prometheus: Add a postgres exporter.

puppet/zulip/manifests/common.pp

@@ -112,6 +112,15 @@ class zulip::common {
       },
     },
 
+    # https://github.com/prometheus-community/postgres_exporter/tags
+    'postgres_exporter' => {
+      'version' => '0.12.0',
+      'sha256'  => {
+        'amd64'   => 'e3301d4b8b666b870491f520c098cc4c1ce32bb5dc22ee7f40ec1914d27be891',
+        'aarch64' => '60bde8f9adac2d066ba49c621a25a8d99877e3c2e2ddf9b8ba7c7188085de475',
+      },
+    },
+
     # https://github.com/ncabatoff/process-exporter/releases
     'process_exporter' => {
       'version' => '0.7.10',

puppet/zulip_ops/manifests/profile/chat_zulip_org.pp

@@ -6,6 +6,7 @@ class zulip_ops::profile::chat_zulip_org {
   include zulip_ops::profile::base
   include zulip_ops::app_frontend_monitoring
   include zulip_ops::prometheus::redis
+  include zulip_ops::prometheus::postgresql
   zulip_ops::firewall_allow { 'http': }
   zulip_ops::firewall_allow { 'https': }
   zulip_ops::firewall_allow { 'smtp': }

puppet/zulip_ops/manifests/profile/postgresql.pp

@@ -2,6 +2,7 @@ class zulip_ops::profile::postgresql {
   include zulip_ops::profile::base
   include zulip::profile::postgresql
   include zulip_ops::teleport::db
+  include zulip_ops::prometheus::postgresql
 
   $common_packages = ['xfsprogs']
   package { $common_packages: ensure => installed }

puppet/zulip_ops/manifests/prometheus/postgresql.pp

@@ -0,0 +1,38 @@
+# @summary Prometheus monitoring of postgresql servers
+#
+class zulip_ops::prometheus::postgresql {
+  include zulip_ops::prometheus::base
+  include zulip::supervisor
+
+  $version = $zulip::common::versions['postgres_exporter']['version']
+  $dir = "/srv/zulip-postgres_exporter-${version}"
+  $bin = "${dir}/postgres_exporter"
+
+  zulip::external_dep { 'postgres_exporter':
+    version        => $version,
+    url            => "https://github.com/prometheus-community/postgres_exporter/releases/download/v${version}/postgres_exporter-${version}.linux-${zulip::common::goarch}.tar.gz",
+    tarball_prefix => "postgres_exporter-${version}.linux-${zulip::common::goarch}",
+  }
+
+  exec { 'create prometheus postgres user':
+    command => '/usr/bin/createuser -g pg_monitor prometheus',
+    unless  => '/usr/bin/psql -tAc "select usename from pg_user" | /bin/grep -xq prometheus',
+    user    => 'postgres',
+  }
+
+  zulip_ops::firewall_allow { 'postgres_exporter': port => '9187' }
+  file { "${zulip::common::supervisor_conf_dir}/prometheus_postgres_exporter.conf":
+    ensure  => file,
+    require => [
+      Exec['create prometheus postgres user'],
+      User[prometheus],
+      Package[supervisor],
+      Zulip::External_Dep['postgres_exporter'],
+    ],
+    owner   => 'root',
+    group   => 'root',
+    mode    => '0644',
+    content => template('zulip_ops/supervisor/conf.d/prometheus_postgres_exporter.conf.template.erb'),
+    notify  => Service[supervisor],
+  }
+}

puppet/zulip_ops/templates/supervisor/conf.d/prometheus_postgres_exporter.conf.template.erb

@@ -0,0 +1,9 @@
+[program:prometheus_postgres_exporter]
+command=<%= @bin %> --auto-discover-databases
+environment=DATA_SOURCE_NAME="postgresql://prometheus@:5432/postgres?host=/var/run/postgresql"
+priority=10
+autostart=true
+autorestart=true
+user=prometheus
+redirect_stderr=true
+stdout_logfile=/var/log/zulip/postgres_exporter.log