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Improve srand entropy (and fix Sentinel failures) (#10197)

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As Sentinel relies upon consensus algorithm, all sentinel instances,
randomize a time to initiate their next attempt to become the
leader of the group. But time after time, all raffled the same value.

The problem is in the line `srand(time(NULL)^getpid())` such that
all spinned up containers get same time (in seconds) and same pid
which is always 1. Added material `tv_usec` and verify that even
consecutive calls brings different values and makes the difference.
This commit is contained in:
Moti Cohen 2022-01-30 16:39:23 +02:00 committed by GitHub
parent 4e17154060
commit 52b2fbe970
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 5 additions and 2 deletions
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src/server.c
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@ -6585,9 +6585,12 @@ int main(int argc, char **argv) {
setlocale(LC_COLLATE,"");
tzset(); /* Populates 'timezone' global. */
zmalloc_set_oom_handler(redisOutOfMemoryHandler);
srand(time(NULL)^getpid());
srandom(time(NULL)^getpid());
/* To achieve entropy, in case of containers, their time() and getpid() can
* be the same. But value of tv_usec is fast enough to make the difference */
gettimeofday(&tv,NULL);
srand(time(NULL)^getpid()^tv.tv_usec);
srandom(time(NULL)^getpid()^tv.tv_usec);
init_genrand64(((long long) tv.tv_sec * 1000000 + tv.tv_usec) ^ getpid());
crc64_init();