Will the Leader send Membership Update to all the Followers in Raft?

[Heng Chang]

Hi,

I am a fresh man in Raft, I want to ask a question about the Membership management in Raft:  Will the Leader send Membership Update to all the Followers in Raft?

As my understanding, the Leader uses heartbeat mechanism to know the Membership of the cluster.

To vote for a new Leader, I think the Followers also need to know the Membership of the cluster to send RequestVote RPCs to all other servers and so on, so, how the Followers can get this Membership information?

 

Thanks and Best Regards,  

[Oren Eini (Ayende Rahien)]

That depend on your actual configuration.

Static clusters have the topology (list of members) predefined in a config file, so this is an admin task.

Dynamic cluster starts with all nodes as non voting followers. An admin make a manual change on one node that turn it into a single node cluster for which it is the leader (bootstrap).

At that point, we add additional nodes to the cluster (one at a time). Part of the cluster log is the list of topology changes, so you can be sure that majority nodes in the cluster accepted new nodes when they are done. 

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[Henrik Ingo]

Hi Heng

The dissertation thesis version of Raft publications is the most
recent one, and its chapter 4 describes the algorithm to be used for
adding and removing servers:
https://ramcloud.stanford.edu/~ongaro/thesis.pdf

Note that chapter 4 actually describes 2 different algorithms. To
start you should focus on the first one, as it is much simpler.

henrik

On Mon, Dec 5, 2016 at 5:12 AM, Heng Chang <scutp...@gmail.com> wrote:

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[Heng Chang]

Hi, henrik 

I already looked through chapter 4 of the thesis, and I know that the Leader will maintain the membership of the Cluster. 

What I want to know is that whether the Followers need to know the membership? 

This is seemed not mention in the thesis.

As my understanding, I think  the Followers should also know the membership, so I guess the Leader should the membership information to the Followers time by time.

Best Regards,

 

在 2016年12月5日星期一 UTC+8下午7:24:27，Henrik Ingo写道：

[Oren Eini (Ayende Rahien)]

Yes, they must. Remember that each follower might become a leader at some point

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Oren Eini l CEO l Mobile: + 972-52-548-6969

Office: +972-4-622-7811 l Fax: +972-153-4-622-7811

 

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[Heng Chang]

OK, I see. 

Thanks.

在 2016年12月6日星期二 UTC+8下午2:23:16，Ayende Rahien写道：

[Henrik Ingo]

Hi Heng

In the table on p 33, §4: "Append new configuration entry to log ...
commit it using majority of new configuration."

This step includes the replication to secondaries.

henrik

[Heng Chang]

OK, I see.

Really thanks a lot!

在 2016年12月7日星期三 UTC+8上午1:12:46，Henrik Ingo写道：