RBD: support multiple MON hosts

[ustcweizhou]

Description

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)

Screenshots (if appropriate):

details

How Has This Been Tested?

[DaanHoogland]

the changes look good but they are in a 225 lines method that should be restructured to contain scheme handlers for different schemes with init and prep methods.

[wido]

What does this add? Librados/RBD already handles this by creating a Round Robin DNS name pointing to all three IPs.

There is no need to try and hack this into the URL. Redundancy can already be achieved with DNS.

[weizhouapache]

What does this add? Librados/RBD already handles this by creating a Round Robin DNS name pointing to all three IPs.

@wido libvirt also supports multiple monitors. this provides another option.

[sureshanaparti]

in case the url scheme is not case sensitive, can use:

Suggested change

	if (url != null && url.startsWith("rbd://")) {
	if (url != null && url..toLowerCase().startsWith("rbd://")) {

(or)

Suggested change

	if (url != null && url.startsWith("rbd://")) {
	if (StringUtils.startsWithIgnoreCase(url, "rbd://")) {

[wido]

The PR currently only contains one commit and just a few changes. This seems incomplete to me.

Where do we generate the Libvirt XML?

[weizhouapache]

The PR currently only contains one commit and just a few changes. This seems incomplete to me.

Where do we generate the Libvirt XML?

@wido this does not require any other code changes in kvm plugin.
in libvirt pool definition, it uses host ips instead of single host ip.

<pool type='rbd'>
  <name>uuid</name>
  <uuid>uuid</uuid>
  <capacity unit='bytes'>aaaaaa</capacity>
  <allocation unit='bytes'>aaaaaa</allocation>
  <available unit='bytes'>aaaaaa</available>
  <source>
    <host name='10.11.118.26,10.11.118.27,10.11.118.28' port='6789'/>
    <name>ceph-rbd</name>
    <auth type='ceph' username='cloudstack'>
      <secret uuid='60a41767-1196-3ff3-9105-19de5dc99fce'/>
    </auth>
  </source>
</pool>

[weizhouapache]

closed this ticket.

I do not have a ceph testing env for now.
I will open this ticket when I have verified everything works as expected.

[yadvr]

@weizhouapache I've verified this, it works but not in the syntax you've shared but:

<pool type='rbd'>
  <name><name uuid here></name>
  ....
  <source>
    <host name='192.168.1.11'/>
    <host name='192.168.1.12'/>
    <host name='192.168.1.13'/>
    <name><name of ceph rbd pool here></name>
    <auth type='ceph' username='cloudstack'>
      <secret uuid='<uuid here>'/>
    </auth>
  </source>
</pool>

https://libvirt.org/storage.html#StorageBackendRBD

DNS is good solution @wido but some people including me may like this solution.

[weizhouapache]

re-work on this feature and created a pull request
#6792