Class: DeadBro::SqlSubscriber

Inherits:
Object
  • Object
show all
Defined in:
lib/dead_bro/sql_subscriber.rb

Constant Summary collapse

SQL_EVENT_NAME = 
"sql.active_record"
THREAD_LOCAL_KEY = 
:dead_bro_sql_queries
THREAD_LOCAL_ALLOC_START_KEY = 
:dead_bro_sql_alloc_start
THREAD_LOCAL_ALLOC_RESULTS_KEY = 
:dead_bro_sql_alloc_results
THREAD_LOCAL_BACKTRACE_KEY = 
:dead_bro_sql_backtraces
THREAD_LOCAL_EXPLAIN_PENDING_KEY = 
:dead_bro_explain_pending
MAX_TRACKED_QUERIES = 
1000
SENSITIVE_KV_QUOTED_RE =

Precompiled regexes used by sanitize_sql. Dynamic /…/i literals inside a hot-path method allocate a fresh Regexp on every call — pinning them here removes that allocation entirely.

/\b(password|token|secret|key|ssn|credit_card)\s*=\s*['"][^'"]*['"]/i
SENSITIVE_KV_BARE_RE = 
/\b(password|token|secret|key|ssn|credit_card)\s*=\s*[^'",\s)]+/i
WHERE_EQ_QUOTED_RE = 
/WHERE\s+[^=]+=\s*['"][^'"]*['"]/i
WHERE_EQ_QUOTED_INNER_RE = 
/=\s*['"][^'"]*['"]/
SANITIZE_MAX_LENGTH = 
1000
SANITIZE_SKIP_SENSITIVE_WHEN_NO_KEYWORDS = 
/password|token|secret|key|ssn|credit_card/i
SANITIZE_SKIP_WHERE_WHEN_NO_KEYWORD = 
/WHERE/i
MAX_PENDING_EXPLAINS =

Upper bound on pending EXPLAIN threads per request — stops a slow-query storm from spawning unbounded background threads.

20
EXPLAIN_WAIT_TIMEOUT_SECONDS =

Overall wall-clock we’re willing to block the request thread for pending EXPLAINs. Dropped from 5s → 1s: if the plan isn’t ready by then, skip it rather than stall the request.

1.0
APP_BACKTRACE_MAX_FRAMES = 
25
APP_BACKTRACE_SENSITIVE_RE = 
/\/[^\/]*(password|secret|key|token)[^\/]*\//i

Class Method Summary collapse

Class Method Details

.append_log_to_thread(thread, severity, message) ⇒ Object

Append a log entry directly to a specific thread’s log storage This is used when logging from background threads to ensure logs are collected with the main request thread’s logs



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# File 'lib/dead_bro/sql_subscriber.rb', line 272

def self.append_log_to_thread(thread, severity, message)
  timestamp = Time.now.utc
  log_entry = {
    sev: severity.to_s,
    msg: message.to_s,
    time: timestamp.iso8601(3)
  }

  # Append to the specified thread's log storage
  thread[:dead_bro_logs] ||= []
  thread[:dead_bro_logs] << log_entry

  # Also print the message immediately (using current thread's logger)
  begin
    if defined?(Rails) && Rails.respond_to?(:logger) && Rails.logger
      formatted_message = "[DeadBro] #{timestamp.iso8601(3)} #{severity.to_s.upcase}: #{message}"
      case severity
      when :debug
        Rails.logger.debug(formatted_message)
      when :info
        Rails.logger.info(formatted_message)
      when :warn
        Rails.logger.warn(formatted_message)
      when :error
        Rails.logger.error(formatted_message)
      when :fatal
        Rails.logger.fatal(formatted_message)
      end
    else
      # Fallback to stdout
      $stdout.puts("[DeadBro] #{timestamp.iso8601(3)} #{severity.to_s.upcase}: #{message}")
    end
  rescue
    # Never let logging break the application
    $stdout.puts("[DeadBro] #{severity.to_s.upcase}: #{message}")
  end
end

.build_explain_query(sql, connection) ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 310

def self.build_explain_query(sql, connection)
  adapter_name = connection.adapter_name.downcase

  case adapter_name
  when "postgresql", "postgis"
    # PostgreSQL supports ANALYZE and BUFFERS
    "EXPLAIN (ANALYZE, BUFFERS) #{sql}"
  when "mysql", "mysql2", "trilogy"
    # MySQL uses different syntax - ANALYZE is a separate keyword
    "EXPLAIN ANALYZE #{sql}"
  when "sqlite3"
    # SQLite supports EXPLAIN QUERY PLAN
    "EXPLAIN QUERY PLAN #{sql}"
  else
    # Generic fallback - just EXPLAIN
    "EXPLAIN #{sql}"
  end
end

.capture_app_backtrace ⇒ Object

Cheap app-only backtrace for the current query. Uses caller_locations (lazy frame objects, no string allocations until we render) and keeps only frames under app/ (filtering vendor/). Returns at most N frames.



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# File 'lib/dead_bro/sql_subscriber.rb', line 445

def self.capture_app_backtrace
  locations = caller_locations(1, 100) || []
  frames = []
  locations.each do |loc|
    path = loc.path.to_s
    next unless path.include?("app/")
    next if path.include?("/vendor/")
    frames << "#{path}:#{loc.lineno}:in `#{loc.label}'".gsub(APP_BACKTRACE_SENSITIVE_RE, "/[FILTERED]/")
    break if frames.length >= APP_BACKTRACE_MAX_FRAMES
  end
  frames
rescue
  []
end

.current_queries_array ⇒ Object

Current queries array (top of stack); nil if no active tracking.



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# File 'lib/dead_bro/sql_subscriber.rb', line 37

def self.current_queries_array
  stack = Thread.current[THREAD_LOCAL_KEY]
  return nil unless stack.is_a?(Array) && stack.any?
  stack.last
end

.format_explain_result(result, connection) ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 369

def self.format_explain_result(result, connection)
  adapter_name = connection.adapter_name.downcase

  case adapter_name
  when "postgresql", "postgis"
    # PostgreSQL returns ActiveRecord::Result from select_all
    if result.respond_to?(:rows)
      # ActiveRecord::Result object - rows is an array of arrays
      # Each row is [query_plan_string]
      plan_text = result.rows.map { |row| row.is_a?(Array) ? row.first.to_s : row.to_s }.join("\n")
      return plan_text unless plan_text.strip.empty?
    end

    # Try alternative methods to extract the plan
    if result.respond_to?(:each) && result.respond_to?(:columns)
      # ActiveRecord::Result with columns
      plan_column = result.columns.find { |col| col.downcase.include?("plan") || col.downcase.include?("query") } || result.columns.first
      plan_text = result.map { |row|
        if row.is_a?(Hash)
          row[plan_column] || row[plan_column.to_sym] || row.values.first
        else
          row
        end
      }.join("\n")
      return plan_text unless plan_text.strip.empty?
    end

    if result.is_a?(Array)
      # Array of hashes or arrays
      plan_text = result.map do |row|
        if row.is_a?(Hash)
          row["QUERY PLAN"] || row["query plan"] || row[:query_plan] || row.values.first.to_s
        elsif row.is_a?(Array)
          row.first.to_s
        else
          row.to_s
        end
      end.join("\n")
      return plan_text unless plan_text.strip.empty?
    end

    # Fallback to string representation
    result.to_s
  when "mysql", "mysql2", "trilogy"
    # MySQL returns Mysql2::Result object which needs to be converted to array
    if result.respond_to?(:to_a)
      # Convert Mysql2::Result to array of hashes
      rows = result.to_a
      rows.map { |row| row.is_a?(Hash) ? row.values.join(" | ") : row.to_s }.join("\n")
    elsif result.is_a?(Array)
      result.map { |row| row.is_a?(Hash) ? row.values.join(" | ") : row.to_s }.join("\n")
    else
      result.to_s
    end
  when "sqlite3"
    # SQLite returns rows
    if result.is_a?(Array)
      result.map { |row| row.is_a?(Hash) ? row.values.join(" | ") : row.to_s }.join("\n")
    else
      result.to_s
    end
  else
    # Generic fallback
    result.to_s
  end
rescue
  # Fallback to string representation
  result.to_s
end

.interpolate_sql_with_binds(sql, binds, connection) ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 329

def self.interpolate_sql_with_binds(sql, binds, connection)
  return sql if binds.nil? || binds.empty?
  return sql unless connection

  interpolated_sql = sql.dup

  # Handle $1, $2 style placeholders (PostgreSQL)
  if interpolated_sql.include?("$1")
    binds.each_with_index do |val, index|
      # Get value from bind param (handle both raw values and ActiveRecord::Relation::QueryAttribute)
      value = val
      if val.respond_to?(:value_for_database)
        value = val.value_for_database
      elsif val.respond_to?(:value)
        value = val.value
      end

      quoted_value = connection.quote(value)
      interpolated_sql = interpolated_sql.gsub("$#{index + 1}", quoted_value)
    end
  elsif interpolated_sql.include?("?")
    # Handle ? style placeholders (MySQL, SQLite)
    # We need to replace ? one by one in order
    binds.each do |val|
      # Get value from bind param
      value = val
      if val.respond_to?(:value_for_database)
        value = val.value_for_database
      elsif val.respond_to?(:value)
        value = val.value
      end

      quoted_value = connection.quote(value)
      interpolated_sql = interpolated_sql.sub("?", quoted_value)
    end
  end

  interpolated_sql
end

.safe_query_trace(data, captured_backtrace = nil) ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 460

def self.safe_query_trace(data, captured_backtrace = nil)
  return [] unless data.is_a?(Hash)

  # Build trace from available data fields
  trace = []

  # Use filename, line, and method if available
  if data[:filename] && data[:line] && data[:method]
    trace << "#{data[:filename]}:#{data[:line]}:in `#{data[:method]}'"
  end

  # Use the captured backtrace from when the query started (most accurate)
  if captured_backtrace && captured_backtrace.is_a?(Array) && !captured_backtrace.empty?
    # Filter to only include frames that contain "app/" (application code)
    app_frames = captured_backtrace.select do |frame|
      frame.include?("app/") && !frame.include?("/vendor/")
    end

    caller_trace = app_frames.map do |line|
      # Remove any potential sensitive information from file paths
      line.gsub(/\/[^\/]*(password|secret|key|token)[^\/]*\//i, "/[FILTERED]/")
    end

    trace.concat(caller_trace)
  else
    # Fallback: try to get backtrace from current context
    begin
      # Get all available frames - we'll filter to find application code
      all_frames = Thread.current.backtrace || []

      if all_frames.empty?
        # Fallback to caller_locations if backtrace is empty
        locations = caller_locations(1, 50)
        all_frames = locations.map { |loc| "#{loc.path}:#{loc.lineno}:in `#{loc.label}'" } if locations
      end

      # Filter to only include frames that contain "app/" (application code)
      app_frames = all_frames.select do |frame|
        frame.include?("app/") && !frame.include?("/vendor/")
      end

      caller_trace = app_frames.map do |line|
        line.gsub(/\/[^\/]*(password|secret|key|token)[^\/]*\//i, "/[FILTERED]/")
      end

      trace.concat(caller_trace)
    rescue
      # If backtrace fails, try caller as fallback
      begin
        caller_stack = caller(20, 50) # Get more frames to find app/ frames
        app_frames = caller_stack.select { |frame| frame.include?("app/") && !frame.include?("/vendor/") }
        caller_trace = app_frames.map do |line|
          line.gsub(/\/[^\/]*(password|secret|key|token)[^\/]*\//i, "/[FILTERED]/")
        end
        trace.concat(caller_trace)
      rescue
        # If caller also fails, we still have the immediate location
      end
    end
  end

  # If we have a backtrace in the data, use it (but it's usually nil for SQL events)
  if data[:backtrace] && data[:backtrace].is_a?(Array)
    # Filter to only include frames that contain "app/"
    app_backtrace = data[:backtrace].select do |line|
      line.is_a?(String) && line.include?("app/") && !line.include?("/vendor/")
    end

    backtrace_trace = app_backtrace.map do |line|
      case line
      when String
        line.gsub(/\/[^\/]*(password|secret|key|token)[^\/]*\//i, "/[FILTERED]/")
      else
        line.to_s
      end
    end
    trace.concat(backtrace_trace)
  end

  # Remove duplicates and return all app/ frames (no limit)
  trace.uniq.map do |line|
    case line
    when String
      # Remove any potential sensitive information from file paths
      line.gsub(/\/[^\/]*(password|secret|key|token)[^\/]*\//i, "/[FILTERED]/")
    else
      line.to_s
    end
  end
rescue
  []
end

.sanitize_sql(sql) ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 175

def self.sanitize_sql(sql)
  return sql unless sql.is_a?(String)

  # Cap length first — most "expensive" queries from the app's perspective
  # are big UPDATE/INSERT with long literal blobs; don't burn regex time on
  # those when we're going to truncate anyway.
  sql = sql[0..SANITIZE_MAX_LENGTH] + "..." if sql.length > SANITIZE_MAX_LENGTH

  # Only scan for sensitive KV pairs if one of the keywords is actually
  # present — saves two regex passes on the vast majority of queries.
  if sql.match?(SANITIZE_SKIP_SENSITIVE_WHEN_NO_KEYWORDS)
    sql = sql.gsub(SENSITIVE_KV_QUOTED_RE, '\1 = ?')
    sql = sql.gsub(SENSITIVE_KV_BARE_RE, '\1 = ?')
  end

  # Same short-circuit for WHERE rewrite.
  if sql.match?(SANITIZE_SKIP_WHERE_WHEN_NO_KEYWORD)
    sql = sql.gsub(WHERE_EQ_QUOTED_RE) do |match|
      match.gsub(WHERE_EQ_QUOTED_INNER_RE, "= ?")
    end
  end

  sql
end

.should_continue_tracking?(current_queries_array, max_count) ⇒ Boolean

Check if we should continue tracking based on count and time limits

Returns:

  • (Boolean) 


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# File 'lib/dead_bro/sql_subscriber.rb', line 44

def self.should_continue_tracking?(current_queries_array, max_count)
  return false unless current_queries_array.is_a?(Array)

  # Check count limit
  return false if current_queries_array.length >= max_count

  # Check time limit
  start_time = Thread.current[DeadBro::TRACKING_START_TIME_KEY]
  if start_time
    elapsed_seconds = Time.now - start_time
    return false if elapsed_seconds >= DeadBro::MAX_TRACKING_DURATION_SECONDS
  end

  true
end

.should_explain_query?(duration_ms, sql) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/dead_bro/sql_subscriber.rb', line 200

def self.should_explain_query?(duration_ms, sql)
  return false unless DeadBro.configuration.explain_analyze_enabled
  return false if duration_ms < DeadBro.configuration.slow_query_threshold_ms
  return false unless sql.is_a?(String)
  return false if sql.strip.empty?

  # Skip EXPLAIN for certain query types that don't benefit from it
  sql_upper = sql.upcase.strip
  return false if sql_upper.start_with?("EXPLAIN")
  return false if sql_upper.start_with?("BEGIN")
  return false if sql_upper.start_with?("COMMIT")
  return false if sql_upper.start_with?("ROLLBACK")
  return false if sql_upper.start_with?("SAVEPOINT")
  return false if sql_upper.start_with?("RELEASE")

  true
end

.start_explain_analyze_background(sql, connection_id, query_info, binds = nil) ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 218

def self.start_explain_analyze_background(sql, connection_id, query_info, binds = nil)
  return unless defined?(ActiveRecord)
  return unless ActiveRecord::Base.respond_to?(:connection)

  # Cap pending EXPLAINs per request. A slow-query storm that would have
  # spawned 200 threads and starved the AR pool now drops excess plans
  # instead of cascading into a timeout.
  pending = Thread.current[THREAD_LOCAL_EXPLAIN_PENDING_KEY] ||= []
  if pending.length >= MAX_PENDING_EXPLAINS
    query_info[:explain_plan] = nil
    return
  end

  # Capture the main thread reference to append logs to the correct thread
  main_thread = Thread.current

  # Run EXPLAIN in a background thread to avoid blocking the main request.
  # We use `with_connection` so the connection returns to the pool even if
  # the thread is killed or the block raises — the previous manual
  # checkout/checkin could leak a connection under pathological paths.
  explain_thread = Thread.new do
    begin
      ActiveRecord::Base.connection_pool.with_connection do |connection|
        final_sql = interpolate_sql_with_binds(sql, binds, connection)
        explain_sql = build_explain_query(final_sql, connection)

        adapter_name = connection.adapter_name.downcase
        result = if adapter_name == "postgresql" || adapter_name == "postgis"
          connection.select_all(explain_sql)
        else
          connection.execute(explain_sql)
        end

        explain_plan = format_explain_result(result, connection)
        query_info[:explain_plan] = if explain_plan && !explain_plan.to_s.strip.empty?
          explain_plan
        end
      end
    rescue => e
      # Silently fail — don't let EXPLAIN break the application.
      append_log_to_thread(main_thread, :debug, "Failed to capture EXPLAIN ANALYZE: #{e.message}")
      query_info[:explain_plan] = nil
    end
  end

  pending << explain_thread
rescue => e
  # Use DeadBro.logger here since we're still in the main thread
  DeadBro.logger.debug("Failed to start EXPLAIN ANALYZE thread: #{e.message}")
end

.start_request_tracking ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 122

def self.start_request_tracking
  # Stack allows nested job tracking (e.g. one job performing others in the same thread)
  (Thread.current[THREAD_LOCAL_KEY] ||= []) << []
  Thread.current[THREAD_LOCAL_ALLOC_START_KEY] = {}
  Thread.current[THREAD_LOCAL_ALLOC_RESULTS_KEY] = {}
  Thread.current[THREAD_LOCAL_BACKTRACE_KEY] = {}
  Thread.current[THREAD_LOCAL_EXPLAIN_PENDING_KEY] = []
end

.stop_request_tracking ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 131

def self.stop_request_tracking
  # Wait for any pending EXPLAIN ANALYZE queries to complete (with timeout)
  # This must happen BEFORE we get the queries array reference to ensure
  # all explain_plan fields are populated
  wait_for_pending_explains(EXPLAIN_WAIT_TIMEOUT_SECONDS)

  stack = Thread.current[THREAD_LOCAL_KEY]
  queries = (stack.is_a?(Array) && stack.any?) ? stack.pop : []
  # Clear thread locals when stack is empty so "tracking not started" behaves correctly
  if stack.nil? || stack.empty?
    Thread.current[THREAD_LOCAL_KEY] = nil
    Thread.current[THREAD_LOCAL_ALLOC_START_KEY] = nil
    Thread.current[THREAD_LOCAL_ALLOC_RESULTS_KEY] = nil
    Thread.current[THREAD_LOCAL_BACKTRACE_KEY] = nil
    Thread.current[THREAD_LOCAL_EXPLAIN_PENDING_KEY] = nil
  end
  queries
end

.subscribe! ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 60

def self.subscribe!
  # Subscribe with a start/finish listener to measure allocations per query
  if ActiveSupport::Notifications.notifier.respond_to?(:subscribe)
    begin
      ActiveSupport::Notifications.notifier.subscribe(SQL_EVENT_NAME, SqlAllocListener.new)
    rescue
    end
  end

  ActiveSupport::Notifications.subscribe(SQL_EVENT_NAME) do |name, started, finished, _unique_id, data|
    next if data[:name] == "SCHEMA" || data[:name] == "CACHE" || data[:name] == "BEGIN" || data[:name] == "COMMIT" || data[:name] == "ROLLBACK" || data[:name] == "SAVEPOINT" || data[:name] == "RELEASE"
    # Only track queries that are part of the current request (top of stack for nested jobs)
    current = current_queries_array
    next unless current
    unique_id = _unique_id
    allocations = nil
    begin
      alloc_results = Thread.current[THREAD_LOCAL_ALLOC_RESULTS_KEY]
      allocations = alloc_results && alloc_results.delete(unique_id)
    rescue
    end

    duration_ms = ((finished - started) * 1000.0).round(2)
    original_sql = data[:sql]

    # Only capture a backtrace for queries we actually care about tracing
    # (slow). This skips the ~O(stack-depth) allocation on the 99% of queries
    # that are fast. An N+1 of 100 x 1ms queries no longer eats a thousand
    # frame allocations for traces nobody will read.
    threshold = begin
      DeadBro.configuration.slow_query_threshold_ms
    rescue
      500
    end
    captured_trace = (duration_ms >= threshold.to_f) ? capture_app_backtrace : []

    query_info = {
      sql: sanitize_sql(original_sql),
      name: data[:name],
      duration_ms: duration_ms,
      cached: data[:cached] || false,
      connection_id: data[:connection_id],
      trace: captured_trace,
      allocations: allocations
    }

    # Run EXPLAIN ANALYZE for slow queries in the background
    if should_explain_query?(duration_ms, original_sql)
      # Store reference to query_info so we can update it when EXPLAIN completes
      query_info[:explain_plan] = nil # Placeholder
      # Capture binds if available (type_casted_binds is preferred as they are ready for quoting)
      binds = data[:type_casted_binds] || data[:binds]
      start_explain_analyze_background(original_sql, data[:connection_id], query_info, binds)
    end

    # Add to current context (top of stack), but only if we haven't exceeded the limits
    if should_continue_tracking?(current, MAX_TRACKED_QUERIES)
      current << query_info
    end
  end
end

.tracking_active? ⇒ Boolean

True when there is at least one active tracking context (e.g. for nested jobs).

Returns:

  • (Boolean) 


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# File 'lib/dead_bro/sql_subscriber.rb', line 31

def self.tracking_active?
  stack = Thread.current[THREAD_LOCAL_KEY]
  stack.is_a?(Array) && stack.any?
end

.wait_for_pending_explains(timeout_seconds) ⇒ Object 



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# File 'lib/dead_bro/sql_subscriber.rb', line 158

def self.wait_for_pending_explains(timeout_seconds)
  pending = Thread.current[THREAD_LOCAL_EXPLAIN_PENDING_KEY]
  return unless pending && !pending.empty?

  start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
  pending.each do |thread|
    remaining_time = timeout_seconds - (Process.clock_gettime(Process::CLOCK_MONOTONIC) - start_time)
    break if remaining_time <= 0

    begin
      thread.join(remaining_time)
    rescue => e
      DeadBro.logger.debug("Error waiting for EXPLAIN ANALYZE: #{e.message}")
    end
  end
end