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Tag: mta

CAP

[CAP] Timeout on long-running endpoint

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

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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

CAP

[CAP] Download MTA deployment logs after deployment

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With this simple command, you can download the MTA deployment logs of your recent deployment. Instead of manually having to use cf dmol -i <operation id>, just save the command (replace appId with your Id) as a shell script, make it executable (chmod +x) and run the script after your deployment. It stores the recent logs into the folder logs.

dmol is short for download-mta-op-logs

cf download-mta-op-logs --mta <appId> --last 1 -d logs

To just have a quick look at the recent logs, use

cf logs <appId>-srv --recent