But I still use this framework, since my backend software is written in Rails, so here is one thing which I think can be useful for You.

Often we want to pass ID of current user to Rails model internals. Most answers are don’t do that, this is controller work to do authorization stuff, MVC is to prevent such thins, etc.

here was not related picture (as usual on this blog). Some readers were complaining it was not only unrelated but even offending. Well, maybe they were right, so, I have removed that picture.

Yeah, right, but what if we want to keep some kind of audit trail what is happening with given model? This is not authorization, just who done what.

Since in my application case audit records are created in observers simple passing user id as some additional parameter is no go for me – I don’t want to change interface just to pass user info, that breaks too much things.

So, I have chosen this approach:

def with_user user, &block
  if user.blank?
    yield
  else
    Thread.current[:user] = user.id
    yield
    Thread.current[:user] = nil
  end
end

And each operation I want to track I invoke:

with_user(current_user) do
 model.do_some_stuff
end

Thread.current acts as a hash accessible in current thread and allow us to pass some info skipping MVC isolation (You wanted that, right? :) )

In observers I can access user ID and store it with record. If it is not present, audit trails is being marked as created by System. That means probably cron job, or console action (well on console I can run code inside with_user block when needed).

This is safe as long each request is being processed in single thread and we make sure that user ID will be cleared after our operation. When ID will stay in Thread.current, next request being processed by this Rails app instance will have access to that value and wrong audit records will be created.

Code has to be updated, since any exception will occur inside block, code after yield will be skipped and user ID won’t be erased from Thread.current. Here it is, final version:

def with_user user, &block
  if user.blank?
    yield
  else
    Thread.current[:user] = user.id

    begin
      yield
    ensure
      Thread.current[:user] = nil
    end
  end
end

Code inside ensure will be executed each time – both when exception was raised and when execution was clean.

at depth 0 - 20: unable to get local issuer certificate
F, [2011-01-18T10:13:40.816069 #4035]
FATAL -- app: Detected an exception. Stopping ...
SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B:
certificate verify failed (OpenSSL::SSL::SSLError)

HTTPClient (this is gem used by SOAP4r to do all HTTP communication) tries to validate SSL certificates by default. Good, this is what SSL was thought for :) HTTPClient allows to use own CA (which is better solution than to lower security, especially on production :) ), however I don’t know how to pass this via SOPA4r abstraction (ssl-config.set-trust-ca('path') in HTTPClient (UPDATE – OK I think here You can find info how to specify CA, client key and cert in SOAP client). We can tell HTTPClient not to check SSL certs via options of SOAP::RPC::Driver when using client code:

d = SomeSOAP::ClientClass.new
d.options['protocol.http.ssl_config.verify_mode'] = OpenSSL::SSL::VERIFY_NONE

This may be not very wise, so use that if You know what You are doing.

And what about wsdl2ruby.rb

Above example relates to scenario when You have generated client code, which should connect to HTTPS. But how to recover from certificate verify failed when running wsdl2ruby.rb (in other words – when generating client code and WSDL is on HTTPS server with self signed cert)?

First solution is to download WSDL and generate client code from local file. Will do the trick unless WSDL imports some additional XSDs via HTTPS URL…

This gist gave me idea how to solve that (BTW – very useful trick to debug HTTP traffic if You can not use proxy like Charles Proxy). I did checked out SOAP4r gem code and updated wsdl2ruby.rb adding at begin:

BEGIN {
  require 'rubygems'
  require 'httpclient'
  HTTPClient.class_eval do
    alias_method '__initialize__', 'initialize'

    def initialize(*args,&block)
      __initialize__(*args, &block)
    ensure
      self.ssl_config.verify_mode=OpenSSL::SSL::VERIFY_NONE
    end
  end
}

That’s it. Well, almost. I was unlucky – due to some configuration twists WSDL and other referenced resources were hosted in some dev environment with wrong network configuration. Fixing that was totally out of my reach.

What was wrong? WSDL was accessible via HTTPS. All resources imported inside were referenced via HTTPS, too. But. When accessing these HTTPS URLs (other than WSDL) from outside network (where I was) plain HTTP error message was displayed, so SOAP code could not be generated. When URL was changed to HTTP – proper XML file was available.

So, another hack to wsdl2ruby.rb:

class  HTTPClient
    alias_method '__get_content__', 'get_content'
    def get_content(uri, query = nil, extheader = {}, &block)
     uri = URI.parse(uri.to_s.gsub(/^https:/,'http:'))
     if block_given?
       __get_content__(uri, query, extheader) {block}
     else
       __get_content__(uri, query, extheader)
     end
    end
end

Now all requests to HTTPS are converted to plain HTTP. Again – do it when You understand what You are doing :)

Where Ruby brought me

When I started this blog (Apr 2006) I’ve just have discovered Ruby on Rails. During this almost five years many things have changed. And finally Ruby brought me to this place:

Massimo and Arduino Logo at Maker Faire 2010 in NYC
CC by http://www.flickr.com/photos/mattrichardson/

And now small announcement. As You can see I was publishing on this blog very seldom in recent months. And reason is very simple. Almost two years ago I have started side business (do freelancer have side businesses? :)) ) selling Arduinos in Poland (and whole Europe). After slow start, it have took off, and between my work as freelancer and running shop there were no time to write on this blog.

Recently I have made decision to stop freelancing and devote all my time to Arduino (and electronics) related topics. Will I stop writing about Ruby? I guess not. Shop is on some hosted platform, but I do run some custom RoR software as backend. I plan to migrate at some point to own e-commerce solution, so I’m not leaving Ruby world.

ActiveMerchant::Billing::QuantumGateway.wiredump_device = File.open("/tmp/q.log", "a+")
ActiveMerchant::Billing::QuantumGateway.wiredump_device.sync = true

Just remember – it will work ONLY You have one application instance, since it uses simple file handle to write all traffic. And replace QunatumGateway with gateway used by You.

Marshal CC http://www.flickr.com/photos/qmnonic/

Logs were showing that it happens when Rails was trying to create session object. Session store was in ActiveRecord and sessions table was not corrupted.

After watching that for a while it have shown that places in code were this exception was thrown were random but there was pattern. Page visited before was common in each case.

It have turned out that application was storing in session whole ActiveRecord object. Like:

 session[:some_info] = @variable

And later we were trying to use that way:

@variable = Model.find session[:some_info]

Due to Rails magic AcitiveRecord’s find when provided with AR object will return that object (of course if is the same model). Code was working well (maybe not very effectively since You should avoid storing large objects in session) until object stored that way started to grow. Application was collecting some data and amount of data stored have grown to that point that after Marshal.dump size of string was more than 64 kB. And this is default size of text field used to store session data in MySQL.

When You try to store too much data in text field in MySQL, excessive data is being truncated, so Marshal.load throws that exception.

To have that error solved is enough to store just object id in session (session[:some_info] = @variable.id).

If You have drank Linux KoolAid, then You can run on problems when You get some CHM file. It is old format and I think it has place where it can live (like many other proprietary data formats):

Place where we should send .chm files (c) Marcin Wichary

But still, You can get documentation in such format, chances are high if You are trying to interface some .Net SOAP service. In Linux – no viewer for CHM.

Or rather no standalone viewer. There is solution – CHM Reader addon for Firefox. It is not perfect (no global search), but allows to navigate through that file. Printouts to PDF usually are stripped from hyperlinks, so navigating through 800 pages is reason why PDF printout is not an option…

It is module by default installed on FreeBSD, but on Debian based Linux You have to add it by hand (apt-get install php5-gd).

I had to move my blogs to new, temporary host, with Linux on board instead of FreeBSD. Then I have noticed that when I want to publish new post I can only insert in it uploaded image in original size – not very handy. It took 15 minutes of googling and finally dive into wp-includes/media.php to check how these thumbnails are generated.

Step back and think again. Image CC by Vivianna_love

From some time I do use following regexp to verify email address:

 /.+@.+[.].+/

This should check if:

• there is @ sign somewhere inside
• at least one character is before @ sign
• at least 3 chars (with one dot) are after @ sign

Why such simple rules? I have found comment on StackOverflow, that man should step back and think why is checking email address?

I want just to help users and stop them making simple mistakes in theirs emails. Like not providing @ at all. Or eating .com in gmail.com address. And that’s it – email will be probably shortly after that verified with only reliable method via sending email to this address.

And if You insist to verify emails with more strict regular expression, please do remember that plus sign is perfectly valid character before @. Many regexps found via google are forgetting that…

Why I do use them instead of Factory Girl or other solution like that? Well, fixtures can be much more closer to real data than mocks from Factory. How come, You ask? Fixtures are imaginary data exactly like mocks from other sources!

My answer is: that depends how You create fixtures. If You create them by hand, indeed they are disconnected from real world (like all mocks).

What is Your real data/mocks ratio? CC by hsing

But I prefer to extract fixtures from real (production) database. That way I can easily pick entries created by users which are edge cases. The only trouble is with creating fixtures. For some time I’m using modified extract_fixtures rake task. I have added some conditions to extracting process – SQL condition to select only particular records and adjusted syntax to recent rake.

This is useful especially when You are about to take over application code which has no tests. Extracting real data is quick way to start write integration tests (in such case they have are most efficient – time invested and application code coverage).

How to extract fixtures without pain?

Now I want to share with You next improvement to this recipe. Old fixtures can be left unchanged (as long You don’t use ERb to spice them up).

Rake task load old fixtures file and add new records as selected from database by arguments You are providing. More – it keeps old fixtures names so all Your tests using some_table :fixture will work (but don’t You dare to create attribute called fixtures_old_key_value :)) ). As a bonus attributes in Your fixture file will be sorted by attribute name!

OK some examples (written by hand not real YML files I hope there are no mistakes ;)) :

cat test/fixtures/entries.yml
one:
  attr1: value
  attr2: value
  created_at: 2009-09-10 11:22

rake extract_fixtures[entries,1,"created_at<'2009-09-01'"]
cat test/fixtures/entries.yml
one:
  attr1: value
  attr2: value
  created_at: 2009-09-10 11:22
  id: 1
entries_2:
  attr1: value from DB
  attr2: Also value from DB
  created_at: 2009-08-01 22:11
  id: 2

All is clear? In file there was fixture named :one, after rake task we have added new one selected from database, new fixture has name TABLE_NAME_ID, old fixture has unchanged name.

You can add DISCARD=true and old fixtures will be well… discarded :)

Rake task take following arguments:

1. table name
2. limit number of records extracted from database
3. WHERE condition

Rake has one limitation – it treats all commas as arguments separators, so it is not possible to use IN operator. Instead of rake extract_fixtures[entries,10,"id IN (1,2,3)"] write rake extract_fixtures[entries,10,"id=1 OR id=2 OR id=3)"].

You can download rake task file: http://nhw.pl/download/extract_fixtures.rake

This approach is especially useful when something wrong is happening and trigger is unknown. Placing many logging directives can provide data for analysis what could be a reason.

CC by Admond

Default Rails logger has one serious flaw which makes logs on production sites almost useless – messages are not grouped in calls. If You have many processes of Rails running and logging to single file, some requests will be processed in parallel and You have log entries mixed. With default log format there is no way to say which entry is from which process.

Since Rails 2.0 we have ActiveSupport::BufferedLogger, but it solves other problem – number of disk writes and file locks – You can set after how many entries log will be flushed to disk.

AnnotatedLogger

Here comes AnnotatedLogger for a rescue. The idea is to take each message and prefix it with PID of Rails process. As long You don’t run Rails in multithread mode, this is unique ID which will make log entry distinguishable.

class AnnotatedLogger < Logger

  def initialize *args
    super *args

    [:info, :debug, :warn, :error, :fatal].each {|m|
      AnnotatedLogger.class_eval %Q|
      def #{m} arg=nil, &block
        pid = "%.5d:" % $$
        if block_given?
          arg = yield
        end
        super "%s %s" % [pid, arg.gsub(/\n/,"\n%s" % pid)]
      end
      |

    }
  end
end

Now in Rails::Initializer.run do |config| section of config/environment.rb define AnnotatedLogger as default Rails logger:

 config.logger = AnnotatedLogger.new "log/#{RAILS_ENV}.log"

Of course You can add other data to log entries (timestamp?). Here is an example of log entries:

24551:Processing SearchController#processing (for [FILTERED] at 2009-09-15 15:11:24) [GET]
24551:   Session ID: df260892836fc619ec666f894e7d8e88
24551:   Parameters: {[FILTERED]}
24542:   Airport Load (0.216460)   SELECT * FROM [FILTERED]
24542: Completed in 0.24903 (4 reqs/sec) | Rendering: 0.01298 (5%) | DB: 0.22554 (90%) | 200 OK [FILTERED]
24551:   Search Columns (0.004711)   SHOW FIELDS FROM [FILTERED]
24551: Rendering template within layouts/blank
24551: Rendering search/processing

Without PIDs You would expect that Airport Load entry is part of SearchController#processing for session with ID df260892836fc619ec666f894e7d8e88. In reality this is output from processing different request.

What else?

This how I do deal with logs from Rails application. Do You have other ideas how to make logging more usable not only in development environment?

PS
I have just other idea – probably You could use BufferedLogger with disabled auto flushing and patch ActionController to flush manually all entries after request was processed – then all messages would be dumped in single block.