I want to host a static website on Heroku, but not sure how many dynos to start off with.
It says on this page: https://devcenter.heroku.com/articles/dyno-requests that the number of requests a dyno can serve, depends on the language and framework used. But I have also read somewhere that 1 dyno only handles one request at a time.
A little confused here, should 1 web dyno be enough to host a static website with very small traffic (<1000 views/month, <10/hour)? And how would you go about estimating additional use of dynos as traffic starts to increase?
Hope I worded my question correctly. Would really appreciate your input, thanks in advance!
A little miffed since I had a perfectly valid answer deleted but here's another attempt.
Heroku dynos are single threaded, so they are capable of dealing with a single request at a time. If you had a dynamic page (php, ruby etc) then you would look at how long a page takes to respond at the server, say it took 250ms to respond then a single dyno could deal with 4 requests a second. Adding more dynos increases concurrency NOT performance. So if you had 2 dynos, in this scenario you be able to deal with 8 requests per second.
Since you're only talking static pages, their response time should be much faster than this. Your best way to identify if you need more is to look at your heroku log output and see if you have sustained levels of the 'queue' value; this means that the dynos are unable to keep up and requests are being queued for processing.
Since most HTTP 1.1 clients will create two TCP connections to the webserver when requesting resources, I have a hunch you'll see better performance on single clients if you start two dynos, so the client's pipelined resources requests can be handled pipelined as well.
You'll have to decide if it is worth the extra money for the (potentially slight) improved performance of a single client.
If you ever anticipate having multiple clients requesting information at once, then you'll probably want more than two dynos, just to make sure at least one is readily available for additional clients.
In this situation, if you stay with one dyno. The first one is free, the second one puts you over the monthly minimum and starts to trigger costs.
But, you should also realize with one dyno on Heroku, the app will go to sleep if it hasn't been accessed recently (I think this is around 30 minutes). In that case, it can take 5-10 seconds to wake up again and can give your users a very slow initial experience.
There are web services that will ping your site, testing for it's response and keeping it awake. http://www.wekkars.com/ for example.
Related
I'm thinking about launching an web app with heroku but I have no idea to calculate the performance cost. According to their website 1 dyno to professional support is at least $ 25 /month gives a machine with "512MB or 1GB RAM".
If my website has a standard load assets and I have 1,000 people everyday access, how many "dynos" should be recommended to have a reasonable good speed for users?
This will likely get shut down as it's not a 'programming' question. I'll try to answer quickly.
It all depends on how fast your page executes on the server, if it's slow then you run the risk of requests being timed out before they can be served by the app server. Adding more dyno's does not make your application faster though, changing the dyno type, standard-1x, 2x, PM, PL does as it makes more resources available however, slow code will always be slow code - throwing more resources at it is like a band-aid for a period of time.
In short, it's very application dependent both from a code point of view and traffic point of view - do those 1000 users arrive at the same time or are they spreadout?
I am using New Relic standard and Rails 3 on Heroku to build a web site. But not sure what indicators shown on New Relic should I keep an eye on to scale up the web dyno when certain criteria are met?
Say, indicator A comes to X level, I should add one Dyno to put it down.
Thank you!
Primarily you want to be looking at your logs and at the queue attribute on the heroku[router] - if this starts going up (and importantly staying up) then you have too many requests that are being queued and can't be processed fast enough.
If you're seeing long queue-wait times in the New Relic dashboard and there are no other good explanations (i.e. high variability in response times, use of Thin web server instead of Unicorn, etc.), that's generally a good indication requests are waiting in queue to be processed by a dyno.
I was curious as to what the difference between web and worker dynos is on Heroku. They give a one sentence explanation on their pricing page, but this just left me confused. How do I know how many to pick of each? Is there a ratio I should aim for? I'm pretty new to this stuff, so can someone give an in depth explanation, or maybe some sort of way I can calculate how many and which kind of dynos I would need?
Also, I'm confused about what they mean by the amount of hours for each dyno.
http://www.heroku.com/pricing
I also happened upon this article. As one of their suggested solutions, they said to increase the amount of dynos. Which type of dyno are they referring to here?
http://devcenter.heroku.com/articles/backlog-too-deep
Your best indication if you need more dynos (aka processes on Cedar) is your heroku logs. Make sure you upgrade to expanded logging (it's free) so that you can tail your log.
You are looking for the heroku.router entries and the value you are most interested is the queue value - if this is constantly more than 0 then it's a good sign you need to add more dynos. Essentially this means than there are more requests coming in than your process can handle so they are being queued. If they are queued too long without returning any data they will be timed out.
There's no ideal ratio I'm afraid, you could have an app doing 100 requests a second needing many web processes but just doesn't make use of workers. You only need worker processes if you are doing processing in the background like sending emails etc etc.
ps Backlog too deep would be a Dyno web process that would cause it.
UPDATE: On March 26 2013 Heroku removed queue and wait fields from the log out put.
queue and wait fields have been removed from router log messages.
Also, the Heroku router no longer sets X-Heroku-Dynos-In-Use,
X-Heroku-Queue-Depth and X-Heroku-Queue-Wait-Time HTTP headers for
incoming requests.
Dynos are basically processes that run on your instance. With the new Cedar stack, they can be set up to execute any arbitrary shell command. For web applications, you generally have one process called "web" which is responsible for responding to HTTP requests from users. All other processes are what were previously called "workers." These run continuously in the background for things like cron, processing queues, and any heavy computation that you don't want to tie up your web processes. You can also scale each type of process, so that multiple processes of each type will be booted up for additional concurrency. The amount of each that you use really depends on the needs of your application and the load it receives. You can use tools like the New Relic plugin to monitor these things. Take a look at the articles on the Process Model and the Procfile in Heroku's dev center for more details.
A number of people have mentioned that there is no known ratio and that the ratio of web workers to 'background' workers you will want is dependent on how you designed your application - that is correct. However I thought it might be useful to add that as a general rule of thumb, you want your web workers - and thus the controller actions they are serving - to be lightning quick and very lightweight, to reduce latency in response times from browser actions. If there is some browser action that would require more than, say, about a half a second of real time to serve, then you will probably want to architect some sort of system that pushes the bulk of that action on to a queue.
You would then design an offline worker dyno(s) that will service this queue. They can take much longer because there are no HTTP responses pending on their output. Perhaps the page you rendered from the initial browser request that pushed the action will serve some Javascript that starts a thread that checks to see if the request has finished every 5 seconds, or something along those lines.
I still can't give you a ratio to work with for the same reason others have given, but hopefully this helps you decide how to architect your app. (I should also mention this is just one design out of many valid ones.)
https://stackoverflow.com/a/19965981/1233555 - Heroku has gone to random routing, so some dynos can have queues stacking up (while they serve a lengthy request) while other dynos are free. Avoid this by making sure that all requests are handled very quickly in your web dynos. This will reduce the number of web dynos you need, while requiring more worker dynos.
You also need to care about your web app supporting concurrency, which only some Rails configs do - try Unicorn, or carefully-written code (for I/O that doesn't block the EventMachine) with Thin.
You probably have to try, rather than calculate, to see how many dynos of each kind you need. Make sure their New Relic reports the dyno queue - see the above link.
Short answer is that you need as many as you need to keep your queues down.
As John describes, if you start seeing a queue in your logs then you need more dynos. If you start seeing your background queues getting too long (how you get this info is dependant on what you have implemented) then you need more workers.
There is no ratio as it's very much dependent on your application design and usage.
Can anyone have an estimate of how much data can be inserted in a 5MB database?
Also, would 1 Dyno handle a slashdot,hackernews, etc frontpage?
Thanks.
Quiet a surprising amount... well enough to get you started thats for sure.
I use 1 dyno all the time for low traffic (like my personal website and a few xml servers, but obviously the great thing is if you start getting loads of visitors to your site and are having performance issues all it takes is one little click to add extra dynos.
You should also consider the worker hours, not sure about what you are doing, but a lot of apps could need background process.
This service could be interesting if you are using Ruby, it scales dynos on Heroku:
http://hirefireapp.com
I created two very simple Heroku apps to test out the service, but it's often taking several seconds to load the page when I first visit them:
Cropify - Basic Sinatra App (on github)
Textile2HTML - Even more basic Sinatra App (on github)
All I did was create a simple Sinatra app and deploy it. I haven't done anything to mess with or test the Heroku servers. What can I do to improve response time? It's very slow right now and I'm not sure where to start. The code for the projects are on github if that helps.
If your application is unused for a while it gets unloaded (from the server memory).
On the first hit it gets loaded and stays loaded until some time passes without anyone accessing it.
This is done to save server resources. If no one uses your app why keep resources busy and not let someone who really needs use them ?
If your app has a lot of continous traffic it will never be unloaded.
There is an official note about this.
You might also want to investigate the caching options you have on Heroku w/ Varnish and Memcached. These are persisted independent of the dynos.
For example, if you have an unchanging homepage, you can cache that for extended periods in Varnish by adding Cache-Control headers to the response. Then your users won't experience the load hit until they want to "do something" rather than when they arrive.
You should check out Tom Robinson's answer to "Scalability: How Does Heroku Work?" on Quora: http://www.quora.com/Scalability/How-does-Heroku-work
Heroku divides up server resources among many different customers/applications. Your app is allotted blocks of computing power. Heroku partitions based on resource demand. When you have a popular application that demands more power, you can pay for more 'dynos' (application containers) and then get a larger chunk of the pie in return.
In your case though, you are running a free app that few people--if any outside of you--are visiting/using. Therefore, Heroku cuts down on the resources you're getting by unloading your app--putting it in hibernation essentially--until there is a request made to your address. When that happens, and your app has been idling for a long time, it takes time to reload.
Add 1 extra dyno to keep your app from falling asleep, if that reload time is important.
I am having the same problem. I deployed a Rails 3 (1.9.2) app last night and it's slow. I know that 1.9.2/Rails 3 is in BETA on Heroku but the support ticket said it should be fine using some instructions they sent me.
I understand that the first request after a long time takes the longest. Makes sense. But simply loading pages that don't even connect to a DB taking 10 seconds sometimes is pretty bad.
Anyway, you might want to try what I'm going to do. That is profile my app and see how long it takes locally. If it's taking 400ms then something is wrong. But if I get 50ms locally and it still takes 10 seconds on Heroku then something is definitely wrong.
Obviously, caching helps but you only get 5MB for free and once again, with ONE person using the site, it shouldn't be that slow.
I had the same problem with every app I have put on via heroku's free account. Now there are options of adding dynos so that your app does not get offloaded while it is not being used for a while, you can also try using redis or memcached for caching. But I used a hacky solution for my small scale project, I basically built web scraper put it inside an infinite loop with sleep and tada the website actually had much better response times(I guess it was not getting offloaded because of the script).