64fc002e03
Failover is pushed entirely down to the data plane by creating envoy
clusters and putting each successive destination in a different load
assignment priority band. For example this shows that normally requests
go to 1.2.3.4:8080 but when that fails they go to 6.7.8.9:8080:
- name: foo
load_assignment:
cluster_name: foo
policy:
overprovisioning_factor: 100000
endpoints:
- priority: 0
lb_endpoints:
- endpoint:
address:
socket_address:
address: 1.2.3.4
port_value: 8080
- priority: 1
lb_endpoints:
- endpoint:
address:
socket_address:
address: 6.7.8.9
port_value: 8080
Mesh gateways route requests based solely on the SNI header tacked onto
the TLS layer. Envoy currently only lets you configure the outbound SNI
header at the cluster layer.
If you try to failover through a mesh gateway you ideally would
configure the SNI value per endpoint, but that's not possible in envoy
today.
This PR introduces a simpler way around the problem for now:
1. We identify any target of failover that will use mesh gateway mode local or
remote and then further isolate any resolver node in the compiled discovery
chain that has a failover destination set to one of those targets.
2. For each of these resolvers we will perform a small measurement of
comparative healths of the endpoints that come back from the health API for the
set of primary target and serial failover targets. We walk the list of targets
in order and if any endpoint is healthy we return that target, otherwise we
move on to the next target.
3. The CDS and EDS endpoints both perform the measurements in (2) for the
affected resolver nodes.
4. For CDS this measurement selects which TLS SNI field to use for the cluster
(note the cluster is always going to be named for the primary target)
5. For EDS this measurement selects which set of endpoints will populate the
cluster. Priority tiered failover is ignored.
One of the big downsides to this approach to failover is that the failover
detection and correction is going to be controlled by consul rather than
deferring that entirely to the data plane as with the prior version. This also
means that we are bound to only failover using official health signals and
cannot make use of data plane signals like outlier detection to affect
failover.
In this specific scenario the lack of data plane signals is ok because the
effectiveness is already muted by the fact that the ultimate destination
endpoints will have their data plane signals scrambled when they pass through
the mesh gateway wrapper anyway so we're not losing much.
Another related fix is that we now use the endpoint health from the
underlying service, not the health of the gateway (regardless of
failover mode).
88 lines
3 KiB
Go
88 lines
3 KiB
Go
package proxycfg
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import (
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"context"
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"github.com/hashicorp/consul/agent/structs"
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"github.com/mitchellh/copystructure"
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)
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type configSnapshotConnectProxy struct {
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Leaf *structs.IssuedCert
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DiscoveryChain map[string]*structs.CompiledDiscoveryChain // this is keyed by the Upstream.Identifier(), not the chain name
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WatchedUpstreams map[string]map[string]context.CancelFunc
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WatchedUpstreamEndpoints map[string]map[string]structs.CheckServiceNodes
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WatchedGateways map[string]map[string]context.CancelFunc
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WatchedGatewayEndpoints map[string]map[string]structs.CheckServiceNodes
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UpstreamEndpoints map[string]structs.CheckServiceNodes // DEPRECATED:see:WatchedUpstreamEndpoints
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}
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type configSnapshotMeshGateway struct {
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WatchedServices map[string]context.CancelFunc
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WatchedDatacenters map[string]context.CancelFunc
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ServiceGroups map[string]structs.CheckServiceNodes
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ServiceResolvers map[string]*structs.ServiceResolverConfigEntry
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GatewayGroups map[string]structs.CheckServiceNodes
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}
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// ConfigSnapshot captures all the resulting config needed for a proxy instance.
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// It is meant to be point-in-time coherent and is used to deliver the current
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// config state to observers who need it to be pushed in (e.g. XDS server).
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type ConfigSnapshot struct {
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Kind structs.ServiceKind
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Service string
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ProxyID string
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Address string
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Port int
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TaggedAddresses map[string]structs.ServiceAddress
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Proxy structs.ConnectProxyConfig
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Datacenter string
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Roots *structs.IndexedCARoots
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// connect-proxy specific
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ConnectProxy configSnapshotConnectProxy
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// mesh-gateway specific
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MeshGateway configSnapshotMeshGateway
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// Skip intentions for now as we don't push those down yet, just pre-warm them.
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}
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// Valid returns whether or not the snapshot has all required fields filled yet.
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func (s *ConfigSnapshot) Valid() bool {
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switch s.Kind {
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case structs.ServiceKindConnectProxy:
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// TODO(rb): sanity check discovery chain things here?
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return s.Roots != nil && s.ConnectProxy.Leaf != nil
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case structs.ServiceKindMeshGateway:
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// TODO (mesh-gateway) - what happens if all the connect services go away
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return s.Roots != nil && len(s.MeshGateway.ServiceGroups) > 0
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default:
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return false
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}
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}
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// Clone makes a deep copy of the snapshot we can send to other goroutines
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// without worrying that they will racily read or mutate shared maps etc.
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func (s *ConfigSnapshot) Clone() (*ConfigSnapshot, error) {
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snapCopy, err := copystructure.Copy(s)
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if err != nil {
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return nil, err
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}
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snap := snapCopy.(*ConfigSnapshot)
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// nil these out as anything receiving one of these clones does not need them and should never "cancel" our watches
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switch s.Kind {
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case structs.ServiceKindConnectProxy:
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snap.ConnectProxy.WatchedUpstreams = nil
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snap.ConnectProxy.WatchedGateways = nil
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case structs.ServiceKindMeshGateway:
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snap.MeshGateway.WatchedDatacenters = nil
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snap.MeshGateway.WatchedServices = nil
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}
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return snap, nil
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}
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