Update 24/07/2017 : when using the web dispatcher configuration below, the applications are all behind the same origin. The drawback of this is that the kernel of front- and backend server need to be the same version. See SAP Note 2477189 – SAP NetWeaver Gateway, ICM, Web Dispatcher, S/4HANA and Kernel compatibility info
An updated webdispatcher configuration where multiple origins are used is described in the 1709 UI Technology guide: https://help.sap.com/doc/61634ead9e5144b89e7eca2b1d4b8bce/1709%20000/en-US/UITECH_OP1709.pdf
The blog below is kept as a reference, please use the configuration from the UI Technology guide, chapter 3.7.2 instead of the configuration described in the blog below.
SAP Fiori applications are HTML5 applications based on the SAPUI5 java script library. They are made of a combination of resources like java script, html, xml, css and image files. At runtime they are downloaded first and after running locally in the client (end-users browser).
SAP Fiori applications retrieve or send updates to application data using OData calls provided by a SAP Gateway (aka frontend) server. OData is an open standard based on existing standards like HTTP, REST, XML, JSON and more. This frontend server provides data from SAP backends (this can be a S/4H, ERP, CRM or other system) via the OData format. However some Fiori apps also need Analytic or Enterprise Search data provided directly by the backend. Other apps launched from the Fiori Launchpad will need direct webdypro, web gui content be provided by the backend directly. See figure below:
A reverse proxy, like the SAP Web Dispatcher, needs to be placed in front of the front-end server and backend-server to route calls to the right server. Such reverse proxy is needed because of its capabilities like URL redirection and rewriting and adding certificate authentication. This reverse proxy can be hardware or a software application like the SAP Web Dispatcher.
If no reverse proxy some SAP Fiori apps like UI5 analytic apps will not work and no load balancing will be done in case multiple application servers are used.
In the next table a list of the routing mapping configuration needed in the reverse proxy for web traffic between a SAP Frontend and S/4H backend systems.
|/sap/bc/ui5_ui5/||Frontend||SAPUI5 Application Handler|
|/sap/bc/lrep||Frontend||LREP HTTP handler|
|/sap/opu/odata||Frontend||OData Standard Mode|
|/sap/bc/nwbc/||Frontend||NetWeaver Business Client|
|/sap/bc/bsp||Frontend||BUSINESS SERVER PAGES (BSP) RUNTIME|
|/sap/bc/webdynpro/||Backend||Web Dynpro (WD) Runtime|
|/sap/bc/gui/||Backend||ITS-Based GUI Services|
|/sap/bc/apc||Backend||ABAP Push Channel Framework|
|/sap/bw/Mime/DS/Content||Backend||MIME IN WEB REPORTING|
The above routing mapping would translate to the following Web Dispatcher configuration file —
!!! 10/2017 : depricated, please use UI Techology guide configuration !!
wdisp/system_0 = SID=XXX, MSHOST=FRONTEND-FQDN, MSPORT=XXXX, SSL_ENCRYPT=1, SRCSRV=*:44310, SRCURL=/sap/bc/ui5_ui5/;/sap/bc/ui2/;/sap/bc/lrep;/sap/opu/odata;/sap/bc/nwbc/;/sap/public/;/sap/bc/bsp;/sap/saml2
wdisp/system_1 = SID=XXX, MSHOST=S4HBACKEND-FQDN, MSPORT=XXXX, SSL_ENCRYPT=1, SRCSRV=*:44310, SRCURL=/sap/bc/webdynpro/;/sap/es/;/sap/bc/gui/;/sap/bc/apc;/sap/bw/ina;/sap/bw/Mime/DS/Content
This configuration is based on the Web Dispatcher configuration mentioned here, with some changes. https://blogs.sap.com/2016/10/12/sap-fiori-s4hana-10-lessons-learned-s4hana-1511-projects/
This configuration should be complete for most customers but there might still be specific cases not covered. Also a customer might, because of security reasons want to limit the urls redirected. Therefore the configuration is to be discussed and implemented together with the network and security experts from the customer.
The recommended deployment option for SAP Gateway is to use a separate server (aka central hub deployment), see http://go.sap.com/documents/2016/06/e8e53e50-767c-0010-82c7-eda71af511fa.html# . However it is also possible to deploy the SAP Gateway on the backend system (aka embedded deployment) In this case a reverse proxy is technically not needed but preferred for security reasons.
Note that earlier releases like SAP Suite on Hana, SFIN 1.0 and SFIN 2.0 need a different configuration. In this case some urls need to be redirected directly to the SAP Hana Database. This is not the case anymore in S/4H. http://help.sap.com/saphelp_hba/helpdata/en/5e/9d0c52bcc19b33e10000000a44538d/content.htm?frameset=/en/42/de5f52eddd6f2de10000000a44176d/frameset.htm
Some further related information:
The S/4HANA Fiori Foundation Configuration (MAA) also describes the Web Dispatcher installation and more. https://blogs.sap.com/2016/11/11/fiori-for-s4hana-getting-started-with-documentation/
Fiori frontend architecture when working with multiple clients in the backend. https://blogs.sap.com/2016/10/11/configure-fiori-multi-clients/
Hope this information provides some insight and can help in your next S/4HANA implementation project!
S/4HANA RIG team