Rate Limiting in COBOL

Rate limiting is an important mechanism for controlling resource utilization and maintaining quality of service. COBOL can implement rate limiting using timers and file handling.

       IDENTIFICATION DIVISION.
       PROGRAM-ID. RATE-LIMITING.
       ENVIRONMENT DIVISION.
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT REQUEST-FILE ASSIGN TO "REQUESTS.DAT"
               ORGANIZATION IS LINE SEQUENTIAL.

       DATA DIVISION.
       FILE SECTION.
       FD REQUEST-FILE.
       01 REQUEST-RECORD.
           05 REQUEST-NUMBER PIC 9(5).

       WORKING-STORAGE SECTION.
       01 WS-EOF             PIC X VALUE 'N'.
       01 WS-CURRENT-TIME    PIC 9(8).
       01 WS-LAST-TIME       PIC 9(8) VALUE 0.
       01 WS-TIME-DIFF       PIC 9(8).
       01 WS-DELAY           PIC 9(8) VALUE 200.

       PROCEDURE DIVISION.
       MAIN-PROCEDURE.
           OPEN INPUT REQUEST-FILE.
           PERFORM PROCESS-REQUESTS UNTIL WS-EOF = 'Y'.
           CLOSE REQUEST-FILE.
           STOP RUN.

       PROCESS-REQUESTS.
           READ REQUEST-FILE
               AT END
                   MOVE 'Y' TO WS-EOF
               NOT AT END
                   PERFORM RATE-LIMIT
                   DISPLAY "Request " REQUEST-NUMBER 
                           " processed at " WS-CURRENT-TIME.

       RATE-LIMIT.
           ACCEPT WS-CURRENT-TIME FROM TIME.
           COMPUTE WS-TIME-DIFF = WS-CURRENT-TIME - WS-LAST-TIME.
           IF WS-TIME-DIFF < WS-DELAY
               CALL "CBL_OC_NANOSLEEP" USING WS-DELAY
           END-IF.
           MOVE WS-CURRENT-TIME TO WS-LAST-TIME.

In this COBOL implementation, we simulate rate limiting by processing requests from a file and introducing delays between each request.

First, we define a file to store our requests:

       FILE-CONTROL.
           SELECT REQUEST-FILE ASSIGN TO "REQUESTS.DAT"
               ORGANIZATION IS LINE SEQUENTIAL.

We use a working storage section to keep track of time and define our delay:

       01 WS-CURRENT-TIME    PIC 9(8).
       01 WS-LAST-TIME       PIC 9(8) VALUE 0.
       01 WS-TIME-DIFF       PIC 9(8).
       01 WS-DELAY           PIC 9(8) VALUE 200.

The main procedure reads requests from the file and processes them:

       MAIN-PROCEDURE.
           OPEN INPUT REQUEST-FILE.
           PERFORM PROCESS-REQUESTS UNTIL WS-EOF = 'Y'.
           CLOSE REQUEST-FILE.
           STOP RUN.

The rate limiting is implemented in the RATE-LIMIT procedure:

       RATE-LIMIT.
           ACCEPT WS-CURRENT-TIME FROM TIME.
           COMPUTE WS-TIME-DIFF = WS-CURRENT-TIME - WS-LAST-TIME.
           IF WS-TIME-DIFF < WS-DELAY
               CALL "CBL_OC_NANOSLEEP" USING WS-DELAY
           END-IF.
           MOVE WS-CURRENT-TIME TO WS-LAST-TIME.

This procedure checks the time difference between the current request and the last request. If it’s less than our defined delay, we use the CBL_OC_NANOSLEEP function to introduce a delay.

To run this program, you would need to compile it with a COBOL compiler and prepare a REQUESTS.DAT file with request numbers. The program will then process these requests with rate limiting.

Note that this is a basic implementation and doesn’t include features like burst capability. In COBOL, implementing more complex rate limiting schemes might require additional external libraries or more sophisticated timing mechanisms.

Waitgroups in COBOL

Atomic Counters in COBOL

Learn X By Example

Title here

Rate Limiting in COBOL