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# frozen_string_literal: true
# Copyright (C) 2025-present MongoDB Inc.
#
# Licensed under the Apache License, Version 2.0 (the 'License');
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an 'AS IS' BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
module Mongo
module Tracing
module OpenTelemetry
# OperationTracer is responsible for tracing MongoDB driver operations using OpenTelemetry.
#
# @api private
class OperationTracer
extend Forwardable
def_delegators :@parent_tracer,
:cursor_context_map,
:parent_context_for,
:transaction_context_map,
:transaction_map_key
# Initializes a new OperationTracer.
#
# @param otel_tracer [ OpenTelemetry::Trace::Tracer ] the OpenTelemetry tracer.
# @param parent_tracer [ Mongo::Tracing::OpenTelemetry::Tracer ] the parent tracer
# for accessing shared context maps.
def initialize(otel_tracer, parent_tracer)
@otel_tracer = otel_tracer
@parent_tracer = parent_tracer
end
# Trace a MongoDB operation.
#
# Creates an OpenTelemetry span for the operation, capturing attributes such as
# database name, collection name, operation name, and cursor ID. The span is finished
# automatically when the operation completes or fails.
#
# @param operation [ Mongo::Operation ] the MongoDB operation to trace.
# @param operation_context [ Mongo::Operation::Context ] the context of the operation.
# @param op_name [ String | nil ] an optional name for the operation. If nil, the
# operation class name is used.
#
# @yield the block representing the operation to be traced.
#
# @return [ Object ] the result of the operation.
#
# rubocop:disable Lint/RescueException
def trace_operation(operation, operation_context, op_name: nil, &block)
span = create_operation_span(operation, operation_context, op_name)
execute_with_span(span, operation, &block)
rescue Exception => e
handle_span_exception(span, e)
raise e
ensure
span&.finish
end
# rubocop:enable Lint/RescueException
private
# Creates an OpenTelemetry span for the operation.
#
# @param operation [ Mongo::Operation ] the operation.
# @param operation_context [ Mongo::Operation::Context ] the operation context.
# @param op_name [ String | nil ] optional operation name.
#
# @return [ OpenTelemetry::Trace::Span ] the created span.
def create_operation_span(operation, operation_context, op_name)
parent_context = parent_context_for(operation_context, operation.cursor_id)
@otel_tracer.start_span(
operation_span_name(operation, op_name),
attributes: span_attributes(operation, op_name),
with_parent: parent_context,
kind: :client
)
end
# Executes the operation block within the span context.
#
# @param span [ OpenTelemetry::Trace::Span ] the span.
# @param operation [ Mongo::Operation ] the operation.
#
# @yield the block to execute.
#
# @return [ Object ] the result of the block.
def execute_with_span(span, operation)
::OpenTelemetry::Trace.with_span(span) do |s, c|
yield.tap do |result|
process_cursor_context(result, operation.cursor_id, c, s)
end
end
end
# Handles exception for the span.
#
# @param span [ OpenTelemetry::Trace::Span ] the span.
# @param exception [ Exception ] the exception.
def handle_span_exception(span, exception)
return unless span
span.record_exception(exception)
span.status = ::OpenTelemetry::Trace::Status.error(
"Unhandled exception of type: #{exception.class}"
)
end
# Returns the operation name from the provided name or operation class.
#
# @param operation [ Mongo::Operation ] the operation.
# @param op_name [ String | nil ] optional operation name.
#
# @return [ String ] the operation name in lowercase.
def operation_name(operation, op_name = nil)
op_name || operation.class.name.split('::').last.downcase
end
# Builds span attributes for the operation.
#
# @param operation [ Mongo::Operation ] the operation.
# @param op_name [ String | nil ] optional operation name.
#
# @return [ Hash ] OpenTelemetry span attributes following MongoDB semantic conventions.
def span_attributes(operation, op_name)
{
'db.system' => 'mongodb',
'db.namespace' => operation.db_name.to_s,
'db.collection.name' => collection_name(operation),
'db.operation.name' => operation_name(operation, op_name),
'db.operation.summary' => operation_span_name(operation, op_name),
'db.mongodb.cursor_id' => operation.cursor_id,
}.compact
end
# Processes cursor context after operation execution.
#
# Updates the cursor context map based on the result. Removes closed cursors
# and stores context for newly created cursors.
#
# @param result [ Object ] the operation result.
# @param cursor_id [ Integer | nil ] the cursor ID before the operation.
# @param context [ OpenTelemetry::Context ] the OpenTelemetry context.
# @param span [ OpenTelemetry::Trace::Span ] the current span.
def process_cursor_context(result, cursor_id, context, span)
return unless result.is_a?(Cursor)
if result.id.zero?
# If the cursor is closed, remove it from the context map.
cursor_context_map.delete(cursor_id)
elsif result.id && cursor_id.nil?
# New cursor created, store its context.
cursor_context_map[result.id] = context
span.set_attribute('db.mongodb.cursor_id', result.id)
end
end
# Extracts the collection name from the operation.
#
# @param operation [ Mongo::Operation ] the operation.
#
# @return [ String | nil ] the collection name, or nil if not applicable.
def collection_name(operation)
return operation.coll_name.to_s if operation.respond_to?(:coll_name) && operation.coll_name
extract_collection_from_spec(operation)
end
# Extracts collection name from operation spec based on operation type.
#
# @param operation [ Mongo::Operation ] the operation.
#
# @return [ String | nil ] the collection name, or nil if not found.
def extract_collection_from_spec(operation)
collection_key = collection_key_for_operation(operation)
return nil unless collection_key
value = if collection_key == :first_value
operation.spec[:selector].values.first
else
operation.spec[:selector][collection_key]
end
value&.to_s
end
# Returns the collection key for a given operation type.
#
# @param operation [ Mongo::Operation ] the operation.
#
# @return [ Symbol | nil ] the collection key symbol or nil.
def collection_key_for_operation(operation)
case operation
when Operation::Aggregate then :aggregate
when Operation::Count then :count
when Operation::Create then :create
when Operation::Distinct then :distinct
when Operation::Drop then :drop
when Operation::WriteCommand then :first_value
end
end
# Generates the span name for the operation.
#
# @param operation [ Mongo::Operation ] the operation.
# @param op_name [ String | nil ] optional operation name.
#
# @return [ String ] span name in format "operation_name db.collection" or "operation_name db".
def operation_span_name(operation, op_name = nil)
coll_name = collection_name(operation)
if coll_name && !coll_name.empty?
"#{operation_name(operation, op_name)} #{operation.db_name}.#{coll_name}"
else
"#{operation_name(operation, op_name)} #{operation.db_name}"
end
end
end
end
end
end
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