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2963939 - IOException:Unable to tunnel through proxy. Proxy returns HTTP/1.1 503 Service Unavailable - Cloud Platform Integration (CPI)


  1. A CPI iflow which communicates with onPrem SAP ERP has failed one or multiple times in a given period with the following error details:

    Inbound processing in endpoint at {endpoint} failed with message "Fault:Sequential processing failed for number 0. Exchange[xyz]. Caused by: [org.apache.cxf.interceptor.Fault - Could not send Message.]", caused by "IOException:Unable to tunnel through proxy. Proxy returns "HTTP/1.1 503 Service Unavailable""

  2. You check the execution logs and observe the iflow is failing when communicating with the ERP endpoint:

Image/data in this KBA is from SAP internal systems, sample data, or demo systems. Any resemblance to real data is purely coincidental.



  • SAP SuccessFactors HXM Suite
  • SAP Cloud Platform Integration (CPI)


Cloud Integration all versions ; SAP ERP all versions ; SAP SuccessFactors HXM Suite all versions ; SAP SuccessFactors HXM Suite, integration for SAP ERP all versions


CPI, HCI, standard package, integration, exception, error, bib, failed, failing, communication

org.apache.cxf.interceptor.Fault: Could not send Message., cause: Unable to tunnel through proxy. Proxy returns "HTTP/1.1 503 Service Unavailable"
, KBA , LOD-SF-INT-CPI , Standard SF to 3rd Party CPI (HCI) Content , LOD-SF-INT , Integrations , Problem

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