From a0e9dc07cd1622b34ec8bb16b7b6f7414d5cfac5 Mon Sep 17 00:00:00 2001
From: Albert Bertram <bertrama@umich.edu>
Date: Thu, 6 Feb 2025 16:28:38 -0500
Subject: [PATCH] EXPERIMENTAL

Add metrics for api_response_duration_seconds histograms.
---
 config.ru                                        |  2 ++
 config/puma.rb                                   |  6 ++++++
 lib/alma_rest_client/monkey_patch.rb             | 16 ++++++++++++++++
 .../lib/spectrum/search_engines/primo/engine.rb  | 16 +++++++++++++++-
 .../lib/spectrum/search_engines/solr.rb          |  6 +++++-
 5 files changed, 44 insertions(+), 2 deletions(-)
 create mode 100644 lib/alma_rest_client/monkey_patch.rb

diff --git a/config.ru b/config.ru
index a689b3ab..deee8645 100644
--- a/config.ru
+++ b/config.ru
@@ -13,6 +13,8 @@ end
 Bundler.require
 Spectrum::Json.configure(__dir__, ENV["RAILS_RELATIVE_URL_ROOT"])
 
+require 'alma_rest_client/monkey_patch'
+
 use Rack::ReverseProxy do
   reverse_proxy %r{^/browse.css}, "https://#{ENV["BROWSE_HOST"]}/$1"
   reverse_proxy %r{^/catalog/browse/(.*)$}, "https://#{ENV["BROWSE_HOST"]}/$1"
diff --git a/config/puma.rb b/config/puma.rb
index 71eb4286..f0aa03b4 100644
--- a/config/puma.rb
+++ b/config/puma.rb
@@ -65,6 +65,12 @@
       labels: %i[method path],
       buckets: Prometheus::Client::Histogram::DEFAULT_BUCKETS + [15, 20, 30]
     )
+    Prometheus::Client.registry.histogram(
+      :api_response_duration_seconds,
+      docstring: "The API response duration for requests made by Spectrum.",
+      labels: %i[source],
+      buckets: Prometheus::Client::Histogram::DEFAULT_BUCKETS + [15, 20, 30]
+    )
     Yabeda.configure!
 
     plugin :yabeda
diff --git a/lib/alma_rest_client/monkey_patch.rb b/lib/alma_rest_client/monkey_patch.rb
new file mode 100644
index 00000000..27c9bf90
--- /dev/null
+++ b/lib/alma_rest_client/monkey_patch.rb
@@ -0,0 +1,16 @@
+module AlmaRestClient
+  class Client
+    [:get, :post, :delete, :put].each do |name|
+      old_method = instance_method(name)
+      define_method(name) do |url, options = {}|
+        @metrics ||= Prometheus::Client.registry.get(:api_response_duration_seconds)
+        response = nil
+        duration = Benchmark.realtime do
+          response = old_method.bind(self).(url, options)
+        end
+        @metrics.observe(duration, labels: {source: "alma"})
+        response
+      end
+    end
+  end
+end
diff --git a/local-gems/spectrum-config/lib/spectrum/search_engines/primo/engine.rb b/local-gems/spectrum-config/lib/spectrum/search_engines/primo/engine.rb
index a88410b6..aa702eeb 100644
--- a/local-gems/spectrum-config/lib/spectrum/search_engines/primo/engine.rb
+++ b/local-gems/spectrum-config/lib/spectrum/search_engines/primo/engine.rb
@@ -24,6 +24,7 @@ def initialize(
           if defined?(Rails) && Rails.respond_to?(:logger)
             @logger = Rails.logger
           end
+          @metrics = Prometheus::Client.registry.get(:api_response_duration_seconds)
         end
 
         def results
@@ -36,8 +37,21 @@ def total_items
 
 
         def search
+          return @results if @results
           @logger&.info { url }
-          @results ||= Response.for_json(HTTParty.get(url)).with_libkey(libkey)
+
+          response = nil
+          duration = Benchmark.realtime do
+            response = Response.for_json(HTTParty.get(url))
+          end
+          @metrics.observe(duration, labels: {source: 'primo'})
+
+          duration = Benchmark.realtime do
+            @results = response.with_libkey(libkey)
+          end
+          @metrics.observe(duration, labels: {source: 'libkey'})
+
+          @results
         end
 
         def url
diff --git a/local-gems/spectrum-config/lib/spectrum/search_engines/solr.rb b/local-gems/spectrum-config/lib/spectrum/search_engines/solr.rb
index 420b05bc..a39d6670 100644
--- a/local-gems/spectrum-config/lib/spectrum/search_engines/solr.rb
+++ b/local-gems/spectrum-config/lib/spectrum/search_engines/solr.rb
@@ -32,7 +32,11 @@ def initialize(original_options)
 
         @params[:qq] ||= '"' + RSolr.solr_escape(@params[:q]) + '"'
 
-        @response = Response.for(@solr.post("select", params: @params))
+        @metrics = Prometheus::Client.registry.get(:api_response_duration_seconds)
+        duration = Benchmark.realtime do
+          @response = Response.for(@solr.post("select", params: @params))
+        end
+        @metrics.observe(duration, labels: {source: @source.id})
       end
 
       def total_items