Cluster re-set/start with old state

[Robert Erneborg]

Hi,

What I would like to do is restarting the cluster from scratch while keeping the old state. That is, I want the bootstrap server to have an non-empty initial state. Is this possible, and how would one go about achieving this?

Best Regards,
Robert Erneborg

[Archie Cobbs]

On Monday, May 16, 2016 at 4:19:36 AM UTC-5, Robert Erneborg wrote:

What I would like to do is restarting the cluster from scratch while keeping the old state. That is, I want the bootstrap server to have an non-empty initial state. Is this possible, and how would one go about achieving this?

I'd recommend you not muck with the core Raft workings.

Instead, add an import/export capability to your cluster:

1. Prior to shutdown, export your total state machine state.
2. Reset the cluster, wiping out all state
3. Restart the cluster, now initially empty
4. Import your state machine state saved from before

How exactly you perform the 'export' and 'import' depends on your implementation.

-Archie

[philip...@yahoo.com]

I agree with Archie -- backup your system and then rebuild your new cluster from that state.

>> How exactly you perform the 'export' and 'import' depends on your implementation.

But yes, what you actually need to do will depend on your actual system. For example, to do this with rqlite (https://github.com/rqlite/rqlite) one backs up the SQLite database, creates a brand new cluster, and then replays the database back into the new cluster. There is no real difference between restoring a cluster from scratch, and just performing normal operations on the cluster.

Philip


-----------------------------------------
http://www.philipotoole.com

On Monday, May 16, 2016 7:40 AM, Archie Cobbs <archie...@gmail.com> wrote:



On Monday, May 16, 2016 at 4:19:36 AM UTC-5, Robert Erneborg wrote:
What I would like to do is restarting the cluster from scratch while keeping the old state. That is, I want the bootstrap server to have an non-empty initial state. Is this possible, and how would one go about achieving this?
>

I'd recommend you not muck with the core Raft workings.

Instead, add an import/export capability to your cluster:

1. Prior to shutdown, export your total state machine state.
2. Reset the cluster, wiping out all state
3. Restart the cluster, now initially empty
4. Import your state machine state saved from beforeHow exactly you perform the 'export' and 'import' depends on your implementation.

-Archie



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[Diego Ongaro]

I'm a little late here but to satisfy my curiosity: Robert, can you say a little more about why you want to do this?

-Diego

[Thông Phạm Văn]

I have the same question, when I restart a node, what is state of my node, follower or candidate or leader?

And what I should do if my leader lost 3/5 connection to its members?

I'm sorry because of my English.

Vào 07:34:40 UTC+7 Thứ Bảy, ngày 28 tháng 5 năm 2016, Diego Ongaro đã viết:

[Oren Eini (Ayende Rahien)]

I start them as followers, and a leader that can't get majority votes will automatically become candidate after timeout perido

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