From bb7cd97439aa91698bee192cddd7ceb18d628a00 Mon Sep 17 00:00:00 2001 From: Yossi Gottlieb Date: Thu, 28 Jan 2021 12:09:11 +0200 Subject: Add hostname support in Sentinel. (#8282) This is both a bugfix and an enhancement. Internally, Sentinel relies entirely on IP addresses to identify instances. When configured with a new master, it also requires users to specify and IP and not hostname. However, replicas may use the replica-announce-ip configuration to announce a hostname. When that happens, Sentinel fails to match the announced hostname with the expected IP and considers that a different instance, triggering reconfiguration, etc. Another use case is where TLS is used and clients are expected to match the hostname to connect to with the certificate's SAN attribute. To properly implement this configuration, it is necessary for Sentinel to redirect clients to a hostname rather than an IP address. The new 'resolve-hostnames' configuration parameter determines if Sentinel is willing to accept hostnames. It is set by default to no, which maintains backwards compatibility and avoids unexpected DNS resolution delays on systems with DNS configuration issues. Internally, Sentinel continues to identify instances by their resolved IP address and will also report the IP by default. The new 'announce-hostnames' parameter determines if Sentinel should prefer to announce a hostname, when available, rather than an IP address. This applies to addresses returned to clients, as well as their representation in the configuration file, REPLICAOF configuration commands, etc. This commit also introduces SENTINEL CONFIG GET and SENTINEL CONFIG SET which can be used to introspect or configure global Sentinel configuration that was previously was only possible by directly accessing the configuration file and possibly restarting the instance. Co-authored-by: myl1024 Co-authored-by: sundb --- sentinel.conf | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'sentinel.conf') diff --git a/sentinel.conf b/sentinel.conf index 39d6929e7..8647379d8 100644 --- a/sentinel.conf +++ b/sentinel.conf @@ -321,3 +321,21 @@ sentinel deny-scripts-reconfig yes # is possible to just rename a command to itself: # # SENTINEL rename-command mymaster CONFIG CONFIG + +# HOSTNAMES SUPPORT +# +# Normally Sentinel uses only IP addresses and requires SENTINEL MONITOR +# to specify an IP address. Also, it requires the Redis replica-announce-ip +# keyword to specify only IP addresses. +# +# You may enable hostnames support by enabling resolve-hostnames. Note +# that you must make sure your DNS is configured properly and that DNS +# resolution does not introduce very long delays. +# +SENTINEL resolve-hostnames no + +# When resolve-hostnames is enabled, Sentinel still uses IP addresses +# when exposing instances to users, configuration files, etc. If you want +# to retain the hostnames when announced, enable announce-hostnames below. +# +SENTINEL announce-hostnames no -- cgit v1.2.1