@@ -664,7 +664,41 @@ fn rolegroup_config_map(
664664 )
665665 . add ( "dfs.datanode.registered.hostname" , "${env.POD_ADDRESS}" )
666666 . add ( "dfs.datanode.registered.port" , "${env.DATA_PORT}" )
667- . add ( "dfs.datanode.registered.ipc.port" , "${env.IPC_PORT}" ) ;
667+ . add ( "dfs.datanode.registered.ipc.port" , "${env.IPC_PORT}" )
668+ // The following two properties are set to "true" because there is a minor chance that data
669+ // written to HDFS is not synced to disk even if a block has been closed.
670+ // Users in HBase can control this explicitly for the WAL, but for flushes and compactions
671+ // I believe they can't as easily (if at all).
672+ // In theory, HBase should be able to recover from these failures, but that comes at a cost
673+ // and there's always a risk.
674+ // Enabling this behavior causes HDFS to sync to disk as soon as possible.
675+ . add ( "dfs.datanode.sync.behind.writes" , "true" )
676+ . add ( "dfs.datanode.synconclose" , "true" )
677+ // Defaults to 10 since at least 2011.
678+ // This controls the concurrent number of client connections (this includes DataNodes)
679+ // to the NameNode. Ideally, we'd scale this with the number of DataNodes but this would
680+ // lead to restarts of the NameNode.
681+ // This should lead to better performance due to more concurrency.
682+ . add ( "dfs.namenode.handler.count" , "50" )
683+ // Defaults to 10 since at least 2012.
684+ // This controls the concurrent number of client connections to the DataNodes.
685+ // We have no idea how many clients there may be, so it's hard to assign a good default.
686+ // Increasing to 50 should lead to better performance due to more concurrency, especially
687+ // with use-cases like HBase.
688+ . add ( "dfs.datanode.handler.count" , "50" )
689+ // The following two properties default to 2 and 4 respectively since around 2013.
690+ // They control the number of maximum replication "jobs" a NameNode assigns to
691+ // a DataNode in a single heartbeat.
692+ // Increasing this number will increase network usage during replication events
693+ // but can lead to faster recovery.
694+ . add ( "dfs.namenode.replication.max-streams" , "4" )
695+ . add ( "dfs.namenode.replication.max-streams-hard-limit" , "8" )
696+ // Defaults to 4096 and hasn't changed since at least 2011.
697+ // The number of threads used for actual data transfer, so not very CPU heavy
698+ // but IO bound. This is why the number is relatively high.
699+ // But today's Java and IO should be able to handle more, so bump it to 8192 for
700+ // better performance/concurrency.
701+ . add ( "dfs.datanode.max.transfer.threads" , "8192" ) ;
668702 if hdfs. has_https_enabled ( ) {
669703 hdfs_site. add ( "dfs.datanode.registered.https.port" , "${env.HTTPS_PORT}" ) ;
670704 } else {
@@ -683,7 +717,10 @@ fn rolegroup_config_map(
683717 . ha_zookeeper_quorum ( )
684718 . security_config ( hdfs, cluster_info)
685719 . context ( BuildSecurityConfigSnafu ) ?
686- . enable_prometheus_endpoint ( ) ;
720+ . enable_prometheus_endpoint ( )
721+ // The default (4096) hasn't changed since 2009.
722+ // Increase to 128k to allow for faster transfers.
723+ . add ( "io.file.buffer.size" , "131072" ) ;
687724 if let Some ( hdfs_opa_config) = hdfs_opa_config {
688725 hdfs_opa_config. add_core_site_config ( & mut core_site) ;
689726 }
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