Finish improvements to push client

lib/prometheus/client/metric.rb

@@ -7,7 +7,7 @@ module Prometheus
   module Client
     # Metric
     class Metric
-      attr_reader :name, :docstring, :preset_labels
+      attr_reader :name, :docstring, :labels, :preset_labels
 
       def initialize(name,
                      docstring:,

lib/prometheus/client/push.rb

@@ -1,35 +1,44 @@
 # encoding: UTF-8
 
+require 'base64'
 require 'thread'
 require 'net/http'
 require 'uri'
 require 'erb'
+require 'set'
 
 require 'prometheus/client'
 require 'prometheus/client/formats/text'
+require 'prometheus/client/label_set_validator'
 
 module Prometheus
   # Client is a ruby implementation for a Prometheus compatible client.
   module Client
     # Push implements a simple way to transmit a given registry to a given
     # Pushgateway.
     class Push
+      class HttpError < StandardError; end
+      class HttpRedirectError < HttpError; end
+      class HttpClientError < HttpError; end
+      class HttpServerError < HttpError; end
+
       DEFAULT_GATEWAY = 'http://localhost:9091'.freeze
       PATH            = '/metrics/job/%s'.freeze
-      INSTANCE_PATH   = '/metrics/job/%s/instance/%s'.freeze
       SUPPORTED_SCHEMES = %w(http https).freeze
 
-      attr_reader :job, :instance, :gateway, :path
+      attr_reader :job, :gateway, :path
 
-      def initialize(job:, instance: nil, gateway: DEFAULT_GATEWAY, **kwargs)
+      def initialize(job:, gateway: DEFAULT_GATEWAY, grouping_key: {}, **kwargs)
         raise ArgumentError, "job cannot be nil" if job.nil?
         raise ArgumentError, "job cannot be empty" if job.empty?
+        @validator = LabelSetValidator.new(expected_labels: grouping_key.keys)
+        @validator.validate_symbols!(grouping_key)
 
         @mutex = Mutex.new
         @job = job
-        @instance = instance
         @gateway = gateway || DEFAULT_GATEWAY
-        @path = build_path(job, instance)
+        @grouping_key = grouping_key
+        @path = build_path(job, grouping_key)
         @uri = parse("#{@gateway}#{@path}")
 
         @http = Net::HTTP.new(@uri.host, @uri.port)
@@ -70,26 +79,85 @@ def parse(url)
         raise ArgumentError, "#{url} is not a valid URL: #{e}"
       end
 
-      def build_path(job, instance)
-        if instance && !instance.empty?
-          format(INSTANCE_PATH, ERB::Util::url_encode(job), ERB::Util::url_encode(instance))
-        else
-          format(PATH, ERB::Util::url_encode(job))
+      def build_path(job, grouping_key)
+        path = format(PATH, ERB::Util::url_encode(job))
+
+        grouping_key.each do |label, value|
+          if value.include?('/')
+            encoded_value = Base64.urlsafe_encode64(value)
+            path += "/#{label}@base64/#{encoded_value}"
+          # While it's valid for the urlsafe_encode64 function to return an
+          # empty string when the input string is empty, it doesn't work for
+          # our specific use case as we're putting the result into a URL path
+          # segment. A double slash (`//`) can be normalised away by HTTP
+          # libraries, proxies, and web servers.
+          #
+          # For empty strings, we use a single padding character (`=`) as the
+          # value.
+          #
+          # See the pushgateway docs for more details:
+          #
+          # https://github.com/prometheus/pushgateway/blob/6393a901f56d4dda62cd0f6ab1f1f07c495b6354/README.md#url
+          elsif value.empty?
+            path += "/#{label}@base64/="
+          else
+            path += "/#{label}/#{ERB::Util::url_encode(value)}"
+          end
         end
+
+        path
       end
 
       def request(req_class, registry = nil)
+        validate_no_label_clashes!(registry) if registry
+
         req = req_class.new(@uri)
         req.content_type = Formats::Text::CONTENT_TYPE
         req.basic_auth(@uri.user, @uri.password) if @uri.user
         req.body = Formats::Text.marshal(registry) if registry
 
-        @http.request(req)
+        response = @http.request(req)
+        validate_response!(response)
+
+        response
       end
 
       def synchronize
         @mutex.synchronize { yield }
       end
+
+      def validate_no_label_clashes!(registry)
+        # There's nothing to check if we don't have a grouping key
+        return if @grouping_key.empty?
+
+        # We could be doing a lot of comparisons, so let's do them against a
+        # set rather than an array
+        grouping_key_labels = @grouping_key.keys.to_set
+
+        registry.metrics.each do |metric|
+          metric.labels.each do |label|
+            if grouping_key_labels.include?(label)
+              raise LabelSetValidator::InvalidLabelSetError,
+                "label :#{label} from grouping key collides with label of the " \
+                "same name from metric :#{metric.name} and would overwrite it"
+            end
+          end
+        end
+      end
+
+      def validate_response!(response)
+        status = Integer(response.code)
+        if status >= 300
+          message = "status: #{response.code}, message: #{response.message}, body: #{response.body}"
+          if status <= 399
+            raise HttpRedirectError, message
+          elsif status <= 499
+            raise HttpClientError, message
+          else
+            raise HttpServerError, message
+          end
+        end
+      end
     end
   end
 end