Follow-Up: Receiving Inbound Email and Creating Data in Rail


#1

I just wanted to post back to the group with my potential solution for
receiving inbound email and creating data in my Rails application,
including
attached images. Hope this will be helpful for others. Of course,
suggestions for improving my ideas is always welcome.

Thanks to everyone who took the time to post helpful responses to my
original (multiple) inquiries.

Nathan

Overall Requirement

I needed a feature in my Rails application that would receive inbound
emails
(from a Palm Treo 680, in particular) including an attached image. I
wanted
to use this data to create an entry in a product database for an online
shopping web site. This requirement supports a small business owner who
travels, finds products to buy and resell, and wanted immediate (easy)
posting of available items on the site using a mobile device.

Design:

I decided to use a plain text email, with a defined format…

  • Subject = product title
  • 1st line = product description
  • 2nd line = product price
  • 3rd line = product cost (for accounting application sync)
  • 4th line = product quantity
  • Attachment = product image

I created a “mailer” model inheriting from ActionMailer. The mailer
model
had two important methods (among others). The first was the “check”
method
which will use Net::IMAP to poll the INBOX folder for new mail. The
check
method would then call the “receive” method which will take an
individual
mail, create a product, and create an associated image in the database.
Finally, there is a “delete” method which removes the processed mail
from
the inbox.

PROBLEM: I could not get IMAP to allow deletion of the old messages. I
actually had to use POP3 to do it. Something wacky here that may just
be my
ignorance on this topic.

One of the bigger questions for me was how to periodically process the
mail. There were several possibilities here and may well be others that
I
didn’t know about or consider. Here are a couple of the more popular
ones…

  • Use a server script to periodically “push” the mail into the Rails
    app using cron
  • Use BackgroundRb to create a Rails background process for reading
    the mail periodically

However, I chose something a little simpler and possibly weird. I used
the
application controller to call the check mail function once per
user/browser
session. So inside the application.rb I have a before filter that calls
a
method. The method checks for a session variable that indicates whether
mail has been checked yet or not. If not, it calls the model method for
doing so. I don’t know the complete implications or trade-offs here, so
this is an area where I would be happy to get input from Ruby/Rails
experts. Given the low usage of the site and small number of products
being
entered, I chose to use this given that the only downside seemed to be a
small wait (1-2 seconds) on the initial site load for the mail to be
checked
and the parts/images loaded.

Development/Code:

class Mailer < ActionMailer::Base
.
.
.
def self.check_mail
begin
imap = Net::IMAP.new(‘mail.***.com’)
if RAILS_ENV == “production”
imap.authenticate(‘LOGIN’, ‘prduser’, ‘prdpasswd’)
else
imap.authenticate(‘LOGIN’, ‘devuser’, ‘devpasswd’)
end
imap.examine(‘INBOX’)
imap.search([‘FROM’, ‘validuser@***.com’]).each do |message_id|
msg = imap.fetch(message_id,‘RFC822’)[0].attr[‘RFC822’]
envelope = imap.fetch(message_id,
“ENVELOPE”)[0].attr[“ENVELOPE”]
Mailer.receive(msg)
end
imap.logout
return true
rescue
RAILS_DEFAULT_LOGGER.error("Mailer Import Error: " + $!)
return false
end
end

def receive(email) return unless email.has_attachments?
emailbody = email.body.to_s.gsub(/\r/, ’ ')
part = Part.new
part.description = email.subject
part.notes = emailbody.split(/\n/)[0]
part.sellprice = emailbody.split(/\n/)[1].to_f
part.lastcost = emailbody.split(/\n/)[2].to_f
part.onhand = emailbody.split(/\n/)[3].to_i
part.partsgroup_id = 10280
if part.save!
email.attachments.each do |attachment|
next unless attachment.original_filename[-4…-1] == ‘.jpg’
picture = Picture.new
picture.name = email.subject
picture.part_id = part.id
picture.imagedata = attachment.read
picture.content_type = ‘image/jpeg’
picture.save!
end
end
end

def self.delete_mail
if RAILS_ENV ==“production”
Net::POP3.delete_all(‘mail.***.com’, 110, ‘prduser’, ‘prdpasswd’)
else
Net::POP3.delete_all(‘mail.***.com’, 110, ‘devuser’, ‘devpasswd’)
end
rescue
RAILS_DEFAULT_LOGGER.error("Mailer Import Error: " + $!)
end
end

class ApplicationController < ActionController::Base
before_filter :env

def env
if !session[:checked_mail]
if Mailer.check_mail
session[:checked_mail] = true
Mailer.delete_mail
end
end
end
.
.
.
end

Testing:

So far, this solution seems to work pretty well. I have not tested
large
numbers of emails or large numbers of concurrent users. This is only a
potential solution and not one I would recommend for a larger site.
Let’s
have it…what do you think? How can this be improved?


#2

Nathan L. wrote:

Overall Requirement

model had two important methods (among others). The first was the
One of the bigger questions for me was how to periodically process the
used the application controller to call the check mail function once

    imap.authenticate ('LOGIN', 'prduser', 'prdpasswd')
  return true
part.notes = emailbody.split(/\n/)[0]
    picture.imagedata = attachment.read
  Net::POP3.delete_all('mail.***.com', 110, 'devuser', 'devpasswd')
if !session[:checked_mail]

Testing:

So far, this solution seems to work pretty well. I have not tested
large numbers of emails or large numbers of concurrent users. This is
only a potential solution and not one I would recommend for a larger
site. Let’s have it…what do you think? How can this be improved?
hmmm,

The biggest thing is as you said, checking the email on each session
will not scale. In fact, the first request for each user will have to
wait on the mail to fetched and parsed. cron or backgroundrb would be
much better for that.

I think there should be a more rubyesque way for the emailbody.split
lines but nothing comes to mind.

You should put the dev and production email passwords into the
environment in the config folder along with the database password. Then
just use the value set by the environment.

Sincerely,
Jason


#3

On Fri, 2007-04-06 at 18:47 -0400, Jason E. wrote:

environment in the config folder along with the database password. Then
just use the value set by the environment.

Sincerely,
Jason

Jason,

Great points. I will move the settings to the config folder and try to
find another way to process the email body.

I am considering the other two background email processing options. I
do have another idea to improve the current call to the Mailer model.
Not sure how feasible it is for production, but it seems to be working
in development ok.

I was wondering about using a process fork to call the email
check/receive. Take a look at this code that would reside in the
application controller…

if !session[:checked_mail]
  Process.detach fork {
    if Mailer.check_mail
      session[:checked_mail] = true
    end
  }
end

Would it alleviate the performance and/or scaling issues? Will this
cause problems?

Nathan


#4

Backgroundrbis here :http://backgroundrb.rubyforge.org/

Note that it can integrate with rails easily :wink: as long as you work on
a unix machine.

The latest Backgroundrb (0.2.1) runs fine on cygwin (=unix-like env
for windows)

/Nils


#5

Nathan L. wrote:

On Fri, 2007-04-06 at 18:47 -0400, Jason E. wrote:

environment in the config folder along with the database password. Then
just use the value set by the environment.

Sincerely,
Jason

Jason,

Great points. I will move the settings to the config folder and try to
find another way to process the email body.

I am considering the other two background email processing options. I
do have another idea to improve the current call to the Mailer model.
Not sure how feasible it is for production, but it seems to be working
in development ok.

I was wondering about using a process fork to call the email
check/receive. Take a look at this code that would reside in the
application controller…

if !session[:checked_mail]
  Process.detach fork {
    if Mailer.check_mail
      session[:checked_mail] = true
    end
  }
end

Would it alleviate the performance and/or scaling issues? Will this
cause problems?

Nathan

Hi nathan,

May be you need to look to check backgroundrb and create a scheduled
worker that will check for email every x minutes … or hours …

I will have a try soon as I want my users to be able to upload photos by
email :wink:

Backgroundrb is here : http://backgroundrb.rubyforge.org/

Note that it can integrate with rails easily :wink: as long as you work on
a unix machine.

Happy rails coding everyone !