Class: Mbeditor::LogTailService

Inherits:
Object
  • Object
show all
Defined in:
app/services/mbeditor/log_tail_service.rb

Overview

Reads a log file incrementally from a byte offset. Pure Ruby, no subprocess.

read_since(offset) -> { lines: Array, offset: Integer, reset: Boolean } offset == nil -> initial load: last INITIAL_TAIL_BYTES, reset: true offset > size -> file rotated/truncated: re-read from 0, reset: true else -> read new bytes from offset, capped at BYTE_CAP

Only complete lines (terminated by "\n") are ever returned; the byte offset advances solely past consumed complete lines, so a partial trailing line is held back and delivered once its newline arrives.

Constant Summary collapse

BYTE_CAP = 
256 * 1024
INITIAL_TAIL_BYTES = 
64 * 1024

Instance Method Summary collapse

Constructor Details

#initialize(log_path) ⇒ LogTailService

Returns a new instance of LogTailService.



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# File 'app/services/mbeditor/log_tail_service.rb', line 20

def initialize(log_path)
  @log_path = Pathname.new(log_path.to_s)
end

Instance Method Details

#read_since(offset) ⇒ Object 



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# File 'app/services/mbeditor/log_tail_service.rb', line 24

def read_since(offset)
  return empty(0) unless @log_path.exist?

  size = @log_path.size
  if offset.nil?
    start = [size - INITIAL_TAIL_BYTES, 0].max
    read_range(start, size, reset: true, trim_leading: start.positive?)
  elsif offset.to_i > size
    read_range(0, [size, BYTE_CAP].min, reset: true, trim_leading: false)
  else
    start = offset.to_i
    read_range(start, [start + BYTE_CAP, size].min, reset: false, trim_leading: false)
  end
end