HathiTrust DEV-1350: /var/log/babel for web apps

Currently, the web applications log to NFS, which is suboptimal for many
reasons -- processes have to write to individual files rather than being
able to share a log file, and logs can't easily be collected from there
and sent to retention or query systems (filebeat, loki).

This:

* creates /var/log/babel and makes it writable by the web server
* adds a logrotate config to ensure logs are rotated (similar to apache
  logs)
* adds an alloy config to send these logs to loki

manifests/profile/hathitrust/babel_logs.pp

@@ -0,0 +1,34 @@
+# Copyright (c) 2024 The Regents of the University of Michigan.
+# All Rights Reserved. Licensed according to the terms of the Revised
+# BSD License. See LICENSE.txt for details.
+
+# nebula::profile::hathitrust::babel_logs
+#
+# Configure a log directory and Grafana Alloy for shipping logs from babel
+# applications to loki
+#
+# @example
+#   include nebula::profile::hathitrust::babel_logs
+class nebula::profile::hathitrust::babel_logs (
+  String $log_path = '/var/log/babel',
+  String $log_owner = 'nobody',
+  String $log_group = 'nogroup',
+) {
+
+  file { $log_path:
+    ensure => 'directory',
+    owner  => $log_owner,
+    group  => $log_group,
+    mode   => '0644'
+  }
+
+  file { '/etc/alloy/babel.alloy':
+    ensure  => 'file',
+    content => template('nebula/profile/hathitrust/babel_logs/alloy.erb'),
+  }
+
+  file { '/etc/logrotate.d/babel':
+    ensure  => 'file',
+    content => template('nebula/profile/hathitrust/babel_logs/logrotate.erb'),
+  }
+}

manifests/role/webhost/htvm.pp

@@ -21,6 +21,7 @@
   include nebula::profile::hathitrust::dependencies
   include nebula::profile::hathitrust::perl
   include nebula::profile::hathitrust::php
+  include nebula::profile::hathitrust::babel_logs
 
   class { 'nebula::profile::hathitrust::imgsrv':
     sdrview  => 'full'

spec/classes/profile/hathitrust/babel_logs_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+# Copyright (c) 2023 The Regents of the University of Michigan.
+# All Rights Reserved. Licensed according to the terms of the Revised
+# BSD License. See LICENSE.txt for details.
+require 'spec_helper'
+
+require_relative '../../../support/contexts/with_htvm_setup'
+
+describe 'nebula::profile::hathitrust::babel_logs' do
+  on_supported_os.each do |os, os_facts|
+    context "on #{os}" do
+      it { is_expected.to compile }
+
+      it { is_expected.to contain_file('/var/log/babel').with_owner('nobody') }
+      it { is_expected.to contain_file('/etc/alloy/babel.alloy').with_content(%r(/var/log/babel)) }
+      it { is_expected.to contain_file('/etc/logrotate.d/babel').with_content(%r(/var/log/babel)) }
+    end
+  end
+end

templates/profile/hathitrust/babel_logs/alloy.erb

@@ -0,0 +1,15 @@
+local.file_match "babel_logs" {
+  path_targets = [
+  {__path__ = "<%= @log_path %>/*.log"},
+  ]
+}
+
+loki.source.file "babel_logs_files" {
+  targets    = local.file_match.babel_logs.targets
+  forward_to = [loki.process.service__babel.receiver]
+}
+
+loki.process "service__babel" {
+  stage.static_labels {values = {"service" = "babel"}}
+  forward_to = [loki.process.hostname.receiver]
+}

templates/profile/hathitrust/babel_logs/logrotate.erb

@@ -0,0 +1,11 @@
+<%= @log_path %>/*.log {
+        daily
+        missingok
+        rotate 7
+        dateext
+        dateyesterday
+        compress
+        delaycompress
+        notifempty
+        create 644 <%= @log_owner %> <%= @log_group %>
+}