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  • Block SMTP session with sender domain which doesn't itself accept SMTP connection.

    - by bignose
    I'm administrating a mail service for a small business. Their mail host's internet connection is an ADSL service with a permanent IP address. Unfortunately, many misconfigured mail systems will happily deliver to this host, but, when the host attempts to send mail back (e.g. a bounce notice, or a normal response from someone), the declared sender's domain has an MX which refuses to receive connections from this host. That misconfiguration makes their system a one-way mail sender, which is a problem. How can I configure Postfix on this customer's mail host to refuse SMTP sessions that declare a sender domain which itself refuses SMTP from this host? That is, if the SMTP client declares a domain that we can't make SMTP connections back to, then there's not much point accepting the incoming connection in the first place. Note that I'm not, as some commenters have assumed, talking about checking whether the SMTP client will receive messages. The check I want is whether the declared sender's domain (regardless of who the current SMTP client is) will accept SMTP connections from here. In other words: when we get around to sending a message back, we'll need the sender's domain to accept SMTP connections; I want to do that check before accepting the incoming session. I'm imagining a late check (after the low-cost checks to winnow most of the rubbish connections) that keeps the client on the other end while it attempts an SMTP client connection back to the declared domain of the sender. If that connection is rejected, the incoming one is also rejected. I'm also open to other suggestions for how this problem might be addressed (short of not using this mail host at all, which isn't an option).

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  • Block SMTP connections from mail domains which don't themselves accept SMTP connection.

    - by bignose
    I'm administrating a mail service for a small business. Their mail host's internet connection is an ADSL service with a permanent IP address. Unfortunately, many misconfigured mail systems will happily deliver to this host, but, when the host attempts to send mail back (e.g. a bounce notice, or a normal response from someone), the original sender refuses to receive connections from this host. That misconfiguration makes their system a one-way mail sender, which is a problem. How can I configure Postfix on this customer's mail host to refuse SMTP sessions that declare a sender domain which itself refuses SMTP from this host? That is, if the SMTP client declares a domain that we can't make SMTP connections back to, then there's not much point accepting the incoming connection in the first place. I'm imagining a late check (after the low-cost checks to winnow most of the rubbish connections) that keeps the client on the other end while it attempts an SMTP client connection back to the declared domain of the sender. If that connection is rejected, the incoming one is also rejected. I'm also open to other suggestions for how this problem might be addressed (short of not using this mail host at all, which isn't an option).

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  • DVD/CD burning .zip: is it more reliable, faster, longer lasting to burn a zip of files rather than the files as a folder?

    - by Rob
    Is it more reliable, faster, longer lasting to burn to CD/DVD a zip (or a few large zips) of files rather than the files as a folder? Just thinking if 1000s of small files would not be as efficiently recorded compared with one or a few large zips. Also, even after the burning program verifies the disc, I also use Beyond Compare to compare the files with those on the disc. Always binary compares as identical but I hear the drive stuttering presumably as the head is being shifted only slightly each time to seek the next file, which leads me to think that its best to make one or more zips and copy those locally to compare. Or is it that burning invidual files to the disc is not as readable which causes the head to stutter. There aren't any problems, my disc burns are reliable, just thinking more of efficiency and longevity, the discs burn and verify fast enough on my 18x DVD burner. I'm using ImgBurn mostly. Also used Nero in the past. I burn whole discs closed, finalised. Not sure which write mode but would think Disc At Once from a temporary cached image made by the burning program would be the most reliable.

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  • What's the most reliable (i.e. time-proof) solution for organizing photos?

    - by digitxp
    I pooled together my photos from an old external hard drive, various Picasa Web caches, flickr, flash drives, and an old computer. They're all on my external hard drive, using extremely creative labeling, like allpictures pixix pix2 images familyphotos and so on (hey, I was 7 when I organized them last). My computer's hard drive can die at any minute, and the external is new but who knows what that means? I am planning to start reorganizing these picture, probably by face or time. I have Bridge CS5, Picasa, etc., but which one is the most likely to not crash and burn like my Vista laptop did with a ZIP file filled with pictures of a funeral?

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  • redundant http load balancer

    - by jrydberg
    Got a simple scenario with two web servers for redundancy and to scale. But how do I make a two web-server setup fully redundant? I can think of two solutions; two web servers, one load balancer spreading the load. one extra machine for the load balancer. but how will the load balancer be redundant? two machines, each running the web server AND running a load balancer, spreading the load over. have a DNS entry point to both of the machines. no extra machines needed for load balancing. How do you guys normally solve this kind of problem?

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  • NO-SQL reliable for small bussines app?

    - by mamcx
    I'm deciding between go for a NON-SQL engine or a regular SQL one for a document managment system for small bussines. I have experience with firebird/sql server and found a good track of reliability (specially with firebird). This market is full of crappy "servers" (clon-made PC, the mayority), cheap harddisk, rarely use of RAID or anything like that, some are in locations where a power-off is normal, some not have a UPS, etc... (I will include off-site auto-backup to external servers, but that no change the internal setup). (I know about end-user education about such proper setups, but is stupid depend on that, so stick to te point) From the desing point of view, a schema-less database is the way to go for my system, but, I worry if any of the actual solutions (MongoDb, Tokyo Cabinet, etc) are like firebird and survice crash, malfunctions & abuse so data corruption is very rare. The plan is store the office documents there & provide a central repository.

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  • Force memcached to write to all servers in pool

    - by Industrial
    Hi everyone, I have thought a bit on how to make sure that a particular key is distributed to ALL memcached servers in a pool. My current, untested solution is to make another instance of memcached, something like this: $cluster['local'] = array('host' => '192.168.1.1', 'port' => '11211', 'weight' => 50); foreach ($this->cluster() as $cluster) { @$this->tempMemcache = new Memcache; @$this->tempMemcache->connect($cluster['host'], $cluster['port']); @$this->tempMemcache->set($key, $value, $this->compress, $expireTime); @$this->tempMemcache->close(); } What is common sense to do in this case, when certain keys need to be stored on ALL servers for reliability?

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  • CA2000 passing object reference to base constructor in C#

    - by Timothy
    I receive a warning when I run some code through Visual Studio's Code Analysis utility which I'm not sure how to resolve. Perhaps someone here has come across a similar issue, resolved it, and is willing to share their insight. I'm programming a custom-painted cell used in a DataGridView control. The code resembles: public class DataGridViewMyCustomColumn : DataGridViewColumn { public DataGridViewMyCustomColumn() : base(new DataGridViewMyCustomCell()) { } It generates the following warning: CA2000 : Microsoft.Reliability : In method 'DataGridViewMyCustomColumn.DataGridViewMyCustomColumn()' call System.IDisposable.Dispose on object 'new DataGridViewMyCustomCell()' before all references to it are out of scope. I understand it is warning me DataGridViewMyCustomCell (or a class that it inherits from) implements the IDisposable interface and the Dispose() method should be called to clean up any resources claimed by DataGridViewMyCustomCell when it is no longer. The examples I've seen on the internet suggest a using block to scope the lifetime of the object and have the system automatically dispose it, but base isn't recognized when moved into the body of the constructor so I can't write a using block around it... which I'm not sure I'd want to do anyway, since wouldn't that instruct the run time to free the object which could still be used later inside the base class? My question then, is the code okay as is? Or, how could it be refactored to resolve the warning? I don't want to suppress the warning unless it is truly appropriate to do so.

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  • How may I teach that SOAP is not a reliable transport?

    - by Eduardo
    I need to teach that a HTTP SOAP call may be received but the caller may not get the response due to a network failure (among other problems). (This problem made WS-ReliableMessaging be developed) How would you guys show this problem to a web service developer so they can develop taking into account that duplicate messages may be received?

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  • Can you safely rely upon Yahoo Pipes to offload ETL for your application?

    - by Daniel DiPaolo
    Yahoo Pipes are a very intriguing choice for sort of a poor-man's server-free ETL solution, but would it be a good idea to build an application around one or many Pipes? I've really only used them for toy things here and there, with the only thing I've used longer than a week or two being one amalgamated and filtered RSS feed that I've plugged into Google Reader (which has worked great, but if it goes out for a while I wouldn't notice). So, my question is, would building an application around Yahoo Pipes be reliable (available most of the time)? Ideally it'd be something I could rely on being up 99+% of the time. It looks like the Pipes Terms of Use permit building apps around it, but I am unfamiliar with anyone building anything significant using them.

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  • How much trust can I put behind a computer system? How can I measure trust?

    - by danmine
    How much trust can I put in a standard computer running windows? To what certainty can I be sure it will run my code the way I wrote it? How can I be sure that if I declare something like "int j = 5;", j will alway be 5? Is there a way to measure trust in a standard x86 computer system? What kind of protections are there to make sure that j = 5? I'm thinking about critical systems where nothing can be off even by one bit and everything must run exactly the way it was written to run.

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  • Building a life-critical System using Agile

    - by Ben Breen
    Looking at the general trend of comments in my question about Building an Aircraft using Agile, the biggest problem other than cost appears to be safety. Do people feel that it is not possible to build a safe system (or prove it is safe) using agile? Doesn’t all the iterative testing mitigate this? Is it likely that a piece of software developed using agile will never be as reliable as counterparts such as waterfall?

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  • Sending a large file over network continuously

    - by David Parunakian
    Hello, We need to write software that would continuously (i.e. new data is sent as it becomes available) send very large files (several Tb) to several destinations simultaneously. Some destinations have a dedicated fiber connection to the source, while some do not. Several questions arise: We plan to use TCP sockets for this task. What failover procedure would you recommend in order to handle network outages and dropped connections? What should happen upon upload completion: should the server close the socket? If so, then is it a good design decision to have another daemon provide file checksums on another port? Could you recommend a method to handle corrupted files, aside from downloading them again? Perhaps I could break them into 10Mb chunks and calculate checksums for each chunk separately? Thanks.

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  • What email providers have extremely high reliability and robust SLAs?

    - by Benjamin Manns
    My dad is a professor who does part-time law practice. He had been using his university email address for professional correspondence, when he found out that the university had permanently lost 16 business-related emails in their spam filter (with no apology, notification, or compensation). What I am looking for now is an email provider (preferably with Exchange, but not required) with very high reliability and a SLA that is basically an insurance policy. I have looked at Google Apps's SLA, but this will not suit. I am looking for a provider who will take $X per month in registration fees, and will: Alert me when there is any downtime. Promptly fix the issue Pay me a fee ($Y) whenever there is downtime. I want a significant, contractual reason for them to be diligent in their service. Free service for me is not enough.

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  • Are there any USB flash drives or SD cards which use RAID or redundant storage for additional reliability?

    - by Luke Dennis
    I'm looking to get a fault-tolerant USB flash drive, which saves data to multiple independent locations, whether using RAID or some other means to back up data. Has a product like this ever been created, or are my only options to hack something together? (By the way: I'm aware that RAID doesn't prevent data corruption from software or the file system. I'm just looking for something that can handle one of the memory sticks going dead.)

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  • How is dynamic memory allocation handled when extreme reliability is required?

    - by sharptooth
    Looks like dynamic memory allocation without garbage collection is a way to disaster. Dangling pointers there, memory leaks here. Very easy to plant an error that is sometimes hard to find and that has severe consequences. How are these problems addressed when mission-critical programs are written? I mean if I write a program that controls a spaceship like Voyager 1 that has to run for years and leave a smallest leak that leak can accumulate and halt the program sooner or later and when that happens it translates into epic fail. How is dynamic memory allocation handled when a program needs to be extremely reliable?

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  • Oracle eAM Webcast Series Announced (May-Dec 2010)

    - by [email protected]
    A series of free webinars with ReliabilityWeb will present key product capabilitiesof Oracle eAM and how they support maintenance and reliability best practices. Through this web-seminar series,companies can understand how to achieve better ROI. ReliabilityWeb will be using this as a key component of their initiative tobuild a stronger Oracle community.  For Oracle this program demonstrates leadership and commitment to the Maintenance SystemsMarketplace. Topics: (note all times are EAST)1. How can Oracle eAM enhance and support your reliability program? (May 13,2010) (1-2PM - all times East)) 2. Upgrading to Oracle eAM R12  - What's the value, when's the right time,what's involved and how do you get there? (June 17, 2010) (1-2PM) 3. Improving maintenance and reliability by aligning people, processes andsystems. (July 15, 2010) (1-2PM) 4. Using Oracle eAM to drive your Condition Based Maintenance program. (July29, 2010) (1-2PM) 5. Why and how do you get the power of Oracle eAM out to the people that arereally doing maintenance the technicians. (August 12, 2010) (1-2PM) 6. Standardizing and streamlining your maintenance work with Oracle eAM.(September 16, 2010 (1-2PM) 7. Standardizing maintenance and reliability data - How do you get there?(October 21, 2010 (1-2PM) 8. Using Oracle eAM to establish a Failure Reporting and Corrective ActionSystems (FRACAS). (November 18, 2010) (1-2PM)9. Maintenance Work Scheduling in Oracle eAM - Capabilities and Limitations(December 16, 2010) (1-2PM)to Register:   <http://img.gotomeeting.com/g2mimages/1x1.gif> <http://www1.gotomeeting.com/g2w/images/298420256/73664767535782300/embed.jpg>For additional information contact Jay West, EAM Master,+1.205.515.4326            

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  • invalid context 0x0 under iOS 7.0 and system degradation

    - by Alex
    I've read as many search results I could find on this dreaded problem, unfortunatelly, each one seems to focus on a specific function call. My problem is that I get the same error from multiple functions, which I am guessing are being called back from functions that I use. To make matters worse, the actual code is within a custom private framework which is being imported in another project, and as such, debugging isn't as simple? Can anyone point me to the right direction? I have a feeling I'm calling certain methods wrongly or with bad context, but the output from xcode is not very helpful at this point. : CGContextSetFillColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. : CGContextSetStrokeColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. CGContextSaveGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. : CGContextSetFlatness: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. : CGContextAddPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. : CGContextDrawPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. : CGContextRestoreGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. : CGContextGetBlendMode: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. Those errors may occur when a custom view is presented, or one of its inherited classes. At which point they spawn multiple times, until the keyboard won't provide any input. Touch events are still registered, but system slows down, and eventually may lead to unallocated object errors.

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  • Internet Protocol Suite: Transition Control Protocol (TCP) vs. User Datagram Protocol (UDP)

    How do we communicate over the Internet?  How is data transferred from one machine to another? These types of act ivies can only be done by using one of two Internet protocols currently. The collection of Internet Protocol consists of the Transition Control Protocol (TCP) and the User Datagram Protocol (UDP).  Both protocols are used to send data between two network end points, however they both have very distinct ways of transporting data from one endpoint to another. If transmission speed and reliability is the primary concern when trying to transfer data between two network endpoints then TCP is the proper choice. When a device attempts to send data to another endpoint using TCP it creates a direct connection between both devices until the transmission has completed. The direct connection between both devices ensures the reliability of the transmission due to the fact that no intermediate devices are needed to transfer the data. Due to the fact that both devices have to continuously poll the connection until transmission has completed increases the resources needed to perform the transmission. An example of this type of direct communication can be seen when a teacher tells a students to do their homework. The teacher is talking directly to the students in order to communicate that the homework needs to be done.  Students can then ask questions about the assignment to ensure that they have received the proper instructions for the assignment. UDP is a less resource intensive approach to sending data between to network endpoints. When a device uses UDP to send data across a network, the data is broken up and repackaged with the destination address. The sending device then releases the data packages to the network, but cannot ensure when or if the receiving device will actually get the data.  The sending device depends on other devices on the network to forward the data packages to the destination devices in order to complete the transmission. As you can tell this type of transmission is less resource intensive because not connection polling is needed,  but should not be used for transmitting data with speed or reliability requirements. This is due to the fact that the sending device can not ensure that the transmission is received.  An example of this type of communication can be seen when a teacher tells a student that they would like to speak with their parents. The teacher is relying on the student to complete the transmission to the parents, and the teacher has no guarantee that the student will actually inform the parents about the request. Both TCP and UPD are invaluable when attempting to send data across a network, but depending on the situation one protocol may be better than the other. Before deciding on which protocol to use an evaluation for transmission speed, reliability, latency, and overhead must be completed in order to define the best protocol for the situation.  

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  • How To Build An Enterprise Application - Introduction

    - by Tuan Nguyen
    An enterprise application is a software which fulfills 4 core quality attributes: Reliability Flexibility Reusability Maintainability Reliability is the ability of a system or component to perform its required functions under stated conditions for a specific period of time. Because there are no ways more than testing to make sure a system is reliability, we can exchange the term reliability with the term testability. Flexibility is the ability of changing a system's core features without violating unrelated features or components. Although flexibility can helps us to achieve interoperability easily but the opposite is not true. For example, a program might run on multiple platforms, contains logic for many scenarios but that wouldn't mean it was flexibility if it forces us rewrite code in all components when we just want to change some aspects of a feature it had. Reusability is the ability of sharing one or more system's components for another system. We should just open a component's reusability in the context in which it is used. For example, we write classes that implement UI logic and deliver them to only classes which implementing UI. Maintainability is the ability of adding or removing features to a system after it was released. Maintainability consists of many factors such as readability, analyzability, extensibility therein extensibility is critical. Maintainability requires us to write code that is longer and complexer than normal but it doesn't mean we introduce unneccessarily complex code. We always try to make our code clear and transparent to everyone. An application enterprise is built on an enterprise design which consists of two parts: low-level design and high-level design. At low-level design, it focuses on building loose-coupled classes or components. Particularly, it recommends: Each class or component undertakes only single responsibility (design based on unit test) Classes or components implement and work through interfaces (design based on contract) Dependency relationship between classes and components could be injected at run-time (design based on dependency) At high-level design, it focuses on architecting system into tiers and layers. Particularly, it recommends: Divide system into subsystems for deployment. Each subsytem is called a tier. Typical, an enterprise application would have 3 tiers as illustrated in the following figure: Arrange classes and components to logical containers called layers. Typical, an enterprise application would have 5 layers as illustrated in the following figure

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  • Best/Easiest Technology for a RESTful webservice [closed]

    - by user1751547
    So I'm going to be creating a phone app + website that will need to utilize a web service. Webservices are completely outside my domain so I'm not entirely sure where to start. Does anybody have any suggestions on the technology stack I should use? (mainly in terms of ease of use and reliability) So far what I've looked at are: RoR Python + Django + TastyPie Python + Flask Microsoft WCF 3.5 PHP + some framework I would rather not do anything with Java I'm leaning towards the Python + Django + TastyPie route as it seems like it would be easy to get up and going and learn in general. My only concern with it is the reliability of the libraries (feature breaking updates, abandonment, etc). Also I would prefer to create the website with the same framework so I wouldn't have to deal with learning and using two different ones. Any advice would be helpful, thanks.

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