nixos/postgresql: add upgrade documentation

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danbst 2020-03-16 19:16:25 +02:00
parent 30631f74a0
commit 759fd9b0b0

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@ -63,8 +63,51 @@ Type "help" for help.
<title>Upgrading</title>
<para>
FIXME: document dump/upgrade/load cycle.
</para>
Major PostgreSQL upgrade requires PostgreSQL downtime and a few imperative steps to be called. To simplify this process, use the following NixOS module:
<programlisting>
containers.temp-pg.config.services.postgresql = {
enable = true;
package = pkgs.postgresql_12;
## set a custom new dataDir
# dataDir = "/some/data/dir";
};
environment.systemPackages =
let newpg = config.containers.temp-pg.config.services.postgresql;
in [
(pkgs.writeScriptBin "upgrade-pg-cluster" ''
set -x
export OLDDATA="${config.services.postgresql.dataDir}"
export NEWDATA="${newpg.dataDir}"
export OLDBIN="${config.services.postgresql.package}/bin"
export NEWBIN="${newpg.package}/bin"
install -d -m 0700 -o postgres -g postgres "$NEWDATA"
cd "$NEWDATA"
sudo -u postgres $NEWBIN/initdb -D "$NEWDATA"
systemctl stop postgresql # old one
sudo -u postgres $NEWBIN/pg_upgrade \
--old-datadir "$OLDDATA" --new-datadir "$NEWDATA" \
--old-bindir $OLDBIN --new-bindir $NEWBIN \
"$@"
'')
];
</programlisting>
</para>
<para>
The upgrade process is:</para>
<orderedlist>
<listitem><para>Rebuild nixos configuration with the configuration above added to your <filename>configuration.nix</filename>. Alternatively, add that into separate file and reference it in <literal>imports</literal> list.</para></listitem>
<listitem><para>Login as root (<literal>sudo su -</literal>)</para></listitem>
<listitem><para>Run <literal>upgrade-pg-cluster</literal>. It will stop old postgresql, initialize new one and migrate old one to new one. You may supply arguments like <literal>--jobs 4</literal> and <literal>--link</literal> to speedup migration process. See <link xlink:href="https://www.postgresql.org/docs/current/pgupgrade.html" /> for details.</para></listitem>
<listitem><para>Change postgresql package in NixOS configuration to the one you were upgrading to, and change <literal>dataDir</literal> to the one you have migrated to. Rebuild NixOS. This should start new postgres using upgraded data directory.</para></listitem>
<listitem><para>After upgrade you may want to <literal>ANALYZE</literal> new db.</para></listitem>
</orderedlist>
</section>
<section xml:id="module-services-postgres-options">
<title>Options</title>