rados_nobjects_list_get_pg_hash_position returns 0

[Denis Tingajkin <denis.tingajkin@xxxxxxxxx>]

Hello,

We faced an issue that https://docs.ceph.com/en/latest/rados/api/librados/#c.rados_nobjects_list_get_pg_hash_position always returns 0 for our pools. 

Ceph version is 16.2.15

Scenario is:
#include <rados/librados.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>


#define POOL_NAME "TODO"  // Change this to your pool name


int main(int argc, const char **argv) {

    rados_t cluster;

    char cluster_name[] = "ceph";

    char user_name[] = "";

    uint64_t flags = 0;

    int ret;


    // Initialize the cluster handle

    ret = rados_create(&cluster, NULL);

    if (ret < 0) {

        fprintf(stderr, "Couldn't initialize the cluster handle! error %d\n", ret);

        exit(EXIT_FAILURE);

    }


    fprintf(stdout, "cluster: %p\n", cluster);


    // Read the Ceph configuration file

    ret = rados_conf_read_file(cluster, "/etc/ceph/ceph.conf");

    if (ret < 0) {

        fprintf(stderr, "Cannot read config file: %d\n", ret);

        exit(EXIT_FAILURE);

    }


    fprintf(stdout, "read conf: %d\n", ret);



  // Connect to the cluster

    ret = rados_connect(cluster);

    if (ret < 0) {

        fprintf(stderr, "Cannot connect to cluster: %d\n", ret);

        exit(EXIT_FAILURE);

    }


    // Open the pool

    rados_ioctx_t io_ctx;

    ret = rados_ioctx_create(cluster, POOL_NAME, &io_ctx);

    if (ret < 0) {

        fprintf(stderr, "Cannot open pool %s: %d\n", POOL_NAME, ret);

        exit(EXIT_FAILURE);

    }



    // Create an iterator for all objects in the pool

    rados_list_ctx_t  list_ctx;

    ret = rados_nobjects_list_open(io_ctx, &list_ctx);

    if (ret < 0) {

        fprintf(stderr, "Cannot list objects: %d\n", ret);

        rados_ioctx_destroy(io_ctx);

        exit(EXIT_FAILURE);

    }


    printf("Objects in pool '%s':\n", POOL_NAME);

    printf("--------------------------------\n");


    // Iterate through all objects

    const char *entry;

    const char *key;

    const char *ns;



    while (rados_nobjects_list_next(list_ctx, &entry, &key, &ns) == 0) {

        printf("%s\n", entry);

        printf("ns: %s\n", ns);

 printf("key: %s\n", key);

        printf("hash: %d\n", rados_nobjects_list_get_pg_hash_position(list_ctx)); // here we're getting 0 for all objects/pools

    }

    // Clean up

    rados_nobjects_list_close(list_ctx);

    rados_ioctx_destroy(io_ctx);


    return 0;
}

By my investigation, I found if I use get/seek cursor and after that call  rados_nobjects_list_get_pg_hash_position then it returns the corrct hash position.

Questions:

1. Could you please have a look and provide thoughts on why we're getting 0 values in the code?

2. Can it be related to our osd configuraiton like sortbitwise or something else?

3. I found in the code that this hash position is moving only on seeking. Is it bug?

4.  Can we add some new C API like rados_nobjects_list_get_cursor_hash_position for getting the hash from the cursor handle (since the cursor handle is actually an hobject, we can simply return get_hash() based on the passed cursor for this API)?


--
Best Regards,
Denis Tingaikin

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