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Don't stutter in send_diffs

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When the master sees a burst of updates (perhaps sustained), the
slaves "I_HAVE" messages can fall behind the version we've already
sent, and the unpatched code would retransmit already sent diffs!

This can result in substantial amplification (in a local test, 3000
ops turned into 427,000 ops).  Though the number of *messages* sent
was actually somewhat smaller, the ever growing message size
ultimately leads to failure.
This commit is contained in:
Viktor Dukhovni
2019-09-14 22:30:52 -04:00
committed by Nico Williams
parent 2709f28a1b
commit 7680c92047
1 changed files with 8 additions and 9 deletions
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17
lib/kadm5/ipropd_master.c
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@@ -129,6 +129,7 @@ struct slave {
krb5_auth_context ac;
uint32_t version;
uint32_t version_tstamp;
uint32_t version_ack;
time_t seen;
unsigned long flags;
#define SLAVE_F_DEAD 0x1
@@ -305,6 +306,7 @@ add_slave (krb5_context context, krb5_keytab keytab, slave **root,
krb5_warnx (context, "connection from %s", s->name);
s->version = 0;
s->version_ack = 0;
s->flags = 0;
slave_seen(s);
s->next = *root;
@@ -698,7 +700,7 @@ send_diffs (kadm5_server_context *server_context, slave *s, int log_fd,
krb5_warn(context, ret, "send_diffs: failed to send to slave");
slave_dead(context, s);
}
krb5_warnx(context, "slave %s in sync already at version %ld",
krb5_warnx(context, "slave %s version %ld already sent",
s->name, (long)s->version);
}
return ret;
@@ -903,8 +905,8 @@ process_msg (kadm5_server_context *server_context, slave *s, int log_fd,
/* new started slave that have old log */
if (s->version == 0 && tmp != 0) {
if (current_version < tmp) {
krb5_warnx(context, "Slave %s (version %u) have later version "
"the master (version %u) OUT OF SYNC",
krb5_warnx(context, "Slave %s (version %u) has later version "
"than the master (version %u) OUT OF SYNC",
s->name, tmp, current_version);
}
if (verbose)
@@ -912,11 +914,8 @@ process_msg (kadm5_server_context *server_context, slave *s, int log_fd,
s->name, s->version, tmp);
s->version = tmp;
}
if (tmp < s->version) {
krb5_warnx(context, "Slave %s claims to not have "
"version we already sent to it", s->name);
s->version = tmp;
}
if ((s->version_ack = tmp) < s->version)
break;
ret = send_diffs(server_context, s, log_fd, database, current_version,
current_tstamp);
break;
@@ -1031,7 +1030,7 @@ write_stats(krb5_context context, slave *slaves, uint32_t current_version)
} else
rtbl_add_column_entry(tbl, SLAVE_ADDRESS, "<unknown>");
snprintf(str, sizeof(str), "%u", (unsigned)slaves->version);
snprintf(str, sizeof(str), "%u", (unsigned)slaves->version_ack);
rtbl_add_column_entry(tbl, SLAVE_VERSION, str);
if (slaves->flags & SLAVE_F_DEAD)