Traffic management

Requests are routed to a services within a service mesh with virtual services. Each virtual service consists of a set of routing rules that are evaluated in order. Red Hat OpenShift Service Mesh matches each given request to the virtual service to a specific real destination within the mesh.

Without virtual services, Red Hat OpenShift Service Mesh distributes traffic using round-robin load balancing between all service instances. With a virtual service, you can specify traffic behavior for one or more hostnames. Routing rules in the virtual service tell Red Hat OpenShift Service Mesh how to send the traffic for the virtual service to appropriate destinations. route destinations can be versions of the same service or entirely different services.

The following example routes requests to different versions of a service depending on which user connects to the application. Use this command to apply this example YAML file, or one you create.

The hosts field lists the virtual service’s user-addressable destination that these routing rules apply to. This is the address or addresses the client uses when sending requests to the service.

The virtual service hostname can be an IP address, a DNS name, or, depending on the platform, a short name that resolves to a fully qualified domain name.

The http section contains the virtual service’s routing rules, describing match conditions and actions for routing HTTP/1.1, HTTP2, and gRPC traffic sent to the destination specified in the hosts field. A routing rule consists of the destination where you want the traffic to go and zero or more match conditions, depending on your use case.

The first routing rule in the example has a condition and begins with the match field. In this example, this routing applies to all requests from the user jason. Add the headers, end-user, and exact fields to select the appropriate requests.

The destination field in the route section specifies the actual destination for traffic that matches this condition. Unlike the virtual service’s host, the destination’s host must be a real destination that exists in the Red Hat OpenShift Service Mesh service registry. This can be a mesh service with proxies or a non-mesh service added using a service entry. In this example, the host name is a Kubernetes service name:

Destination rules are applied after virtual service routing rules are evaluated, so they apply to the traffic’s real destination. Virtual services route traffic to a destination. Destination rules configure what happens to traffic at that destination.

You can use a gateway to manage inbound and outbound traffic for your mesh to specify which traffic you want to enter or leave the mesh. Gateway configurations are applied to standalone Envoy proxies that are running at the edge of the mesh, rather than sidecar Envoy proxies running alongside your service workloads.

Unlike other mechanisms for controlling traffic entering your systems, such as the Kubernetes Ingress APIs, Red Hat OpenShift Service Mesh gateways let you use the full power and flexibility of traffic routing. The Red Hat OpenShift Service Mesh gateway resource can layer 4-6 load balancing properties such as ports to expose, Red Hat OpenShift Service Mesh TLS settings. Instead of adding application-layer traffic routing (L7) to the same API resource, you can bind a regular Red Hat OpenShift Service Mesh virtual service to the gateway and manage gateway traffic like any other data plane traffic in a service mesh.

Gateways are primarily used to manage ingress traffic, but you can also configure egress gateways. An egress gateway lets you configure a dedicated exit node for the traffic leaving the mesh, letting you limit which services have access to external networks, or to enable secure control of egress traffic to add security to your mesh, for example. You can also use a gateway to configure a purely internal proxy.

The following example shows a possible gateway configuration for external HTTPS ingress traffic:

This gateway configuration lets HTTPS traffic from ext-host.example.com into the mesh on port 443, but doesn’t specify any routing for the traffic.

To specify routing and for the gateway to work as intended, you must also bind the gateway to a virtual service. You do this using the virtual service’s gateways field, as shown in the following example:

You can then configure the virtual service with routing rules for the external traffic.

A service entry adds an entry to the service registry that Red Hat OpenShift Service Mesh maintains internally. After you add the service entry, the Envoy proxies can send traffic to the service as if it was a service in your mesh. Configuring service entries allows you to manage traffic for services running outside of the mesh, including the following tasks:

The following example mesh-external service entry adds the ext-resource external dependency to the Red Hat OpenShift Service Mesh service registry:

Specify the external resource using the hosts field. You can qualify it fully or use a wildcard prefixed domain name.

You can configure virtual services and destination rules to control traffic to a service entry in the same way you configure traffic for any other service in the mesh. For example, the following destination rule configures the traffic route to use mutual TLS to secure the connection to the ext-svc.example.com external service that is configured using the service entry:

By default, Red Hat OpenShift Service Mesh configures every Envoy proxy to accept traffic on all the ports of its associated workload, and to reach every workload in the mesh when forwarding traffic. You can use a sidecar configuration to do the following:

You can specify that you want a sidecar configuration to apply to all workloads in a particular namespace, or choose specific workloads using a workloadSelector. For example, the following sidecar configuration configures all services in the bookinfo namespace to only reach services running in the same namespace and the Red Hat OpenShift Service Mesh control plane (currently needed to use the Red Hat OpenShift Service Mesh policy and telemetry features):