444 lines
15 KiB
XML
444 lines
15 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
|
|
xmlns:xlink="http://www.w3.org/1999/xlink"
|
|
xmlns:xi="http://www.w3.org/2001/XInclude"
|
|
version="5.0"
|
|
xml:id="module-services-foundationdb">
|
|
<title>FoundationDB</title>
|
|
<para>
|
|
<emphasis>Source:</emphasis>
|
|
<filename>modules/services/databases/foundationdb.nix</filename>
|
|
</para>
|
|
<para>
|
|
<emphasis>Upstream documentation:</emphasis>
|
|
<link xlink:href="https://apple.github.io/foundationdb/"/>
|
|
</para>
|
|
<para>
|
|
<emphasis>Maintainer:</emphasis> Austin Seipp
|
|
</para>
|
|
<para>
|
|
<emphasis>Available version(s):</emphasis> 5.1.x, 5.2.x, 6.0.x
|
|
</para>
|
|
<para>
|
|
FoundationDB (or "FDB") is an open source, distributed, transactional
|
|
key-value store.
|
|
</para>
|
|
<section xml:id="module-services-foundationdb-configuring">
|
|
<title>Configuring and basic setup</title>
|
|
|
|
<para>
|
|
To enable FoundationDB, add the following to your
|
|
<filename>configuration.nix</filename>:
|
|
<programlisting>
|
|
services.foundationdb.enable = true;
|
|
services.foundationdb.package = pkgs.foundationdb52; # FoundationDB 5.2.x
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The <option>services.foundationdb.package</option> option is required, and
|
|
must always be specified. Due to the fact FoundationDB network protocols and
|
|
on-disk storage formats may change between (major) versions, and upgrades
|
|
must be explicitly handled by the user, you must always manually specify
|
|
this yourself so that the NixOS module will use the proper version. Note
|
|
that minor, bugfix releases are always compatible.
|
|
</para>
|
|
|
|
<para>
|
|
After running <command>nixos-rebuild</command>, you can verify whether
|
|
FoundationDB is running by executing <command>fdbcli</command> (which is
|
|
added to <option>environment.systemPackages</option>):
|
|
<programlisting>
|
|
$ sudo -u foundationdb fdbcli
|
|
Using cluster file `/etc/foundationdb/fdb.cluster'.
|
|
|
|
The database is available.
|
|
|
|
Welcome to the fdbcli. For help, type `help'.
|
|
fdb> status
|
|
|
|
Using cluster file `/etc/foundationdb/fdb.cluster'.
|
|
|
|
Configuration:
|
|
Redundancy mode - single
|
|
Storage engine - memory
|
|
Coordinators - 1
|
|
|
|
Cluster:
|
|
FoundationDB processes - 1
|
|
Machines - 1
|
|
Memory availability - 5.4 GB per process on machine with least available
|
|
Fault Tolerance - 0 machines
|
|
Server time - 04/20/18 15:21:14
|
|
|
|
...
|
|
|
|
fdb>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
You can also write programs using the available client libraries. For
|
|
example, the following Python program can be run in order to grab the
|
|
cluster status, as a quick example. (This example uses
|
|
<command>nix-shell</command> shebang support to automatically supply the
|
|
necessary Python modules).
|
|
<programlisting>
|
|
a@link> cat fdb-status.py
|
|
#! /usr/bin/env nix-shell
|
|
#! nix-shell -i python -p python pythonPackages.foundationdb52
|
|
|
|
import fdb
|
|
import json
|
|
|
|
def main():
|
|
fdb.api_version(520)
|
|
db = fdb.open()
|
|
|
|
@fdb.transactional
|
|
def get_status(tr):
|
|
return str(tr['\xff\xff/status/json'])
|
|
|
|
obj = json.loads(get_status(db))
|
|
print('FoundationDB available: %s' % obj['client']['database_status']['available'])
|
|
|
|
if __name__ == "__main__":
|
|
main()
|
|
a@link> chmod +x fdb-status.py
|
|
a@link> ./fdb-status.py
|
|
FoundationDB available: True
|
|
a@link>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
FoundationDB is run under the <command>foundationdb</command> user and group
|
|
by default, but this may be changed in the NixOS configuration. The systemd
|
|
unit <command>foundationdb.service</command> controls the
|
|
<command>fdbmonitor</command> process.
|
|
</para>
|
|
|
|
<para>
|
|
By default, the NixOS module for FoundationDB creates a single SSD-storage
|
|
based database for development and basic usage. This storage engine is
|
|
designed for SSDs and will perform poorly on HDDs; however it can handle far
|
|
more data than the alternative "memory" engine and is a better default
|
|
choice for most deployments. (Note that you can change the storage backend
|
|
on-the-fly for a given FoundationDB cluster using
|
|
<command>fdbcli</command>.)
|
|
</para>
|
|
|
|
<para>
|
|
Furthermore, only 1 server process and 1 backup agent are started in the
|
|
default configuration. See below for more on scaling to increase this.
|
|
</para>
|
|
|
|
<para>
|
|
FoundationDB stores all data for all server processes under
|
|
<filename>/var/lib/foundationdb</filename>. You can override this using
|
|
<option>services.foundationdb.dataDir</option>, e.g.
|
|
<programlisting>
|
|
services.foundationdb.dataDir = "/data/fdb";
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
Similarly, logs are stored under <filename>/var/log/foundationdb</filename>
|
|
by default, and there is a corresponding
|
|
<option>services.foundationdb.logDir</option> as well.
|
|
</para>
|
|
</section>
|
|
<section xml:id="module-services-foundationdb-scaling">
|
|
<title>Scaling processes and backup agents</title>
|
|
|
|
<para>
|
|
Scaling the number of server processes is quite easy; simply specify
|
|
<option>services.foundationdb.serverProcesses</option> to be the number of
|
|
FoundationDB worker processes that should be started on the machine.
|
|
</para>
|
|
|
|
<para>
|
|
FoundationDB worker processes typically require 4GB of RAM per-process at
|
|
minimum for good performance, so this option is set to 1 by default since
|
|
the maximum amount of RAM is unknown. You're advised to abide by this
|
|
restriction, so pick a number of processes so that each has 4GB or more.
|
|
</para>
|
|
|
|
<para>
|
|
A similar option exists in order to scale backup agent processes,
|
|
<option>services.foundationdb.backupProcesses</option>. Backup agents are
|
|
not as performance/RAM sensitive, so feel free to experiment with the number
|
|
of available backup processes.
|
|
</para>
|
|
</section>
|
|
<section xml:id="module-services-foundationdb-clustering">
|
|
<title>Clustering</title>
|
|
|
|
<para>
|
|
FoundationDB on NixOS works similarly to other Linux systems, so this
|
|
section will be brief. Please refer to the full FoundationDB documentation
|
|
for more on clustering.
|
|
</para>
|
|
|
|
<para>
|
|
FoundationDB organizes clusters using a set of
|
|
<emphasis>coordinators</emphasis>, which are just specially-designated
|
|
worker processes. By default, every installation of FoundationDB on NixOS
|
|
will start as its own individual cluster, with a single coordinator: the
|
|
first worker process on <command>localhost</command>.
|
|
</para>
|
|
|
|
<para>
|
|
Coordinators are specified globally using the
|
|
<command>/etc/foundationdb/fdb.cluster</command> file, which all servers and
|
|
client applications will use to find and join coordinators. Note that this
|
|
file <emphasis>can not</emphasis> be managed by NixOS so easily:
|
|
FoundationDB is designed so that it will rewrite the file at runtime for all
|
|
clients and nodes when cluster coordinators change, with clients
|
|
transparently handling this without intervention. It is fundamentally a
|
|
mutable file, and you should not try to manage it in any way in NixOS.
|
|
</para>
|
|
|
|
<para>
|
|
When dealing with a cluster, there are two main things you want to do:
|
|
</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
Add a node to the cluster for storage/compute.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Promote an ordinary worker to a coordinator.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>
|
|
A node must already be a member of the cluster in order to properly be
|
|
promoted to a coordinator, so you must always add it first if you wish to
|
|
promote it.
|
|
</para>
|
|
|
|
<para>
|
|
To add a machine to a FoundationDB cluster:
|
|
</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
Choose one of the servers to start as the initial coordinator.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Copy the <command>/etc/foundationdb/fdb.cluster</command> file from this
|
|
server to all the other servers. Restart FoundationDB on all of these
|
|
other servers, so they join the cluster.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
All of these servers are now connected and working together in the
|
|
cluster, under the chosen coordinator.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>
|
|
At this point, you can add as many nodes as you want by just repeating the
|
|
above steps. By default there will still be a single coordinator: you can
|
|
use <command>fdbcli</command> to change this and add new coordinators.
|
|
</para>
|
|
|
|
<para>
|
|
As a convenience, FoundationDB can automatically assign coordinators based
|
|
on the redundancy mode you wish to achieve for the cluster. Once all the
|
|
nodes have been joined, simply set the replication policy, and then issue
|
|
the <command>coordinators auto</command> command
|
|
</para>
|
|
|
|
<para>
|
|
For example, assuming we have 3 nodes available, we can enable double
|
|
redundancy mode, then auto-select coordinators. For double redundancy, 3
|
|
coordinators is ideal: therefore FoundationDB will make
|
|
<emphasis>every</emphasis> node a coordinator automatically:
|
|
</para>
|
|
|
|
<programlisting>
|
|
fdbcli> configure double ssd
|
|
fdbcli> coordinators auto
|
|
</programlisting>
|
|
|
|
<para>
|
|
This will transparently update all the servers within seconds, and
|
|
appropriately rewrite the <command>fdb.cluster</command> file, as well as
|
|
informing all client processes to do the same.
|
|
</para>
|
|
</section>
|
|
<section xml:id="module-services-foundationdb-connectivity">
|
|
<title>Client connectivity</title>
|
|
|
|
<para>
|
|
By default, all clients must use the current <command>fdb.cluster</command>
|
|
file to access a given FoundationDB cluster. This file is located by default
|
|
in <command>/etc/foundationdb/fdb.cluster</command> on all machines with the
|
|
FoundationDB service enabled, so you may copy the active one from your
|
|
cluster to a new node in order to connect, if it is not part of the cluster.
|
|
</para>
|
|
</section>
|
|
<section xml:id="module-services-foundationdb-authorization">
|
|
<title>Client authorization and TLS</title>
|
|
|
|
<para>
|
|
By default, any user who can connect to a FoundationDB process with the
|
|
correct cluster configuration can access anything. FoundationDB uses a
|
|
pluggable design to transport security, and out of the box it supports a
|
|
LibreSSL-based plugin for TLS support. This plugin not only does in-flight
|
|
encryption, but also performs client authorization based on the given
|
|
endpoint's certificate chain. For example, a FoundationDB server may be
|
|
configured to only accept client connections over TLS, where the client TLS
|
|
certificate is from organization <emphasis>Acme Co</emphasis> in the
|
|
<emphasis>Research and Development</emphasis> unit.
|
|
</para>
|
|
|
|
<para>
|
|
Configuring TLS with FoundationDB is done using the
|
|
<option>services.foundationdb.tls</option> options in order to control the
|
|
peer verification string, as well as the certificate and its private key.
|
|
</para>
|
|
|
|
<para>
|
|
Note that the certificate and its private key must be accessible to the
|
|
FoundationDB user account that the server runs under. These files are also
|
|
NOT managed by NixOS, as putting them into the store may reveal private
|
|
information.
|
|
</para>
|
|
|
|
<para>
|
|
After you have a key and certificate file in place, it is not enough to
|
|
simply set the NixOS module options -- you must also configure the
|
|
<command>fdb.cluster</command> file to specify that a given set of
|
|
coordinators use TLS. This is as simple as adding the suffix
|
|
<command>:tls</command> to your cluster coordinator configuration, after the
|
|
port number. For example, assuming you have a coordinator on localhost with
|
|
the default configuration, simply specifying:
|
|
</para>
|
|
|
|
<programlisting>
|
|
XXXXXX:XXXXXX@127.0.0.1:4500:tls
|
|
</programlisting>
|
|
|
|
<para>
|
|
will configure all clients and server processes to use TLS from now on.
|
|
</para>
|
|
</section>
|
|
<section xml:id="module-services-foundationdb-disaster-recovery">
|
|
<title>Backups and Disaster Recovery</title>
|
|
|
|
<para>
|
|
The usual rules for doing FoundationDB backups apply on NixOS as written in
|
|
the FoundationDB manual. However, one important difference is the security
|
|
profile for NixOS: by default, the <command>foundationdb</command> systemd
|
|
unit uses <emphasis>Linux namespaces</emphasis> to restrict write access to
|
|
the system, except for the log directory, data directory, and the
|
|
<command>/etc/foundationdb/</command> directory. This is enforced by default
|
|
and cannot be disabled.
|
|
</para>
|
|
|
|
<para>
|
|
However, a side effect of this is that the <command>fdbbackup</command>
|
|
command doesn't work properly for local filesystem backups: FoundationDB
|
|
uses a server process alongside the database processes to perform backups
|
|
and copy the backups to the filesystem. As a result, this process is put
|
|
under the restricted namespaces above: the backup process can only write to
|
|
a limited number of paths.
|
|
</para>
|
|
|
|
<para>
|
|
In order to allow flexible backup locations on local disks, the FoundationDB
|
|
NixOS module supports a
|
|
<option>services.foundationdb.extraReadWritePaths</option> option. This
|
|
option takes a list of paths, and adds them to the systemd unit, allowing
|
|
the processes inside the service to write (and read) the specified
|
|
directories.
|
|
</para>
|
|
|
|
<para>
|
|
For example, to create backups in <command>/opt/fdb-backups</command>, first
|
|
set up the paths in the module options:
|
|
</para>
|
|
|
|
<programlisting>
|
|
services.foundationdb.extraReadWritePaths = [ "/opt/fdb-backups" ];
|
|
</programlisting>
|
|
|
|
<para>
|
|
Restart the FoundationDB service, and it will now be able to write to this
|
|
directory (even if it does not yet exist.) Note: this path
|
|
<emphasis>must</emphasis> exist before restarting the unit. Otherwise,
|
|
systemd will not include it in the private FoundationDB namespace (and it
|
|
will not add it dynamically at runtime).
|
|
</para>
|
|
|
|
<para>
|
|
You can now perform a backup:
|
|
</para>
|
|
|
|
<programlisting>
|
|
$ sudo -u foundationdb fdbbackup start -t default -d file:///opt/fdb-backups
|
|
$ sudo -u foundationdb fdbbackup status -t default
|
|
</programlisting>
|
|
</section>
|
|
<section xml:id="module-services-foundationdb-limitations">
|
|
<title>Known limitations</title>
|
|
|
|
<para>
|
|
The FoundationDB setup for NixOS should currently be considered beta.
|
|
FoundationDB is not new software, but the NixOS compilation and integration
|
|
has only undergone fairly basic testing of all the available functionality.
|
|
</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
There is no way to specify individual parameters for individual
|
|
<command>fdbserver</command> processes. Currently, all server processes
|
|
inherit all the global <command>fdbmonitor</command> settings.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Ruby bindings are not currently installed.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Go bindings are not currently installed.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</section>
|
|
<section xml:id="module-services-foundationdb-options">
|
|
<title>Options</title>
|
|
|
|
<para>
|
|
NixOS's FoundationDB module allows you to configure all of the most relevant
|
|
configuration options for <command>fdbmonitor</command>, matching it quite
|
|
closely. A complete list of options for the FoundationDB module may be found
|
|
<link linkend="opt-services.foundationdb.enable">here</link>. You should
|
|
also read the FoundationDB documentation as well.
|
|
</para>
|
|
</section>
|
|
<section xml:id="module-services-foundationdb-full-docs">
|
|
<title>Full documentation</title>
|
|
|
|
<para>
|
|
FoundationDB is a complex piece of software, and requires careful
|
|
administration to properly use. Full documentation for administration can be
|
|
found here: <link xlink:href="https://apple.github.io/foundationdb/"/>.
|
|
</para>
|
|
</section>
|
|
</chapter>
|