Marton Elek created HDDS-3586:
---------------------------------
Summary: OM HA can be started with 3 isolated LEADER instead of
one OM ring
Key: HDDS-3586
URL: https://issues.apache.org/jira/browse/HDDS-3586
Project: Hadoop Distributed Data Store
Issue Type: Improvement
Reporter: Marton Elek
Steps to reproduce:
Imagine that I have 3 different om with the following DNS names:
{code}
ozone-om-0.ozone-om
ozone-om-1.ozone-om
ozone-om-2.ozone-om
{code}
I configured the three hosts as the following:
{code}
OZONE-SITE.XML_ozone.om.nodes.omservice: om1,om2,om3
OZONE-SITE.XML_ozone.om.address.omservice.om1: ozone-om-0
OZONE-SITE.XML_ozone.om.address.omservice.om2: ozone-om-1
OZONE-SITE.XML_ozone.om.address.omservice.om3: ozone-om-2
OZONE-SITE.XML_ozone.om.ratis.enable: "true"
{code}
But unfortunately the DNS is not reliable. All the hosts can resolve only the
LOCAL hostname.
OMHANodeDetails.java ignores ALL the configuration which are not resolvable:
{code}
if (!addr.isUnresolved()) {
if (!isPeer && OmUtils.isAddressLocal(addr)) {
localRpcAddress = addr;
localOMServiceId = serviceId;
localOMNodeId = nodeId;
localRatisPort = ratisPort;
found++;
} else {
// This OMNode belongs to same OM service as the current OMNode.
// Add it to peerNodes list.
// This OMNode belongs to same OM service as the current OMNode.
// Add it to peerNodes list.
peerNodesList.add(getHAOMNodeDetails(conf, serviceId,
nodeId, addr, ratisPort));
}
}
{code}
As a result I will have 3 running server but each has 1 one-node Ratis ring
(peerNodesList is empty as only the local hostname can be resolved).
Group ID is the same for all. But they have separated database and they work as
separated OM which is VERY dangerous.
1. Option one: we can accept any unresolved address and retry with connection
create if it couldn't be connected
2. Option two: at least the error handling should be fixed. When I configured 3
om, there supposed to be 3 om.
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