Add max_open_files parameter for systemd systems

manifests/config.pp

@@ -4,6 +4,8 @@
 
   assert_private()
 
+  $max_open_files = $prometheus::max_open_files
+
   if $prometheus::server::init_style {
     if( versioncmp($prometheus::server::version, '2.0.0') < 0 ){
       # helper variable indicating prometheus version, so we can use on this information in the template

manifests/init.pp

@@ -141,6 +141,11 @@
 #  creating the appropriate prometheus scrape configs for each endpoint. All scrape_config
 #  options can be passed as hash elements. Only the job_name is mandatory.
 #
+#  [*max_open_files*]
+#  The maximum number of file descriptors for the prometheus server.
+#  Defaults to `undef`, but set to a large integer to override your default OS limit.
+#  Currently only implemented for systemd based service.
+#
 # Actions:
 #
 # Requires: see Modulefile
@@ -194,6 +199,7 @@
   String $os            = downcase($facts['kernel']),
   Optional[Variant[Stdlib::HTTPUrl, Stdlib::Unixpath, String[1]]] $external_url = undef,
   Optional[Array[Hash[String[1], Any]]] $collect_scrape_jobs = [],
+  Optional[Integer] $max_open_files = undef,
 ) {
 
   case $arch {

spec/classes/prometheus_spec.rb

@@ -126,6 +126,24 @@
                 'content' => File.read(fixtures('files', "prometheus#{prom_major}.systemd"))
               )
             }
+            describe 'max_open_files' do
+              context 'by default' do
+                it {
+                  content = catalogue.resource('systemd::unit_file', 'prometheus.service').send(:parameters)[:content]
+                  expect(content).not_to include('LimitNOFILE')
+                }
+              end
+              context 'when set to 1000000' do
+                let(:params) do
+                  parameters.merge('max_open_files' => 1_000_000)
+                end
+
+                it {
+                  content = catalogue.resource('systemd::unit_file', 'prometheus.service').send(:parameters)[:content]
+                  expect(content).to include('LimitNOFILE=1000000')
+                }
+              end
+            end
           elsif ['ubuntu-14.04-x86_64'].include?(os)
             # init_style = 'upstart'
 

templates/prometheus.systemd.erb

@@ -12,6 +12,9 @@ ExecStart=<%= scope.lookupvar('prometheus::server::bin_dir') %>/prometheus \
 ExecReload=/bin/kill -HUP $MAINPID
 KillMode=process
 Restart=always
+<% if @max_open_files -%>
+LimitNOFILE=<%= @max_open_files %>
+<% end -%>
 
 [Install]
 WantedBy=multi-user.target