any marker or method can indicated the binlog sync has stared？

[lonely-root-number2]

story：
I want to cache some data from the database in the application. I need to wait until binlog synchronization has started before starting pulling data from the database so that updates are not lost. (If synchronization has not started when pulling data, some updates will be lost).
I noticed that there was a variable called running in syncer, but it was not exposed to the public. Judging by synedPosition doesn't seem very accurate.

[ljluestc]

#define _GNU_SOURCE
#include "cJSON.h"
#include <fenv.h>
#include <math.h>
#include <stdio.h>

int main()
{
    feenableexcept(FE_INVALID); // Enable FE_INVALID
    cJSON *n1 = cJSON_CreateNumber(NAN);
    printf("NAN: valueint=%d, valuedouble=%f\n", n1->valueint, n1->valuedouble);

    cJSON *n2 = cJSON_CreateNumber(INFINITY);
    printf("INF: valueint=%d, valuedouble=%f\n", n2->valueint, n2->valuedouble);

    cJSON *n3 = cJSON_CreateNumber(-INFINITY);
    printf("-INF: valueint=%d, valuedouble=%f\n", n3->valueint, n3->valuedouble);

    cJSON *n4 = cJSON_CreateNumber(1e308); // Overflow
    printf("Overflow: valueint=%d, valuedouble=%f\n", n4->valueint, n4->valuedouble);

    cJSON_Delete(n1);
    cJSON_Delete(n2);
    cJSON_Delete(n3);
    cJSON_Delete(n4);
    return 0;
}
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[dveeden]

@ljluestc That looks unrelated to this issue. Or not?

[dveeden]

What about connecting to the database, running SHOW BINARY LOG STATUS to get the position and then starting the binlog stream from that position? Then that will include any changes after that position even if you started the process later.

Note that this won't work for forever as eventually the binlogs would get purged (depending on your settings).