Implement appender of slow queries to system_views.slow_queries table

patch by Stefan Miklosovic; reviewed by Dmitry Konstantinov, Bernardo Botella for CASSANDRA-13001

Author: smiklosovic

conf/cassandra.yaml

@@ -1396,6 +1396,10 @@ request_timeout: 10000ms
 # How long before a node logs slow queries. Select queries that take longer than
 # this timeout to execute, will generate an aggregated log message, so that slow queries
 # can be identified. Set this value to zero to disable slow query logging.
+#
+# It is possible to log slow queries into system_views.slow_queries virtual table.
+# Consult logback.xml to uncomment specific appender and logger to enable this functionality.
+#
 # Min unit: ms
 slow_query_log_timeout: 500ms
 

conf/logback.xml

@@ -119,6 +119,19 @@ appender reference in the root level section below.
     </filter>
   </appender> -->
 
+  <!-- Uncomment below configuration and corresponding appender-ref in slow_queries logger to activate
+       logging into system_views.slow_queries virtual table. -->
+  <!-- <appender name="SLOW_QUERIES_TO_VTABLE" class="org.apache.cassandra.utils.logging.SlowQueriesAppender"/> -->
+
+  <!-- Log slow queries to system_views.slow_queries virtual table -->
+  <logger name="slow_queries" additivity="false" level="DEBUG">
+    <appender-ref ref="DEBUGLOG"/>
+    <!-- uncomment this appender reference together with appender definition above
+         to start to put slow queries into system_views.slow_queries virtual table
+    <appender-ref ref="SLOW_QUERIES_TO_VTABLE"/>
+    -->
+  </logger>
+
   <root level="INFO">
     <appender-ref ref="SYSTEMLOG" />
     <appender-ref ref="STDOUT" />

src/java/org/apache/cassandra/config/CassandraRelevantProperties.java

@@ -27,6 +27,7 @@
 
 import accord.utils.Invariants;
 import org.apache.cassandra.db.virtual.LogMessagesTable;
+import org.apache.cassandra.db.virtual.SlowQueriesTable;
 import org.apache.cassandra.exceptions.ConfigurationException;
 import org.apache.cassandra.utils.FBUtilities;
 import org.apache.cassandra.utils.StorageCompatibilityMode;
@@ -363,6 +364,8 @@ public enum CassandraRelevantProperties
     LOG4J2_DISABLE_JMX_LEGACY("log4j2.disable.jmx"),
     LOG4J_SHUTDOWN_HOOK_ENABLED("log4j.shutdownHookEnabled"),
     LOGBACK_CONFIGURATION_FILE("logback.configurationFile"),
+    /** Maximum number of rows in system_views.slow_queries */
+    LOGS_SLOW_QUERIES_VIRTUAL_TABLE_MAX_ROWS("cassandra.virtual.slow_queries.max.rows", convertToString(SlowQueriesTable.LOGS_VIRTUAL_TABLE_DEFAULT_ROWS)),
     /** Maximum number of rows in system_views.logs table */
     LOGS_VIRTUAL_TABLE_MAX_ROWS("cassandra.virtual.logs.max.rows", convertToString(LogMessagesTable.LOGS_VIRTUAL_TABLE_DEFAULT_ROWS)),
     /**

src/java/org/apache/cassandra/db/AbstractReadQuery.java

@@ -118,4 +118,16 @@ public String toCQLString()
     }
 
     protected abstract void appendCQLWhereClause(StringBuilder sb);
+
+    @Override
+    public String monitoredOnKeyspace()
+    {
+        return metadata().keyspace;
+    }
+
+    @Override
+    public String monitoredOnTable()
+    {
+        return metadata().name;
+    }
 }

src/java/org/apache/cassandra/db/monitoring/Monitorable.java

@@ -20,6 +20,8 @@
 
 public interface Monitorable
 {
+    Monitorable NO_OP = new NoOp();
+
     String name();
     long creationTimeNanos();
     long timeoutNanos();
@@ -33,4 +35,76 @@ public interface Monitorable
 
     boolean abort();
     boolean complete();
+
+    default String monitoredOnKeyspace() { return null; };
+    default String monitoredOnTable() { return null; };
+
+    class NoOp implements Monitorable
+    {
+        @Override
+        public String name()
+        {
+            return null;
+        }
+
+        @Override
+        public long creationTimeNanos()
+        {
+            return 0;
+        }
+
+        @Override
+        public long timeoutNanos()
+        {
+            return 0;
+        }
+
+        @Override
+        public long slowTimeoutNanos()
+        {
+            return 0;
+        }
+
+        @Override
+        public boolean isInProgress()
+        {
+            return false;
+        }
+
+        @Override
+        public boolean isAborted()
+        {
+            return false;
+        }
+
+        @Override
+        public boolean isCompleted()
+        {
+            return false;
+        }
+
+        @Override
+        public boolean isSlow()
+        {
+            return false;
+        }
+
+        @Override
+        public boolean isCrossNode()
+        {
+            return false;
+        }
+
+        @Override
+        public boolean abort()
+        {
+            return false;
+        }
+
+        @Override
+        public boolean complete()
+        {
+            return false;
+        }
+    }
 }