How a request goes from one server to another before sending response back to web browser?
When tried online, I got web browser to web server, but what about other servers like app server and Db server etc.?
Related
my use case is
I am trying to build an API that takes images as input and does some
image processing operations and return the output JSON back to the
client.
Multiple clients can concurrently request Server and as the server
does take 2 to 3 minutes time to process.
Initially I thought of a normal flask Application, where client
would poll the server for a response on a timely basis
But as Flask-SocketIO can respond back to the client event-based, I
want to use Flask-SocketIO
As the other APIs in my project are hosted on IIS, I wanted to use
the same IIS as the hosting server
my questions are
Can I use Flask-SocketIO for my use case, where API takes 2 to 3
minutes to respond back
If not IIS, how to deploy flask-socketIO on
the windows machine, I have gone through the documentation but I did
not find any deployment strategy for hosting it on windows machine
The best way to achieve concurrency in this case
Thanks in advance
Prasad.
I'm running a local web server written in Go and I can debug traffic going to it from my browser; but, I can't see the http request that it makes to external services.
Do I have to run some particular configuration of the web server in order to get the traffic to appear in fiddler? It is running as a background process.
Short answer: you can't...
...unless your web application is written to open a connection to a Proxy server and route requests through that connection (e.g. connect to a remote proxy, and then send requests through it).
Typically what developers do is just dump the Web Request/Response to a debug file to inspect during development (or to debug on a live server, by enabling it with a flag at runtime).
Fiddler is a "proxy" service/server. When you are using it normally to debug browser requests, your Browser is configured to connect to a Proxy server. That is, it will send all web requests through your fiddler's local server (I think it's localhost:8888 if i remember from my Windows days of using Fiddler) which in turn makes a connection to your local web server that you are debugging.
You can read more about Proxies at Wikipedia.
In that picture above, your local web server would be Alice. Meaning, Alice would need to be configured to connect to a proxy server and then make web requests through it.
EDIT:
(for the "I really need this" crowd)
If you really want to modify your web server to send requests through a proxy, there are a few Go packages already written to help you. GoProxy is one such package.
I have 3 Web API Servers which have the same functionality. I am going to add another Web API server which will be used only for Proxy. So All clients from anywhere and any devices will call Web API Proxy server and the Proxy server will transfer randomly the client requests to the other 3 Web API servers.
I am doing this way because:
There are a lot of client requests in a minute and I can not use only 1 Web API server.
If one server was dead, clients can still send request to the other servers. (I need at least 1 web servers response to the clients )
The Question is:
What is the best way to implement the Web API Proxy server?
Is there a better way to handle high volume client requests?
I need at least 1 web server response to the clients. If I have 3 servers and 2 of them are dead.
Please give me some links or documents that can help me.
Thanks
Sounds like you need a reverse proxy. Apache HTTP Server and NGINX can be configured to act as a load balanced reverse proxy.
NGINX documentation: http://nginx.com/resources/admin-guide/reverse-proxy/
Apache HTTP Server documentation: http://httpd.apache.org/docs/2.2/mod/mod_proxy.html
What you are describing is call Load Balancing and Azure (which seems you are using from your comments) provides it out of the box both for Cloud Services and Websites. You should create as many instances as you like under the same cloud service and open a specific port (which will be load balanced) under cloud service endpoints.
This is a general question based on how web sessions work across multiple servers, my knowledge around web sessions is not very deep but afaik a web session is typically stored directly in memory of the running web server application so when a request comes in it doesn't have to make database requests to fetch the session data. If a popular website needs multiple servers to handle the level of traffic it is receiving, when a request comes in I assume that it could get directed to any of the servers by some load balancer, but how does the server handling that request get the associated session data if the previous request was handled by a different server? do multi server sites require special session handling infrastructure, or do the load balancers know some how to route requests from the same client to the same server?
This question on ServerFault is the same as this question. with a good answer. in overview there are 3 common methods:
Session information stored in cookies only
Load balancer always directs user to the same machine
Shared backend database or key/value store.
See link for more indepth details of each.
Our Spring application is running on several different servers. For one of those servers POST requests do not seem to be working. All site functionality that uses GET requests works completely fine; however, as soon as I hit something that uses a POST request (ex. form submit) the site just hangs permanently. The server won't give any response. We can see the requests in Tomcat Manager but they don't time out.
Has anyone ever seen this?
We have found the problem. Our DBA accidentally deleted the MySQL database files on that particular server (/sigh). In our Spring application we use GET requests for record retrieval and the records we were trying to retrieve must have been cached by MySQL. This made it seem as if GET requests were working. When trying to add new data to the database, which we use POST requests to do, Tomcat would wait for a response, which never came, from MySQL.
In my experience if you're getting a timeout error it's almost always due to not having correct ports open for your application. For example, go into your virtual machine's rules and insure port 8080, 8443 or 80, 443 are open for http and https traffic.
In google cloud platform: its under VPC networking -> firewall rules. Azure and AWS are similar.