Differential D16913 Diff 40725 src/docs/user/cluster/cluster_partitioning.diviner

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src/docs/user/cluster/cluster_partitioning.diviner

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	Partitioning generally does not do much to increase resiliance or make it			Partitioning generally does not do much to increase resiliance or make it
	easier to recover from disasters, and is primarily a mechanism for scaling.			easier to recover from disasters, and is primarily a mechanism for scaling.

	If you are considering partitioning, you likely want to configure replication			If you are considering partitioning, you likely want to configure replication
	with a single master first. Even if you choose not to deploy replication, you			with a single master first. Even if you choose not to deploy replication, you
	should review and understand how replication works before you partition. For			should review and understand how replication works before you partition. For
	details, see @{Cluster:Databases}.			details, see @{Cluster:Databases}.

				Databases also support some advanced configuration options. Briefly:

				- `persistent`: Allows use of persistent connections, reducing pressure on
				outbound ports.

				See "Advanced Configuration", below, for additional discussion.


	What Partitioning Does			What Partitioning Does
	======================			======================

	When you partition Phabricator, you move all of the data for one or more			When you partition Phabricator, you move all of the data for one or more
	applications (like Maniphest) to a new master database host. This is possible			applications (like Maniphest) to a new master database host. This is possible
	because Phabricator stores data for each application in its own logical			because Phabricator stores data for each application in its own logical
	database (like `phabricator_maniphest`) and performs no joins between databases.			database (like `phabricator_maniphest`) and performs no joins between databases.
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	Launching a new Partition			Launching a new Partition
	=========================			=========================

	To add a new partition, follow these steps:			To add a new partition, follow these steps:

	- Set up the new database host or hosts.			- Set up the new database host or hosts.
	- Add the new database to `cluster.database`, but keep its "partition"			- Add the new database to `cluster.databases`, but keep its "partition"
	configuration empty (just an empty list). If this is the first time you			configuration empty (just an empty list). If this is the first time you
	are partitioning, you will need to configure your existing master as the			are partitioning, you will need to configure your existing master as the
	new "default". This will let Phabricator interact with it, but won't send			new "default". This will let Phabricator interact with it, but won't send
	any traffic to it yet.			any traffic to it yet.
	- Run `bin/storage partition`.			- Run `bin/storage partition`.
	- Run `bin/storage upgrade` to initialize the schemata on the new hosts.			- Run `bin/storage upgrade` to initialize the schemata on the new hosts.
	- Stop writes to the applications you want to move by putting Phabricator			- Stop writes to the applications you want to move by putting Phabricator
	in read-only mode, or shutting down the webserver and daemons, or telling			in read-only mode, or shutting down the webserver and daemons, or telling
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	of which patches have been applied to that particular master so that			of which patches have been applied to that particular master so that
	`bin/storage upgrade` can upgrade hosts correctly.			`bin/storage upgrade` can upgrade hosts correctly.

	Phabricator does not perform joins across logical databases, so there are no			Phabricator does not perform joins across logical databases, so there are no
	meaningful differences in runtime behavior if two applications are on the same			meaningful differences in runtime behavior if two applications are on the same
	physical host or different physical hosts.			physical host or different physical hosts.


				Advanced Configuration
				======================

				Separate from partitioning, some advanced configuration is supported. These
				options must be set on database specifications in `cluster.databases`. You can
				configure them without actually building a cluster by defining a cluster with
				only one master.

				`persistent` //(bool)// Enables persistent connections. Defaults to off.

				With persitent connections enabled, Phabricator will keep a pool of database
				connections open between web requests and reuse them when serving subsequent
				requests.

				The primary benefit of using persistent connections is that it will greatly
				reduce pressure on how quickly outbound TCP ports are opened and closed. After
				a TCP port closes, it normally can't be used again for about 60 seconds, so
				rapidly cycling ports can cause resource exuastion. If you're seeing failures
				because requests are unable to bind to an outbound port, enabling this option
				is likely to fix the issue. This option may also slightly increase performance.

				The cost of using persistent connections is that you may need to raise the
				MySQL `max_connections` setting: although Phabricator will make far fewer
				connections, the connections it does make will be longer-lived. Raising this
				setting will increase MySQL memory requirements and may run into other limits,
				like `open_files_limit`, which may also need to be raised.

				Persistent connections are enabled per-database. If you always want to use
				them, set the flag on each configured database in `cluster.databases`.


	Next Steps			Next Steps
	==========			==========

	Continue by:			Continue by:

	- returning to @{article:Clustering Introduction}.			- returning to @{article:Clustering Introduction}.