (CASSANDRA-9504)
  * Fix empty partition assertion in unsorted sstable writing tools 
(CASSANDRA-9071)
  * Ensure truncate without snapshot cannot produce corrupt responses 
(CASSANDRA-9388) 
  * Consistent error message when a table mixes counter and non-counter

http://git-wip-us.apache.org/repos/asf/cassandra/blob/80ef2825/NEWS.txt
----------------------------------------------------------------------
diff --git a/NEWS.txt b/NEWS.txt
index 6610d15..2f4166a 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -15,6 +15,7 @@ using the provided 'sstableupgrade' tool.
 
 2.1.5
 =====
+
 Upgrading
 ---------
     - The option to omit cold sstables with size tiered compaction has been
@@ -24,8 +25,13 @@ Upgrading
 
 2.1.4
 =====
+
+Upgrading
+---------
 The default JMX config now listens to localhost only. You must enable 
 the other JMX flags in cassandra-env.sh manually.
+
+
 2.1.3
 =====
 
@@ -37,6 +43,7 @@ Upgrading
     - Incremental replacement of compacted SSTables has been disabled for this
       release.
 
+
 2.1.2
 =====
 
@@ -45,6 +52,7 @@ Upgrading
     - Nothing specific to this release, but please see 2.1 if you are upgrading
       from a previous version.
 
+
 2.1.1
 =====
 
@@ -59,6 +67,7 @@ New features
      reason you want to disable it pass, the following system property
      -Dcassandra.native.epoll.enabled=false
 
+
 2.1
 ===
 
@@ -106,6 +115,11 @@ New features
 
 Upgrading
 ---------
+   - commitlog_sync_batch_window_in_ms behavior has changed from the
+     maximum time to wait between fsync to the minimum time.  We are 
+     working on making this more user-friendly (see CASSANDRA-9533) but in the
+     meantime, this means 2.1 needs a much smaller batch window to keep
+     writer threads from starving.  The suggested default is now 2ms.
    - Rolling upgrades from anything pre-2.0.7 is not supported. Furthermore
      pre-2.0 sstables are not supported. This means that before upgrading
      a node on 2.1, this node must be started on 2.0 and
@@ -126,6 +140,7 @@ Upgrading
      has been deprecated.
    - support for supercolumns has been removed from json2sstable
 
+
 2.0.11
 ======
 

http://git-wip-us.apache.org/repos/asf/cassandra/blob/80ef2825/conf/cassandra.yaml
----------------------------------------------------------------------
diff --git a/conf/cassandra.yaml b/conf/cassandra.yaml
index 2b43ba7..9d6d135 100644
--- a/conf/cassandra.yaml
+++ b/conf/cassandra.yaml
@@ -226,13 +226,16 @@ counter_cache_save_period: 7200
 # saved_caches_directory: /var/lib/cassandra/saved_caches
 
 # commitlog_sync may be either "periodic" or "batch." 
+# 
 # When in batch mode, Cassandra won't ack writes until the commit log
-# has been fsynced to disk.  It will wait up to
-# commitlog_sync_batch_window_in_ms milliseconds for other writes, before
-# performing the sync.
+# has been fsynced to disk.  It will wait
+# commitlog_sync_batch_window_in_ms milliseconds between fsyncs.
+# This window should be kept short because the writer threads will
+# be unable to do extra work while waiting.  (You may need to increase
+# concurrent_writes for the same reason.)
 #
 # commitlog_sync: batch
-# commitlog_sync_batch_window_in_ms: 50
+# commitlog_sync_batch_window_in_ms: 2
 #
 # the other option is "periodic" where writes may be acked immediately
 # and the CommitLog is simply synced every commitlog_sync_period_in_ms

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