Class: SemanticLogger::Appender::File

Inherits:
Subscriber show all
Defined in:
lib/semantic_logger/appender/file.rb

Instance Attribute Summary collapse

Attributes inherited from Subscriber

#application, #environment, #formatter, #host, #logger, #metrics

Attributes inherited from Base

#filter, #name

Instance Method Summary collapse

Methods inherited from Subscriber

#close, #console_output?, #default_formatter, #level, #should_log?

Methods inherited from Base

#backtrace, #fast_tag, #level, #level=, #measure, #named_tags, #pop_tags, #push_tags, #should_log?, #silence, #tagged, #tags

Constructor Details

#initialize(file_name, retry_count: 1, append: true, reopen_period: nil, reopen_count: 0, reopen_size: 0, encoding: Encoding::BINARY, exclusive_lock: false, **args, &block) ⇒ File

Create an appender to log to a named file.

Parameters

file_name [String]
  Name of the file to write to.

  File name format directives:
    p - Process Id
    n - Short hostname (SemanticLogger.host). Everything before the first period in the hostname.
    %N - Full hostname (SemanticLogger.host)
    a - Application name (SemanticLogger.application)
    e - Environment name (SemanticLogger.environment)
    D - Current Date. Equivalent to "%Y%m%d"
    T - Current Time. Equivalent to "%H%M%S"
    %% - Literal `%` character

  Date:
    %Y - Year with century
    %C - year / 100 (round down.  20 in 2009)
    %y - year % 100 (00..99)
    %m - Month of the year, zero-padded (01..12)
    %d - Day of the month, zero-padded (01..31)
    %j - Day of the year (001..366)
    %U - Week number of the year.  The week starts with Sunday.  (00..53)
    %W - Week number of the year.  The week starts with Monday.  (00..53)

  Time:
    %H - 24 Hour of the day, zero-padded (00..23)
    %M - Minute of the hour (00..59)
    %S - Second of the minute (00..60)

  Examples:
    Create a log file name consisting of the short host name, process id, date, and time.
      "log/production-%n-%p-%D-%T.log"

:level [:trace | :debug | :info | :warn | :error | :fatal]
  Override the log level for this appender.
  Default: SemanticLogger.default_level

:formatter: [Object|Proc]
  An instance of a class that implements #call, or a Proc to be used to format
  the output from this appender
  Default: Use the built-in formatter (See: #call)

:filter [Regexp|Proc]
  RegExp: Only include log messages where the class name matches the supplied
  regular expression. All other messages will be ignored.
  Proc: Only include log messages where the supplied Proc returns true
        The Proc must return true or false.

:append [true|false]
  Append to the log file if already present?
  Default: true

:exclusive_lock [true|false]
  Obtain an exclusive lock on the file, for operating systems that support it.
  Prevents multiple processes from trying to write to the same log file.
  Default: false

:encoding ["UTF-8", "UTF-16", etc.]
  Encoding to use when writing to the file.
  Default: Encoding::BINARY

:retry_count [Integer]
  Number of times to attempt to re-open the file name when an error occurs trying to
  write to the file.
  Note: Set to 0 to disable retries.
  Default: 1

:reopen_period [String]
  Specify a period after which to re-open the log file, specified in minutes, hours, or days.
  The format of the duration must start with an Integer or Float number,
  followed by the duration specified as:
    "m" : minutes
    "h" : hours
    "d" : days
  The time is rounded down to the specified time interval, so that:
  - "1h" will re-open every hour at the beginning of the hour.
  - "30m" will re-open every 30 minutes at the beginning of the 30th minute.
  - "1d" will re-open every day at midnight.
  Examples:
    "60m" : Every 60 minutes at the beginning of the minute: 10:24:00, 11:24:00, 12:24:00, ...
    "1h"  : Every hour at the beginning of the hour: 10:00:00, 11:00:00, 12:00:00, ...
    "1d"  : Every day at the beginning of the day: "20211008 00:00:00", "20211009 00:00:00", ...
  Default: nil (Disabled)

:reopen_count [Integer]
  Close and re-open the log file after every `reopen_count` number of logged entries.
  Default: 0 (Disabled)

:reopen_size [Integer]
  Approximate number of bytes to write to a log file by this process before closing and re-opening it.
  Notes:
  - When `append: true` and the file already exists, it reads the size of the current log file
    and starts with that size.
    - If the current log file size already exceeds the `reopen_size`, its current size is ignored.
  - The `reopen_size` is only the amount of bytes written by this process, it excludes data
    written by other processes. Use a unique filename to prevent multiple processes from writing to
    the same log file at the same time.
  Default: 0 (Disabled)

Example

require "semantic_logger"

# Enable trace level logging
SemanticLogger.default_level = :info

# Log to a file
SemanticLogger.add_appender(file_name: "application.log", formatter: :color)

logger = SemanticLogger["test"]
logger.info "Hello World"



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# File 'lib/semantic_logger/appender/file.rb', line 125

def initialize(file_name, retry_count: 1, append: true, reopen_period: nil, reopen_count: 0, reopen_size: 0, encoding: Encoding::BINARY, exclusive_lock: false, **args, &block)
  if !file_name.is_a?(String) || file_name.empty?
    raise(ArgumentError, "SemanticLogging::Appender::File file_name must be a non-empty string")
  end

  @file_name      = file_name
  @retry_count    = retry_count
  @file           = nil
  @append         = append
  @reopen_period  = reopen_period
  @reopen_count   = reopen_count
  @reopen_size    = reopen_size
  @encoding       = encoding
  @exclusive_lock = exclusive_lock
  @log_count      = 0
  @log_size       = 0
  @reopen_at      = nil

  super(**args, &block)
end

Instance Attribute Details

#append ⇒ Object

Returns the value of attribute append.



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# File 'lib/semantic_logger/appender/file.rb', line 9

def append
  @append
end

#current_file_name ⇒ Object

Returns the value of attribute current_file_name.



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# File 'lib/semantic_logger/appender/file.rb', line 11

def current_file_name
  @current_file_name
end

#encoding ⇒ Object

Returns the value of attribute encoding.



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# File 'lib/semantic_logger/appender/file.rb', line 9

def encoding
  @encoding
end

#exclusive_lock ⇒ Object

Returns the value of attribute exclusive_lock.



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# File 'lib/semantic_logger/appender/file.rb', line 9

def exclusive_lock
  @exclusive_lock
end

#file_name ⇒ Object

Returns the value of attribute file_name.



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# File 'lib/semantic_logger/appender/file.rb', line 9

def file_name
  @file_name
end

#log_count ⇒ Object

Returns the value of attribute log_count.



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# File 'lib/semantic_logger/appender/file.rb', line 11

def log_count
  @log_count
end

#log_size ⇒ Object

Returns the value of attribute log_size.



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# File 'lib/semantic_logger/appender/file.rb', line 11

def log_size
  @log_size
end

#reopen_at ⇒ Object

Returns the value of attribute reopen_at.



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# File 'lib/semantic_logger/appender/file.rb', line 11

def reopen_at
  @reopen_at
end

#reopen_count ⇒ Object

Returns the value of attribute reopen_count.



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# File 'lib/semantic_logger/appender/file.rb', line 9

def reopen_count
  @reopen_count
end

#reopen_period ⇒ Object

Returns the value of attribute reopen_period.



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# File 'lib/semantic_logger/appender/file.rb', line 9

def reopen_period
  @reopen_period
end

#reopen_size ⇒ Object

Returns the value of attribute reopen_size.



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# File 'lib/semantic_logger/appender/file.rb', line 9

def reopen_size
  @reopen_size
end

#retry_count ⇒ Object

Returns the value of attribute retry_count.



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# File 'lib/semantic_logger/appender/file.rb', line 9

def retry_count
  @retry_count
end

Instance Method Details

#flush ⇒ Object

Flush all pending logs to disk.

Waits for all sent documents to be written to disk



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# File 'lib/semantic_logger/appender/file.rb', line 205

def flush
  @file&.flush
end

#log(log) ⇒ Object

Since only one appender thread will be writing to the file at a time it is not necessary to protect access to the file with a semaphore.



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# File 'lib/semantic_logger/appender/file.rb', line 183

def log(log)
  reopen if time_to_reopen?

  count = 0
  begin
    message = formatter.call(log, self) << "\n"
    @file.write(message)
    @log_count += 1
    @log_size  += message.size
  rescue StandardError => e
    if count < retry_count
      count += 1
      reopen
      retry
    end
    raise(e)
  end
  true
end

#reopen ⇒ Object

After forking an active process call #reopen to re-open open the file handles etc to resources.



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# File 'lib/semantic_logger/appender/file.rb', line 148

def reopen
  begin
    @file&.close
  rescue StandardError
    nil
  end

  self.current_file_name = apply_format_directives(file_name)
  if ::File.directory?(file_name)
    raise(ArgumentError, "The supplied log file_name: #{current_file_name} is already a directory.")
  end

  self.log_count = 0
  if append && reopen_size && ::File.exist?(current_file_name)
    self.log_size = ::File.size(current_file_name)
    self.log_size = 0 if log_size >= reopen_size
  else
    self.log_size = 0
  end

  self.reopen_at = reopen_period ? next_reopen_period(reopen_period) : nil

  options = ::File::WRONLY | ::File::CREAT
  options |= ::File::APPEND if append
  @file = ::File.open(current_file_name, options)
  # Force all log entries to write immediately without buffering
  # Allows multiple processes to write to the same log file simultaneously
  @file.sync = true
  @file.set_encoding(encoding) if @file.respond_to?(:set_encoding)
  @file.flock(::File::LOCK_EX) if exclusive_lock
  @file
end