Grow your own tools - VilniusRB

Grow your own tools
debugging & profiling story
Remigijus Jodelis - SameSystem
VilniusRB Vilnius Ruby Community

Debugging
#<ActiveSupport::Logger:0x007f1aa39426f8
@default_formatter=#<Logger::Formatter:0x007f1aa3942450 @datetime_format=nil>,
@formatter=
#<ActiveSupport::Logger::SimpleFormatter:0x007f1aa4c0c900
@datetime_format=nil>,
@level=0,
@logdev=
#<Logger::LogDevice:0x007f1aa39422c0
@dev=#<File:/vagrant/samesystem/log/development.log>,
@filename=nil,
@mutex=
#<Logger::LogDevice::LogDeviceMutex:0x007f1aa3942298
@mon_count=0,
@mon_mutex=#<Mutex:0x007f1aa3942090>,
@mon_owner=nil>,
@shift_age=nil,
@shift_size=nil>,
@progname=nil>
=> #<ActiveSupport::Logger:0x007f1aa39426f8 @progname=nil, @level=0,
@default_formatter=#<Logger::Formatter:0x007f1aa3942450 @datetime_format=nil>,
@formatter=#<ActiveSupport::Logger::SimpleFormatter:0x007f1aa4c0c900 @datetime_format=nil>,
@logdev=#<Logger::LogDevice:0x007f1aa39422c0 @shift_size=nil, @shift_age=nil,
@filename=nil, @dev=#<File:/vagrant/samesystem/log/development.log>,
@mutex=#<Logger::LogDevice::LogDeviceMutex:0x007f1aa3942298 @mon_owner=nil, @mon_count=0,
@mon_mutex=#<Mutex:0x007f1aa3942090>>>>

Debugging
We need to do
better

Debugging
# initializers/wtf.rb
def WTF?(*args)
p args
end

Debugging
def sync_records(resource, local_idx, remote_idx, key_name, options={})
options.reverse_merge!(@opt)
cross_idx, actions = diff_collection(local_idx, remote_idx)
actions.each do |action, items|
@cnt["#{resource.name}_#{action}"] = items.size
end
WTF? resource.name.to_s, *actions, :line, :file
actions.each { |action, items| items.clear unless options[action] }
if options[:create_many]
resource.create_many(*actions[:create]) if actions[:create].any?
else
actions[:create].each do |record|
remote = resource.create(record) or next
if local = local_idx[remote[key_name.to_s]]
cross_idx[local.id] = remote['id']
end

Debugging
def WTF?(*args)
if args.last == :pp
args.pop
pp args
else
p args
end
end
WTF? my_struct, :pp

Debugging
WTF? my_struct, :pp
WTF? my_var, :yaml
WTF? my_var, other_var, :pp, :file
WTF? *other_things, :json, :file, :time
But I want even more...

Debugging
def WTF?(*args)
allowed = [:pp, :yaml, :json]
options = {}
while allowed.include?(args.last)
options[args.pop] = true
end
case
when options[:yaml]
puts args.to_yaml
# ...

Debugging
data = ""
data << "[%s] " % Time.now if options[:time]
rx = %r{([^/]+?)(?:.rb)?:(d+):in `(.*)'$} # <- WTF is this?
data << "WTF (%s/%s:%s)" % caller[0].match(rx).values_at(1,3,2)
data << ": " <<
case
when options[:pp]
args.pretty_inspect.gsub(/^[|]$/,'') # removes array marks
when options[:yaml]
YAML.dump(args)
when options[:json]
JSON::pretty_generate(args)
when options[:text]
args.map(&:to_s).join("n")

Debugging
WTF (search_controller/browse:15):
#<Paginator:0x007fd0199e6bf0
@count=169,
@per_page=20,
def browse
if params[:search].present?
joins = search_joins
conditions = search_conditions
includes = search_includes
count = klass.joins(joins).includes(includes).where(conditions).count
pager = ::Paginator.new(count, search_config.per_page) do |offset, per_page|
klass.joins(joins).where(conditions).includes(includes).
end
WTF? pager, :pp

Debugging
STEP 3
More
output options

Debugging
case
when options[:page]
(Thread.current[:wtf] ||= []) << data
when options[:file]
time = Time.now.strftime('%m%d_%H%M%S')
filename = "wtf_#{time}_#{rand(10000)}.txt"
File.write("#{Rails.root}/tmp/#{filename}", data)
when options[:raise]
raise data
when options[:redis]
REDIS.rpush 'wtf', data
REDIS.expire 'wtf', 30*60
else
Rails.logger.info data
end

Debugging
OK, I got it
But, where do we place all this code?

Debugging
module Kernel
WTF_OPTIONS = [:time, # prefix
:pp, :yaml, :json, :csv, :text, :line, # format
:bare, # modifiers
:page, :file, :raise, :redis, :log] # output
def WTF?(*args)
The same place as p

Debugging
Object.class_eval do
def WTF?(*args)
WTF::Dumper.new(*args)
end
end
module WTF
class Dumper
OPTIONS = [:time, :nl, :none,
# ...

Profiling
class Overview
# loading dependent data and calculations
def load!
load_departments
@budget_repo = Overviews::BudgetRepository.new(@period, @shops)
@data = {}
columns.each do |col|
calculate(col)
end
# … few more lines …
end
# … 50 more methods …
The problem lurks somewhere here

Profiling
Let’s try the profiler

Profiling
WTF am I looking at?

Profiling
Second shot
start with a simple thing

Profiling
def load!
st = Time.now
# ...
WTF? Time.now - st
end
WTF (overview/load!:250): 180.3073...

Profiling
What if I tried this
on EVERY method
in the same class

Profiling
module MethodTracker
class << self
def included(base)
methods = base.instance_methods(false) + base.private_instance_methods(false)
base.class_eval do
methods.each do |name|
original_method = instance_method(name)
define_method(name) do |*args, &block|
MethodTracker.on_start(base, name)
return_value = original_method.bind(self).call(*args, &block)
MethodTracker.on_end
return_value
end
end
end
end

Profiling
In Ruby 2.x we can do nicer
hint: prepend OverridesModule

Profiling
def override_method(base, name)
%{
def #{name}(*args)
WTF::MethodTracker.on_start(#{base}, :#{name})
return_value = super
WTF::MethodTracker.on_end
return_value
end
}
end

Profiling
def prepare(base)
methods = base.instance_methods(false) +
base.private_instance_methods(false)
compiled = methods.map do |name|
override_method(base, name)
end
base.module_eval %{
module Tracking
#{compiled.join}
end
prepend Tracking
}
end

Public interface
module WTF
class << self
def track(*objects)
MethodTracker.setup(*objects)
MethodTracker.reset_state
end
def track_finish
MethodTracker.finish
end
end
end
class Overview
def load!
WTF.track(self, Overview::Helpers) # with additional classes
# ...
WTF.track_finish
end
end

Collecting data
require 'absolute_time'
def add_stats(at_start = nil)
stat = stats[stack.last]
this_time = AbsoluteTime.now
stat[:time] += this_time - last_time
self.last_time = this_time
this_heap = GC.stat[:heap_length]
stat[:heap] += this_heap - last_heap
self.last_heap = this_heap
stats[at_start][:freq] += 1 if at_start
end

Profiling
What about the output?

Profiling
Let’s look at one more problem.
I got some Rails logs...

Profiling
WTF is generating this query?

Profiling
I want to do this
def load!
WTF.sql %(SELECT `weekly_balance_lines`.* FROM `weekly_balance_lines
load_shops
@budget_repo = Overviews::BudgetRepository.new(@period, @shops)
@salary_repo = Overviews::SalaryRepository.new(@period, @shops, @c

Profiling
… and get the answer
SQL: "SELECT `weekly_balance_lines`.`date`, `weekly_balance_lines`.`context_id`,
"(eval):4:in `log'"
"/home/vagrant/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activerecord-4.1
"/vagrant/samesystem/app/models/overview.rb:350:in `weekly_balance_lines_for_p
"/vagrant/samesystem/app/models/overview.rb:342:in `weekly_balance_lines'"
"/vagrant/samesystem/app/models/overview.rb:870:in `sales'"
"/vagrant/samesystem/app/models/overview.rb:396:in `calculate'"
"/vagrant/samesystem/app/models/overview.rb:241:in `block in

Profiling
ActiveRecord::ConnectionAdapters::AbstractAdapter.module_eval %(
module TrackingSQL
def log(sql, *args, &block)
WTF::QueryTracker.on_sql(sql) # callback and WTF? caller
super(sql, *args, &block)
end
end
prepend TrackingSQL
)
Easy! The key piece is here

Conclusion
Does it look like a gem?
YES!

github.com/remigijusj/wtf-tools
Please check out the repo!

Grow your own tools - VilniusRB

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