I have configured jconsole to view jvm health.And I want to send an email to subscribers with jvm statics (which displayed by jconsole) can any one tell me how to do this.
You could try the Management Console that comes JRockit. It works like JConsole but it allows you to create triggers that can send an email when a JMX-attribute exceeds a threshold for a certain period of time. See this documentation for more information.
Related
I'm trying to run an MQTT broker and I want to store the published data, but I need to know which user sent the message so I can store payload for each user and study them later. The problem is when two different user try to publish message on same topic I can not tell whose data it is. Is there a way to figure out the publisher of a message? I'm using Mosquitto btw.
Short answer, you don't.
MQTT messages do not contain any information about the user or client that sent it, unless you choose to encode it in the message (as part of the payload for v3.x or alternatively in the header properties for v5.0)
Longer answer:
Some MQTT brokers have plugin APIs that may allow you access to more meta data for a message. You may be able to write a plugin that will take the message + the meta data and then store them. Last time I looked, mosquitto's plugin API was only for writing authentication plugins, and did not give access to the messages themselves. But a different broker may allow this.
I have my application integrated with Datadog for monitoring purpose. At the same time I want the notifications/calls to be sent to the team if any of the metric fails to achieve the desires value. I used Webhooks integration in Datadog for this purpose. In the webhooks configuration I have set the URL (Twilio request) and I do get a call on my number. Now I am looking for an scenario wherein if the user doesn't pick the call for say 30secs then try calling the second number. How do I achieve this?
Just use a find me Twimlet. Enter up to 10 numbers and a timeout between moving on to the next number. Twilio will do the rest.
https://www.twilio.com/labs/twimlets/findme
If you are looking for a more full featured paid solution I'd recommend PagerDuty. DataDog has an integration for PagerDuty. Any monitor that gets triggered that mentions #pagerduty-myteamname(as example) in the monitor message will cause PagerDuty to page the on call person. If that person does not acknowledge the page you can configure it to go through list of people to contact next until it is acknowledged by someone.
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.
Following a specific action the user takes on my website, a number of messages must be sent to different emails. Is it possible to have a separate thread or worker take care of sending multiple emails so as to avoid having the response from the server take a while to return if there are a lot of emails to send?
I would like to avoid using system process or scheduled tasks, email queues.
You can definitely spawn off a background thread in your controller to handle the emails asynchronously.
I know you want to avoid queues, but another thing i have done in the past is written a windows service that pulls email from a DB queue and processes it at certain intervals. This way you can separate the 2 applications if there is a lot of email to be sent.
This can be done in many different ways, depending on how large your application is and what kind of reliability you want. Any of these ways should help you achieve what you want (in ascending order based on complexity):
If you're using IIS SMTP Server or another mail server that supports a pickup directory option, you can go with that. With this option, instead of sending the emails directly, they are saved first in the pickup directory. Your call will immediately return after the email is saved in the pickup directory, so the user won't have to wait until the email is sent. On the other hand, the server will try to send the email as soon as it's saved in the pickup directory so it's almost immediate (just without blocking the call).
You can use a background thread like described in other answers. You'll need to be careful with this option as the thread can end unexpectedly before it finishes its job. You'll need to add some code to make sure this works reliably (personally, I'd prefer not to use this option).
Using a messaging queue server like MSMQ. This is more work and you probably should only look into this if you have a large scale application or have good reasons not to use the first option with the pickup directory.
There are a few ways you could do this.
You could store enough details about the message in the database, and write a windows service to loop through them and send the email. When the user submits the form it just inserts the required data about the message and trusts the service will pick it up. Almost an email queue which you said you didn't want, but you're going to end up in a queue situation with almost any solution.
Another option would be to drop in NServiceBus. Use that for these kinds of tasks.
I typically compile the message body and store that in a table in the db along with the from and to addresses, a subject, and a timestamp indicating when the email was sent. Then I have a background task check the table periodically and pull any that haven't been sent. This task attempts to send each email and updates the timestamp accordingly. One advantage of storing the compiled message body up front is that the background task doesn't have to do any processing of context-specific data, and therefore can be pretty darn simple.
Whenever an operation like is hingent upon an event, there is always the possibility something will go wrong.
In ASP.NET you can spawn multiple threads and have those threads do the action. Make sure you tell the thread it's a background thread, otherwise ASP.NET might way for the thread to finish before rendering your page:
myThread.IsBackground = true;
I know you said you didn't want to use system process or scheduled tasks, but a windows service would be a viable approach to this as well. The approach would be to use MS Queue, or save the actions needing to be done in a DataBase table. Then have a windows service check every minute or so and do those actions.
This way, if something fails (Email server down) those emails / actions can still be done.
They will also be recorded for audit's (which is very nice to have).
This method allows you're web site to function as a website while offloading these tasks to another service. The last thing you need is for multiple ASP.NET processes to be used up waiting for emails to send. let something else handle that.
When a user completes an order at my online store, he gets an email confirmation.
Currently we're sending this email via Gmail (which we chose over sendmail for greater portability) after we authorize the user's credit card and before we show him a confirmation message (i.e., synchronously).
It's working fine in development, but I'm wondering if this will cause a problem in production. Will it require making the user wait too long? Will many simultaneous Gmail connections get us in trouble? Any other general caveats?
If sending the emails synchronously will be a problem, could someone recommend an asynchronous solution (is ar_mailer any good?)
The main issue I can think of is that Gmail limits the amount of email you can send daily, so if you get too many orders a day it might break.
As they say :
"In an effort to fight spam and
prevent abuse, Google will temporarily
disable your account if you send a
message to more than 500 recipients or
if you send a large number of
undeliverable messages. If you use a
POP or IMAP client (Microsoft Outlook
or Apple Mail, e.g.), you may only
send a message to 100 people at a
time. Your account should be
re-enabled within 24 hours. "
http://mail.google.com/support/bin/answer.py?hl=en&answer=22839
I would recommend using sendmail on your server in order to have greater control over what's going on and don't depend on another service, especially when sendmail is not really complicated to set up.
The internet is not as resilient as some people would have you believe, the link between you and GMail will break at some point or GMail will go offline causing the user to think that they have not paid sucessfully.
I would put some other queue in place, sendmail sounds acceptable and you can't create your site now for where it 'might' be hosted in the future.
Ryan
If the server waits for the email to be sent before giving the user any feedback, were there problems connecting to the mailserver (timeouts, server down etc) the user request would timeout too and he wouldn't be told anything about the status of his order, so I believe you should really do this asynchronously.
Also, you should check whether doing that is even allowed by GMail's TOS. If that's not the case, you may check if that's allowed if you purchase one of their subscriptions. Also, there's surely a limit to the number of outgoing emails you may send within a given timeframe so if you're expecting your online store to be successful, you may hit that limit and bump into some nasty issue. If you're not self-hosting the site, you should check whether your host offers email servers (several plans include them for free) as then using your host's ISP would be the most obvious choice.
FACT: Gmail crashes. Not often, but it happens, and you can't control it or test it.
The simplest quick-fix is to start a separate thread or fork a subprocess to send the email. Yes, there likely will arise problems from using Gmail, and I really have no input on that vs. the alternatives. But from a design perspective, there's just no reason to make the user wait for that process to complete.
From a testing perspective, this might be where a proxy pattern might come in handy. It might be easy for you to directly invoke Gmail to send a message. Make it harder. Put in a proxy object that does the mailing for you that you can turn off (because heaven knows you can't for testing purposes make Gmail crash). Just make your team follow what happens in the event of an email malfunction by turning off the proxy and trying to complete an order. If you are doing it synchronously, then all the plagues mentioned here by other posters will rear their heads. If you are doing it asynchronously, you should be able to allow it to fail silently (from the user's perspective--from your perspective there should be enormous logging statements and text messages in the middle of the night and possibly a mild electric current arcing across the surface of someone's skin).