My customer has 2 Windows Server 2019.
On both of them, an instance of a SOAP Web Service is running.
URLs:
https://host1.domainname.com/SOAPService
and
https://host2.domainname.com/SOAPService
Now, the requirement of the customer is to provide a single, unique URL that the clients can use to consume the SOAP WebService(s).
I read through several websites and if I got it right, I need a tool that is called "reserve proxy"... Using this tool, clients can access the webservice by using an URL such as https://host.domainname.com/SOAPService and the tool will automatically route the request to the available webservice.
Correct?
I also have an architectural question:
On which machine do I have to run such a Reserve Proxy?
Is it on host1 or host2 or do I need a dedicated machine (like a supervisor)?
If it is a dediciated machine, how can I apply high availability of this Reverse Proxy? E.g. is it possible to run 2 Reserve Proxies in parallel on different machines? Which tool could afford this?
Thanks
At present we have a lot of ASP.net WebAPI service applications hosted on premises. We are planning to move these to Azure AKS. We've identified a lot of common code across these applications which is mostly implemented as ASP.Net reusable middleware components so that the logic is not duplicated in code.
In a K8s environment it makes sense to offload this common functionality to one or more proxy applications which intercepts the requests being forwarded from the ingress to the services (assuming this is the correct approach). Some of the request inspection / manipulation logic is based on the service host and path to be defined in the ingress and even on the headers in the incoming requests.
For e.g. I considered using OAuth2_proxy but found that even though authentication is quite easy to implement, Azure AD group based authorization is impossible to do out of the box with that. So what's the idiomatic way one goes about setting up such a custom proxy application? (I'm familiar with using libraries such as ProxyKit middleware in ASP.Net to develop http proxies.)
One approach that comes to mind is to deploy such proxies as sidecar containers in each service application pod but that would mean there'd be unnecessary resource usage by all such duplicate container instances in each pod. I don't see the benefit over the use of middleware components as mentioned previously. :(
The ideal setup would be ingress --> custom proxy 1 --> custom proxy 2 --> custom proxy n --> service where custom proxies would be separately deployable and scalable.
So after a lot of reading and googling I found that the solution was to use API Gateways that are available as libraries (preferrably based on .Net):
Ocelot placed behind the nginx ingress fits the bill perfectly
Ocelot is a .NET API Gateway. This project is aimed at people using .NET running a micro services / service oriented architecture that need a unified point of entry into their system. However it will work with anything that speaks HTTP and run on any platform that ASP.NET Core supports.
Ocelot is currently used by Microsoft and Tencent.
The custom middleware and header/query/claims transformation solves my problem. Here are some worthy links
Microsoft Docs: Implement API Gateways with Ocelot
Ocelot on Github
Ocelot Documentation
Features
A quick list of Ocelot's capabilities for more information see the documentation.
Routing
Request Aggregation
Service Discovery with Consul & Eureka
Service Fabric
Kubernetes
WebSockets
Authentication
Authorisation
Rate Limiting
Caching
Retry policies / QoS
Load Balancing
Logging / Tracing / Correlation
Headers / Query String / Claims Transformation
Custom Middleware / Delegating Handlers
Configuration / Administration REST API
Platform / Cloud Agnostic
I am developing a website using which is based on a microservices architecture which is containerized with docker. Now I want to communicate with microservices using rest API. I read some articles which show some diagrams that API gateway make some connections to microservices. I am confused about the main purpose of the API gateway.
Gateways are used for cross cutting concerns like authentication, logging and redirect to respective backend services. They are usual the single point of entry for applications and are exposed publicly. the rest of the services can sit behind the firewall that your gateway has access to making backend services secure. you also write your resiliency logic in the gateway by implementing retry or circuit breaker patterns etc.
Since gateway has advantages but it can be single point of failure. so make sure it's highly available by deploying redundant copies
I got a webservice endpoint and I stumple upon how to correctly implement it.
It seems to be an parameterized exe-file which returns an XML Reply.
There is no documentation.
I am used to soap, wcf and rest but this is completely unknown to me, has anyone a guide or a best case how to implement such a service?
I can consume it with a HTTP GET but there are some questions left to me:
I know the questions are quite broad... But I could not find anything about it in the interwebz.
Is there a secure way to publish exe files as webservice?
Are there any critical downsides implementing such an interface?
Make I myself a fool and this is just an alias?
Example Url:
http://very.exhausting.company/Version/SuperStrange.exe?parameter=String
Web servers
What you call a webservice endpoint is nothing else than a web server listening on some host (normally 0.0.0.0) and some port on a physical or virtual machine and responding with some HTTP response to HTTP requests sent to that host, port and URIs that the web server cares to process.
Any web server is itself an application or a static or dynamic component of an application as the following examples illustrate:
JBoss, Glassfish, Tomcat etc. are applications, known as application servers, into which containers/servlets/plugins implementing web servers and corresponding endpoints are deployed. These listen on some port exposing generic web servers routing requests to those containers and their servlets;
a fat jar started with java -jar on a JVM which deploys a vert.x verticle featuring a vert.x HttpServer listening on some port is nothing else than a web server;
an interpreter such as node.js parsing and executing JavaScript code based on the express module will most likely deploy a web server on some port;
finally, a statically or dynamically linked application written in languages such as C++ or Go can expose a web server listing on some port.
All of the above cases feature different deployment mechanisms, but what they deploy is essentially the same: a piece of software that listens for HTTP requests on some port, executes some logic based on request and returns HTTP responses to the caller.
Your windows exe file is most likely a statically linked application that provides a web server.
Protocols
So we know you have a web server as it reacts to an HTTP GET. How does it relate to REST, SOAP etc? Effectively, REST, SOAP etc are higher level protocols. TCP is the low level, HTTP is based on top of that and your server supports that. REST, SOAP and everything else that you mention are higher level protocols that are based, among others, on HTTP. So all you know is that your application (web server) supports HTTP, but you do not know which higher level data exchange protocol it implements. It definitely implements some, at least a custom one that its author came up with to exchange data between a client and this application.
You can try to reverse engineer it, but it is not clear how would you find out about all possible endpoints, arguments, payload structures, accepted headers etc. Essentially, you have a web server publishing some sort of an API, but there is no generic way of telling what that API is.
Security
The world around you does not have to know how the API is published. You can put any of the above 4 web server implementations behind exactly the same firewall or a reverse proxy with SSL termination exposing just one host and port over SSL. So there is no difference in security, with respect to the world, whether you deploy it as exe or as a war into JBoss. This is not to say, that your exe file is secure: depending on how it is implemented it may allow all sorts of attacks, but again, this is equally true for any mechanism.
After watching the BUILD conference videos for Azure Service Fabric, I'm left imagining how this might be a good fit for our current microservice-based architecture. There is one thing I'm not entirely sure how I would go about solving, however - the API gateway/proxy.
Consider a less-than-trivial microservice architecture where you have N number of services running within the Azure Service Fabric exposing REST endpoints. In many situations, you want to package these fragmented API endpoints up into a single-entry API for consumers to use, to avoid having them connecting to the service fabric-instances directly. The Azure Service Fabric solution seems so complete in every way that I'm sort of wondering if I missed something obvious when I don't see a way to trivially solve this within the capabilities mentioned during the BUILD talks.
Services like Vulcan aim to solve this problem by having the services register the paths they want routed to them in etcd. I'm guessing one way of solving this may be to create a separate stateful web service that other services can register themselves with, providing service name and the paths they need routed to them. The stateful web service can then route traffic to the correct instance based on its state. This doesn't seem entirely ideal, though, with stuff like removing routes when applications are removed and generally keeping the state in sync with the services deployed within the cluster. Has anybody given this any thought, or have any ideas how one might go about solving this within Azure Service Fabric?
The service registration/discoverability you need to do this is actually already there. There's a stateful system service called the Naming Service, which is basically a registrar of service instances and the endpoints they're listening on. So when you start up a service - either stateless or stateful - and open some listener on it, the address gets registered with the Naming Service.
Now the part you'd need to fill in is the "gateway" that users interact with. This doesn't have to be stateful because the Naming Service manages the stateful part. But you'd have to come up with an addressing scheme that works for you, and then it would just forward requests along to the right place. Basically something like this:
Receive request.
Use NS to find the service that can take the request.
Forward the request to it and the response back to the user.
If the service doesn't exist anymore, 404.
In general we don't like to dictate anything about how your services talk to each other, but we are thinking of ways to solve this problem for HTTP as a complete built-in solution.
We implemented a HTTP gateway service for this purpose as well. To make sure we can have one HTTP gateway for any internal protocol, we implemented the gateway for HTTP based internal services (like ASP.NET WebAPIs) using an ASP.NET 5 middleware. It routes requests from e.g /service to an internal Service Fabric address like fabric:/myapp/myservice by using the ServicePartitionClient and some retry logic from CommunicationClientFactoryBase.
We open-sourced this middleware and you can find it here:
https://github.com/c3-ls/ServiceFabric-HttpServiceGateway
There's also some more documentation in the wiki of the project.
This feature is build in for http endpoints, starting with release 5.0 of service fabric. The documentation is available at https://azure.microsoft.com/en-us/documentation/articles/service-fabric-reverseproxy/
We have used an open source project called Traefik with amazing success. There is an Azure Service Fabric wrapper around it - it's essentially a GoLang exe that is deployed onto the cluster as Managed Executable.
It supports circuit breakers, weighted round robin LB, path & header version routing (this is awesome for hosting multiple API versions), the list goes on. And its got a handy portal to view the config and health stats.
The real power in it lies in how you configure it. It's done via the service itself in the ServiceManifest.xml. This allows you to deploy new services and have them immediately able to be routed to - no need to update a routing table etc.
Example
<StatelessServiceType ServiceTypeName="WebServiceType">
<Extensions>
<Extension Name="Traefik">
<Labels xmlns="http://schemas.microsoft.com/2015/03/fabact-no-schema">
<Label Key="traefik.frontend.rule.example">PathPrefixStrip: /a/path/to/service</Label>
<Label Key="traefik.enable">true</Label>
<Label Key="traefik.frontend.passHostHeader">true</Label>
</Labels>
</Extension>
</Extensions>
</StatelessServiceType>
Highly recommended!
Azure Service Fabric makes it easy to implement the standard architecture for this scenario: a gateway service as a frontend for the clients to connect to and all the N backend services communicating with the front end gateway. There are a few communication API stacks available as part of Service Fabric that make it easy to communicate from clients to services and within services themselves. The communication API stacks provided by Service Fabric hide the details of discovering, connecting and retrying connections so that you can focus on the actual exchange of information. When using the Service Fabric communication APIs the services do not have to implement the mechanism of registering their names and endpoints to a specific routing service except what are the usual steps as part of creating the service itself. The communication APIs take in the service URI and partition key and automatically resolve and connect to the right service instance. This article provides a good starting point to help make a decision with regards to which communication APIs will be best suited for your particular case depending on whether you are using Reliable Actors or Reliable Services, or protocols such as HTTP or WCF, or the choice of programming language that the services are written in. At the end of the article you will find links to more detailed articles and tutorials for different communication APIs. For a tutorial on communication in Web API services see this.
We are using SF with a gateway pattern and about 13 services behind the gateway. We use the built in DNS service that SF provides, see: https://learn.microsoft.com/en-us/azure/service-fabric/service-fabric-dnsservice, this allows the internal service to service calls with known (internal to SF) DNS names, including gateway service to internal services. There are some well known asp.net core gateways (Ocelot, ProxyKit) to use, but we rolled our own. We have an external load balancer to route to multiple gateway instances in SF.
When a service is started, it registers it's endpoint with the fabric naming service. Using the Fabric client APIs you can then ask fabric for the registered endpoints, associated with the registered service name.
So yes, just as you described your case, you would have a gateway that would accept an incoming URI for connection, and then use that path information as the service name lookup, to then create a proxy connection between the incoming request and the actual internal endpoint location.
Looks like the team as posted one the samples that shows how to do this: https://github.com/Azure/servicefabric-samples/tree/master/samples/Services/VS2015/WordCount