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  • Interconnect nodes in a Java distributed infrastructure for tweet processing

    - by David Moreno García
    I'm working in a new version of an old project that I used to download and process user statuses from Twitter. The main problem of that project was its infrastructure. I used multiple instances of a java application (trackers) to download from Twitter given an specific task (basically terms to search for), connected with a central node (a web application) that had to process all tweets once per day and generate a new task for each trackers once each 15 minutes. The central node also had to monitor all trackers and enable/disable them under user petition. This, as I said, was too slow because I had multiple bottlenecks, so in this new version I want to improve the infrastructure and isolate all functionalities in specific nodes. I also need a good notification system to receive notifications for any node. So, in the next diagram I show the components that I'll need in this new version: As you can see, there are more nodes. Here are some notes about them: Dashboard: Controls trackers statuses and send a single task to each of them (under user request). The trackers will use this task until replaced with a new one (if done, not each 15 minutes like before). Search engine: I need to store all the tweets. They are firstly stored in a local database for each tracker but after that I'm thinking on using something like Elasticsearch to be able to do fast searches. Tweet processor: Just and isolated component with its own database (maybe something like the search engine to have fast access to info generated by the module). In the future more could be added. Application UI: A web application with a shared database with the Dashboard (mainly to store users information and preferences). Indeed, both could be merged into a single web. The main difference with the previous version of the project is that now they will be isolated and they will only show information and send requests. I will not do any heavy task in them (like process tweets as I did before). So, having this components, my main headache is how to structure all to not have to rewrite a lot of code every time I need to access any new data. Another headache is how can I interconnect nodes. I could use sockets but that is a pain in the ass. Maybe a REST layer? And finally, if all the nodes are isolated, how could I generate notifications for each user which info is only in the database used by the Application UI? I'm programming this using Java and Spring (at least I used them in the last version) but I have no problems with changing the language if I can take advantage of a tool/library/engine to make my life easier and have a better platform. Any comment will be appreciated.

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  • Synchronizing local and remote cache in distributed caching

    - by ltfishie
    With a distributed cache, a subset of the cache is kept locally while the rest is held remotely. In a get operation, if the entry is not available locally, the remote cache will be used and and the entry is added to local cache. In a put operation, both the local cache and remote cache are updated. Other nodes in the cluster also need to be notified to invalidate their local cache as well. What's a simplest way to achieve this if you implemented it yourself, assuming that nodes are not aware of each other. Edit My current implementation goes like this: Each cache entry contains a time stamp. Put operation will update local cache and remote cache Get operation will try local cache then remote cache A background thread on each node will check remote cache periodically for each entry in local cache. If the timestamp on remote is newer overwrite the local. If entry is not found in remote, delete it from local.

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  • Scalable distributed file system for blobs like images and other documents

    - by Pinnacle
    Cassandra & HBase both do not efficiently support storage of blobs like images. Storing directly on HDFS stresses the Namenode because of huge number of files. Facebook uses Haystack for images and attachments storage, but this is not open source. So is Lustre a good choice for distributed blob storage? I have read that Amazon S3 is used by many, but this would cost money and personally, I would not like to rely on third party system. What are other suggestions?

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  • How should I host our scalable worker processes?

    - by Pieter Breed
    We are designing a new architecture for an enterprise business. The principles we've followed so far is not to develop what you can (possible buy and) deploy, ie, don't reinvent any wheels. In this way we've decided on CQRS, RabbitMQ, Riak and a bunch of other things. We still need to write /some/ business code though and these will be in the form of worker processes, which will consume commands from a message queue and after any side-effects, produce events onto another message queue. The idea behind this is that via the competing-consumers design we will have a scalable design right out of the box. One option is of writing a management infrastructure that will know how to: deploy code instantiate processes kill processes update configuration etc IE provide fault tolerance and scalability. Also, this is exactly what something like GAE and Heroku does for you, but in a public setting and in our organization, public is bad. My question is, is there an out-of-the-box solution that we can use to host our consumers in? Like a private cloud or private platform-as-a-service. Private Heroku or GAE. Is there some kind of software or software product with which we can do all of these things and thereby get scalability and fault tolerance over our consumers?

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  • Is there a canonical resource on multi-tenancy web applications using ruby + rails

    - by AlexC
    Is there a canonical resource on multi-tenancy web applications using ruby + rails. There are a number of ways to develop rails apps using cloud capabilities with real elastic properties but there seems to be a lack of clarity with how to achieve multitenancy, specifically at the model / data level. Is there a canonical resource on options to developing multitenancy rails applications with the required characteristics of data seperation, security, concurrency and contention required by an enterprise level cloud application.

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  • Using EC2 instance as main development platform

    - by David
    My problem I am working as a consultant for various companies. Each company provides me with a laptop with their software on and I also have my own, where I have my development environment. I tend to buy a new laptop every second year and find myself spending lots of time configuring and installing software. I also spend a lot of time waiting for my laptop to process things. To solve all these issues, I am now considering using EC2 (running windows instances) as my main development platform and just access this from any PC I happen to be at. I calculated that running the Large instance (cheapest 64-bit) for 8 hours a day for a year costs me 960$ per year, which is acceptable. I imagine that when I approach the workplace each day, I will make a single tap on my phone to fire up the instance, so it is ready when I get to work. I should have different icons on my phone to fire up the various instance types. The same software should of course automatically be loaded on the various hardware (sometimes I would even need their instance with 68.4 GB of memory). Another advantage is that if I am having a specific problem with my instance, I could fire up another instance and have someone look into the problem and update the image. My question: Does anyone have experience with such a setup on EC2? What kind of problems do you foresee?

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  • Erlang node acts like it connects, but doesn't [migrated]

    - by Malfist
    I'm trying to setup a distributed network of nodes across a few firewalls and it's not going so well. My application is structured like this: there is a central server that always running a node ([email protected]) and my co-worker's laptops connect to it on startup. This works if we're all in the office, but if someone is at home, they can connect to the masternode, but they fail to connect to the other nodes in the swarm. I.E., erlang fails to gossip correctly. To correct this, I've change epmd's port number and changed the inet_dist_listen ports to a known open port (1755 and 7070 respectively). However, something fishy is going on. I can run net_adm:world() and it reports that it connects to master node, but when I run nodes() I get an empty array. Same with net_adm:ping('[email protected]'). See: Eshell V5.9 (abort with ^G) ([email protected])1> net_adm:world(). ['[email protected]'] ([email protected])2> nodes(). [] ([email protected])3> net_adm:ping('[email protected]'). pong ([email protected])4> nodes(). [] ([email protected])5> What's going on, and how can I fix it?

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  • How can i manage my personal notes , code snippets files in one place online [closed]

    - by user1758043
    Whenever i work on any project , then i have so much notes , diagrams files , image s, brainstorming ideas which i want to keep. i want to put them in one place so that i can see the history of my work. Is there any toll whichere i can store this online. my company is using confluence but thats costly for me. I want something for single user but online in clou where i can store Notes Code snippets Diagrams , flowchart Attah files , images Books marks , sites

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  • How to determine the source of a request in a distributed service system?

    - by Kabumbus
    Map/Reduce is a great concept for sorting large quantities of data at once. What to do if you have small parts of data and you need to reduce it all the time? Simple example - choosing a service for request. Imagine we have 10 services. Each provides services host with sets of request headers and post/get arguments. Each service declares it has 30 unique keys - 10 per set. service A: name id ... Now imagine we have a distributed services host. We have 200 machines with 10 services on each. Each service has 30 unique keys in there sets. but now to find to which service to map the incoming request we make our services post unique values that map to that sets. We can have up to or more than 10 000 such values sets on each machine per each service. service A machine 1 name = Sam id = 13245 ... service A machine 1 name = Ben id = 33232 ... ... service A machine 100 name = Ron id = 777888 ... So we get 200 * 10 * 30 * 30 * 10 000 == 18 000 000 000 and we get 500 requests per second on our gateway each containing 45 items 15 of which are just noise. And our task is to find a service for request (at least a machine it is running on). On all machines all over cluster for same services we have same rules. We can first select to which service came our request via rules filter 10 * 30. and we will have 200 * 30 * 10 000 == 60 000 000. So... 60 mil is definitely a problem... I hope to get on idea of mapping 30 * 10 000 onto some artificial neural network alike Perceptron that outputs 1 if 30 words (some hashes from words) from the request are correct or if less than Perceptron should return 0. And I’ll send each such Perceptron for each service from each machine to gateway. So I would have a map Perceptron <-> machine for each service. Can any one tall me if my Perceptron idea is at least “sane”? Or normal people do it some other way? Or if there are better ANNs for such purposes?

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  • Using the @ in SQL Azure Connections

    - by BuckWoody
    The other day I was working with a client on an application they were changing to a hybrid architecture – some data on-premise and other data in SQL Azure and Windows Azure Blob storage. I had them make a couple of corrections - the first was that all communications to SQL Azure need to be encrypted. It’s a simple addition to the connection string, depending on the library you use. Which brought up another interesting point. They had been using something that looked like this, using the .NET provider: Server=tcp:[serverName].database.windows.net;Database=myDataBase; User ID=LoginName;Password=myPassword; Trusted_Connection=False;Encrypt=True; This includes most of the formatting needed for SQL Azure. It specifies TCP as the transport mechanism, the database name is included, Trusted_Connection is off, and encryption is on. But it needed one more change: Server=tcp:[serverName].database.windows.net;Database=myDataBase; User ID=[LoginName]@[serverName];Password=myPassword; Trusted_Connection=False;Encrypt=True; Notice the difference? It’s the User ID parameter. It includes the @ symbol and the name of the server – not the whole DNS name, just the server name itself. The developers were a bit surprised, since it had been working with the first format that just used the user name. Why did both work, and why is one better than the other? It has to do with the connection library you use. For most libraries, the user name is enough. But for some libraries (subject to change so I don’t list them here) the server name parameter isn’t sent in the way the load balancer understands, so you need to include the server name right in the login, so the system can parse it correctly. Keep in mind, the string limit for that is 128 characters – so take the @ symbol and the server name into consideration for user names. The user connection info is detailed here: http://msdn.microsoft.com/en-us/library/ee336268.aspx Upshot? Include the @servername on your connection string just to be safe. And plan for that extra space…  

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  • High Availability for IaaS, PaaS and SaaS in the Cloud

    - by BuckWoody
    Outages, natural disasters and unforeseen events have proved that even in a distributed architecture, you need to plan for High Availability (HA). In this entry I'll explain a few considerations for HA within Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). In a separate post I'll talk more about Disaster Recovery (DR), since each paradigm has a different way to handle that. Planning for HA in IaaS IaaS involves Virtual Machines - so in effect, an HA strategy here takes on many of the same characteristics as it would on-premises. The primary difference is that the vendor controls the hardware, so you need to verify what they do for things like local redundancy and so on from the hardware perspective. As far as what you can control and plan for, the primary factors fall into three areas: multiple instances, geographical dispersion and task-switching. In almost every cloud vendor I've studied, to ensure your application will be protected by any level of HA, you need to have at least two of the Instances (VM's) running. This makes sense, but you might assume that the vendor just takes care of that for you - they don't. If a single VM goes down (for whatever reason) then the access to it is lost. Depending on multiple factors, you might be able to recover the data, but you should assume that you can't. You should keep a sync to another location (perhaps the vendor's storage system in another geographic datacenter or to a local location) to ensure you can continue to serve your clients. You'll also need to host the same VM's in another geographical location. Everything from a vendor outage to a network path problem could prevent your users from reaching the system, so you need to have multiple locations to handle this. This means that you'll have to figure out how to manage state between the geo's. If the system goes down in the middle of a transaction, you need to figure out what part of the process the system was in, and then re-create or transfer that state to the second set of systems. If you didn't write the software yourself, this is non-trivial. You'll also need a manual or automatic process to detect the failure and re-route the traffic to your secondary location. You could flip a DNS entry (if your application can tolerate that) or invoke another process to alias the first system to the second, such as load-balancing and so on. There are many options, but all of them involve coding the state into the application layer. If you've simply moved a state-ful application to VM's, you may not be able to easily implement an HA solution. Planning for HA in PaaS Implementing HA in PaaS is a bit simpler, since it's built on the concept of stateless applications deployment. Once again, you need at least two copies of each element in the solution (web roles, worker roles, etc.) to remain available in a single datacenter. Also, you need to deploy the application again in a separate geo, but the advantage here is that you could work out a "shared storage" model such that state is auto-balanced across the world. In fact, you don't have to maintain a "DR" site, the alternate location can be live and serving clients, and only take on extra load if the other site is not available. In Windows Azure, you can use the Traffic Manager service top route the requests as a type of auto balancer. Even with these benefits, I recommend a second backup of storage in another geographic location. Storage is inexpensive; and that second copy can be used for not only HA but DR. Planning for HA in SaaS In Software-as-a-Service (such as Office 365, or Hadoop in Windows Azure) You have far less control over the HA solution, although you still maintain the responsibility to ensure you have it. Since each SaaS is different, check with the vendor on the solution for HA - and make sure you understand what they do and what you are responsible for. They may have no HA for that solution, or pin it to a particular geo, or perhaps they have a massive HA built in with automatic load balancing (which is often the case).   All of these options (with the exception of SaaS) involve higher costs for the design. Do not sacrifice reliability for cost - that will always cost you more in the end. Build in the redundancy and HA at the very outset of the project - if you try to tack it on later in the process the business will push back and potentially not implement HA. References: http://www.bing.com/search?q=windows+azure+High+Availability  (each type of implementation is different, so I'm routing you to a search on the topic - look for the "Patterns and Practices" results for the area in Azure you're interested in)

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  • Upcoming Speaking Engagements

    - by gsusx
    This summer, I took a brief break from speaking engagements to focus on shipping our new software in Tellago Studios and not stress my already hectic travel schedule. However, I’ve accepted a few invites to speak at different conferences during the fall and winter. Here is a brief list of the ones that are already confirmed: Software Architect Conference (London) http://www.software-architect.co.uk NodeJS for the .Net Developer I am a .NET developer but I have an iPhone and an Android Oredev (Malmö...(read more)

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  • What is the canonical resource on multi-tenancy web applications using ruby + rails

    - by AlexC
    What is the canonical resource on multi-tenancy web applications using ruby + rails. There are a number of ways to develop rails apps using cloud capabilities with real elastic properties but there seems to be a lack of clarity with how to achieve multitenancy, specifically at the model / data level. Is there a canonical resource on options to developing multitenancy rails applications with the required characteristics of data seperation, security, concurrency and contention required by an enterprise level cloud application.

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  • Creating a Corporate Data Hub

    - by BuckWoody
    The Windows Azure Marketplace has a rich assortment of data and software offerings for you to use – a type of Software as a Service (SaaS) for IT workers, not necessarily for end-users. Among those offerings is the “Data Hub” – a  codename for a project that ironically actually does what the codename says. In many of our organizations, we have multiple data quality issues. Finding data is one problem, but finding it just once is often a bigger problem. Lots of departments and even individuals have stored the same data more than once, and in some cases, made changes to one of the copies. It’s difficult to know which location or version of the data is authoritative. Then there’s the problem of accessing the data. It’s fairly straightforward to publish a database, share or other location internally to store the data. But then you have to figure out who owns it, how it is controlled, and pass out the various connection strings to those who want to use it. And then you need to figure out how to let folks access the internal data externally – bringing up all kinds of security issues. Finally, in many cases our user community wants us to combine data from the internally sources with external data, bringing up the security, strings, and exploration features up all over again. Enter the Data Hub. This is an online offering, where you assign an administrator and data stewards. You import the data into the service, and it’s available to you - and only you and your organization if you wish. The basic steps for this service are to set up the portal for your company, assign administrators and permissions, and then you assign data areas and import data into them. From there you make them discoverable, and then you have multiple options that you or your users can access that data. You’re then able, if you wish, to combine that data with other data in one location. So how does all that work? What about security? Is it really that easy? And can you really move the data definition off to the Subject Matter Experts (SME’s) that know the particular data stack better than the IT team does? Well, nothing good is easy – but using the Data Hub is actually pretty simple. I’ll give you a link in a moment where you can sign up and try this yourself. Once you sign up, you assign an administrator. From there you’ll create data areas, and then use a simple interface to bring the data in. All of this is done in a portal interface – nothing to install, configure, update or manage. After the data is entered in, and you’ve assigned meta-data to describe it, your users have multiple options to access it. They can simply use the portal – which actually has powerful visualizations you can use on any platform, even mobile phones or tablets.     Your users can also hit the data with Excel – which gives them ultimate flexibility for display, all while using an authoritative, single reference for the data. Since the service is online, they can do this wherever they are – given the proper authentication and permissions. You can also hit the service with simple API calls, like this one from C#: http://msdn.microsoft.com/en-us/library/hh921924  You can make HTTP calls instead of code, and the data can even be exposed as an OData Feed. As you can see, there are a lot of options. You can check out the offering here: http://www.microsoft.com/en-us/sqlazurelabs/labs/data-hub.aspx and you can read the documentation here: http://msdn.microsoft.com/en-us/library/hh921938

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  • What makes Erlang suitable for cloud applications?

    - by Duncan
    We are starting a new project and implementing on our corporations's instantiation of an openstack cloud (see http://www.openstack.org/). The project is security tooling for our corporation. We currently run many hundreds of dedicated servers for security tools and are moving them to our corporations instantiation of openstack. Other projects in my company currently use erlang in several distributed server applications, and other Q/A point out erlang is used in several popular cloud services. I am trying to convince others to consider where it might be applicable on our project. What are erlang's strengths for cloud programming? Where are areas it is particularly appropriate to use erlang?

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  • ERP/CRM Systems. Desktop Based ? Web based? [closed]

    - by Parhs
    I have seen 2-3 ERPs in action. I am wondering what is better. Desktop based application or webbased displayed on a browser. My first experience was with a web based ERP when i was 14 years old.. It was web based and terribly slow... For most simple task you had to do lots of clicks... no keyboard support ..... Pages took ages to load. Last year I worked for migrating to a newer computer some old terminal based cobol application. The computer that worked till today and still has no problem was from 1993. The user interface ofcourse was textbased.. The speed that guys placed orders was amazing! just typing the name of the customer , then 5-10 keys to add a product to order.... Comparing to this ERP the page for placing orders Link (click sales orders) seems terribly slow to add a product... No keyboard shortcut works to save what you added and generally I believe you need 4 times more time to place an order compared to the text interface... Having to use both mouse and keyboard for this task is BAD and sadistic... So how can the heck these people ever use a system like that ??? So in the long run desktop application seems the only way... Of course browsers support shortcuts but the way to overide the defaults that browsers uses isn't cross compatible... That is a huge problem. Finnaly, if we MUST/forced use cloud in near future what about keyboard shortcuts?? I feel confused... I have seen converters of desktop applications to browser applications but are SLOW as hell... The question is what about user friendliness? What kind of application would you use?

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  • How to manage many mobile device users at server side?

    - by Rami
    I built a social Android application in which users can see other users around them by GPS location. At the beginning thing went well as I had low number of users, but now that I have increasing number of users (about 1500 +100 every day) it has revealed a major problem in my design. In my Google App Engine servlet I have static HashMap that holds all the users profiles objects, currently 1500 and this number will increase as more users register. Why I'm doing it? Every user that requests for the users around him compares his GPS with other users and checks if they are in his 10km radius. This happens every five minutes on average. Consequently, I can't get the users from db every time because GAE read/write operation quota will tear me apart. The problem with this design is? As the number of users increases, the Hashmap turns to null every 4-6 hours, I think that this time is getting shorter, but I'm not sure. I'm fixing this by reloading the users from the db every time I detect that it becomes null, but this causes DOS to my users for 30 sec, so I'm looking for better solution. I'm guessing that it happens because the size of the hashmap. Am I right? I have been advised to use a spatial database, but that means that I can't work with GAE any more and it means that I need to build my big server all over again and lose my existing DB. Is there something I can do with the existing tools? Thanks.

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  • Creating a Corporate Data Hub

    - by BuckWoody
    The Windows Azure Marketplace has a rich assortment of data and software offerings for you to use – a type of Software as a Service (SaaS) for IT workers, not necessarily for end-users. Among those offerings is the “Data Hub” – a  codename for a project that ironically actually does what the codename says. In many of our organizations, we have multiple data quality issues. Finding data is one problem, but finding it just once is often a bigger problem. Lots of departments and even individuals have stored the same data more than once, and in some cases, made changes to one of the copies. It’s difficult to know which location or version of the data is authoritative. Then there’s the problem of accessing the data. It’s fairly straightforward to publish a database, share or other location internally to store the data. But then you have to figure out who owns it, how it is controlled, and pass out the various connection strings to those who want to use it. And then you need to figure out how to let folks access the internal data externally – bringing up all kinds of security issues. Finally, in many cases our user community wants us to combine data from the internally sources with external data, bringing up the security, strings, and exploration features up all over again. Enter the Data Hub. This is an online offering, where you assign an administrator and data stewards. You import the data into the service, and it’s available to you - and only you and your organization if you wish. The basic steps for this service are to set up the portal for your company, assign administrators and permissions, and then you assign data areas and import data into them. From there you make them discoverable, and then you have multiple options that you or your users can access that data. You’re then able, if you wish, to combine that data with other data in one location. So how does all that work? What about security? Is it really that easy? And can you really move the data definition off to the Subject Matter Experts (SME’s) that know the particular data stack better than the IT team does? Well, nothing good is easy – but using the Data Hub is actually pretty simple. I’ll give you a link in a moment where you can sign up and try this yourself. Once you sign up, you assign an administrator. From there you’ll create data areas, and then use a simple interface to bring the data in. All of this is done in a portal interface – nothing to install, configure, update or manage. After the data is entered in, and you’ve assigned meta-data to describe it, your users have multiple options to access it. They can simply use the portal – which actually has powerful visualizations you can use on any platform, even mobile phones or tablets.     Your users can also hit the data with Excel – which gives them ultimate flexibility for display, all while using an authoritative, single reference for the data. Since the service is online, they can do this wherever they are – given the proper authentication and permissions. You can also hit the service with simple API calls, like this one from C#: http://msdn.microsoft.com/en-us/library/hh921924  You can make HTTP calls instead of code, and the data can even be exposed as an OData Feed. As you can see, there are a lot of options. You can check out the offering here: http://www.microsoft.com/en-us/sqlazurelabs/labs/data-hub.aspx and you can read the documentation here: http://msdn.microsoft.com/en-us/library/hh921938

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  • What kind of hosting do I need?

    - by Robert Smith
    I migrated this question from serverfault. Hopefully this is the appropriate place. I have been trying to answer this question but I haven't found an specific answer to my situation. As I want to pay for what I need, I thought I could get a good answer here. I have a custom made forum (rather than a built-in forum like the ones you can find in plugins, e.g. WP-Forum or phpBB type of software) in Django. I don't want to use Apache and modwsgi because it's usually very memory-hungry and I can't afford a big server. I prefer a combination of nginx and gunicorn which I think is very efficient (maybe you can also tell me what you think about that). I'm expecting to receive 10,000 to 20,000 visits each month with 15,000 to 30,000 page impressions. I have reviewed some cloud services like Amazon EC2 or Rackspace and other more traditional services (Linodo). This site won't use videos or big images and I certainly don't need a huge amount of bandwidth (200GB would be definitely too much). I need shell access so shared hosting is out of the question. What do I need to run a website like that without problems? What about RAM? 256MB would be enough (that's the amount of RAM offered by small instances in Amazon and Rackspace)? Do you know of any alternative to those I mentioned? If you need more information to provide a useful answer, please don't hesitate to ask. By the way, I was told that Linodo is not all that different to Amazon EC2 but this website is supposed to work 24/7, so I can't take advantage of Linodo's flexibility regarding creating and deleting instances. Thanks in advance.

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  • Hosting and scaling of a facebook application on cloud?

    - by DhruvPathak
    We would be building a facebook application in django(Python), but still not sure of where to host it economically,and with a good provision to scale in case the app gets viral. Some details about the app: i) Would be HTML based like a website,using django as a framework. ii) 100K is the number of expected pageviews in a day,if the app is viral. iii) The users will not generate any media content,only some database data will be generated by them. It would be great if someone with more experience can guide on following points: A) Hosting on google app engine or Amazon EC2 or some other cloud like RackSpace : Preferable points found in AppEngine were ease of deployment,cost effectiveness and easy scaling. For EC2: Full hold of the virtual machine,Amazon NoSQL and RDMBS database services in case we decide to use them. B) Does backend technology affect monthly cost ? eg. would CPU and memory usage difference of Django over , for example , PHP framework like CodeIgnitor really make remarkable difference in running costs. ( Here is the article that triggered this thought process : http://journal.dedasys.com/2010/01/12/rough-estimates-of-the-dollar-cost-of-scaling-web-platforms-part-i#comments) C) Does something like Heroku , which provides additional services over Amazon EC2, prove to be better than raw cloud management ? It is not that we are trying for premature scaling, we just want to have a good start so that we are ready to handle unpredicted growth and scale.

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  • Any frameworks or library allow me to run large amount of concurrent jobs schedully?

    - by Yoga
    Are there any high level programming frameworks that allow me to run large amount of concurrent jobs schedully? e.g. I have 100K of urls need to check their uptime every 5 minutes Definitely I can write a program to handle this, but then I need to handle concurrency, queuing, error handling, system throttling, job distribution etc. Will there be a framework that I only focus on a particular job (i.e. the ping task) and the system will take care of the scaling and error handling for me? I am open to any language.

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  • How to rewrite a TCP MMOG server designed to run in a single machine, in a distributed way?

    - by Dokkat
    I have a MMOG server running on C++, using winsockets. My server won't support more than 200 players. I had the idea of redesigning it so it will use multiple servers instead of one, so, maybe, for example, each server could take care of a number of players, and, if it was too laggy, it could transfer the responsability of that player to other server. I'm not sure of how to program a consistent game logic like that, though. Are there techniques for this?

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  • Hosting and scaling a Facebook application in the cloud? [migrated]

    - by DhruvPathak
    We would be building a Facebook application in Django (Python), but still not sure of where to host it economically, and with a good provision to scale in case the app gets viral. Some details about the app: Would be HTML based like a website,using django as a framework. 100K is the number of expected pageviews in a day, if the app is viral. The users will not generate any media content, only some database data will be generated by them. It would be great if someone with more experience can guide on following points: A) Hosting on Google app engine or Amazon EC2 or some other cloud like RackSpace : Preferable points found in AppEngine were ease of deployment, cost effectiveness and easy scaling. For EC2: Full hold of the virtual machine,Amazon NoSQL and RDMBS database services in case we decide to use them. B) Does backend technology affect monthly cost? eg. would CPU and memory usage difference of Django over , for example , PHP framework like CodeIgnitor really make remarkable difference in running costs. (Here is the article that triggered this thought process : http://journal.dedasys.com/2010/01/12/rough-estimates-of-the-dollar-cost-of-scaling-web-platforms-part-i#comments) C) Does something like Heroku , which provides additional services over Amazon EC2, prove to be better than raw cloud management? It is not that we are trying for premature scaling, we just want to have a good start so that we are ready to handle unpredicted growth and scale.

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  • Combine auto-syncing cloud and VCS

    - by ComFreek
    This question brought me to another question: is there any VCS/tool for a VCS which automatically backups your source code between the last checkout and current changes? I had the problem of loosing uncommited source code changes just one week ago. I did not want to commit yet because the changes were incomplete. But then, an error when moving the data to an USB stick caused the data loss. That's the opposite what a cloud service (like Google Drive, SkyDrive, DropBox, ...) does: it tracks each change you made! Have you lost your data? That's no problem because you have the latest version online. So what would a combined solution look like? It would offer full functionality of a VCS including auto-syncing of any intermediate changes between two commits/checkouts to a temporary online location.

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  • Use a custom value object or a Guid as an entity identifier in a distributed system?

    - by Kazark
    tl;dr I've been told that in domain-driven design, an identifier for an entity could be a custom value object, i.e. something other than Guid, string, int, etc. Can this really be advisable in a distributed system? Long version I will invent an situation analogous to the one I am currently facing. Say I have a distributed system in which a central concept is an egg. The system allows you to order eggs and see spending reports and inventory-centric data such as quantity on hand, usage, valuation and what have you. There area variety of services backing these behaviors. And say there is also another app which allows you to compose recipes that link to a particular egg type. Now egg type is broken down by the species—ostrich, goose, duck, chicken, quail. This is fine and dandy because it means that users don't end up with ostrich eggs when they wanted quail eggs and whatnot. However, we've been getting complaints because jumbo chicken eggs are not even close to equivalent to small ones. The price is different, and they really aren't substitutable in recipes. And here we thought we were doing users a favor by not overwhelming them with too many options. Currently each of the services (say, OrderSubmitter, EggTypeDefiner, SpendingReportsGenerator, InventoryTracker, RecipeCreator, RecipeTracker, or whatever) are identifying egg types with an industry-standard integer representation the species (let's call it speciesCode). We realize we've goofed up because this change could effect every service. There are two basic proposed solutions: Use a predefined identifier type like Guid as the eggTypeID throughout all the services, but make EggTypeDefiner the only service that knows that this maps to a speciesCode and eggSizeCode (and potentially to an isOrganic flag in the future, or whatever). Use an EggTypeID value object which is a combination of speciesCode and eggSizeCode in every service. I've proposed the first solution because I'm hoping it better encapsulates the definition of what an egg type is in the EggTypeDefiner and will be more resilient to changes, say if some people now want to differentiate eggs by whether or not they are "organic". The second solution is being suggested by some people who understand DDD better than I do in the hopes that less enrichment and lookup will be necessary that way, with the justification that in DDD using a value object as an ID is fine. Also, they are saying that EggTypeDefiner is not a domain and EggType is not an entity and as such should not have a Guid for an ID. However, I'm not sure the second solution is viable. This "value object" is going to have to be serialized into JSON and URLs for GET requests and used with a variety of technologies (C#, JavaScript...) which breaks encapsulation and thus removes any behavior of the identifier value object (is either of the fields optional? etc.) Is this a case where we want to avoid something that would normally be fine in DDD because we are trying to do DDD in a distributed fashion? Summary Can it be a good idea to use a custom value object as an identifier in a distributed system (solution #2)?

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