Istio integration

Emissary-ingress and Istio: Edge Proxy and Service Mesh together in one. Emissary-ingress is deployed at the edge of your network and routes incoming traffic to your internal services (aka "north-south" traffic). Istio is a service mesh for microservices, and is designed to add application-level Layer (L7) observability, routing, and resilience to service-to-service traffic (aka "east-west" traffic). Both Istio and Emissary-ingress are built using Envoy.

Emissary-ingress and Istio can be deployed together on Kubernetes. In this configuration, Emissary-ingress manages traditional edge functions such as authentication, TLS termination, and edge routing. Istio mediates communication from Emissary-ingress to services, and communication between services.

This allows the operator to have the best of both worlds: a high performance, modern edge service (Emissary-ingress) combined with a state-of-the-art service mesh (Istio). While Istio has introduced a Gateway abstraction, Emissary-ingress still has a much broader feature set for edge routing than Istio. For more on this topic, see our blog post on API Gateway vs Service Mesh.

This guide explains how to take advantage of both Emissary-ingress and Istio to have complete control and observability over how requests are made in your cluster:

• Install Istio and configure auto-injection
• Install Emissary-ingress with Istio integration
• Configure an mTLS TLSContext
• Route to services using mTLS

If desired, you may also

• Enable strict mTLS
• Configure Prometheus metrics collection
• Configure Istio distributed tracing

To follow this guide, you need:

• A Kubernetes cluster version 1.15 and above
• kubectl
• Istio version 1.10 or higher

Install Istio

Start by installing Istio. Any supported installation method for Istio will work for use with Emissary-ingress.

Configure Istio Auto-Injection

Istio functions by supplying a sidecar container running Envoy with every service in the mesh (including Emissary-ingress). The sidecar is what enforces Istio policies for traffic to and from the service, notably including mTLS encryption and certificate handling. As such, it is very important that the sidecar be correctly supplied for every service in the mesh!

While it is possible to manage sidecars by hand, it is far easier to allow Istio to automatically inject the sidecar as necessary. To do this, set the istio-injection label on each Kubernetes Namespace for which you want auto-injection:

Install Emissary-ingress with Istio Integration

Properly integrating Emissary-ingress with Istio provides support for:

• Mutual TLS (mTLS), with certificates managed by Istio, to allow end-to-end encryption for east-west traffic;
• Automatic generation of Prometheus metrics for services; and
• Istio distributed tracing for end-to-end observability.

The simplest way to enable everything is to install Emissary-ingress using Helm, though you can use manual installation with YAML if you wish.

Installation with Helm (Recommended)

To install with Helm, write the following YAML to a file called istio-integration.yaml:

To install Emissary-ingress with Helm, use these values to configure Istio integration:

1. Create the emissary Namespace:

2. Enable Istio auto-injection for it:

3. Make sure the Helm repo is configured:

4. Use Helm to install Emissary-ingress in emissary:

Installation Using YAML

To install using YAML files, you need to manually incorporate the contents of the istio-integration.yaml file shown above into your deployment YAML:

• pod-annotations should be configured as Kubernetes annotations on the Emissary-ingress Pods;
• volumes, volumeMounts, and env contents should be included in the emissary-ingress Deployment; and
• you must also label the emissary Namespace for auto-injection as described above.

Configuring an Existing Installation

If you have already installed Emissary-ingress and want to enable Istio:

1. Install Istio.
2. Label the emissary namespace for Istio auto-injection, as above.
3. Edit the Emissary-ingress Deployments to contain the annotations, volumes, volumeMounts, and env elements shown above.
   • If you installed with Helm, you can use helm upgrade with -f istio-integration.yaml to modify the installation for you.
4. Restart the Emissary-ingress pods.

Configure an mTLS TLSContext

After configuring Emissary-ingress for Istio integration, the Istio mTLS certificates are available within Emissary-ingress:

• Both the istio-proxy sidecar and Emissary-ingress mount the istio-certs volume at /etc/istio-certs.

• The istio-proxy sidecar saves the mTLS certificates into /etc/istio-certs (per the OUTPUT_CERTS environment variable).

• Emissary-ingress reads the mTLS certificates from /etc/istio-certs (per the AMBASSADOR_ISTIO_SECRET_DIR environment variable) and creates a Secret named istio-certs.

  At present, the Secret name istio-certs cannot be changed.

To make use of the istio-certs Secret, create a TLSContext referencing it:

Once the TLSContext is created, a Mapping can use it for TLS origination. An example might be:

This Mapping will use mTLS when communicating with its upstream service.

Route to Services Using mTLS

After integrating Emissary-ingress with Istio, Emissary-ingress's feature-rich routing capabilities and Istio's mTLS and observability are all available for all incoming traffic. To take full advantage of both, you need to:

• configure upstream services with the Istio sidecar;
• configure Mappings to use mTLS; and
• verify your service port configuration.

Configure Upstream Services with the Istio Sidecar

Upstream services must have the Istio sidecar configured. The easiest way to arrange for this is to use Istio automatic sidecar injection as discussed above.

This will tell Istio to automatically inject the istio-proxy sidecar container into pods in this namespace.

Configure Mappings to Use mTLS

Traffic routing in Emissary-ingress is configured with the Mapping resource. This is a powerful configuration object that lets you configure different routing rules for different services.

To configure a Mapping to use mTLS, you need to use the tls element of the Mapping to tell it to originate TLS using the istio-upstream TLSContext above:

For example, if you have installed the Quote service as described on the Getting Started page, you will have a Mapping as follows:

To take advantage of Istio mTLS, update the above Mapping to originate TLS using the Istio mTLS certificates and to force access on port 80:

The behavior of your service will not seem to change, even though mTLS is active:

This request first went to Emissary-ingress, which routed it over an mTLS connection to the quote service in the default namespace. That connection was intercepted by the istio-proxy which authenticated the request as being from Emissary-ingress, exported various metrics, and finally forwarded it on to the actual quote service.

Configure Service Ports

When mTLS is active, Istio makes TLS connections to your services. Since Istio handles the TLS protocol for you, you don't need to modify your services — however, the TLS connection will still use port 443 if you don't configure your Mappings to explicitly use port 80.

If your upstream service was not written to use TLS, its Service resource may only map port 80. If Istio attempts a TLS connection on port 443 when port 443 is not defined by the Service resource, the connection will hang even though the Istio sidecar is active, because Kubernetes itself doesn't know how to handle the connection to port 443.

As shown above, one simple way to deal with this situation is to explicitly specify port 80 in the Mapping's service:

Another way is to set up your Kubernetes Service to map both port 80 and port 443. For example, the Quote (which listens on port 8080 in its pod) might use a Service like this:

Note that ports 80 and 443 are both mapped to targetPort 8080, where the service is actually listening. This permits Istio routing to work whether mTLS is active or not.

Enable Strict mTLS

Istio defaults to permissive mTLS, where mTLS is allowed between services, but not required. Configuring strict mTLS requires all connections within the cluster be encrypted. To switch Istio to use strict mTLS, apply a PeerAuthentication resource in each namespace that should operate in strict mode:

To test strict mTLS, remove the tls configuration from the quote-backend Mapping and send a request:

Make sure to restore the tls configuration when testing is complete!

Configure Prometheus Metrics Collection

By default, the Istio sidecar provides Prometheus metrics using prometheus.io annotations. To take advantage of these metrics, you must install Prometheus.

Configure Istio Distributed Tracing

The Istio sidecar also supports distributed tracing by default. To take advantage of this support, you need to:

1. Install a tracing provider, for example Zipkin into your cluster.

2. Add a TracingService to tell Emissary-ingress to send tracing to your tracing provider, for example:

After adding a TracingService, restart Emissary-ingress for the configuration to take effect. Istio propagates the tracing headers automatically, allowing for end-to-end observability within the cluster.

FAQ

How to test Istio certificate rotation

By default, Istio mTLS certificates are valid for 90 days, but get rotated every day.

Emissary-ingress updates the mTLS certificates as they are rotated, so you don't need to worry about certificate expiration.

To test that Emissary-ingress is properly rotating certificates, shorten the TTL of the Istio certificates by setting the following environment variables in the istiod container in the istio-system Namespace:

This makes the certificates Istio issues expire in one hour so testing certificate rotation is much easier.