Class: Raindrops::Watcher

Inherits:
Object
  • Object
show all
Includes:
Rack::Utils, Linux
Defined in:
lib/raindrops/watcher.rb

Overview

Raindrops::Watcher is a stand-alone Rack application for watching any number of TCP and UNIX listeners (all of them by default).

It depends on the Aggregate RubyGem

In your Rack config.ru:

run Raindrops::Watcher(options = {})

It takes the following options hash:

  • :listeners - an array of listener names, (e.g. %w(0.0.0.0:80 /tmp/sock))

  • :delay - interval between stats updates in seconds (default: 1)

Raindrops::Watcher is compatible any thread-safe/thread-aware Rack middleware. It does not work well with multi-process web servers but can be used to monitor them. It consumes minimal resources with the default :delay.

HTTP endpoints

GET /

Returns an HTML summary listing of all listen interfaces watched on

GET /active/$LISTENER.txt

Returns a plain text summary + histogram with X-* HTTP headers for active connections.

e.g.: curl yhbt.net/raindrops-demo/active/0.0.0.0%3A80.txt

GET /active/$LISTENER.html

Returns an HTML summary + histogram with X-* HTTP headers for active connections.

e.g.: curl yhbt.net/raindrops-demo/active/0.0.0.0%3A80.html

GET /queued/$LISTENER.txt

Returns a plain text summary + histogram with X-* HTTP headers for queued connections.

e.g.: curl yhbt.net/raindrops-demo/queued/0.0.0.0%3A80.txt

GET /queued/$LISTENER.html

Returns an HTML summary + histogram with X-* HTTP headers for queued connections.

e.g.: curl yhbt.net/raindrops-demo/queued/0.0.0.0%3A80.html

POST /reset/$LISTENER

Resets the active and queued statistics for the given listener.

GET /tail/$LISTENER.txt?active_min=1&queued_min=1

Streams chunked a response to the client. Interval is the preconfigured :delay of the application (default 1 second)

The response is plain text in the following format:

ISO8601_TIMESTAMP LISTENER_NAME ACTIVE_COUNT QUEUED_COUNT LINEFEED

Query parameters:

  • active_min - do not stream a line until this active count is reached

  • queued_min - do not stream a line until this queued count is reached

Response headers (mostly the same names as Raindrops::LastDataRecv)

  • X-Count - number of samples polled

  • X-Last-Reset - date since the last reset

The following headers are only present if X-Count is greater than one.

  • X-Min - lowest number of connections recorded

  • X-Max - highest number of connections recorded

  • X-Mean - mean number of connections recorded

  • X-Std-Dev - standard deviation of connection count

  • X-Outliers-Low - number of low outliers (hopefully many for queued)

  • X-Outliers-High - number of high outliers (hopefully zero for queued)

  • X-Current - current number of connections

  • X-First-Peak-At - date of when X-Max was first reached

  • X-Last-Peak-At - date of when X-Max was last reached

Demo Server

There is a server running this app at yhbt.net/raindrops-demo/ The Raindrops::Middleware demo is also accessible at yhbt.net/raindrops-demo/_raindrops

The demo server is only limited to 30 users, so be sure not to abuse it by using the /tail/ endpoint too much.

Defined Under Namespace

Classes: Peak, Tailer

Constant Summary collapse

DOC_URL = 
"https://yhbt.net/raindrops/Raindrops/Watcher.html"

Constants included from Linux

Linux::PROC_NET_UNIX_ARGS

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Linux

tcp_listener_stats, unix_listener_stats

Constructor Details

#initialize(opts = {}) ⇒ Watcher

Returns a new instance of Watcher.



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# File 'lib/raindrops/watcher.rb', line 112

def initialize(opts = {})
  @tcp_listeners = @unix_listeners = nil
  if l = opts[:listeners]
    tcp, unix = [], []
    Array(l).each { |addr| (addr =~ %r{\A/} ? unix : tcp) << addr }
    unless tcp.empty? && unix.empty?
      @tcp_listeners = tcp
      @unix_listeners = unix
    end
  end

  @agg_class = opts[:agg_class] || Aggregate
  @start_time = Time.now.utc
  @active = Hash.new { |h,k| h[k] = @agg_class.new }
  @queued = Hash.new { |h,k| h[k] = @agg_class.new }
  @resets = Hash.new { |h,k| h[k] = @start_time }
  @peak_active = Hash.new { |h,k| h[k] = Peak.new(@start_time, @start_time) }
  @peak_queued = Hash.new { |h,k| h[k] = Peak.new(@start_time, @start_time) }
  @snapshot = [ @start_time, {} ]
  @delay = opts[:delay] || 1
  @lock = Mutex.new
  @start = Mutex.new
  @cond = ConditionVariable.new
  @thr = nil
end

Instance Attribute Details

#snapshot ⇒ Object (readonly)

:stopdoc:



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# File 'lib/raindrops/watcher.rb', line 106

def snapshot
  @snapshot
end

Instance Method Details

#active_stats(addr) ⇒ Object

:nodoc:



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# File 'lib/raindrops/watcher.rb', line 197

def active_stats(addr) # :nodoc:
  @lock.synchronize do
    time, combined = @snapshot
    stats = combined[addr] or return non_existent_stats(time)
    tmp, peak = @active[addr], @peak_active[addr]
    [ time, @resets[addr], tmp.dup, stats.active, peak ]
  end
end

#agg_to_hash(reset_at, agg, current, peak) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 228

def agg_to_hash(reset_at, agg, current, peak)
  {
    "X-Count" => agg.count.to_s,
    "X-Min" => agg.min.to_s,
    "X-Max" => agg.max.to_s,
    "X-Mean" => agg.mean.to_s,
    "X-Std-Dev" => std_dev(agg),
    "X-Outliers-Low" => agg.outliers_low.to_s,
    "X-Outliers-High" => agg.outliers_high.to_s,
    "X-Last-Reset" => reset_at.httpdate,
    "X-Current" => current.to_s,
    "X-First-Peak-At" => peak.first.httpdate,
    "X-Last-Peak-At" => peak.last.httpdate,
  }
end

#aggregate!(agg_hash, peak_hash, addr, number, now) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 159

def aggregate!(agg_hash, peak_hash, addr, number, now)
  agg = agg_hash[addr]
  if (max = agg.max) && number > 0 && number >= max
    peak = peak_hash[addr]
    peak.first = now if number > max
    peak.last = now
  end
  agg << number
end

#aggregator_thread(logger) ⇒ Object

:nodoc:



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# File 'lib/raindrops/watcher.rb', line 169

def aggregator_thread(logger) # :nodoc:
  @socket = sock = Raindrops::InetDiagSocket.new
  thr = Thread.new do
    begin
      combined = tcp_listener_stats(@tcp_listeners, sock)
      combined.merge!(unix_listener_stats(@unix_listeners))
      @lock.synchronize do
        now = Time.now.utc
        combined.each do |addr,stats|
          aggregate!(@active, @peak_active, addr, stats.active, now)
          aggregate!(@queued, @peak_queued, addr, stats.queued, now)
        end
        @snapshot = [ now, combined ]
        @cond.broadcast
      end
    rescue => e
      logger.error "#{e.class} #{e.inspect}"
    end while sleep(@delay) && @socket
    sock.close
  end
  wait_snapshot
  thr
end

#call(env) ⇒ Object

rack endpoint



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# File 'lib/raindrops/watcher.rb', line 143

def call(env)
  @start.synchronize { @thr ||= aggregator_thread(env["rack.logger"]) }
  case env["REQUEST_METHOD"]
  when "GET"
    get env
  when "HEAD"
    r = get(env)
    r[2] = []
    r
  when "POST"
    post env
  else
    Rack::Response.new(["Method Not Allowed"], 405).finish
  end
end

#get(env) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 272

def get(env)
  retried = false
  begin
    case env["PATH_INFO"]
    when "/"
      index
    when %r{\A/active/(.+)\.txt\z}
      histogram_txt(active_stats(unescape($1)))
    when %r{\A/active/(.+)\.html\z}
      addr = unescape $1
      histogram_html(active_stats(addr), addr)
    when %r{\A/queued/(.+)\.txt\z}
      histogram_txt(queued_stats(unescape($1)))
    when %r{\A/queued/(.+)\.html\z}
      addr = unescape $1
      histogram_html(queued_stats(addr), addr)
    when %r{\A/tail/(.+)\.txt\z}
      tail(unescape($1), env)
    else
      not_found
    end
  rescue Errno::EDOM
    raise if retried
    retried = true
    wait_snapshot
    retry
  end
end

#histogram_html(agg, addr) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 254

def histogram_html(agg, addr)
  updated_at, reset_at, agg, current, peak = *agg
  headers = agg_to_hash(reset_at, agg, current, peak)
  body = "<html>" \
    "<head><title>#{hostname} - #{escape_html addr}</title></head>" \
    "<body><table>" <<
    headers.map { |k,v|
      "<tr><td>#{k.gsub(/^X-/, '')}</td><td>#{v}</td></tr>"
    }.join << "</table><pre>#{escape_html agg}</pre>" \
    "<form action='../reset/#{escape addr}' method='post'>" \
    "<input type='submit' name='x' value='reset' /></form>" \
    "</body>"
  headers["Content-Type"] = "text/html"
  headers["Expires"] = (updated_at + @delay).httpdate
  headers["Content-Length"] = body.size.to_s
  [ 200, headers, [ body ] ]
end

#histogram_txt(agg) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 244

def histogram_txt(agg)
  updated_at, reset_at, agg, current, peak = *agg
  headers = agg_to_hash(reset_at, agg, current, peak)
  body = agg.to_s # 7-bit ASCII-clean
  headers["Content-Type"] = "text/plain"
  headers["Expires"] = (updated_at + @delay).httpdate
  headers["Content-Length"] = body.size.to_s
  [ 200, headers, [ body ] ]
end

#hostname ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 138

def hostname
  Socket.gethostname
end

#index ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 331

def index
  updated_at, all = snapshot
  headers = {
    "Content-Type" => "text/html",
    "Last-Modified" => updated_at.httpdate,
    "Expires" => (updated_at + @delay).httpdate,
  }
  body = "<html><head>" \
    "<title>#{hostname} - all interfaces</title>" \
    "</head><body><h3>Updated at #{updated_at.iso8601}</h3>" \
    "<table><tr>" \
      "<th>address</th><th>active</th><th>queued</th><th>reset</th>" \
    "</tr>" <<
    all.sort do |a,b|
      a[0] <=> b[0] # sort by addr
    end.map do |addr,stats|
      e_addr = escape addr
      "<tr>" \
        "<td><a href='tail/#{e_addr}.txt' " \
          "title='&quot;tail&quot; output in real time'" \
          ">#{escape_html addr}</a></td>" \
        "<td><a href='active/#{e_addr}.html' " \
          "title='show active connection stats'>#{stats.active}</a></td>" \
        "<td><a href='queued/#{e_addr}.html' " \
          "title='show queued connection stats'>#{stats.queued}</a></td>" \
        "<td><form action='reset/#{e_addr}' method='post'>" \
          "<input title='reset statistics' " \
            "type='submit' name='x' value='x' /></form></td>" \
      "</tr>" \
    end.join << "</table>" \
    "<p>" \
      "This is running the #{self.class}</a> service, see " \
      "<a href='#{DOC_URL}'>#{DOC_URL}</a> " \
      "for more information and options." \
    "</p>" \
    "</body></html>"
  headers["Content-Length"] = body.size.to_s
  [ 200, headers, [ body ] ]
end

#non_existent_stats(time) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 193

def non_existent_stats(time)
  [ time, @start_time, @agg_class.new, 0, Peak.new(@start_time, @start_time) ]
end

#not_found ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 301

def not_found
  Rack::Response.new(["Not Found"], 404).finish
end

#post(env) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 305

def post(env)
  case env["PATH_INFO"]
  when %r{\A/reset/(.+)\z}
    reset!(env, unescape($1))
  else
    not_found
  end
end

#queued_stats(addr) ⇒ Object

:nodoc:



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# File 'lib/raindrops/watcher.rb', line 206

def queued_stats(addr) # :nodoc:
  @lock.synchronize do
    time, combined = @snapshot
    stats = combined[addr] or return non_existent_stats(time)
    tmp, peak = @queued[addr], @peak_queued[addr]
    [ time, @resets[addr], tmp.dup, stats.queued, peak ]
  end
end

#reset!(env, addr) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 314

def reset!(env, addr)
  @lock.synchronize do
    @active.include?(addr) or return not_found
    @active.delete addr
    @queued.delete addr
    @resets[addr] = Time.now.utc
    @cond.wait @lock
  end
  req = Rack::Request.new(env)
  res = Rack::Response.new
  url = req.referer || "#{req.host_with_port}/"
  res.redirect(url)
  res["Content-Type"] = "text/plain"
  res.write "Redirecting to #{url}"
  res.finish
end

#shutdown ⇒ Object

shuts down the background thread, only for tests



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# File 'lib/raindrops/watcher.rb', line 422

def shutdown
  @socket = nil
  @thr.join if @thr
  @thr = nil
end

#std_dev(agg) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 222

def std_dev(agg)
  agg.std_dev.to_s
rescue Errno::EDOM
  "NaN"
end

#tail(addr, env) ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 371

def tail(addr, env)
  Tailer.new(self, addr, env).finish
end

#wait_snapshot ⇒ Object 



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# File 'lib/raindrops/watcher.rb', line 215

def wait_snapshot
  @lock.synchronize do
    @cond.wait @lock
    @snapshot
  end
end