From 176d4bac22c356c80e275dcb4040bc5cbd0da1c2 Mon Sep 17 00:00:00 2001
From: Jason Brown <jasedbrown@gmail.com>
Date: Fri, 20 Jul 2018 16:05:18 -0700
Subject: [PATCH] Make PeriodicCommitLogService.blockWhenSyncLagsNanos
 configurable

patch by jasobrown; reviewed by Jordan West for CASSANDRA-14580
---
 CHANGES.txt                                               | 1 +
 conf/cassandra.yaml                                       | 4 ++++
 src/java/org/apache/cassandra/config/Config.java          | 1 +
 .../org/apache/cassandra/config/DatabaseDescriptor.java   | 8 ++++++++
 .../cassandra/db/commitlog/PeriodicCommitLogService.java  | 4 +++-
 5 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index faf37ea9be..4ba3313a12 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 4.0
+ * Make PeriodicCommitLogService.blockWhenSyncLagsNanos configurable (CASSANDRA-14580)
  * Improve logging in MessageInHandler's constructor (CASSANDRA-14576)
  * Set broadcast address in internode messaging handshake (CASSANDRA-14579)
  * Wait for schema agreement prior to building MVs (CASSANDRA-14571)
diff --git a/conf/cassandra.yaml b/conf/cassandra.yaml
index 7ff056df5a..439b85a1ee 100644
--- a/conf/cassandra.yaml
+++ b/conf/cassandra.yaml
@@ -389,6 +389,10 @@ counter_cache_save_period: 7200
 commitlog_sync: periodic
 commitlog_sync_period_in_ms: 10000
 
+# When in periodic commitlog mode, the number of milliseconds to block writes
+# while waiting for a slow disk flush to complete.
+# periodic_commitlog_sync_lag_block_in_ms: 
+
 # The size of the individual commitlog file segments.  A commitlog
 # segment may be archived, deleted, or recycled once all the data
 # in it (potentially from each columnfamily in the system) has been
diff --git a/src/java/org/apache/cassandra/config/Config.java b/src/java/org/apache/cassandra/config/Config.java
index d9250bb181..0d4760ee96 100644
--- a/src/java/org/apache/cassandra/config/Config.java
+++ b/src/java/org/apache/cassandra/config/Config.java
@@ -204,6 +204,7 @@ public class Config
     public int commitlog_segment_size_in_mb = 32;
     public ParameterizedClass commitlog_compression;
     public int commitlog_max_compression_buffers_in_pool = 3;
+    public Integer periodic_commitlog_sync_lag_block_in_ms;
     public TransparentDataEncryptionOptions transparent_data_encryption_options = new TransparentDataEncryptionOptions();
 
     public Integer max_mutation_size_in_kb;
diff --git a/src/java/org/apache/cassandra/config/DatabaseDescriptor.java b/src/java/org/apache/cassandra/config/DatabaseDescriptor.java
index 91ee63a782..2dc3737313 100644
--- a/src/java/org/apache/cassandra/config/DatabaseDescriptor.java
+++ b/src/java/org/apache/cassandra/config/DatabaseDescriptor.java
@@ -1866,6 +1866,14 @@ public class DatabaseDescriptor
         return conf.commitlog_sync_period_in_ms;
     }
 
+    public static long getPeriodicCommitLogSyncBlock()
+    {
+        Integer blockMillis = conf.periodic_commitlog_sync_lag_block_in_ms;
+        return blockMillis == null
+               ? (long)(getCommitLogSyncPeriod() * 1.5)
+               : blockMillis;
+    }
+
     public static void setCommitLogSyncPeriod(int periodMillis)
     {
         conf.commitlog_sync_period_in_ms = periodMillis;
diff --git a/src/java/org/apache/cassandra/db/commitlog/PeriodicCommitLogService.java b/src/java/org/apache/cassandra/db/commitlog/PeriodicCommitLogService.java
index efd3394988..e94c616e44 100644
--- a/src/java/org/apache/cassandra/db/commitlog/PeriodicCommitLogService.java
+++ b/src/java/org/apache/cassandra/db/commitlog/PeriodicCommitLogService.java
@@ -17,11 +17,13 @@
  */
 package org.apache.cassandra.db.commitlog;
 
+import java.util.concurrent.TimeUnit;
+
 import org.apache.cassandra.config.DatabaseDescriptor;
 
 class PeriodicCommitLogService extends AbstractCommitLogService
 {
-    private static final long blockWhenSyncLagsNanos = (long) (DatabaseDescriptor.getCommitLogSyncPeriod() * 1.5e6);
+    private static final long blockWhenSyncLagsNanos = TimeUnit.MILLISECONDS.toNanos(DatabaseDescriptor.getPeriodicCommitLogSyncBlock());
 
     public PeriodicCommitLogService(final CommitLog commitLog)
     {