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Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
Overview of Postgres Utility Processes
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Overview of Postgres Utility Processes

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This technical presentation by EDB Dave Thomas, Systems Engineer provides an overview of: …

This technical presentation by EDB Dave Thomas, Systems Engineer provides an overview of:

1) BGWriter/Writer Process
2) Wall Writer Process
3) Stats Collector Process
4) Autovacuum Launch Process
5) Syslogger Process/Logger process
6) Archiver Process
7) WAL Send/Receive Processes

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  • 1. © 2013 EnterpriseDB, Corp. All Rights Reserved. 1 Overview of Postgres Utilities Processes Dave Thomas | 8.22.13 Techie Topic Series
  • 2. © 2013 EnterpriseDB, Corp. All Rights Reserved. 2 •  Overview – What are all these processes? •  Logger Process •  Checkpointer Process •  Writer Process •  WAL Writer Process •  Autovacuum Launcher Process •  Stats Collector Process •  Streaming Replication Process •  Resources Presentation Agenda
  • 3. © 2013 EnterpriseDB, Corp. All Rights Reserved. 3 What are all these processes? •  PostgreSQL utilizes separate processes instead of threads, which results in the above ps output for a freshly started cluster •  Each connection to the cluster will cause the postmaster to spawn a process which may look like the following: •  The above shows a connection from 127.0.0.1 to the test database by the user Postgres.
  • 4. © 2013 EnterpriseDB, Corp. All Rights Reserved. 4 •  Logging is an optional process, the default is OFF •  All the utility processes + user backends + postmaster daemon attach to the logger process •  All process information is logged under $PGDATA/pg_log in the file name specified by log_filename −  If the data directory is created with INITDB command, then the pg_log directory will need to be created manually. −  You can also log to syslog and CSV formatted files •  Increasing the amount of logging will increase the I/O load on the server. •  http://www.enterprisedb.com/docs/en/9.2/pg/runtime-config-logging.html Logger Process
  • 5. © 2013 EnterpriseDB, Corp. All Rights Reserved. 5 •  This process is responsible for flushing all dirty data pages to disk (called a checkpoint) −  This process can cause a significant I/O load on the server. •  Checkpoints are performed every checkpoint_timeout seconds or when all checkpoint_segments are filled, whichever comes first. •  More frequent checkpoints will provide for faster after-crash recovery, but this must be balanced by the increased I/O load generated. •  http://www.enterprisedb.com/docs/en/9.2/pg/wal-configuration.html Checkpointer Process
  • 6. © 2013 EnterpriseDB, Corp. All Rights Reserved. 6 •  Also known as BGWRITER process and is a mandatory process. •  Wakes every bgwriter_delay seconds and searches through the shared buffer pool looking for modified pages, writes them to disk, and evicts those pages from the shared buffer pool. •  No more than bgwriter_lru_maxpages buffers will be written by the background writer in a given pass. •  http://www.enterprisedb.com/docs/en/9.2/pg/runtime-config- resource.html#RUNTIME-CONFIG-RESOURCE-BACKGROUND-WRITER Writer Process
  • 7. © 2013 EnterpriseDB, Corp. All Rights Reserved. 7 •  This is a mandatory process •  Writes and syncs Write Ahead Logs(WAL) to disk upon transaction commit •  WALs allow transactions to be recovered in the event of a system crash •  http://www.enterprisedb.com/docs/en/9.2/pg/wal-configuration.html WAL Writer Process
  • 8. © 2013 EnterpriseDB, Corp. All Rights Reserved. 8 •  Autovacuuming is an optional process, default is ON. •  Automates the execution of VACUUM and ANALYZE commands •  A daemon which spawns autovacuum worker processes for each database −  Starts one worker on each database (up to autovacuum_max_workers) every autovacuum_naptime seconds −  Worker processes check each table and index in a database and executes VACUUM or ANALYZE as needed. •  http://www.enterprisedb.com/docs/en/9.2/pg/runtime-config-autovacuum.html Autovacuum Launcher Process
  • 9. © 2013 EnterpriseDB, Corp. All Rights Reserved. 9 •  Stats collector process is an optional process, default is ON. •  Collects information about cluster activity. −  Number of access to the tables and indexes −  Total number of rows in each table −  Information about VACUUM and ANALYZE actions for each table. •  Collection of statistics adds some overhead to query execution, but allows the query planner to make better choices. •  http://www.enterprisedb.com/docs/en/9.2/pg/monitoring-stats.html Stats Collector Process
  • 10. © 2013 EnterpriseDB, Corp. All Rights Reserved. 10 •  WAL Sender −  This process sends WALs the standby server. −  One process for each standby server. •  WAL Receiver −  This process receives WALs from the the primary server. −  The WALs are then replayed to bring the standby in sync with the primary. •  http://www.enterprisedb.com/docs/en/9.2/pg/warm-standby.html#STREAMING-REPLICATION Streaming Replication Processes
  • 11. © 2013 EnterpriseDB, Corp. All Rights Reserved. 11 •  Software Downloads & Documentation −  EnterpriseDB > Products > Postgres Plus Advanced Server −  EnterpriseDB > Products > Postgres Enterprise Manager −  EnterpriseDB > Products > Documentation −  EnterpriseDB > Products > Subscriptions •  Tutorials, Quick Starts, Webcasts, White Papers & Community −  EnterpriseDB > Resources •  Email us! −  Dave.thomas@enterprisedb.com −  lyn.vercellone@enterprisedb.com −  sales@enterprisedb.com Additional Resources- on EnterpriseDB.com
  • 12. © 2013 EnterpriseDB, Corp. All Rights Reserved. 12

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