Module: RailsOtelContext::ActiveRecordContext

Defined in:
lib/rails_otel_context/activerecord_context.rb

Overview

Extracts ActiveRecord model name, method, and scope from sql.active_record notifications and scope instrumentation.

Two mechanisms work together:

  1. sql.active_record subscriber — captures model name + AR operation type (e.g., “Transaction Load”) at query time via payload.

  2. Scope tracking — wraps scope-generated methods to store the scope name on the Relation object, then captures it at materialization time via Relation#exec_queries. This handles lazy scopes like Transaction.recent_completed.to_a where the scope method returns before SQL fires.

Defined Under Namespace

Modules: ClassMethodScopeTracking, RelationScopeCapture, ScopeNameTracking Classes: Subscriber

Constant Summary collapse

DB_SLOW_ATTR = 
'db.slow'

Class Method Summary collapse

Class Method Details

.app_root ⇒ Object 



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# File 'lib/rails_otel_context/activerecord_context.rb', line 179

def app_root
  @app_root
end

.apply_to_span(span, ctx) ⇒ Object

Applies AR context directly to a span. Used by Subscriber#start to enrich spans created by driver-level OTel instrumentation (Trilogy, PG) before our notification subscriber runs. Also reads code.namespace/code.function already set by CallContextProcessor#on_start so the span_name_formatter has full context.



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# File 'lib/rails_otel_context/activerecord_context.rb', line 241

def apply_to_span(span, ctx)
  return unless span.context.valid?

  span.set_attribute('code.activerecord.model', ctx[:model_name]) if ctx[:model_name]
  span.set_attribute('code.activerecord.method', ctx[:method_name]) if ctx[:method_name]
  span.set_attribute('code.activerecord.scope', ctx[:scope_name]) if ctx[:scope_name]
  span.set_attribute('db.query_count', ctx[:query_count]) if ctx[:query_count]
  span.set_attribute('db.async', true) if ctx[:async]

  formatter = RailsOtelContext.configuration.span_name_formatter
  return unless formatter
  return unless span.respond_to?(:attributes) && span.attributes&.key?('db.system')

  # Dup deferred to here: set_attribute calls above need only the original ctx keys.
  # The formatter may inspect code.namespace/code.function already on the span.
  ar_ctx = ctx.dup
  if span.respond_to?(:attributes)
    ar_ctx[:code_namespace] = span.attributes['code.namespace']
    ar_ctx[:code_function]  = span.attributes['code.function']
  end

  original_name = span.name
  new_name = formatter.call(original_name, ar_ctx)
  return unless new_name && new_name != original_name && span.respond_to?(:name=)

  span.set_attribute('l9.orig.name', original_name)
  span.name = new_name
rescue StandardError
  nil
end

.ar_table_model_map ⇒ Object

Lazy table_name → model_name index. Built on first use after all models are loaded (eager_load! in production). In development, call reset_ar_table_model_map! after a code reload to get a fresh index.



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# File 'lib/rails_otel_context/activerecord_context.rb', line 346

def ar_table_model_map
  @ar_table_model_map ||= begin
    next_map = {}
    if defined?(::ActiveRecord::Base)
      ::ActiveRecord::Base.descendants.each do |m|
        model_name = begin
          m.name
        rescue StandardError
          next
        end
        next unless model_name
        # Skip STI subclasses — they share the parent's table_name.
        # Without this guard, AdminUser < User would overwrite users → User
        # with users → AdminUser in the map, giving wrong model names on
        # SQL-named spans (counter caches, update_all).
        next unless m.base_class == m

        table = begin
          m.table_name
        rescue StandardError
          next
        end
        next unless table

        next_map[table] = model_name
      end
    end
    next_map
  end
end

.clear! ⇒ Object 



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# File 'lib/rails_otel_context/activerecord_context.rb', line 187

def clear!
  Thread.current[THREAD_KEY]          = nil
  Thread.current[SCOPE_THREAD_KEY]    = nil
  Thread.current[PENDING_PREPARE_KEY] = nil
end

.current ⇒ Object 



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# File 'lib/rails_otel_context/activerecord_context.rb', line 183

def current
  Thread.current[THREAD_KEY]
end

.extract_table_after(sql, keyword) ⇒ Object

Extracts a table name from sql starting after keyword. Skips one optional leading quote character (‘ “ ’), reads word chars until the next delimiter (space, quote, comma). Returns nil when keyword not found. Saves 1 alloc vs regex: index()+slice allocates only the result String.



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# File 'lib/rails_otel_context/activerecord_context.rb', line 327

def extract_table_after(sql, keyword)
  idx = sql.index(keyword)
  return nil unless idx

  start = idx + keyword.length
  first = sql.getbyte(start)
  start += 1 if first == BYTE_BACKTICK || first == BYTE_DQUOTE || first == BYTE_SQUOTE # rubocop:disable Style/MultipleComparison

  stop = start
  stop += 1 while stop < sql.length &&
                  (b = sql.getbyte(stop)) != BYTE_SPACE &&
                  b != BYTE_BACKTICK && b != BYTE_DQUOTE && b != BYTE_SQUOTE && b != BYTE_COMMA

  stop > start ? sql[start, stop - start] : nil
end

.install!(app_root: nil) ⇒ Object 



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# File 'lib/rails_otel_context/activerecord_context.rb', line 167

def install!(app_root: nil)
  @app_root = File.expand_path(app_root.to_s) if app_root

  return unless defined?(::ActiveSupport::Notifications)
  return unless defined?(::ActiveRecord::Base)

  ActiveSupport::Notifications.subscribe('sql.active_record', Subscriber.new)
  ::ActiveRecord::Base.extend(ScopeNameTracking)
  ::ActiveRecord::Base.extend(ClassMethodScopeTracking)
  ::ActiveRecord::Relation.prepend(RelationScopeCapture)
end

.parse_ar_name(name) ⇒ Object

Parses “Transaction Load” → { model_name: “Transaction”, method_name: “Load” } Uses index+byteslice instead of split to avoid allocating the intermediate Array and two String copies — saves 1 alloc (Array) vs split which returns Array+Strings but with frozen_string_literal the slice shares storage on MRI 3.2+.



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# File 'lib/rails_otel_context/activerecord_context.rb', line 276

def parse_ar_name(name)
  return nil unless name

  idx = name.index(' ')
  return nil unless idx

  model_name  = name[0, idx]
  method_name = name[idx + 1, name.length]

  return nil if model_name == 'ActiveRecord'

  { model_name: model_name, method_name: method_name,
    query_key: "#{model_name}.#{method_name}".freeze }
end

.parse_sql_context(sql) ⇒ Object

Parses raw SQL (payload == “SQL”) to extract model context. Used for counter cache updates, touch_later, and connection.execute calls that fire sql.active_record with name=“SQL” rather than “Model Method”.

Returns nil when the table cannot be mapped to a known AR model, so callers fall through to the existing skip path.



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# File 'lib/rails_otel_context/activerecord_context.rb', line 297

def parse_sql_context(sql)
  return nil unless sql

  verb = sql[SQL_VERB_RE, 1]&.capitalize
  return nil unless verb

  keyword = case verb
            when 'Update'          then KW_UPDATE
            when 'Insert'          then KW_INTO
            when 'Delete', 'Select' then KW_FROM
            end
  return nil unless keyword

  table      = extract_table_after(sql, keyword)
  model_name = table ? ar_table_model_map[table] : nil

  # Fall back to the virtual "SQL" model when the table cannot be resolved
  # (e.g. SELECT SLEEP(0.2), SELECT 1, raw DDL). This lets the span-name
  # formatter produce "SQL.Select" / "SQL.Update" for tab-group purposes
  # instead of leaving the span unnamed.
  model_name ||= 'SQL'

  { model_name: model_name, method_name: verb,
    query_key: "#{model_name}.#{verb}".freeze }
end

.reset_ar_table_model_map! ⇒ Object 



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# File 'lib/rails_otel_context/activerecord_context.rb', line 377

def reset_ar_table_model_map!
  @ar_table_model_map = nil
end

.retroactively_apply_to_span(span, ctx) ⇒ Object

Retroactively applies AR context to a finished span (e.g. PREPARE spans that finished before sql.active_record fired). Uses direct @attributes mutation because span.recording? is false — set_attribute would be a no-op.



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# File 'lib/rails_otel_context/activerecord_context.rb', line 212

def retroactively_apply_to_span(span, ctx)
  attrs = span.instance_variable_get(:@attributes)
  return unless attrs.respond_to?(:store)

  attrs.store(AR_MODEL_ATTR,  ctx[:model_name])  if ctx[:model_name]
  attrs.store(AR_METHOD_ATTR, ctx[:method_name]) if ctx[:method_name]
  attrs.store(AR_SCOPE_ATTR,  ctx[:scope_name])  if ctx[:scope_name]

  formatter = RailsOtelContext.configuration.span_name_formatter
  return unless formatter && span.respond_to?(:name) && attrs.key?('db.system')

  ar_ctx = ctx.dup
  ar_ctx[:code_namespace] = attrs['code.namespace']
  ar_ctx[:code_function]  = attrs['code.function']

  original_name = span.name
  new_name = formatter.call(original_name, ar_ctx)
  return unless new_name && new_name != original_name

  attrs.store(ORIG_NAME_ATTR, original_name)
  span.instance_variable_set(:@name, new_name)
rescue StandardError
  nil
end

.stash_prepare_span(span) ⇒ Object

Called from CallContextProcessor#on_finish when a PREPARE span finishes before its sql.active_record notification. Stashed spans are flushed by Subscriber#start when the notification fires.



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# File 'lib/rails_otel_context/activerecord_context.rb', line 196

def stash_prepare_span(span)
  (Thread.current[PENDING_PREPARE_KEY] ||= []) << span
end

.stub_context(context) ⇒ Object

Test helpers: set AR context directly for unit tests.



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# File 'lib/rails_otel_context/activerecord_context.rb', line 201

def stub_context(context)
  Thread.current[THREAD_KEY] = context
end

.stub_scope(scope_name) ⇒ Object 



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# File 'lib/rails_otel_context/activerecord_context.rb', line 205

def stub_scope(scope_name)
  Thread.current[SCOPE_THREAD_KEY] = scope_name
end