I'm in the process of planning the development of a mail-server to hand the sending of email across our multiple websites. Below is a description of what we are planning to implement and I'd like your opinion/suggestions.
We use ASP.NET MVC and have many web-sites hosted on Azure. We currently send mail internally within each of the web applications using SMTPServer.Send(). Obviously this is not the ideal way to send emails when you have a decently busy set of websites because the send mail call is blocking and cannot guarantee mails are sent. With this I'm worried out getting an influx of mail requests when we launch our next website (we think it'll get a decent amount of traffic and lots of emails will be sent).
My plan of action : to build a centralised mail-server that runs in the background (we use azure and this will be simply another web-application). When each one of our web applications wants to send a mail, instead of doing this internally, it'll call a web method on the mail-server called sendMail() this function will accept certain parameters and insert the mail parameters, content etc. into a database. The mail server will then poll the database at fixed time intervals, select a set of unsent emails and attempt to send them using the same SMTPServer.Send() function. If an email fails for some reason we won't flag it as sent and in the next poll interval the email will be selected again and another send attempt will be made. (we will cap the number of send attempts to say 20).
This will allow each of the websites to run smoothly without having loads of blocking send mail calls internally and the mail server will handle all the sending sequentially and in a controlled environment as a separate standalone web-application.
Thanks in advance!
Looks like a good design, Don't know the entire scenario which let to you building something like an email server. The problem has been solved well by using a service that already exist like Office 365.
Your design is good, My suggestions would be the following,
You can use Azure WebJobs to build the polling agent. You can make the web job run as a scheduled web job that does the polling and sending the mail and it can be written very clean as a simple console app.
You can use Azure API App to build the SendMail() call and you can use the Azure AD Auth on the API to authenticate the caller of the API using the Authentication and Authorization feature to easily secure your email server. You can also enable CORS easily as well to make sure you receive requests from other websites and process it.
Some issues I foresee for you,
Volume and Scaling : You can only process so much email between each polling. If you cannot then you will need to create another polling agent which will making things complicated as they need to know they are picking different sets of emails to send. If you volume is going to be low you should be fine.
Challenge : Why can't the websites send the mail them selves ? And then record it on the database for tracking. All you have to do build module or a component that they use on their web page to create and send the mail. Polymer 1.0 works well for this scenario.
Hope this helps to get you started.
Related
I am working in a Rails application and below is the scenario requiring a solution.
I'm doing some time consuming processes in the background using Sidekiq and saves the related information in the database. Now when each of the process gets completed, we would like to show notifications in a separate area saying that the process has been completed.
So, the notifications area really need to pull things from the back-end (This notification area will be available in every page) and show it dynamically. So, I thought Ajax must be an option. But, I don't know how to trigger it for a particular area only. Or is there any other option by which Client can fetch dynamic content from the server efficiently without creating much traffic.
I know it would be a broad topic to say about. But any relevant info would be greatly appreciated. Thanks :)
You're looking at a perpetual connection (either using SSE's or Websockets), something Rails has started to look at with ActionController::Live
Live
You're looking for "live" connectivity:
"Live" functionality works by keeping a connection open
between your app and the server. Rails is an HTTP request-based
framework, meaning it only sends responses to requests. The way to
send live data is to keep the response open (using a perpetual connection), which allows you to send updated data to your page on its
own timescale
The way to do this is to use a front-end method to keep the connection "live", and a back-end stack to serve the updates. The front-end will need either SSE's or a websocket, which you'll connect with use of JS
The SEE's and websockets basically give you access to the server out of the scope of "normal" requests (they use text/event-stream content / mime type)
Recommendation
We use a service called pusher
This basically creates a third-party websocket service, to which you can push updates. Once the service receives the updates, it will send it to any channels which are connected to it. You can split the channels it broadcasts to using the pub/sub pattern
I'd recommend using this service directly (they have a Rails gem) (I'm not affiliated with them), as well as providing a super simple API
Other than that, you should look at the ActionController::Live functionality of Rails
The answer suggested in the comment by #h0lyalg0rithm is an option to go.
However, primitive options are.
Use setinterval in javascript to perform a task every x seconds. Say polling.
Use jQuery or native ajax to poll for information to a controller/action via route and have the controller push data as JSON.
Use document.getElementById or jQuery to update data on the page.
I've read most of the other answers on this topic, but a lot of them related to either third-party services like MailChimp (which I'm not necessarily opposed to) or how not to upset the host's email server.
I believe this case is unique so that it'll contribute...
I have my own DigitalOcean droplet running a rails app. I need to send out 100-1000 emails every so often, each with a unique message (a link I'm using for tracking clicks originating from the email).
I'm also operating my own iRedMail server.
Can someone recommend how to best-handle this task? I was going to simply cycle through the list of emails and use the template.html.erb to drop in my link, but what types of problems might I run into?
Thank you!
You should decouple your Rails App from the mail sending so that you don't have to wait in your view for the mails to be sent (assuming that you click on something that triggers the start of your mail sending). Use something like delayed_job or another queueing mechanism that Rails offers and only queue up the sending job of the e-mails. Then when the queue comes to execute the particular job you can customize the message with an HTML part and a text part or whatever else you need and pass them on individually to your MTA.
For my client's custom-built CRM, I want users (technicians) to be notified of changes to marked cases via email.
This warrants a simple subscription mapping table between users and cases and automated emails to be sent every time a change is made to a case from within the logging method.
How do I send 10-100 emails to subscribed users without bogging down my logging method? My SMTP server is on a peer on my LAN, so sends should be quick, but ideally this should be handled by an external queuing process.
I can have a cron job send any outstanding emails every 10 minutes, but for this specific client cases are quite time-sensitive and instant notification (as instant as email can be) would be great.
How can I send bulk notification emails from within ASP.NET MVC without bogging down my logging method?
Back in 2007 I was asked to look into a case where Web Server would suddenly freeze and start sending 503 errors and come back after a few minutes. Cutting a long story short it turned out at the end that it was sending email which was blocking the server (in addition to some bad code).
Basically Microsoft's SMTP server is implemented as a single-thread service - last I checked. This will mean that all your valuable ASP.NET threads serving requests will have to queue to a single thread monolithic application to send a not so urgent email. You need to decouple your web site from sending emails - that is what everyone does and there is a good reason for it.
Write your emails to a queue and have a process reading and sending emails.
Sending emails from an ASP.NET application is not a good idea as it might monopolize valuable server resources. A better solution would be to setup a Windows Service to perform this task or even write a Console application which could be scheduled to run with Windows Scheduler. Quartz.NET is a good solution you might take a look at allowing you to schedule jobs.
If you want those email sending to be triggered from within a particular controller action you could also have a separate WCF service which could be invoked asynchronously.
How would i go about to receive mails in a Ruby on Rails application without going through a mail server like PostFix or to fetch them by pop3 etc.
What i was to do is to catch all mails sent to #mydomain.com and just do something with them in my application. I don't need to store the mails or anything like that.
Is this posible?
I just implemented this for my SAAS to autoprocess mailer-bounce notification messages.
Call me, call you?
You call me
You can set up a local mail server. It would then respond to an incoming email, and start up a rails executable to process the email. This method is NOT recommended since starting up rails is a big task (takes multiple secs and lots of memory). You don't want a Rails bad boy started up just because you received an email. You'd be writing your own DDOS attack. (Attacking yourself.)
I call you
Instead, poll for email on your own schedule by using a single job to process all currently waiting emails. You need to set up a background job handler since stock rails is focused on responding to web requests. I use delayed_job, but there are other alternatives including kicking off a cron job every so in often.
Another benefit is that you don't need to manage a mail server. Leave that headache to someone else. Then use the Ruby library net::imap to read the incoming mail and process it.
If your process doesn't recognize the email format, then forward the msg to a human for processing.
And be sure that if the process sends mail in addition to reading/processing it, that the process uses a different email address as its From address. Otherwise, odds are good that sometime along the way, you'll end up in an email loop and many gigabytes of messages going back and forth. For example, your process receives a message, responds to it, but in the meantime the sender (a human) has switched on vacation response. And your robot then responds to the vacation response..... oops....
Writing your own mail server
Re:
How would i go about to receive mails in a Ruby on Rails application without going through a mail server like PostFix or to fetch them by pop3 etc.
What i was to do is to catch all mails sent to #mydomain.com and just do something with them in my application. I don't need to store the mails or anything like that.
Direct answer: Yes, you could do this by writing an smtp server and setting up dns so your machine will be the mail destination for the domain. Your smtp server would process the messages on the fly, they would not be stored on your system at any point.
Is this a good idea? No, not at all. While appearances may be to the contrary, email is a store and forward system. Trying to avoid storing the messages before your app processes them is not smart. It would be a very very poor "optimization." However, using an access protocol (POP3 or IMAP) is a good way to avoid the costs of installing, configuring and managing a mail server.
You can do this if you write your own mail server, or if your mail server supports hooks to run external programs upon receipt of mail (e.g. procmail).
If you don't have procmail available (or, if on something like Exchange Server, don't feel like writing custom rules or extensions), you're simply better off using a pop3 library to fetch mail.
Obviously, writing a mail server is more difficult than any of the alternatives.
If you're mostly worried about checking potentially hundreds of email accounts, that's solvable by configuring your email server properly. If you're on a hosted provider, ask your server administrator about creating a "catch-all" account that routes all mail to unknown addresses to a single account.
If you're aiming to avoid having to poll a server, consider the IMAP IDLE command. I've successfully written a Ruby client that opens a connection to an IMAP server, and gets told by the server when new mail arrives.
I am to build a web application which will accept different events from external sources and present them quickly to the user for further actions. I want to use Ruby on Rails for the web application. This project is a internal development project. I would prefer simple and easy to use solutions for rapid development over high reliable and complex systems.
What it should do
The user has the web application opened in his browser. Now an phone call comes is. The phone call is registered by a PBX monitoring daemon. In this case via the Asterisk Manager Interface. The daemon sends the available information (remote extension, local extension, call direction, channel status, start time, end time) somehow to the web application. Next the user receives a notified about the phone call event. The user now can work with this. For example by entering a summary or by matching the call to a customer profile.
The duration from the first event on the PBX (e.g. the creation of a new channel) to the popup notification in the browser should be short. Given a fast network I would like to be within two seconds. The single pieces of information about an event are created asynchronously. The local extension may be supplied separate from the remote extension. The user can enter a summary before the call has ended. The end time, new status etc. will show up on the interface as soon as one party has hung up.
The PBX monitor is just one data source. There will be more monitors like email or a request via a web form. The monitoring daemons will not necessarily run on the same host as the database or web server. I do not image the application will serve thousands of logged in users or concurrent requests soon. But from the design 200 users with maybe about the same number of events per minute should not be a scalability issue.
How should I do?
I am interested to know how you would design such an application. What technologies would you suggest? How do the daemons communicate their information? When and by whom is the data about an event stored into the main database? How does the user get notified? Should the browser receive a complete dataset on behalf of a daemon or just a short note that new data is available? Which JS library to use and how to create the necessary code on the server side?
On my research I came across a lot of possibilities: Message brokers, queue services, some rails background task solutions, HTTP Push services, XMPP and so on. Some products I am going to look into: ActiveMQ, Starling and Workling, Juggernaut and Bosh.
Maybe I am aiming too hight? If there is a simpler or easier way, like just using the XML or JSON interface of Rails, I would like to read this even more.
I hope the text is not too long :)
Thanks.
If you want to skip Java and Flash, perhaps it makes sense to use a technology in the Comet family to do the push from the server to the browser?
http://en.wikipedia.org/wiki/Comet_%28programming%29
For the sake of simplicity, for notifications from daemons to the Web browser, I'd leave Rails in the middle, create a RESTful interface to that Rails application, and have all of the daemons report to it. Then in your daemons you can do something as simple as use curl or libcurl to post the notifications. The Rails app would then be responsible for collecting the incoming notifications from the various sources and reporting them to the browser, either via JavaScript using a Comet solution or via some kind of fatter client implemented using Flash or Java.
You could approach this a number of ways but my only comment would be: Push, don't pull. For low latency it's not only quicker it's more efficient, as your server now doesn't have to handle n*clients once a second polling the db/queue. ActiveMQ is OK, but Starling will probably serve you better if you're not looking for insane levels of persistence.
You'll almost certainly end up using Flash on the client side (Juggernaut uses it last time I checked) or Java. This may be an issue for your clients (if they don't have Flash/Java installed) but for most people it's not an issue; still, a fallback mechanism onto a pull notification system might be prudent to implement.
Perhaps http://goldfishserver.com might be of some use to you. It provides a simple API to allow push notifications to your web pages. In short, when your data updates, send it (some payload data) to the Goldfish servers and your client browsers will be notified, with the same data.
Disclaimer: I am a developer working on goldfish.
The problem
There is an event - either external (or perhaps internally within your app).
Users should be notified.
One solution
I am myself facing this problem. I haven't solved it yet, but this is how I intend to do it. It may help you too:
(A) The app must learn about the event (via an exposed end point)
Expose an end point by which you app can be notified about external events.
When the end point is hit (and after authentication then users need to be notified).
(B) Notification
You can notify the user directly by changing the DOM on the current web page they are on.
You can notify users by using the Push API (but you need to make sure your browsers can target that).
All of these notification features should be able to be handled via Action Cable: (i) either by updating the DOM to notify you when a phone call comes in, or (ii) via a push notification that pops up in your browser.
Summary: use Action Cable.
(Also: why use an external service like Pusher, when you have ActionCable at your disposal? Some people say scalability, and infrastructure management. But I do not know enough to comment on these issues. )