Node Selector

Abstracting nodes through labels is a core enabler for severless.

The node selector also eases the management of geo-cluster and heterogeneous clusters, allowing nodes selection expressions based on arbitrary labels, like region=eu-west-1 and arch=arm.

Labels are <key>=<value> pairs in the node configuration file:

$ om node get --kw labels.zone
sofa

Labels are embedded in the cluster data:

$ om daemon status --format flat_json | grep labels
.monitor.nodes.nuc-cva.labels.region = eu1
.monitor.nodes.nuc-cva.labels.zone = tv
.monitor.nodes.aubergine.labels.region = eu1
.monitor.nodes.aubergine.labels.zone = sofa

Node Selector Expressions

fnmatch

$ om node ls --node aub*
aubergine

Label Existance

$ om node ls --node zone:
aubergine
nuc-cva

Exact Label

$ om node ls --node zone=sofa
aubergine

Negation

$ om node ls --node '!zone=sofa'
nuc-cva

Or-ed selectors

$ om node ls --node zone=sofa,zone=tv
aubergine
nuc-cva

And-ed selectors

$ om node ls --node zone=sofa+region=eu1
aubergine

wildcard

$ om node ls --node '*'
aubergine
nuc-cva

Node Selector in Service Configurations

Labels can be used in service configurations nodes keyword:

$ om test/registry get --kw nodes
region=eu1

$ om daemon status --format flat_json | grep "'test/registry'" | grep scope
.monitor.nodes.nuc-cva.services.config.'test/registry'.scope[0] = aubergine
.monitor.nodes.nuc-cva.services.config.'test/registry'.scope[1] = nuc-cva
.monitor.nodes.aubergine.services.config.'test/registry'.scope[0] = aubergine
.monitor.nodes.aubergine.services.config.'test/registry'.scope[1] = nuc-cva

$ om test/registry set --kw nodes=zone=sofa

$ om daemon status --format flat_json | grep "'test/registry'" | grep scope
.monitor.nodes.aubergine.services.config.'test/registry'.scope[0] = aubergine