ORA-29273: HTTP request failed intermittent error using the utl_http package

Resolving Intermittent ORA-29273: HTTP Request Failed in Oracle UTL_HTTP

Understand and troubleshoot the common ORA-29273 error when using Oracle's UTL_HTTP package, focusing on intermittent failures and best practices for robust web service calls.

The ORA-29273: HTTP request failed error is a common challenge for Oracle developers integrating with external web services using the UTL_HTTP package. While sometimes indicative of a clear network issue or an invalid URL, its intermittent nature often points to more subtle problems related to network configuration, resource limits, or server-side behavior. This article delves into the causes of intermittent ORA-29273 errors and provides practical solutions to enhance the reliability of your UTL_HTTP calls.

Understanding ORA-29273 and Its Intermittent Nature

The ORA-29273 error is a generic catch-all for various issues that can occur during an HTTP request initiated by UTL_HTTP. It essentially means that the underlying network or HTTP client library failed to complete the request successfully. When this error occurs intermittently, it suggests that the problem isn't a constant misconfiguration but rather something that fluctuates based on system load, network conditions, or the state of the target web service.

Common underlying causes for intermittent ORA-29273 include:

• Network Instability: Temporary packet loss, firewall drops, or routing issues between the Oracle database server and the target web service.
• Target Server Overload/Unavailability: The web service might be temporarily unresponsive, experiencing high load, or undergoing maintenance.
• Resource Exhaustion: The Oracle database server or the network infrastructure might be running out of resources (e.g., open file descriptors, network sockets) under heavy load.
• Proxy Issues: If a proxy server is involved, it might be intermittently failing or experiencing its own resource issues.
• SSL/TLS Handshake Failures: Intermittent issues with certificate validation, cipher suite negotiation, or revocation checks, especially in complex environments.
• DNS Resolution Problems: Temporary failures in resolving the hostname of the target web service.

flowchart TD
    A[Oracle Database] --> B{UTL_HTTP Request}
    B --> C{Network Path}
    C --> D{Firewall/Proxy}
    D --> E{Target Web Service}
    E -- Intermittent Failure --> F[ORA-29273]
    C -- Intermittent Failure --> F
    D -- Intermittent Failure --> F
    subgraph Potential Intermittent Failure Points
        C
        D
        E
    end

Flow of an HTTP request from Oracle and potential intermittent failure points.

Troubleshooting and Resolution Strategies

Addressing intermittent ORA-29273 errors requires a systematic approach, often involving collaboration between database administrators, network engineers, and application developers. Here are key strategies:

1. Implement Robust Error Handling and Retries

Since the error is intermittent, a simple retry mechanism can often resolve the issue without manual intervention. Implement EXCEPTION blocks to catch ORA-29273 and retry the UTL_HTTP call after a short delay.

2. Verify Network Connectivity and Configuration

Ensure that the Oracle database server can consistently reach the target web service. This involves checking firewalls, proxy settings, and DNS resolution.

3. Increase UTL_HTTP Timeout Values

Sometimes, the web service might be slow to respond, leading to a timeout. Increasing the UTL_HTTP timeout can give the service more time to process the request.

4. Monitor Target Web Service and Network Load

Coordinate with the web service provider or network team to monitor the health and load of the target service and the network path during periods when the error occurs.

5. Check Wallet and SSL/TLS Configuration

If using HTTPS, ensure that the Oracle Wallet is correctly configured, accessible, and contains valid certificates. Intermittent SSL handshake issues can cause this error.

6. Review Database and OS Resource Limits

Ensure that the Oracle database server and the underlying operating system have sufficient resources (e.g., open file descriptors, network buffers) to handle the expected load of UTL_HTTP requests.

DECLARE
    l_http_request  UTL_HTTP.req;
    l_http_response UTL_HTTP.resp;
    l_url           VARCHAR2(200) := 'http://example.com/api/data';
    l_response_text VARCHAR2(32767);
    l_retries       NUMBER := 3;
    l_delay_seconds NUMBER := 5;
BEGIN
    FOR i IN 1..l_retries LOOP
        BEGIN
            -- Set timeout (e.g., 60 seconds)
            UTL_HTTP.SET_TRANSFER_TIMEOUT(60);
            UTL_HTTP.SET_DETAILED_SQLCODE(TRUE);
            UTL_HTTP.SET_DETAILED_EXCP_SUPPORT(TRUE);

            l_http_request := UTL_HTTP.BEGIN_REQUEST(l_url, 'GET');
            -- Add headers if necessary
            -- UTL_HTTP.SET_HEADER(l_http_request, 'User-Agent', 'Mozilla/4.0');

            l_http_response := UTL_HTTP.GET_RESPONSE(l_http_request);

            -- Read response
            UTL_HTTP.READ_TEXT(l_http_response, l_response_text);
            DBMS_OUTPUT.PUT_LINE('Response: ' || l_response_text);

            UTL_HTTP.END_RESPONSE(l_http_response);
            EXIT; -- Success, exit retry loop
        EXCEPTION
            WHEN UTL_HTTP.END_OF_BODY THEN
                DBMS_OUTPUT.PUT_LINE('End of body reached.');
                UTL_HTTP.END_RESPONSE(l_http_response);
                EXIT; -- Treat as success if no more data
            WHEN UTL_HTTP.TOO_MANY_REDIRECTS THEN
                DBMS_OUTPUT.PUT_LINE('Too many redirects.');
                UTL_HTTP.END_RESPONSE(l_http_response);
                RAISE;
            WHEN UTL_HTTP.REQUEST_FAILED THEN
                DBMS_OUTPUT.PUT_LINE('HTTP Request Failed (UTL_HTTP.REQUEST_FAILED).');
                UTL_HTTP.END_RESPONSE(l_http_response);
                RAISE;
            WHEN OTHERS THEN
                IF SQLCODE = -29273 THEN
                    DBMS_OUTPUT.PUT_LINE('ORA-29273: HTTP request failed. Retrying in ' || l_delay_seconds || ' seconds... (Attempt ' || i || ')');
                    UTL_HTTP.END_RESPONSE(l_http_response);
                    IF i < l_retries THEN
                        DBMS_LOCK.SLEEP(l_delay_seconds);
                    ELSE
                        DBMS_OUTPUT.PUT_LINE('Max retries reached. Failing.');
                        RAISE; -- Re-raise after max retries
                    END IF;
                ELSE
                    DBMS_OUTPUT.PUT_LINE('An unexpected error occurred: ' || SQLERRM);
                    IF UTL_HTTP.IS_OPEN(l_http_response) THEN
                        UTL_HTTP.END_RESPONSE(l_http_response);
                    END IF;
                    RAISE;
                END IF;
        END;
    END LOOP;
EXCEPTION
    WHEN OTHERS THEN
        DBMS_OUTPUT.PUT_LINE('Final error: ' || SQLERRM);
        IF UTL_HTTP.IS_OPEN(l_http_response) THEN
            UTL_HTTP.END_RESPONSE(l_http_response);
        END IF;
END;
/

PL/SQL block demonstrating robust error handling and retry logic for UTL_HTTP requests.

Advanced Diagnostics and Monitoring

For persistent or hard-to-diagnose intermittent issues, more advanced diagnostics are necessary:

• Network Tracing: Use tools like tcpdump or Wireshark on the Oracle database server to capture network traffic during the failure. This can reveal connection resets, timeouts, or malformed packets.
• Oracle Trace Files: Check the database alert log and trace files for any related errors or warnings that might provide clues.
• Web Service Logs: Analyze the logs of the target web service for errors, connection drops, or performance bottlenecks at the time of the ORA-29273 error.
• Proxy Logs: If a proxy is in use, examine its logs for any indications of connection failures or rejections.
• UTL_HTTP Debugging: While not a full-fledged debugger, enabling detailed exception support (UTL_HTTP.SET_DETAILED_EXCP_SUPPORT(TRUE)) can sometimes provide more specific SQLCODE values or error messages within the ORA-29273 context.

1. Step 1: Enable Detailed UTL_HTTP Exceptions

Before making the UTL_HTTP call, add UTL_HTTP.SET_DETAILED_EXCP_SUPPORT(TRUE); and UTL_HTTP.SET_DETAILED_SQLCODE(TRUE); to get more specific error information in the SQLERRM or SQLCODE.

2. Step 2: Capture Network Traffic

During an intermittent failure, use tcpdump (Linux/Unix) or Wireshark (Windows/Linux) on the database server to capture network packets to and from the target web service's IP address. Analyze the capture for TCP resets, retransmissions, or HTTP error codes.

3. Step 3: Correlate Logs

Compare timestamps of ORA-29273 errors in Oracle logs with logs from firewalls, proxy servers, and the target web service to identify concurrent issues.