Add query blocker tracking based on pg_blocking_pids()

guides/Linux.md

@@ -225,7 +225,7 @@ CREATE TABLE "pghero_connection_stats" (
   "username" text, 
   "captured_at" timestamp
 );
-CREATE  INDEX  "pghero_connection_stats" ("database", "captured_at");
+CREATE INDEX ON "pghero_connection_stats" ("database", "captured_at");
 ```
 
 Schedule the task below to run once a day.
@@ -234,6 +234,14 @@ Schedule the task below to run once a day.
 sudo pghero run rake pghero:capture_connection_stats
 ```
 
+## Historical Query Blockers
+
+To track query blockers over time, create a table to store them.
+
+TODO 
+```sql
+CREATE TABLE ...
+```
 
 ## System Stats
 

guides/Rails.md

@@ -303,6 +303,12 @@ PgHero.drop_user("ganondorf")
 
 ## Upgrading
 
+### 2.x.y
+
+New features
+
+Sample blocker queries - TODO
+
 ### 2.0.0
 
 New features

lib/pghero.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # dependencies
 require "active_support"
 
@@ -9,8 +11,11 @@
 require "pghero/methods/kill"
 require "pghero/methods/maintenance"
 require "pghero/methods/queries"
+require "pghero/methods/query_blockers"
+require "pghero/methods/query_blockers_history"
 require "pghero/methods/query_stats"
 require "pghero/methods/replication"
+require "pghero/methods/repository"
 require "pghero/methods/sequences"
 require "pghero/methods/settings"
 require "pghero/methods/space"
@@ -19,13 +24,14 @@
 require "pghero/methods/tables"
 require "pghero/methods/users"
 
+require "pghero/base_database"
 require "pghero/database"
 require "pghero/engine" if defined?(Rails)
+require "pghero/pg_const"
+require "pghero/repository"
 require "pghero/version"
 
 module PgHero
-  autoload :Connection, "pghero/connection"
-  autoload :QueryStats, "pghero/query_stats"
 
   class Error < StandardError; end
   class NotEnabled < Error; end
@@ -55,7 +61,7 @@ class << self
       :query_stats_available?, :query_stats_enabled?, :query_stats_extension_enabled?, :query_stats_readable?,
       :rds_stats, :read_iops_stats, :region, :relation_sizes, :replica?, :replication_lag, :replication_lag_stats,
       :reset_query_stats, :reset_stats, :running_queries, :secret_access_key, :sequence_danger, :sequences, :settings,
-      :slow_queries, :space_growth, :ssl_used?, :stats_connection, :suggested_indexes, :suggested_indexes_by_query,
+      :slow_queries, :space_growth, :ssl_used?, :suggested_indexes, :suggested_indexes_by_query,
       :suggested_indexes_enabled?, :system_stats_enabled?, :table_caching, :table_hit_rate, :table_stats,
       :total_connections, :transaction_id_danger, :unused_indexes, :unused_tables, :write_iops_stats
 
@@ -100,9 +106,10 @@ def config
 
     def databases
       @databases ||= begin
+        repository = PgHero::Repository.new
         Hash[
           config["databases"].map do |id, c|
-            [id.to_sym, PgHero::Database.new(id, c)]
+            [id.to_sym, PgHero::Database.new(id, c, repository)]
           end
         ]
       end
@@ -115,6 +122,7 @@ def primary_database
     def capture_query_stats(verbose: false)
       each_database do |database|
         next unless database.capture_query_stats?
+
         puts "Capturing query stats for #{database.id}..." if verbose
         database.capture_query_stats(raise_errors: true)
       end
@@ -134,19 +142,40 @@ def capture_connection_stats(verbose: false)
       end
     end
 
-    def capture_query_blockers(verbose: false)
+    def capture_query_blockers(verbose: false, filters: nil)
       each_database do |database|
-        next unless database.capture_query_blockers?
+        if filters && filters.none? { |f| f =~ database.id }
+          puts "Database #{database.id} did not match any filter; skipping." if verbose
+          next
+        elsif !database.capture_query_blockers?
+          if verbose
+            puts "Database #{database.id} capture_query_blockers "\
+               "is disabled via configuration; skipping."
+          end
+          next
+        end
 
-        puts "(Simulating) Capturing query blockers for #{database.id}..." if verbose
-        # TODO: actually implement database.capture_query_blockers
+        puts "Capturing query blockers for #{database.id}..." if verbose
+        begin
+          blocker_sample = database.capture_query_blockers
+          if verbose
+            if blocker_sample
+              puts "Captured blocker sample #{blocker_sample.id} "\
+                   "for #{database.id} with #{blocker_sample.sessions.size} sessions."
+            else
+              puts "No blocker sample returned for #{database.id}."
+            end
+          end
+        rescue NotEnabled => e
+          puts "Query blockers not enabled for #{database.id}: #{e.message}"
+        end
       end
-      true
     end
 
     def analyze_all(**options)
       each_database do |database|
         next if database.replica?
+
         database.analyze_tables(**options)
       end
     end

lib/pghero/base_database.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module PgHero
+  class BaseDatabase
+
+    include Methods::Basic
+
+    # Subclasses must define connection_model returning and ActiveRecord model
+    # for connection management
+
+    def connection
+      connection_model.connection
+    end
+  end
+end

lib/pghero/database.rb

@@ -1,12 +1,17 @@
+# frozen_string_literal: true
+
+require "active_record"
+
 module PgHero
-  class Database
-    include Methods::Basic
+  class Database < BaseDatabase
+
     include Methods::Connections
     include Methods::Explain
     include Methods::Indexes
     include Methods::Kill
     include Methods::Maintenance
     include Methods::Queries
+    include Methods::QueryBlockers
     include Methods::QueryStats
     include Methods::Replication
     include Methods::Sequences
@@ -19,27 +24,24 @@ class Database
 
     attr_reader :id, :config
 
-    def initialize(id, config)
+    def initialize(id, config, repository)
       @id = id
       @config = config || {}
+      @repository = repository
     end
 
     def name
-      @name ||= @config["name"] || id.titleize
+      @name ||= config["name"] || id.titleize
     end
 
     def db_instance_identifier
-      @db_instance_identifier ||= @config["db_instance_identifier"]
+      @db_instance_identifier ||= config["db_instance_identifier"]
     end
 
     def capture_query_stats?
       config["capture_query_stats"] != false
     end
 
-    def capture_query_blockers?
-      config["capture_query_blockers"] != false
-    end
-
     def cache_hit_rate_threshold
       (config["cache_hit_rate_threshold"] || PgHero.config["cache_hit_rate_threshold"] || PgHero.cache_hit_rate_threshold).to_i
     end
@@ -70,10 +72,12 @@ def index_bloat_bytes
 
     private
 
+    attr_reader :repository
+
     def connection_model
       @connection_model ||= begin
         url = config["url"]
-        Class.new(PgHero::Connection) do
+        Class.new(Connection) do
           def self.name
             "PgHero::Connection::Database#{object_id}"
           end
@@ -87,5 +91,9 @@ def self.name
         end
       end
     end
+
+    class Connection < ActiveRecord::Base
+      self.abstract_class = true
+    end
   end
 end