SAP – nocin.eu

CAP

[CAP] Timeout on long-running endpoint

April 25, 2024 April 25, 2024

In my application, I have a function that can take quite a long time to process, depending on the data selected. Two external systems were involved in the processing, so a lot of round trips were made. Of course, I tried to parallelize the calls to the external systems as much as possible, but it still took a long time. During the development in BAS everything worked fine, but during the deployment in BTP I encountered some errors, depending on the amount of data selected.

In the console I could see, that it was a 504 Gateway Timeout.

Luckily, the CAP docs are already explaining the possible reason for this. The approuter has a default timeout of 30 seconds for destinations. This matched my observation, that this issue only occurred when deployed.

https://cap.cloud.sap/docs/get-started/troubleshooting#why-are-long-running-requests-rejected-with-status-504-after-30-seconds-even-though-the-application-continues-processing-the-request

https://www.npmjs.com/package/@sap/approuter#destinations

In my case, the destination for my backend service is configured in the mta.yaml directly on the approuter. By simply adding the timeout property and by increasing the timeout from 30 seconds to 2 minutes, I could get rid of the errors.

  - name: my-approuter
    type: approuter.nodejs
    path: app/approute
    build-parameters:
      builder: npm-ci
      ignore:
        - "node_modules/"
        - "default-env.json"
        - "manifest*.yml"
    requires:
      - name: srv-api
        group: destinations
        properties:
          name: srv-api 
          url: ~{srv-url}
          forwardAuthToken: true
          timeout: 120000 # <--------------------------------- add timeout to your cap service destination
      - name: my-xsuaa
      - name: my-destination
      - name: my-html5-repo-runtime

CAP

[CAP] Get subdomain in a multitenant scenario

April 22, 2024 April 22, 2024

Until recently, I was always decoded the JWT to get the subdomain of a subscribed tenant like this:

const jwt = retrieveJwt(req)
const subdomain = decodeJwt(jwt).ext_attr.zdn

I now noticed that you can also use the original request object and the getSubdomain function of the authInfo object. It’s provided by @sap/xssec and is only available when using XSUAA, means not with mocked authentication. This way you can get the subdomain in a single line:

const subdomain = req.http.req.authInfo.getSubdomain()

And there are some more helpful functions, that are documented here:

CAP

[CAP] Get service and approuter URLs of your running CAP application in a service handler

April 19, 2024 April 19, 2024

In your mta.yaml you can define environment variables, which are filled during deployment. They can be filled with MTA Development and Deployment Parameters. Click here for an overview.

To get the URL of your deployed CAP service, simply use the ${default-url} parameter and pass the value to a variable below the properties attribute, e.g. SRV_URL. The approuter has to provide its default-url, which can then be used in the service for a variable, e.g. APPROUTER_URL.

  #####################################################################################################################
  # Approuter
  #####################################################################################################################
  - name: approuter
    type: approuter.nodejs
    path: app/approuter
    provides: 
      - name: app-api 
        properties:
          app-url: ${default-url}   # <---------------------------- provides approuter url
          app-uri: ${default-uri}   # <---------------------------- provides approuter uri/hostname
          app-protocol: ${protocol} # <---------------------------- provides approuter protocol

  #####################################################################################################################
  # Business Service Module
  #####################################################################################################################
  - name: mySrv
    type: nodejs
    path: gen/srv
    requires:
      - name: app-api # <---------------------------------------- required to access the provided variables of the approuter
    properties:
      SRV_URL: ${default-url}
      APPROUTER_URL: ~{app-api/app-url}
      SUBSCRIPTION_URL: ~{app-api/app-protocol}://\${tenant_subdomain}-~{app-api/app-uri}

After deployment, you can now access the URL via process.env.SRV_URL in a service handler. During development, simply use the .env file to provide the SRV_URL value.

You can check all the variables via the BTP Cockpit: Subaccount → Space → Select application → User-Provided Variables

Fiori / SAPUI5

[SAPUI5] Add your own Logout functionality to the Launchpad Sandbox

April 3, 2024 April 3, 2024

Use the attachLogoutEvent of the ushell container to trigger your approuter logout endpoint, that needs to be configured in your xs-app.json. The code in my launchpad.html looks like this:

    <script>
        sap.ui.getCore().attachInit(() => {

            sap.ushell.Container.createRenderer('fiori2', true).then(renderer => renderer.placeAt("content"))

            sap.ushell.Container.attachLogoutEvent(e => {
                e.preventDefault()
                window.location.replace('/do/logout')
            }, false)

        })
    </script>

This way, you can reuse the default logout dialog logic the launchpad provides.

For completeness, find also my approuter configuration and custom logout page below.

My xs-app.json:

{
  "welcomeFile": "index.html",
  "authenticationMethod": "route",
  "logout": {
    "logoutEndpoint": "/do/logout",
    "logoutPage": "/logged-out.html"
  },
  "sessionTimeout": 60,
  "routes": [
    {
      "source": "^/logged-out.html$",
      "localDir": ".",
      "authenticationType": "none"
    },
    {
      "source": "^/launchpad.html$",
      "localDir": ".",
      "authenticationType": "xsuaa",
      "cacheControl": "no-cache, no-store, must-revalidate"
    },
    {
      "source": "^/appconfig/(.*)$",
      "localDir": ".",
      "authenticationType": "xsuaa"
    },
    {
      "source": "^/user-api(.*)",
      "target": "$1",
      "service": "sap-approuter-userapi",
      "authenticationType": "xsuaa"
    },
...
  ]
}

My logged-out.html file, placed in the approuter folder next to the launchpad.html:

<!DOCTYPE html>
<html>

<head>
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Logged out</title>
    <style>
        h2 {
            font-family: "Arial", sans-serif;
        }
        .centered {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
        }
    </style>
</head>

<body>
    <div class="centered">
        <h2>You are now logged out</h2>
    </div>
</body>

</html>

Fiori / SAPUI5

[SAPUI5] Enable Variant Management in Launchpad Sandbox

March 26, 2024 March 26, 2024

https://sapui5.hana.ondemand.com/sdk/#/topic/642dab291a7b47ec9d46c39b3c482aba

data-sap-ui-flexibilityServices='[{"connector": "LocalStorageConnector"}]'

CAP

[CAP] Select exists

March 25, 2024 March 25, 2024

So far I have not found a better/shorter way to check if a table entry exists than the following:

let exists = await SELECT(1).from(Books,201)
return (exists .length > 0) ? true : false

Found here: https://cap.cloud.sap/docs/node.js/cds-tx#cds-tx-ctx-fn

CAP, Fiori / SAPUI5

[SAPUI5] Add custom header parameter to all oData queries

March 22, 2024 March 22, 2024

Simply go to your Component.js file and add this line to the init function:

this.getModel().setHeaders({"myCustomParameter": "test"})

In a CAP Backend, you get this parameter from the express req object, which can be accessed via the req.http property:

req.http.req.headers['myCustomParameter']

And here is a nice code snippet, on how to read this header parameter in an ABAP system: https://answers.sap.com/answers/425621/view.html

Fiori / SAPUI5

[SAPUI5] Suppress default oData error message / display meaningful error messages

March 22, 2024 March 22, 2024

Create a separate ErrorHandler.js file, like it is described here and either do your own error handler implementation, or take the sample from here. To avoid displaying multiple errors at once, follow this chapter.

Thanks to the provided dsag sample, this is takes only a few minutes and improves the user experience a lot!

ABAP

[ABAP] xsdbool

March 8, 2024 March 8, 2024

Somehow I always forget that there is a boolean function in ABAP. That’s why I’m writing this post to hopefully remember it better. 🙂

If you just want to check something for truthiness, you can do it in the following three ways:

IF sy-subrc = 0.
  result = abap_true.
ELSE.
  result = abap_false.
ENDIF.

result = SWITCH #( sy-subrc WHEN 0 THEN abap_true
                                   ELSE abap_false ).

result = xsdbool( sy-subrc = 0 )

Fiori / SAPUI5

[SAPUI5] Set custom header logo in Launchpad Sandbox

March 7, 2024 March 26, 2024

If you are using the Launchpad Sandbox in your CAP project (like it is done here or here) and you want to change the logo in the header bar, simply add this little CSS snippet in the launchpad.html file:

    <style>
        #shell-header-icon {
            content: url("./logo.png");
        }
    </style>

Of course you could also provide a base64 encoded image:

    <style>
        #shell-header-icon {
            content: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAGGoAAAVNCAYAAAAIhfswAA...);
        }
    </style>