[
https://issues.apache.org/jira/browse/ZOOKEEPER-2965?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Philippe Serreault updated ZOOKEEPER-2965:
------------------------------------------
Comment: was deleted
(was: From f293df54d7890f1870c1460a4d7c0c4850065548 Mon Sep 17 00:00:00 2001
From: Philippe Serreault <[email protected]>
Date: Tue, 9 Jan 2018 18:14:23 +0100
Subject: [PATCH] Prevent DNS queries spam.
---
src/c/src/zk_adaptor.h | 2 ++
src/c/src/zookeeper.c | 28 ++++++++++++++++++++++++----
2 files changed, 26 insertions(+), 4 deletions(-)
diff --git a/src/c/src/zk_adaptor.h b/src/c/src/zk_adaptor.h
index 97995e36..8487dee9 100644
--- a/src/c/src/zk_adaptor.h
+++ b/src/c/src/zk_adaptor.h
@@ -268,6 +268,8 @@ struct _zhandle {
char allow_read_only;
/** Indicates if we connected to a majority server before */
char seen_rw_server_before;
+ /** Indicates hostname modification and triggers a DNS resolve query */
+ char hostname_modified;
};
diff --git a/src/c/src/zookeeper.c b/src/c/src/zookeeper.c
index 47e2ee19..74319439 100644
--- a/src/c/src/zookeeper.c
+++ b/src/c/src/zookeeper.c
@@ -904,9 +904,15 @@ int update_addrs(zhandle_t *zh)
return ZSYSTEMERROR;
}
- // NOTE: guard access to {hostname, addr_cur, addrs, addrs_old, addrs_new}
+ // NOTE: guard access to {hostname, addr_cur, addrs, addrs_old, addrs_new,
hostname_modified}
lock_reconfig(zh);
+ // zh->hostname was unchanged, no need to resolve_hosts
+ if (!zh->hostname_modified)
+ {
+ goto fail;
+ }
+
// Copy zh->hostname for local use
hosts = strdup(zh->hostname);
if (hosts == NULL) {
@@ -919,6 +925,11 @@ int update_addrs(zhandle_t *zh)
{
goto fail;
}
+ else
+ {
+ // resolve successful, prevent further resolution of same hostname
+ zh->hostname_modified = 0;
+ }
// If the addrvec list is identical to last time we ran don't do anything
if (addrvec_eq(&zh->addrs, &resolved))
@@ -1159,6 +1170,7 @@ static zhandle_t *zookeeper_init_internal(const char
*host, watcher_fn watcher,
zh->allow_read_only = flags & ZOO_READONLY;
// non-zero clientid implies we've seen r/w server already
zh->seen_rw_server_before = (clientid != 0 && clientid->client_id != 0);
+ zh->hostname_modified = 1;
init_auth_info(&zh->auth_h);
if (watcher) {
zh->watcher = watcher;
@@ -1258,15 +1270,23 @@ int zoo_set_servers(zhandle_t *zh, const char *hosts)
return ZBADARGUMENTS;
}
- // NOTE: guard access to {hostname, addr_cur, addrs, addrs_old, addrs_new}
+ // NOTE: guard access to {hostname, addr_cur, addrs, addrs_old, addrs_new,
hostname_modified}
lock_reconfig(zh);
+ // No need to update_addrs when new zk servers list is identical to
previous
+ if (zh->hostname && hosts && !strcmp(zh->hostname, hosts))
+ {
+ unlock_reconfig(zh);
+ return ZOK;
+ }
+
// Reset hostname to new set of hosts to connect to
if (zh->hostname) {
free(zh->hostname);
}
zh->hostname = strdup(hosts);
+ zh->hostname_modified = 1;
unlock_reconfig(zh);
@@ -1335,7 +1355,7 @@ static int get_next_server_in_reconfig(zhandle_t *zh)
*/
void zoo_cycle_next_server(zhandle_t *zh)
{
- // NOTE: guard access to {hostname, addr_cur, addrs, addrs_old, addrs_new}
+ // NOTE: guard access to {hostname, addr_cur, addrs, addrs_old, addrs_new,
hostname_modified}
lock_reconfig(zh);
memset(&zh->addr_cur, 0, sizeof(zh->addr_cur));
@@ -1367,7 +1387,7 @@ const char* zoo_get_current_server(zhandle_t* zh)
{
const char *endpoint_info = NULL;
- // NOTE: guard access to {hostname, addr_cur, addrs, addrs_old, addrs_new}
+ // NOTE: guard access to {hostname, addr_cur, addrs, addrs_old, addrs_new,
hostname_modified}
// Need the lock here as it is changed in update_addrs()
lock_reconfig(zh);
--
2.13.6
)
> prevent DNS queries spam
> ------------------------
>
> Key: ZOOKEEPER-2965
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2965
> Project: ZooKeeper
> Issue Type: Improvement
> Components: c client
> Reporter: Philippe Serreault
> Priority: Minor
>
> Hello,
> First of all, some context about the issue and why it became quite apparent
> to me:
> * I'm using the native zookeeper client on linux
> * I'm not declaring -DTHREADED
> * My zookeeper ensemble is made of server names that need to be resolved
> * The ensemble and DNS servers are "next" to each other
> * My client is "far" and uses an unreliable network path that can drop UDP
> requests
> For each run in client's main loop, all servers in ensemble are resolved,
> even if no change in servers list occurred (zookeeper_interest ..
> update_addrs .. resolve_hosts).
> In my situation, DNS requests could timeout and would trigger a reconnection
> to ensemble.
> Please find attached a patch that would prevent DNS queries when hostname was
> not changed.
> Best regards,
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