I have this problem in which I need to compress (zip) multiple files from the web app (on the server) before streaming it down to the browser. I'm pulling the files from a separate service that connects to a SQL database. So there's a huge delay in opening the files from the service as well as a delay in compressing the files before the zipped package can be streamed to the browser. Ideally, I would like to have the DOWNLOAD button on the page make a call to a SignalR method on the server which will then push a notification back to the client once the multiple files are done compressing. That way, the browser won't request the server to stream the zipped file right away. It will only begin streaming once the multiple files are done compressing.
background info: I'm using IIS 7.5 and MVC 4.
I've been reading up and watching videos on SignalR, but have only seen examples of chat hubs and pushing to multiple clients, etc. Would it be possible to only use SignalR for the client that is making the request? And if so, I would appreciate some example code or perhaps a link to a tutorial on how one could accomplish something like this. Thanks!
To achieve what you need, you will have to define 3 clients
The Browser, it will call The Hub when a download is requested, then it will wait for a call from The Hub to download the files.
The Server, receives a notification from The Hub when the browser requests a download, and when all is ready calls The Hub to pass the files.
The Service, received the files from The Hub when its passed from The Server, and make the files ready for download, then send a notification to The Hub to inform The Browser.
Note
Storing large files in memory is not recommended, and passing it through SignalR is not as well, unless its the only way the server and the service can share the files, so if you have a common storage -Disk or Database- then its better to use it
Related
I have a question on how to make SSE worked in multiple server environments.
In UI, there are two steps:
1. source = new EventSource('http://localhost:3000/stream');
source.addEventListener('open', function(e) {
$("#state").text("Connected")
}, false);
user in UI can post to api to update data
after user post to api, server is sending event to UI to udpate UI
In one server environement, this worked perfect fine, no problem at all.
But in multi server instance environments, this won't be working. For example, I have two server instance, and UI subscribed to server 1, then server 1 is remembering the connection, but data update is from server 2, when data is changed, there is no connection for SSE in server 2. Then in this senario, how can server 2 send SSE to UI?
In order to make SSE working in multiple server environments, do we need to adopt any saving solution to save the connection information so that any server instance can send SSE accurately to UI?
Let me clarify this more:
yes, both service 1 and service 2 are behind load balancer, they do not have to have same URL. UI is pure frontend end application, can even be mobile app. So, if UI is sending a eventSource request to LB of server1, then only this instance can use this connection to send event back to UI, right? But if we have multiple instance of server 1, that means any server 1 instance other than current one can NOT send event back to UI.
I believe this is the limitation of SSE unless the connection can be shared among all the instances. But how.
Thanks
If you have two servers, with different URLs, make one SSE connection (from each client) to each server.
Be aware of CORS restrictions, i.e. the same origin policy. (It works identically to xhr2 CORS, so fairly easy to google; my book also covers it in detail, chapter 9.)
If you have two servers behind a load balancer, which is presenting a single URL to the clients, then you just have to make sure the load balancer is configured correctly. I.e. to always pass through that socket to the correct server. If a back-end server dies, and needs replacing, the load balancer should close the SSE socket; the client will then auto-reconnect, and get a new back-end server.
The multiple servers behind a load balancer, should either be having their own data push socket connections to a master data source, or should all be polling the master data source.
We have to develop a Java web service that is running on WebLogic Server 12.2.1 on a Windows Server 2008 R2 server. The web service allows clients to send files to it in BASE64 format, which the web service will then decode and then create actual files on the server with the decoded binary.
The server has Trend Micro OfficeScan Client installed, which I was told that it will scan for any file that is copied to the server. If the binary that I am writing to disk contains a virus, would the IO write fail immediately by the virus detection? I am not exactly sure when the virus scanning will take place. Is it immediately while a file is in the midst of being created on the server, or after a file has already been created on the server?
I need to know this because we want the web service to send an alert back to the client if the file that he sent contains a malware. Therefore how can the web service determine that no virus has been detected by Trend Micro OfficeScan Client?
Thanks.
If "realtime protection" option is enabled in the AV, then it will immediately detect the virus "after" the writing operation is completed.
The best way I can think of for your scenario, is to programmatically invoke the AV to scan the file, using command line options of the AV. Then, you'll know for sure that the AV has finished the scanning and get the scanning results as well.
I have a Web Server implemented using dot net MVC4. There are clients connected to this web server which perform some operations and upload live logs to the server using WebClient.UploadString method. Sending these logs from client to server is being done in group of 2500 characters at a time.
Things work fine until 2-3 client upload logs. However when more than 3 clients try to upload logs simultaneously they start receiving "http 500 internal server error".
I might have to scale up and add more slaves but that will make the situation worse.
I want to implement Jenkins like live logging, where logs from slave are updated live.
Please suggest some better and scalable solution to this problem.
Have you considered looking into SignalR?
It can be used for anything from instant messaging to stocks! I have implemented both a chatbox, and a custom system that sends off messages, does calculations and then passes them back down to client. It is very reliable, there are some nice tutorials, and I think it's awesome.
I'm designing a software system which has some C++ projects and java web applications hosted on Apache/Tomcat. Native code[C++ outputs] will connect to other systems[DB, External Gateways, etc] through web apps as HTTP requests. In order to make a good distributed/modular system, I'm planning to use several [5 to 10] web applications.
But still my system is not finished its developments, but function enough to sell. But even still 20% of its full features, I have to go through a huge deployment procedure since it has much of web apps.
My question is,
Is it good to merge few web apps TEMPORARILY to reduce deployment overhead[I can do this till I get a significant larger source for each] and do http requests within that same web application?
Will it be cause any performance/memory/threading issue?
if you are merging two or three web components and want to deploy an single jvm
than you should not use http request between web components,
for this you can use jboss osgi http://www.jboss.org/jbossas/subprojects/osgienter link description here
The solution I found was to use a hosted JVM, which is an application on either a Servlet container or in a web service.
This way, a single JVM is re-used.
But the problem here is that, you need a communication mechanism between two applications, which I prefer of using TCP sockets.
I am making a DR plan for a web application which is hosted on a production web server. Now that web server also acts as a file storage for storing the feed uploads files (used by the web application as input) and report files( output of web application processing). Now if the web server goes down , the files data is also lost, so need to design a solution and give recomendations which eliminates this single point of failiure.
I have thought of some recommendations as follows-
1) Use a seperate file server however it requires a new resources
2) Attach a data volume mounted on the web server which is mapped to some network filer ( network storage) which can be used to store the feeds and reports. In case the web server goes down , the network filer can be mounted and attached to the contingency web server.
3) There is one more web server which is load balanced however that is not currently being used as file storage , and if we can implement a feature which takes the back up of the file data regularly to that load balanced second web server , we can start using that incase the first web server goes down. The back up can be done through a back up script, or seperate windows service , or some scheduling job for scheduling the backup job every night.
Please help me to review above or suggest new recommendations to help eliminate this single point of failiure problem on the web server. It would be highly appreciated?
Regards
Kapil
I've successfully used Amazon's S3 to store the "output" data of web and non-web applications. Using a service like that is beneficial from the single-point-of-failure perspective because then any other instance of that web application, or a different type of client, on the same server or in a completely different datacenter still has access to the same output files. Another similar option is Rackspace's CloudFiles.
Both of these services are very redundant, and you could use them as the back, and keep the primary storage on your server, or use them as the primary and keep a backup on your other web server. There are lots of options! Hops this info helps.