Class: AwsLogs::Tail

Inherits:
Object
  • Object
show all
Includes:
AwsServices
Defined in:
lib/aws_logs/tail.rb

Constant Summary collapse

@@end_loop_signal =

The stop_follow! results in a little waiting because it signals to break the polling loop. Since it’s in the middle of the loop process, the loop will finish the sleep 5 first. So it can pause from 0-5 seconds.

false

Class Method Summary collapse

Instance Method Summary collapse

Methods included from AwsServices

#cloudwatchlogs

Constructor Details

#initialize(options = {}) ⇒ Tail

Returns a new instance of Tail.



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# File 'lib/aws_logs/tail.rb', line 7

def initialize(options={})
  @options = options
  @log_group_name = options[:log_group_name]
  # Setting to ensure matches default CLI option
  @follow = @options[:follow].nil? ? true : @options[:follow]

  @loop_count = 0
  @output = [] # for specs
  reset
  set_trap
end

Class Method Details

.stop_follow! ⇒ Object 



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# File 'lib/aws_logs/tail.rb', line 129

def self.stop_follow!
  @@end_loop_signal = true
end

Instance Method Details

#check_follow_until! ⇒ Object 



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# File 'lib/aws_logs/tail.rb', line 102

def check_follow_until!
  follow_until = @options[:follow_until]
  return unless follow_until

  messages = @events.map(&:message)
  @@end_loop_signal = messages.detect { |m| m.include?(follow_until) }
end

#display ⇒ Object

Events canduplicated as events can be written to the exact same timestamp. So also track the last_shown_event_id and prevent duplicate log lines from re-appearing.



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# File 'lib/aws_logs/tail.rb', line 84

def display
  new_events = @events
  shown_index = new_events.find_index { |e| e.event_id == @last_shown_event_id }
  if shown_index
    new_events = @events[shown_index+1..-1] || []
  end

  new_events.each do |e|
    time = Time.at(e.timestamp/1000).utc
    line = [time.to_s.color(:green), e.message]
    format = @options[:format] || "detailed"
    line.insert(1, e.log_stream_name.color(:purple)) if format == "detailed"
    say line.join(' ')
  end
  @last_shown_event_id = @events.last&.event_id
  check_follow_until!
end

#output ⇒ Object 



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# File 'lib/aws_logs/tail.rb', line 114

def output
  @output.join("\n") + "\n"
end

#refresh_events(start_time, end_time) ⇒ Object 



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# File 'lib/aws_logs/tail.rb', line 58

def refresh_events(start_time, end_time)
  @events = []
  next_token = :start

  # TODO: can hit throttle limit if there are lots of pages
  while next_token
    options = {
      log_group_name: @log_group_name, # required
      start_time: start_time,
      end_time: end_time,
      # limit: 10,
    }
    options[:log_stream_names] = @options[:log_stream_names] if @options[:log_stream_names]
    options[:log_stream_name_prefix] = @options[:log_stream_name_prefix] if @options[:log_stream_name_prefix]
    options[:filter_pattern] = @options[:filter_pattern] if @options[:filter_pattern]
    resp = cloudwatchlogs.filter_log_events(options)

    @events += resp.events
    next_token = resp.next_token
  end

  @events
end

#reset ⇒ Object 



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# File 'lib/aws_logs/tail.rb', line 19

def reset
  @events = [] # constantly replaced with recent events
  @last_shown_event_id = nil
  @completed = nil
end

#run ⇒ Object

The start and end time is useful to limit results and make the API fast. We’ll leverage it like so:

1. load all events from an initial since time
2. after that load events pass that first window

It’s a sliding window of time we’re using.



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# File 'lib/aws_logs/tail.rb', line 32

def run
  if ENV['AWS_LOGS_NOOP']
    puts "Noop test"
    return
  end

  # We overlap the sliding window because CloudWatch logs can receive or send the logs out of order.
  # For example, a bunch of logs can all come in at the same second, but they haven't registered to CloudWatch logs
  # yet. If we don't overlap the sliding window then we'll miss the logs that were delayed in registering.
  overlap = 60*1000 # overlap the sliding window by a minute
  since, now = initial_since, current_now
  until end_loop?
    refresh_events(since, now)
    display
    since, now = now-overlap, current_now
    loop_count!
    sleep 5 if @follow && !ENV["AWS_LOGS_TEST"]
  end
  # Refresh and display a final time in case the end_loop gets interrupted by stop_follow!
  refresh_events(since, now)
  display
rescue Aws::CloudWatchLogs::Errors::ResourceNotFoundException => e
  puts "ERROR: #{e.class}: #{e.message}".color(:red)
  puts "Log group #{@log_group_name} not found."
end

#say(text) ⇒ Object 



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# File 'lib/aws_logs/tail.rb', line 110

def say(text)
  ENV["AWS_LOGS_TEST"] ? @output << text : puts(text)
end

#set_trap ⇒ Object 



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# File 'lib/aws_logs/tail.rb', line 118

def set_trap
  Signal.trap("INT") {
    puts "\nCtrl-C detected. Exiting..."
    exit # immediate exit
  }
end