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Custom performance logging for Rails
Ruby C

README.rdoc

Time Bandits

About

Time Bandits is a gem plugin for Rails which enhances Rails' controller/view/db benchmark logging.

Usage

Without configuration, the standard Rails 'Completed line' will change from its default format

Completed 200 OK in 56ms (Views: 28.5ms, ActiveRecord: 5.1ms)

to:

Completed 200 OK in 56.278ms (Views: 28.488ms, ActiveRecord: 5.111ms(2q,0h))

“ActiveRecord: 5.111ms(2q,0h)” means that 2 SQL queries were executed and there were 0 SQL query cache hits.

However, non-trivial applications also rather often use external services, which consume time that adds to your total response time, and sometimes these external services are not under your control. In these cases, it's very helpful to have an entry in your log file that records the time spent in the exterrnal service (so that you can prove that it wasn't your rails app that slowed down during your slashdotting, for example ;-).

Additional TimeConsumers can be added to the log using the “Timebandits.add” method.

Example:

TimeBandits.add TimeBandits::TimeConsumers::Memcached
TimeBandits.add TimeBandits::TimeConsumers::GarbageCollection.instance if GC.respond_to? :enable_stats

Here we've added two additional consumers, which are already provided with the plugin. (Note that GC information requires a patched ruby, see prerequistes below.)

Note: if you run a multithreaded program, the numbers reported for garbage collections and heap usage are partially misleading, because the Ruby interpreter collects stats in global variables shared by all threads.

With these two new time consumers, the log line changes to

Completed 200 OK in 680.378ms (Views: 28.488ms, ActiveRecord: 5.111ms(2q,0h), MC: 5.382(6r,0m), GC: 120.100(1), HP: 0(2000000,546468,18682541,934967))

“MC: 5.382(6r,0m)” means that 6 memcache reads were performed and all keys were found in the cache (0 misses).

“GC: 120.100(1)” tells us that 1 garbage collection was triggered during the request, taking 120.100 milliseconds.

“HP: 0(2000000,546468,18682541,934967)” shows statistics on heap usage. The format is g(s,a,b,l), where

g: heap growth during the request (#slots)
s: size of the heap after request processing was completed (#slots)
a: number of object allocations during the request (#slots)
b: number of bytes allocated by the ruby x_malloc call (#bytes)
l: live data set size after last GC (#slots)

Sidenote for Germans: you can use the word “Gesabbel” (eng: drivel) as a mnemonic here ;-)

It's realtively straightforward to write additional time consumers; the more difficult part of this is monkey patching the code which you want to instrument. Have a look at consumers under lib/time_bandits/time_consumers and the corresponding patches under lib/time_bandits/monkey_patches.

Prerequisites

Rails >= 3.x is required. The gem will raise an error if you try to use it with an incompatible version.

You'll need a ruby with the railsexpress GC patches applied, if you want to include GC and heap size information in the completed line. This is very useful, especially if you want to analyze your rails logs using logjam (see github.com/skaes/logjam/).

Ruby only contains a subset of the railsexpress patches. To get the full monty, you can use for example rvm and the railsexpress rvm patchsets (see github.com/skaes/rvm-patchsets).

History

This plugin started from the code of the 'custom_benchmark' plugin written by tylerkovacs. However, we changed so much of the code that is is practically a full rewrite, hence we changed the name.

Running Tests

In order for the test to run you need a running memcached, redis-server and mysql

Release Notes

version 0.7.1

- support measuring sequel gem

version 0.7.0

- switched to byebug (debugger does not fully support 2.0 and 2.1 not at all)
- adapted garbage collection statistics to work for 2.1
- improved rails 4.x compatibility
- GC time consumer now tries to make the most out of an unpatched ruby

version 0.6.0

- added redis time consumer
- fixed rails 4.0 problems with builtin mem_cache_store
- now only consumers which measured something are added to the completed line

version 0.5.1

- added license file

version 0.5:

- has dropped rails 2 support
- relies on ActiveSupport::Notifications
- is supposedly thread safe
- all measurements are thread local (except GC statistics)
- times are all measured in milliseconds internally
- added class TimeBandits::TimeConsumers::BaseConsumer to simplify writing custom consumers

License

Copyright © 2009-2014 Stefan Kaes <skaes@railsexpress.de>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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