This PR implements Nomad built-in support for running Consul Connect
terminating gateways. Such a gateway can be used by services running
inside the service mesh to access "legacy" services running outside
the service mesh while still making use of Consul's service identity
based networking and ACL policies.
https://www.consul.io/docs/connect/gateways/terminating-gateway
These gateways are declared as part of a task group level service
definition within the connect stanza.
service {
connect {
gateway {
proxy {
// envoy proxy configuration
}
terminating {
// terminating-gateway configuration entry
}
}
}
}
Currently Envoy is the only supported gateway implementation in
Consul. The gateay task can be customized by configuring the
connect.sidecar_task block.
When the gateway.terminating field is set, Nomad will write/update
the Configuration Entry into Consul on job submission. Because CEs
are global in scope and there may be more than one Nomad cluster
communicating with Consul, there is an assumption that any terminating
gateway defined in Nomad for a particular service will be the same
among Nomad clusters.
Gateways require Consul 1.8.0+, checked by a node constraint.
Closes#9445
Nomad v1.0.0 introduced a regression where the client configurations
for `connect.sidecar_image` and `connect.gateway_image` would be
ignored despite being set. This PR restores that functionality.
There was a missing layer of interpolation that needs to occur for
these parameters. Since Nomad 1.0 now supports dynamic envoy versioning
through the ${NOMAD_envoy_version} psuedo variable, we basically need
to first interpolate
${connect.sidecar_image} => envoyproxy/envoy:v${NOMAD_envoy_version}
then use Consul at runtime to resolve to a real image, e.g.
envoyproxy/envoy:v${NOMAD_envoy_version} => envoyproxy/envoy:v1.16.0
Of course, if the version of Consul is too old to provide an envoy
version preference, we then need to know to fallback to the old
version of envoy that we used before.
envoyproxy/envoy:v${NOMAD_envoy_version} => envoyproxy/envoy:v1.11.2@sha256:a7769160c9c1a55bb8d07a3b71ce5d64f72b1f665f10d81aa1581bc3cf850d09
Beyond that, we also need to continue to support jobs that set the
sidecar task themselves, e.g.
sidecar_task { config { image: "custom/envoy" } }
which itself could include teh pseudo envoy version variable.
As newer versions of Consul are released, the minimum version of Envoy
it supports as a sidecar proxy also gets bumped. Starting with the upcoming
Consul v1.9.X series, Envoy v1.11.X will no longer be supported. Current
versions of Nomad hardcode a version of Envoy v1.11.2 to be used as the
default implementation of Connect sidecar proxy.
This PR introduces a change such that each Nomad Client will query its
local Consul for a list of Envoy proxies that it supports (https://github.com/hashicorp/consul/pull/8545)
and then launch the Connect sidecar proxy task using the latest supported version
of Envoy. If the `SupportedProxies` API component is not available from
Consul, Nomad will fallback to the old version of Envoy supported by old
versions of Consul.
Setting the meta configuration option `meta.connect.sidecar_image` or
setting the `connect.sidecar_task` stanza will take precedence as is
the current behavior for sidecar proxies.
Setting the meta configuration option `meta.connect.gateway_image`
will take precedence as is the current behavior for connect gateways.
`meta.connect.sidecar_image` and `meta.connect.gateway_image` may make
use of the special `${NOMAD_envoy_version}` variable interpolation, which
resolves to the newest version of Envoy supported by the Consul agent.
Addresses #8585#7665
Seth Hoenig