The anatomy of the Server site
When you finish installing Server, which you will be doing in the coming pages, you will have a placeholder for your services; this placeholder is called the site (hereafter known as Server site). It is where all the configurations are saved. A Server site has its own configurations, services, GIS servers, web servers, and even security parameters that can be managed independently. It is where services will be published and where applications will connect to consume those services.
Server site components
A Server site consists of two main components: the Web server, which accepts the requests, and the GIS server, which processes them.
A Web server hosts many websites. Each website listens on a unique port on the Web server address using the HTTP protocol. For instance, if your Web server IP address is 10.0.0.6, the default website will initially listen on port 80, which is the default HTTP port. Consequently, you can access the website from a browser address bar by typing http://10.0.0.6:80, and since 80 is the default port for HTTP, you can safely remove it from the URL and it will appear as http://10.0.0.6.
Note
HTTP
The Hypertext Transfer Protocol is a web protocol that deals with standards for rendering web pages on a web browser.
Port
A port is a virtual access entrance on a networked host machine that has a unique number on which connections can be established in order to exchange information between the host and remote machine.
Therefore, as long as the Web server 10.0.0.6 is accessible from a given network, you can access the website with any browser from any machine on that network. This is the main power of the Web server: install it in one place and access it from multiple locations using one address. We will explain how to set up a Web server in the Production Track.
A Web server is an essential part of an ArcGIS for Server installation. It receives client requests, translates them, forwards them to the GIS servers for processing, and then returns the results to the client. In a Web server, you can manage what clients should and should not access using customized security parameters, thus having more control over your content. In this book, we will be working with the Windows Web server Internet Information Services (IIS).
Starting with ArcGIS 10.1, Esri installs a hidden Web server along with each GIS server and creates a website listening on port 6080. We will discuss how to link this hidden Web server to a dedicated Web server on a different port in the Production Track.
The GIS server does all the background work to serve a request. It handles tasks such as spatial operations, querying data, analysis, calculating results, and executing geoprocessing tasks such as buffering geometries. The GIS server then returns the processed result to the Web server, which feeds the information to the client who requested it. The GIS server will connect to the Geodatabase. If you are using an Enterprise geodatabase, you have to make sure you have the client Database Management System (DBMS) installed and configured correctly in each GIS server.
The GIS server is also where all the services are running; thus, it will be the one which requires the most resources.
Server site management
A Server site can be managed by the primary administration account, which you will specify in the installation stage. Using the ArcGIS for Server Manager, which is a website that is installed with the Server and allows you to configure the Server site, you will be able to manage the following items in the Server site:
- Services
- Machines
- Output directories
- Configuration stores
- Clusters
- Data stores
- Extensions
- Logfiles
The preceding components are covered in the following sections.
A service is a functionality that exposes certain data to be consumed by remote connections by a request. The Services tab in ArcGIS for Server Manager allows you to manage existing services and add new ones, control what resources should be allocated to what services, monitor service affinity, and recycle those services which drain your resources. We have a dedicated chapter on how to author and publish map services.
The Machines option will allow you to manage GIS servers, add more GIS servers to a Server site, take down some servers for maintenance, and take the load off servers with low resources. The GIS servers are the backbone of your Server site; you need to monitor them regularly.
The output of your GIS server operations goes to output directories. It is important to make sure all your GIS servers have read/write access to these directories. You will learn how to do this later in the Master GIS server installation section under the Software installation section.
Your GIS servers work according to a blueprint that you have provided them with. Similar to the output directories, this set of instructions should be accessible at all times by your GIS servers.
Clustering in ArcGIS for Server is the process of grouping different machines together so that they can be treated as one unit. You can group your GIS servers into clusters to better manage your services. For instance, you may create a cluster and add your GIS servers with high resources (processor and memory) and name it Power cluster. Then create another cluster and add machines with lower specs and resources to it. You can then assign a high-affinity geoprocessing service to this Power cluster and your resourceful GIS servers will execute requests made to that service. This way, the other services can work comfortably on the default cluster. We will discuss more about clusters in Chapter 6, Clustering and Load Balancing.
GIS servers will occasionally require establishing connections to geodatabases. It is recommended that you register these databases in the data store, which we will be doing in Chapter 2, Authoring Web Services, so that your servers can connect to it. Otherwise, the data will have to be copied locally on each GIS server, which might introduce inconsistencies and performance penalties.
Just like ArcGIS for Desktop, ArcGIS for Server allows developers to customize server functionality and extend its capabilities. This option will allow you to register an extension to Server.
The Logfiles tab allows you to see how your GIS servers are doing, analyze the output logfiles on each server, and see what errors emerge so that you can fix them. You may measure the performance of a server by checking the response time between a request and the result. Chapter 8, Server Logs, is a dedicated chapter to learn all there is to know about logfiles.