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Optimize replicaFeedSlaves by removing use of snprintf

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Former-commit-id: 32561a99124542461de283d5035f869b5fc9bc2f
This commit is contained in:
John Sully 2020-04-13 22:11:34 -04:00
parent 6f15ce125c
commit d683a62b43
1 changed files with 35 additions and 11 deletions
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46
src/replication.cpp
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@ -310,6 +310,26 @@ void replicationFeedSlave(client *replica, int dictid, robj **argv, int argc, bo
}
}
static int writeProtoNum(char *dst, const size_t cchdst, long long num)
{
if (cchdst < 1)
return 0;
dst[0] = '$';
int cch = 1;
cch += ll2string(dst + cch, cchdst - cch, digits10(num));
int chCpyT = std::min<int>(cchdst - cch, 2);
memcpy(dst + cch, "\r\n", chCpyT);
cch += chCpyT;
cch += ll2string(dst + cch, cchdst-cch, num);
chCpyT = std::min<int>(cchdst - cch, 3);
memcpy(dst + cch, "\r\n", chCpyT);
if (chCpyT == 3)
cch += 2;
else
cch += chCpyT;
return cch;
}
/* Propagate write commands to slaves, and populate the replication backlog
* as well. This function is used if the instance is a master: we use
* the commands received by our clients in order to create the replication
@ -354,24 +374,28 @@ void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) {
serverAssert(argc > 0);
serverAssert(cchbuf > 0);
char uuid[40] = {'\0'};
char uuid[37];
uuid_unparse(cserver.uuid, uuid);
char proto[1024];
int cchProto = snprintf(proto, sizeof(proto), "*5\r\n$7\r\nRREPLAY\r\n$%d\r\n%s\r\n$%lld\r\n", (int)strlen(uuid), uuid, cchbuf);
cchProto = std::min((int)sizeof(proto), cchProto);
// The code below used to be: snprintf(proto, sizeof(proto), "*5\r\n$7\r\nRREPLAY\r\n$%d\r\n%s\r\n$%lld\r\n", (int)strlen(uuid), uuid, cchbuf);
// but that was much too slow
char proto[1024] = "*5\r\n$7\r\nRREPLAY\r\n$36\r\n00000000-0000-0000-0000-000000000000\r\n$";
int cchProto = strlen(proto);
memcpy(proto + 22, uuid, 36); // Note UUID_STR_LEN includes the \0 trailing byte which we don't want
cchProto += ll2string(proto + cchProto, sizeof(proto)-cchProto, cchbuf);
memcpy(proto + cchProto, "\r\n", 3);
cchProto += 2;
long long master_repl_offset_start = g_pserver->master_repl_offset;
char szDbNum[128];
int cchDictIdNum = snprintf(szDbNum, sizeof(szDbNum), "%d", dictid);
int cchDbNum = snprintf(szDbNum, sizeof(szDbNum), "$%d\r\n%d\r\n", cchDictIdNum, dictid);
cchDbNum = std::min<int>(cchDbNum, sizeof(szDbNum)); // snprintf is tricky like that
int cchDbNum = writeProtoNum(szDbNum, sizeof(szDbNum), dictid);
char szMvcc[128];
incrementMvccTstamp();
uint64_t mvccTstamp = getMvccTstamp();
int cchMvccNum = snprintf(szMvcc, sizeof(szMvcc), "%" PRIu64, mvccTstamp);
int cchMvcc = snprintf(szMvcc, sizeof(szMvcc), "$%d\r\n%" PRIu64 "\r\n", cchMvccNum, mvccTstamp);
cchMvcc = std::min<int>(cchMvcc, sizeof(szMvcc)); // tricky snprintf
int cchMvcc = writeProtoNum(szMvcc, sizeof(szMvcc), getMvccTstamp());
/* Write the command to the replication backlog if any. */
if (g_pserver->repl_backlog)