Class: Rails::Hyperdrive::Tools::TailLogs

Inherits:
Base
  • Object
show all
Defined in:
lib/rails/hyperdrive/tools/tail_logs.rb

Constant Summary collapse

DEFAULT_LINES = 
200
MAX_LINES = 
2_000

Class Method Summary collapse

Methods inherited from Base

respond_error, respond_json, respond_text, with_dev_guard

Class Method Details

.call(lines: DEFAULT_LINES, file: nil, server_context: nil) ⇒ Object 



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# File 'lib/rails/hyperdrive/tools/tail_logs.rb', line 20

def self.call(lines: DEFAULT_LINES, file: nil, server_context: nil)
  with_dev_guard do
    n = [[lines.to_i, 1].max, MAX_LINES].min
    log_dir = ::Rails.root.join("log").expand_path
    requested = file.to_s.empty? ? "#{::Rails.env}.log" : file.to_s
    log_path = resolve_path(log_dir, requested)
    return respond_error("log not allowed: path escapes Rails.root/log/") unless log_path
    return respond_error("log not found: #{log_path}") unless File.exist?(log_path)
    respond_text(tail(log_path, n))
  end
end

.resolve_path(log_dir, requested) ⇒ Object

Path-traversal guard: the resolved target must stay inside log_dir.



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# File 'lib/rails/hyperdrive/tools/tail_logs.rb', line 33

def self.resolve_path(log_dir, requested)
  base = Pathname.new(requested)
  target = base.absolute? ? base : (log_dir + base)
  target = Pathname.new(File.expand_path(target.to_s))
  return nil unless target.to_s == log_dir.to_s || target.to_s.start_with?(log_dir.to_s + File::SEPARATOR)
  target
end

.tail(path, lines) ⇒ Object

Pure-Ruby tail -n — portable and avoids shell-escaping risk.



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# File 'lib/rails/hyperdrive/tools/tail_logs.rb', line 42

def self.tail(path, lines)
  block_size = 8 * 1024
  File.open(path, "rb") do |f|
    f.seek(0, IO::SEEK_END)
    file_size = f.pos
    buffer = +""
    newline_count = 0
    while f.pos > 0 && newline_count <= lines
      read_size = [block_size, f.pos].min
      f.seek(-read_size, IO::SEEK_CUR)
      chunk = f.read(read_size)
      f.seek(-read_size, IO::SEEK_CUR)
      buffer.prepend(chunk)
      newline_count = buffer.count("\n")
    end
    buffer.force_encoding(Encoding.default_external).scrub
    last = buffer.lines.last(lines).join
    last.empty? && file_size > 0 ? buffer : last
  end
end