reports: Update to use report_prefix

This commit removes the report_filename config parameter and adds a
report_prefix parameter.  AFAICT the current code suggests that it will
write all host data to the same file.  However the code writes the old
data to the prom file giving all values -1 which is incorrect

I looked at why this was and i can't find much information on the
original issue[1] and PR[2].  further to this the current implementation
is very racy if one sets REPORT_FILENAME

This also updates the clean stale function toi only act on files with
the report_prefix and avoid deleting files which may have been placed
there by none puppetserver process

[1]voxpupuli#5
[2]voxpupuli#7

README.md

@@ -22,7 +22,7 @@ textfile_directory: /var/lib/prometheus-dropzone
 
 Configuration options include:
 - `textfile_directory` - [String] Location of the node_exporter `collector.textfile.directory` (Required)
-- `report_filename` - [String] If specified, saves all reports to a single file (must end with .prom)
+- `report_prefix` - [String] the prefix to add to the prometheus reprots.  By default this is `puppet_report_`.
 - `environments` - [Array] If specified, only creates metrics on reports from these environments
 - `reports` - [Array] If specified, only creates metrics from reports of this type (changes, events, resources, time)
 - `stale_time` - [Integer] If specified, delete metric files for nodes that haven't sent reports in X days

lib/puppet/reports/prometheus.rb

@@ -18,7 +18,7 @@
   config = YAML.load_file(configfile)
 
   TEXTFILE_DIRECTORY = config['textfile_directory']
-  REPORT_FILENAME = config['report_filename']
+  REPORT_PREFIX = config.fetch('report_prefix', 'puppet_report_')
   ENVIRONMENTS = config['environments']
   REPORTS = config['reports']
   STALE_TIME = config['stale_time']
@@ -27,19 +27,10 @@
     raise(Puppet::ParseError, "#{configfile}: textfile_directory is not set or is missing.")
   end
 
-  unless REPORT_FILENAME.nil? || REPORT_FILENAME.end_with?('.prom')
-    raise(Puppet::ParseError, "#{configfile}: report_filename does not ends with .prom")
-  end
-
   def process
     return unless ENVIRONMENTS.nil? || ENVIRONMENTS.include?(environment)
-    namevar = if REPORT_FILENAME.nil?
-                host + '.prom'
-              else
-                REPORT_FILENAME
-              end
+    namevar = "#{REPORT_PREFIX}#{host}.prom"
 
-    yaml_filename = File.join(TEXTFILE_DIRECTORY, '.' + namevar + '.yaml')
     filename = File.join(TEXTFILE_DIRECTORY, namevar)
 
     common_values = {
@@ -139,30 +130,18 @@ def process
 
     File.open(filename, 'w') do |file|
       file.write(definitions)
-      if File.exist?(yaml_filename)
-        file.write("# Old metrics\n")
-        existing_metrics = YAML.load_file(yaml_filename)
-        existing_metrics.each do |k, _v|
-          file.write("#{k} -1\n") unless new_metrics.include?(k)
-        end
-      end
-
-      file.write("# New metrics\n")
       new_metrics.each do |k, v|
         file.write("#{k} #{v}\n")
       end
     end
-
-    File.open(yaml_filename, 'w') do |yaml_file|
-      yaml_file.write new_metrics.to_yaml
-    end
+    File.chmod(0755, filename)
 
     clean_stale_reports
   end
 
   def clean_stale_reports
     return if STALE_TIME.nil? || STALE_TIME < 1
     Dir.chdir(TEXTFILE_DIRECTORY)
-    Dir.glob('*.prom').each { |filename| File.delete(filename) if (Time.now - File.mtime(filename)) / (24 * 3600) > STALE_TIME }
+    Dir.glob("#{REPORT_PREFIX}*.prom").each { |filename| File.delete(filename) if (Time.now - File.mtime(filename)) / (24 * 3600) > STALE_TIME }
   end
 end