Hello, I want to create a ckuster with the following configuration:
- Node A is first node in cluster, and it will be used as backup node - Node A does not serve SQL queries - Node B and C are 'working' nodes - they will be under load and will receive SQL queries - If B or C crashed, they will receive SST transfer from A only (I suppose it contains the most consistent data) - If A crashed, it will receive SST from B or C.
What value of 'wsrep_urls' I need to have on each node?
My suggestion:
A:
> gcomm:// - at start to form a cluster > gcomm://B,gcomm://C - after cluster start
> Hello,
> I want to create a ckuster with the following configuration:
> - Node A is first node in cluster, and it will be used as backup node
> - Node A does not serve SQL queries
> - Node B and C are 'working' nodes - they will be under load and will
> receive SQL queries
> - If B or C crashed, they will receive SST transfer from A only (I > suppose
> it contains the most consistent data)
> - If A crashed, it will receive SST from B or C.
> What value of 'wsrep_urls' I need to have on each node?
> My suggestion:
> A:
>> gcomm:// - at start to form a cluster
>> gcomm://B,gcomm://C - after cluster start
>> B,C:
>> gcomm://A
> Is my suggestion right or not?
> Thanks.
Hi,
It is right. But it only facilitates reconnection to the cluster. After that the donor will be chosen automatically.
If you want to configure A as a donor for B and C, you ALSO need
A:
wsrep_node_name="nodeA"
B,C:
wsrep_sst_donor="nodeA"
I take it is does not matter who will be a donor for A, so that will suffice.
Regards,
Alex
-- Alexey Yurchenko,
Codership Oy, www.codership.com Skype: alexey.yurchenko, Phone: +358-400-516-011
1) Is it good practice or not - by your opinion? (to have a backup/reference node)
2) Am I right in my actions regarding to setting wsrep_urls?
- I start a cluster with 'gcomm://' on Node A
- then join B and C to cluster
- then change wsrep_urls on Node A to 'gcomm://B,gcomm://C' and restart it
Are these actions exactly correct or may be is there a better way?
Sorry but it's really difficult to understand a mechanism of cluster URLs =)
A lot of howto's about PXC/Galera advise just to leave 'gcomm://' on 1st node, but if I understood right, it's a way to split-brain.
So, I'm a little bit confused with this issue.
Please help.
Thanks in advance.
понедельник, 12 ноября 2012 г., 14:06:30 UTC+4 пользователь Alexey Yurchenko написал:
> On 2012-11-12 08:55, Sergey Rudenko wrote: > > Hello, > > I want to create a ckuster with the following configuration:
> > - Node A is first node in cluster, and it will be used as backup node > > - Node A does not serve SQL queries > > - Node B and C are 'working' nodes - they will be under load and will > > receive SQL queries > > - If B or C crashed, they will receive SST transfer from A only (I > > suppose > > it contains the most consistent data) > > - If A crashed, it will receive SST from B or C.
> > What value of 'wsrep_urls' I need to have on each node?
> > My suggestion:
> > A: > >> gcomm:// - at start to form a cluster > >> gcomm://B,gcomm://C - after cluster start
> >> B,C: > >> gcomm://A
> > Is my suggestion right or not? > > Thanks.
> Hi,
> It is right. But it only facilitates reconnection to the cluster. After > that the donor will be chosen automatically.
> If you want to configure A as a donor for B and C, you ALSO need
> A: > wsrep_node_name="nodeA"
> B,C: > wsrep_sst_donor="nodeA"
> I take it is does not matter who will be a donor for A, so that will > suffice.
> 1) Is it good practice or not - by your opinion? (to have a
> backup/reference node)
If you can afford it - definitely yes.
> 2) Am I right in my actions regarding to setting wsrep_urls?
> - I start a cluster with 'gcomm://' on Node A
If we're talking about wsrep_urls parameter, then I'd do
wsrep_urls=gcomm://B,gcomm://C,gcomm://
this way you would not need to restart it below, only remove gcomm:// part (you need to restart it only because mysqld_safe needs to be restarted to read new wsrep_urls value).
> - then join B and C to cluster
> - then change wsrep_urls on Node A to 'gcomm://B,gcomm://C' and > restart it
> Are these actions exactly correct or may be is there a better way?
Well, see above. And don't forget to specify ports in wsrep_urls.
> Sorry but it's really difficult to understand a mechanism of cluster > URLs =)
> A lot of howto's about PXC/Galera advise just to leave 'gcomm://' on > 1st
> node, but if I understood right, it's a way to split-brain.
No, it is not split-brain, but "split-cluster" which is even worse (a node forms a separate cluster of his own). Never leave gcomm:// in configuration. It is only for bootstrapping the cluster.
> понедельник, 12 ноября 2012 г., 14:06:30 UTC+4 пользователь Alexey
> Yurchenko написал:
>> On 2012-11-12 08:55, Sergey Rudenko wrote:
>> > Hello,
>> > I want to create a ckuster with the following configuration:
>> > - Node A is first node in cluster, and it will be used as backup >> node
>> > - Node A does not serve SQL queries
>> > - Node B and C are 'working' nodes - they will be under load and >> will
>> > receive SQL queries
>> > - If B or C crashed, they will receive SST transfer from A only (I
>> > suppose
>> > it contains the most consistent data)
>> > - If A crashed, it will receive SST from B or C.
>> > What value of 'wsrep_urls' I need to have on each node?
>> > My suggestion:
>> > A:
>> >> gcomm:// - at start to form a cluster
>> >> gcomm://B,gcomm://C - after cluster start
>> >> B,C:
>> >> gcomm://A
>> > Is my suggestion right or not?
>> > Thanks.
>> Hi,
>> It is right. But it only facilitates reconnection to the cluster. >> After
>> that the donor will be chosen automatically.
>> If you want to configure A as a donor for B and C, you ALSO need
>> A:
>> wsrep_node_name="nodeA"
>> B,C:
>> wsrep_sst_donor="nodeA"
>> I take it is does not matter who will be a donor for A, so that will
>> suffice.
No, it is not split-brain, but "split-cluster" which is even worse (a
> node forms a separate cluster of his own). Never leave gcomm:// in > configuration. It is only for bootstrapping the cluster.
How can I automatically detect a 'split-cluster' event in this case?
By monitoring of 'wsrep_cluster_size' on each node? Or is there some other params like 'cluster_id'?
> > So, I'm a little bit confused with this issue.
> > Please help. > > Thanks in advance.
> > понедельник, 12 ноября 2012 г., 14:06:30 UTC+4 пользователь Alexey > > Yurchenko написал:
> >> On 2012-11-12 08:55, Sergey Rudenko wrote: > >> > Hello, > >> > I want to create a ckuster with the following configuration:
> >> > - Node A is first node in cluster, and it will be used as backup > >> node > >> > - Node A does not serve SQL queries > >> > - Node B and C are 'working' nodes - they will be under load and > >> will > >> > receive SQL queries > >> > - If B or C crashed, they will receive SST transfer from A only (I > >> > suppose > >> > it contains the most consistent data) > >> > - If A crashed, it will receive SST from B or C.
> >> > What value of 'wsrep_urls' I need to have on each node?
> >> > My suggestion:
> >> > A: > >> >> gcomm:// - at start to form a cluster > >> >> gcomm://B,gcomm://C - after cluster start
> >> >> B,C: > >> >> gcomm://A
> >> > Is my suggestion right or not? > >> > Thanks.
> >> Hi,
> >> It is right. But it only facilitates reconnection to the cluster. > >> After > >> that the donor will be chosen automatically.
> >> If you want to configure A as a donor for B and C, you ALSO need
> >> A: > >> wsrep_node_name="nodeA"
> >> B,C: > >> wsrep_sst_donor="nodeA"
> >> I take it is does not matter who will be a donor for A, so that will > >> suffice.
> No, it is not split-brain, but "split-cluster" which is even worse (a
>> node forms a separate cluster of his own). Never leave gcomm:// in
>> configuration. It is only for bootstrapping the cluster.
> How can I automatically detect a 'split-cluster' event in this case?
> By monitoring of 'wsrep_cluster_size' on each node?
Mostly yes.
> Or is there some other params like 'cluster_id'?
Depending on how the node was restarted, cluster UUID and even transaction sequence number may be preserved - in order to allow quick resync with the cluster bypassing SST. So it is definitely not the means to detect cluster divergence.
>> > So, I'm a little bit confused with this issue.
>> > Please help.
>> > Thanks in advance.
>> > понедельник, 12 ноября 2012 г., 14:06:30 UTC+4 пользователь Alexey
>> > Yurchenko написал:
>> >> On 2012-11-12 08:55, Sergey Rudenko wrote:
>> >> > Hello,
>> >> > I want to create a ckuster with the following configuration:
>> >> > - Node A is first node in cluster, and it will be used as >> backup
>> >> node
>> >> > - Node A does not serve SQL queries
>> >> > - Node B and C are 'working' nodes - they will be under load >> and
>> >> will
>> >> > receive SQL queries
>> >> > - If B or C crashed, they will receive SST transfer from A only >> (I
>> >> > suppose
>> >> > it contains the most consistent data)
>> >> > - If A crashed, it will receive SST from B or C.
>> >> > What value of 'wsrep_urls' I need to have on each node?
>> >> > My suggestion:
>> >> > A:
>> >> >> gcomm:// - at start to form a cluster
>> >> >> gcomm://B,gcomm://C - after cluster start
>> >> >> B,C:
>> >> >> gcomm://A
>> >> > Is my suggestion right or not?
>> >> > Thanks.
>> >> Hi,
>> >> It is right. But it only facilitates reconnection to the cluster.
>> >> After
>> >> that the donor will be chosen automatically.
>> >> If you want to configure A as a donor for B and C, you ALSO need
>> >> A:
>> >> wsrep_node_name="nodeA"
>> >> B,C:
>> >> wsrep_sst_donor="nodeA"
>> >> I take it is does not matter who will be a donor for A, so that >> will
>> >> suffice.
