hast.conf.5

.\" Copyright (c) 2010 The FreeBSD Foundation
.\" Copyright (c) 2010-2012 Pawel Jakub Dawidek <pawel@dawidek.net>
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.\" This documentation was written by Pawel Jakub Dawidek under sponsorship from
.\" the FreeBSD Foundation.
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.Dd January 25, 2012
.Dt HAST.CONF 5
.Os
.Sh NAME
.Nm hast.conf
.Nd configuration file for the
.Xr hastd 8
daemon and the
.Xr hastctl 8
utility
.Sh DESCRIPTION
The
.Nm
file is used by both
.Xr hastd 8
daemon
and
.Xr hastctl 8
control utility.
Configuration file is designed in a way that exactly the same file can be
(and should be) used on both HAST nodes.
Every line starting with # is treated as comment and ignored.
.Sh CONFIGURATION FILE SYNTAX
General syntax of the
.Nm
file is following:
.Bd -literal -offset indent
# Global section
control <addr>
listen <addr>
replication <mode>
checksum <algorithm>
compression <algorithm>
timeout <seconds>
exec <path>
metaflush on | off
pidfile <path>

on <node> {
	# Node section
        control <addr>
        listen <addr>
        pidfile <path>
}

on <node> {
	# Node section
        control <addr>
        listen <addr>
        pidfile <path>
}

resource <name> {
	# Resource section
	replication <mode>
	checksum <algorithm>
	compression <algorithm>
	name <name>
	local <path>
	timeout <seconds>
	exec <path>
	metaflush on | off

	on <node> {
		# Resource-node section
		name <name>
		# Required
		local <path>
		metaflush on | off
		# Required
		remote <addr>
		source <addr>
	}
	on <node> {
		# Resource-node section
		name <name>
		# Required
		local <path>
		metaflush on | off
		# Required
		remote <addr>
		source <addr>
	}
}
.Ed
.Pp
Most of the various available configuration parameters are optional.
If parameter is not defined in the particular section, it will be
inherited from the parent section.
For example, if the
.Ic listen
parameter is not defined in the node section, it will be inherited from
the global section.
In case the global section does not define the
.Ic listen
parameter at all, the default value will be used.
.Sh CONFIGURATION FILE DESCRIPTION
The
.Aq node
argument can be replaced either by a full hostname as obtained by
.Xr gethostname 3 ,
only first part of the hostname, by node's UUID as found in the
.Va kern.hostuuid
.Xr sysctl 8
variable
or by node's hostid as found in the
.Va kern.hostid
.Xr sysctl 8
variable.
.Pp
The following statements are available:
.Bl -tag -width ".Ic xxxx"
.It Ic control Aq addr
.Pp
Address for communication with
.Xr hastctl 8 .
Each of the following examples defines the same control address:
.Bd -literal -offset indent
uds:///var/run/hastctl
unix:///var/run/hastctl
/var/run/hastctl
.Ed
.Pp
The default value is
.Pa uds:///var/run/hastctl .
.It Ic pidfile Aq path
.Pp
File in which to store the process ID of the main
.Xr hastd 8
process.
.Pp
The default value is
.Pa /var/run/hastd.pid .
.It Ic listen Aq addr
.Pp
Address to listen on in form of:
.Bd -literal -offset indent
protocol://protocol-specific-address
.Ed
.Pp
Each of the following examples defines the same listen address:
.Bd -literal -offset indent
0.0.0.0
0.0.0.0:8457
tcp://0.0.0.0
tcp://0.0.0.0:8457
tcp4://0.0.0.0
tcp4://0.0.0.0:8457
.Ed
.Pp
Multiple listen addresses can be specified.
By default
.Nm hastd
listens on
.Pa tcp4://0.0.0.0:8457
and
.Pa tcp6://[::]:8457
if kernel supports IPv4 and IPv6 respectively.
.It Ic replication Aq mode
.Pp
Replication mode should be one of the following:
.Bl -tag -width ".Ic xxxx"
.It Ic memsync
.Pp
Report the write operation as completed when local write completes and
when the remote node acknowledges the data receipt, but before it
actually stores the data.
The data on remote node will be stored directly after sending
acknowledgement.
This mode is intended to reduce latency, but still provides a very good
reliability.
The only situation where some small amount of data could be lost is when
the data is stored on primary node and sent to the secondary.
Secondary node then acknowledges data receipt and primary reports
success to an application.
However, it may happen that the secondary goes down before the received
data is really stored locally.
Before secondary node returns, primary node dies entirely.
When the secondary node comes back to life it becomes the new primary.
Unfortunately some small amount of data which was confirmed to be stored
to the application was lost.
The risk of such a situation is very small.
The
.Ic memsync
replication mode is the default.
.It Ic fullsync
.Pp
Mark the write operation as completed when local as well as remote
write completes.
This is the safest and the slowest replication mode.
.It Ic async
.Pp
The write operation is reported as complete right after the local write
completes.
This is the fastest and the most dangerous replication mode.
This mode should be used when replicating to a distant node where
latency is too high for other modes.
.El
.It Ic checksum Aq algorithm
.Pp
Checksum algorithm should be one of the following:
.Bl -tag -width ".Ic sha256"
.It Ic none
No checksum will be calculated for the data being send over the network.
This is the default setting.
.It Ic crc32
CRC32 checksum will be calculated.
.It Ic sha256
SHA256 checksum will be calculated.
.El
.It Ic compression Aq algorithm
.Pp
Compression algorithm should be one of the following:
.Bl -tag -width ".Ic none"
.It Ic none
Data send over the network will not be compressed.
.It Ic hole
Only blocks that contain all zeros will be compressed.
This is very useful for initial synchronization where potentially many blocks
are still all zeros.
There should be no measurable performance overhead when this algorithm is being
used.
This is the default setting.
.It Ic lzf
The LZF algorithm by Marc Alexander Lehmann will be used to compress the data
send over the network.
LZF is very fast, general purpose compression algorithm.
.El
.It Ic timeout Aq seconds
.Pp
Connection timeout in seconds.
The default value is
.Va 20 .
.It Ic exec Aq path
.Pp
Execute the given program on various HAST events.
Below is the list of currently implemented events and arguments the given
program is executed with:
.Bl -tag -width ".Ic xxxx"
.It Ic "<path> role <resource> <oldrole> <newrole>"
.Pp
Executed on both primary and secondary nodes when resource role is changed.
.It Ic "<path> connect <resource>"
.Pp
Executed on both primary and secondary nodes when connection for the given
resource between the nodes is established.
.It Ic "<path> disconnect <resource>"
.Pp
Executed on both primary and secondary nodes when connection for the given
resource between the nodes is lost.
.It Ic "<path> syncstart <resource>"
.Pp
Executed on primary node when synchronization process of secondary node is
started.
.It Ic "<path> syncdone <resource>"
.Pp
Executed on primary node when synchronization process of secondary node is
completed successfully.
.It Ic "<path> syncintr <resource>"
.Pp
Executed on primary node when synchronization process of secondary node is
interrupted, most likely due to secondary node outage or connection failure
between the nodes.
.It Ic "<path> split-brain <resource>"
.Pp
Executed on both primary and secondary nodes when split-brain condition is
detected.
.El
.Pp
The
.Aq path
argument should contain full path to executable program.
If the given program exits with code different than
.Va 0 ,
.Nm hastd
will log it as an error.
.Pp
The
.Aq resource
argument is resource name from the configuration file.
.Pp
The
.Aq oldrole
argument is previous resource role (before the change).
It can be one of:
.Ar init ,
.Ar secondary ,
.Ar primary .
.Pp
The
.Aq newrole
argument is current resource role (after the change).
It can be one of:
.Ar init ,
.Ar secondary ,
.Ar primary .
.It Ic metaflush on | off
.Pp
When set to
.Va on ,
flush write cache of the local provider after every metadata (activemap) update.
Flushing write cache ensures that provider will not reorder writes and that
metadata will be properly updated before real data is stored.
If the local provider does not support flushing write cache (it returns
.Er EOPNOTSUPP
on the
.Cm BIO_FLUSH
request),
.Nm hastd
will disable
.Ic metaflush
automatically.
The default value is
.Va on .
.It Ic name Aq name
.Pp
GEOM provider name that will appear as
.Pa /dev/hast/<name> .
If name is not defined, resource name will be used as provider name.
.It Ic local Aq path
.Pp
Path to the local component which will be used as backend provider for
the resource.
This can be either GEOM provider or regular file.
.It Ic remote Aq addr
.Pp
Address of the remote
.Nm hastd
daemon.
Format is the same as for the
.Ic listen
statement.
When operating as a primary node this address will be used to connect to
the secondary node.
When operating as a secondary node only connections from this address
will be accepted.
.Pp
A special value of
.Va none
can be used when the remote address is not yet known (eg. the other node is not
set up yet).
.It Ic source Aq addr
.Pp
Local address to bind to before connecting to the remote
.Nm hastd
daemon.
Format is the same as for the
.Ic listen
statement.
.El
.Sh FILES
.Bl -tag -width ".Pa /var/run/hastctl" -compact
.It Pa /etc/hast.conf
The default
.Xr hastctl 8
and
.Xr hastd 8
configuration file.
.It Pa /var/run/hastctl
Control socket used by the
.Xr hastctl 8
control utility to communicate with the
.Xr hastd 8
daemon.
.El
.Sh EXAMPLES
The example configuration file can look as follows:
.Bd -literal -offset indent
listen tcp://0.0.0.0

on hasta {
	listen tcp://2001:db8::1/64
}
on hastb {
	listen tcp://2001:db8::2/64
}

resource shared {
	local /dev/da0

	on hasta {
		remote tcp://10.0.0.2
	}
	on hastb {
		remote tcp://10.0.0.1
	}
}
resource tank {
	on hasta {
		local /dev/mirror/tanka
		source tcp://10.0.0.1
		remote tcp://10.0.0.2
	}
	on hastb {
		local /dev/mirror/tankb
		source tcp://10.0.0.2
		remote tcp://10.0.0.1
	}
}
.Ed
.Sh SEE ALSO
.Xr gethostname 3 ,
.Xr geom 4 ,
.Xr hastctl 8 ,
.Xr hastd 8
.Sh AUTHORS
The
.Nm
was written by
.An Pawel Jakub Dawidek Aq Mt pjd@FreeBSD.org
under sponsorship of the FreeBSD Foundation.