Github user aweisberg commented on a diff in the pull request:
https://github.com/apache/cassandra/pull/212#discussion_r225735927
--- Diff: src/java/org/apache/cassandra/config/Config.java ---
@@ -376,9 +376,31 @@
public String full_query_log_dir = null;
- // parameters to adjust how much to delay startup until a certain
amount of the cluster is connect to and marked alive
- public int block_for_peers_percentage = 70;
+ /**
+ * When a node first starts up it intially thinks all other peers are
DOWN, and then as the initial gossip
+ * broadcast messages comes back nodes transition to UP. These options
configure how many nodes can remain in
+ * DOWN state before we make this node available as a coordinator, as
well as an overall timeout on this process
+ * to ensure that startup is not delayed too much.
+ *
+ * The defaults are tuned for LOCAL_ONE consistency levels with RF=3,
and have natural settings for other CLs:
+ *
+ * Consistency Level | local_dc | all_dcs
+ * --------------------------------------------------------
+ * LOCAL_ONE | default (2) | default (any)
+ * LOCAL_QUORUM | 1 | default (any)
+ * ONE | any | RF - 1
+ * QUORUM | any | (RF / 2) - 1
+ * ALL | default | 0
+ *
+ * A concrete example with QUORUM would be if you have 3 replicas in 2
datacenters, then you would set
+ * block_for_peers_all_dcs to (6 / 2) - 1 = 2 because that guarantees
that at most 2 hosts in all datacenters
+ * are down when you start taking client traffic, which should
satistfy QUORUM for all RF=6 QUORUM queries.
+ */
+ public int block_for_peers_local_dc = 2;
+ public int block_for_peers_all_dcs = Integer.MAX_VALUE;
--- End diff --
This one of those things where I want to ask around and see if we can get
away with just waiting 10 seconds if a node is down.
Seems like the solution for CCM is to just have CCM set the config it
wants. I'm also wondering if CCM actually waits the 10 seconds anyways just
because it starts one node at a time and waits for a specific log message a lot
of the time and I'm not sure if that message is before or after the
connectivity checker.
I have to go take a look at how CCM works.
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