The existing version constraint uses logic optimized for package
managers, not schedulers, when checking prereleases:
- 1.3.0-beta1 will *not* satisfy ">= 0.6.1"
- 1.7.0-rc1 will *not* satisfy ">= 1.6.0-beta1"
This is due to package managers wishing to favor final releases over
prereleases.
In a scheduler versions more often represent the earliest release all
required features/APIs are available in a system. Whether the constraint
or the version being evaluated are prereleases has no impact on
ordering.
This commit adds a new constraint - `semver` - which will use Semver
v2.0 ordering when evaluating constraints. Given the above examples:
- 1.3.0-beta1 satisfies ">= 0.6.1" using `semver`
- 1.7.0-rc1 satisfies ">= 1.6.0-beta1" using `semver`
Since existing jobspecs may rely on the old behavior, a new constraint
was added and the implicit Consul Connect and Vault constraints were
updated to use it.
Currently, using a Volume in a job uses the following configuration:
```
volume "alias-name" {
type = "volume-type"
read_only = true
config {
source = "host_volume_name"
}
}
```
This commit migrates to the following:
```
volume "alias-name" {
type = "volume-type"
source = "host_volume_name"
read_only = true
}
```
The original design was based due to being uncertain about the future of storage
plugins, and to allow maxium flexibility.
However, this causes a few issues, namely:
- We frequently need to parse this configuration during submission,
scheduling, and mounting
- It complicates the configuration from and end users perspective
- It complicates the ability to do validation
As we understand the problem space of CSI a little more, it has become
clear that we won't need the `source` to be in config, as it will be
used in the majority of cases:
- Host Volumes: Always need a source
- Preallocated CSI Volumes: Always needs a source from a volume or claim name
- Dynamic Persistent CSI Volumes*: Always needs a source to attach the volumes
to for managing upgrades and to avoid dangling.
- Dynamic Ephemeral CSI Volumes*: Less thought out, but `source` will probably point
to the plugin name, and a `config` block will
allow you to pass meta to the plugin. Or will
point to a pre-configured ephemeral config.
*If implemented
The new design simplifies this by merging the source into the volume
stanza to solve the above issues with usability, performance, and error
handling.
When checking driver feasability for an alloc with multiple drivers, we
must check that all drivers are detected and healthy.
Nomad 0.9 and 0.8 have a bug where we may check a single driver only,
but which driver is dependent on map traversal order, which is
unspecified in golang spec.
When a Client declares a volume is ReadOnly, we should only schedule it
for requests for ReadOnly volumes. This change means that if a host
exposes a readonly volume, we then validate that the group level
requests for the volume are all read only for that host.
This adds constraints for asserting that a given attribute or value
exists, or does not exist. This acts as a companion to =, or !=
operators, e.g:
```hcl
constraint {
attribute = "${attrs.type}"
operator = "!="
value = "database"
}
constraint {
attribute = "${attrs.type}"
operator = "is_set"
}
```
This commit allows the ConstraintChecker to test values that do not exist.
This is useful when wanting to _exclude_ given nodes from executing a
job, for example, if you wanted to give canary nodes an attribute, and
not run critical services on them, you may specify something like the
below, but not want to tag all other nodes with the inverse.
```hcl
constraint {
attribute = "${node.attr.canary}
operator = "!="
value = "1"
}
```
This also requires all constraint checkers to allow for nil target
values, as they will no longer be short circuited by resolving a target.
