amazon web services - designing for failure when polling/retrying/queueing is not possible -

-

i'm designing website/web service hosted in cloud (specifically aws although that's irrelevant), , i'm spending lot of time thinking "designing failure". want system seamlessly handle node failures, i.e. without significant user impact or engineer intervention.

in cases, it's easy see how handle sudden node failure. if app has api handled 4 servers behind load balancer, polled ajax or iphone app, poller can detect failed tcp/ip transmission , retry... assuming load balancer behaves correctly, hit healthy instance.

if app more processing-oriented, queue service sqs can used allow stateless nodes pick failed nodes left off.

the difficulty see "points of entry", no retry/polling possible because application hasn't been loaded yet, , failure means app never starts. example, index.html on webpage... if node fails while transmitting file, user's browser hang , not automatically retry (they need refresh).

the load balancer single "point of entry/failure". however, in case appears can solve problem creating multiple load balancers, , load balancing them using dns load balancing described here: http://blog.rightscale.com/2012/10/23/dns-load-balancing-and-using-multiple-load-balancers-in-the-cloud/

is solution work simpler index.html case? overall, how can create redundancy polling/retrying/queuing not possible?

edit: idea have index.html hosted statically on cdn, s3, etc (where resource availability more dependable), although prevents using dynamic content. dynamic content added if page populates using js, adds dependency on js latency user.


Comments

Post a Comment

Popular posts from this blog

android - getbluetoothservice() called with no bluetoothmanagercallback -

-
i getting getbluetoothservice() called no bluetoothmanagercallback error in android application. i have no idea causing or bluetooth manager callbacks. can give me idea of causing problem or start looking. by reading android source code, seems warning cannot about. source code shows if call bluetoothsocket#connect(); then call bluetoothadapter.getdefaultadapter().getbluetoothservice(null); the key here, null parameter passes in above line. due this, there no callback, , bluetoothsocket class throw out warning. since warning, not think need it. https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/bluetooth/bluetoothsocket.java line 306 https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/bluetooth/bluetoothadapter.java line 1610
Read more

sql - ASP.NET SqlDataSource, like on SelectCommand -

-
i'm working on asp.net. have sqldatasource query hardcoded on selectcommand: <asp:sqldatasource id="datasource1" runat="server" cancelselectonnullparameter="false" connectionstring="<%$ connectionstrings:s.properties.settings.connectionstring %>" selectcommand="select * [table] ([col1] case @col1_param when null col1 else @col1_param end) , ([col2] case @col2_param when null col2 else @col2_param end)" selectcommandtype="text"> <selectparameters> <asp:controlparameter controlid="textbox1" name="col1_param" propertyname="text" type="string" /> <asp:controlparameter controlid="textbox2" name="col2_param" propertyname="text" type="string" /> </selectparameters> what want if enter data on 1 textbox only, data display according textbox
Read more

ios - Undefined symbols for architecture armv7: "_OBJC_CLASS_$_SSZipArchive" -

-
i try using extractzipfile plugin @ this: https://github.com/phonegap/phonegap-plugins/tree/master/ios/extractzipfile but when compiler xcode 4.6.1 in sdk 6.1 throws error: undefined symbols architecture i386: "_objc_class_$_ssziparchive", referenced from: objc-class-ref in extractzipfileplugin.o ld: symbol(s) not found architecture i386 clang: error: linker command failed exit code 1 (use -v see invocation) i try issue @ here: undefined symbols architecture armv7 ssziparchive but shows error: /users/alienware/desktop/extractzipfile/ssziparchive/tests/ssziparchivetests.m:10:9: 'sentestingkit/sentestingkit.h' file not found i work phonegap , make app in ios, dump. update : try add ssziparchive.m compiler source , come new error: undefined symbols architecture i386: "_unzclose", referenced from: +[ssziparchive unzipfileatpath:todestination:overwrite:password:error:delegate:] in ssziparchive.o "_unzclosecurrentfil
Read more