Timeouts in COBOL

In COBOL, implementing timeouts is not as straightforward as in more modern languages. However, we can simulate a similar behavior using the CALL statement with the ON EXCEPTION clause. This allows us to set a timeout for external program calls.

IDENTIFICATION DIVISION.
PROGRAM-ID. TIMEOUTS-EXAMPLE.

ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
SPECIAL-NAMES.
    CONSOLE IS CRT.

DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-TIMEOUT    PIC 9(4) VALUE 1000.
01 WS-RESULT     PIC X(20).

PROCEDURE DIVISION.
MAIN-PROCEDURE.
    DISPLAY "Starting timeout example...".

    *> Simulate first operation with 2-second delay
    MOVE 2000 TO WS-TIMEOUT.
    CALL "EXTERNAL-OPERATION" USING WS-RESULT
        ON EXCEPTION
            DISPLAY "Timeout 1"
        NOT ON EXCEPTION
            DISPLAY WS-RESULT
    END-CALL.

    *> Simulate second operation with 3-second timeout
    MOVE 3000 TO WS-TIMEOUT.
    CALL "EXTERNAL-OPERATION" USING WS-RESULT
        ON EXCEPTION
            DISPLAY "Timeout 2"
        NOT ON EXCEPTION
            DISPLAY WS-RESULT
    END-CALL.

    STOP RUN.

In this COBOL example, we’re simulating the concept of timeouts using the CALL statement with the ON EXCEPTION clause. Here’s how it works:

1. We define a WS-TIMEOUT variable to hold the timeout value in milliseconds.

2. For each operation, we set the appropriate timeout value (2000ms for the first, 3000ms for the second).

3. We use the CALL statement to invoke an external program called “EXTERNAL-OPERATION”. This simulates the asynchronous operations in the original example.

4. The ON EXCEPTION clause acts as our timeout handler. If the external program doesn’t complete within the specified timeout, the ON EXCEPTION code is executed.

5. If the operation completes successfully, the NOT ON EXCEPTION code is executed, which displays the result.

Note that COBOL doesn’t have built-in support for concurrency like goroutines or channels. The CALL statement here is blocking, and the timeout functionality would need to be implemented in the operating system or the COBOL runtime.

To run this program, you would compile it and then execute it:

$ cobc -x timeouts.cob
$ ./timeouts
Starting timeout example...
Timeout 1
Result 2

This output assumes that the first operation times out (as it would take longer than the 1-second timeout), while the second operation completes successfully within the 3-second timeout.

Remember that the exact behavior may vary depending on your COBOL implementation and the actual “EXTERNAL-OPERATION” program. This example provides a conceptual equivalent to the original timeout logic, adapted to COBOL’s capabilities.