Global Configuration

The ambassador Module

If present, the ambassador Module defines system-wide configuration. This module can be applied to any Kubernetes service (the ambassador service itself is a common choice). You may very well not need this Module. The defaults in the ambassador Module are:

apiVersion: getambassador.io/v2
kind:  Module
metadata:
  name:  ambassador
spec:
# Use ambassador_id only if you are using multiple ambassadors in the same cluster.
# For more information: ../../running#ambassador_id.
  # ambassador_id: "<ambassador_id>"
  config:
# Use the following table for config fields

Additional config Field Examples

circuit_breakers sets the global circuit breaking configuration that Ambassador will use for all mappings, unless overridden in a mapping. More information at the circuit breaking reference.

circuit_breakers
  max_connections: 2048
  ...

cors sets the default CORS configuration for all mappings in the cluster. See the CORS syntax.

cors:
  origins: http://foo.example,http://bar.example
  methods: POST, GET, OPTIONS
  ...
  ...

diagnostics configures Ambassador's diagnostics services.

• Both the API Gateway and the Edge Stack provide low-level diagnostics at /ambassador/v0/diag/.
• The Ambassador Edge Stack also provides the higher-level Edge Policy Console at /edge_stack/admin/.

By default, both services are enabled:

diagnostics:
  enabled: true

Setting diagnostics.enabled to false will disable the routes for both services (they will remain accessible from inside the Ambassador pod on port 8877):

diagnostics:
  enabled: false

keepalive sets the global keepalive settings. Ambassador will use for all mappings unless overridden in a mapping. No default value is provided by Ambassador. More information at https://www.envoyproxy.io/docs/envoy/latest/api-v2/api/v2/core/address.proto#envoy-api-msg-core-tcpkeepalive

keepalive:
  time: 2
  interval: 2
  probes: 100

liveness_probe defaults on, but you can disable the API route. It will remain accessible on diag_port.

liveness_probe:
      enabled: true

load_balancer sets the global load balancing type and policy that Ambassador will use for all mappings unless overridden in a mapping. Defaults to round-robin with Kubernetes. More information at the load balancer reference.

load_balancer:
  policy: round_robin/least_request/ring_hash/maglev
  ...

readiness_probe defaults on, but you can disable the API route. It will remain accessible on diag_port.

readiness_probe:
  enabled: true

retry_policy lets you add resilience to your services in case of request failures by performing automatic retries.

retry_policy:
  retry_on: "5xx"
  ...

Overriding Default Ports

By default, Ambassador Edge Stack listens for HTTP or HTTPS traffic on ports 8080 or 8443 respectively. This value can be overridden by setting the service_port in the Ambassador Module:

---
apiVersion: getambassador.io/v2
kind: Module
metadata:
  name: ambassador
spec:
  config:
    service_port: 4567

This will configure Ambassador Edge Stack to listen for traffic on port 4567 instead of 8080.

Regular Expressions (regex_type)

If regex_type is unset (the default), or is set to any value other than unsafe, Ambassador Edge Stack will use the RE2 regular expression engine. This engine is designed to support most regular expressions, but keep bounds on execution time. RE2 is the recommended regular expression engine.

If regex_type is set to unsafe, Ambassador Edge Stack will use the modified ECMAScript regular expression engine. This is not recommended since the modified ECMAScript engine can consume unbounded CPU in some cases (mostly relating to backreferences and lookahead); it is provided for backward compatibility if necessary.

Lua Scripts (lua_scripts)

Ambassador Edge Stack supports the ability to inline Lua scripts that get run on every request. This is useful for simple use cases that mutate requests or responses, e.g., add a custom header. Here is a sample:

---
apiVersion: getambassador.io/v2
kind: Module
metadata:
  name: ambassador
spec:
  config:
    lua_scripts: |
      function envoy_on_response(response_handle)
        response_handle:headers():add("Lua-Scripts-Enabled", "Processed")
      end

For more details on the Lua API, see the Envoy Lua filter documentation.

Some caveats around the embedded scripts:

• They run in-process, so any bugs in your Lua script can break every request
• They're inlined in the Ambassador Edge Stack YAML, so you likely won't want to write complex logic in here
• They're run on every request/response to every URL

If you need more flexible and configurable options, Ambassador Edge Stack supports a pluggable Filter system.

Linkerd Interoperability (add_linkerd_headers)

When using Linkerd, requests going to an upstream service need to include the l5d-dst-override header to ensure that Linkerd will route them correctly. Setting add_linkerd_headers does this automatically; see the Mapping documentation for more details.

Upstream Idle Timeout (cluster_idle_timeout_ms)

If set, cluster_idle_timeout_ms specifies the timeout (in milliseconds) after which an idle connection upstream is closed. If no cluster_idle_timeout_ms is specified, upstream connections will never be closed due to idling.

gRPC HTTP/1.1 bridge (enable_grpc_http11_bridge)

Ambassador supports bridging HTTP/1.1 clients to backend gRPC servers. When an HTTP/1.1 connection is opened and the request content type is application/grpc, Ambassador will buffer the response and translate into gRPC requests. For more details on the translation process, see the Envoy gRPC HTTP/1.1 bridge documentation. This setting can be enabled by setting enable_grpc_http11_bridge: true.

gRPC-Web (enable_grpc_web)

gRPC is a binary HTTP/2-based protocol. While this allows high performance, it is problematic for any programs that cannot speak raw HTTP/2 (such as JavaScript in a browser). gRPC-Web is a JSON and HTTP-based protocol that wraps around the plain gRPC to alleviate this problem and extend benefits of gRPC to the browser, at the cost of performance.

The gRPC-Web specification requires a server-side proxy to translate between gRPC-Web requests and gRPC backend services. Ambassador can serve as the service-side proxy for gRPC-Web when enable_grpc_web: true is set. Find more on the gRPC Web client GitHub.

HTTP/1.0 support (enable_http10)

Enable/disable the handling of incoming HTTP/1.0 and HTTP 0.9 requests.

Listener Idle Timeout (listener_idle_timeout_ms)

Controls how Envoy configures the tcp idle timeout on the http listener. Default is no timeout (TCP connection may remain idle indefinitely). This is useful if you have proxies and/or firewalls in front of Ambassador and need to control how Ambassador initiates closing an idle TCP connection. Please see the Envoy documentation for more information.

enable_ivp4 and enable_ipv6

If both IPv4 and IPv6 are enabled, Ambassador Edge Stack will prefer IPv6. This can have strange effects if Ambassador Edge Stack receives AAAA records from a DNS lookup, but the underlying network of the pod doesn't actually support IPv6 traffic. For this reason, the default is IPv4 only.

A Mapping can override both enable_ipv4 and enable_ipv6, but if either is not stated explicitly in a Mapping, the values here are used. Most Ambassador Edge Stack installations will probably be able to avoid overriding these settings in Mappings.

Readiness and Liveness probes (readiness_probe and liveness_probe)

The default liveness and readiness probes map /ambassador/v0/check_alive and ambassador/v0/check_ready internally to check Envoy itself. If you'd like to, you can change these to route requests to some other service. For example, to have the readiness probe map to the quote application's health check, you could do

readiness_probe:
  service: quote
  rewrite: /backend/health

The liveness and readiness probe both support prefix, rewrite, and service, with the same meanings as for mappings. Additionally, the enabled boolean may be set to false (as in the commented-out examples above) to disable support for the probe entirely.

Note well that configuring the probes in the ambassador Module only means that Ambassador Edge Stack will respond to the probes. You must still configure Kubernetes to perform the checks, as shown in the Datawire-provided YAML files.

use_remote_address

In Ambassador 0.50 and later, the default value for use_remote_address to true. When set to true, Ambassador Edge Stack will append to the X-Forwarded-For header its IP address so upstream clients of Ambassador Edge Stack can get the full set of IP addresses that have propagated a request. You may also need to set externalTrafficPolicy: Local on your LoadBalancer as well to propagate the original source IP address. See the Envoy documentation and the Kubernetes documentation for more details.

Note well that if you need to use X-Forwarded-Proto, you must set use_remote_address to false.

use_proxy_proto

Many load balancers can use the PROXY protocol to convey information about the connection they are proxying. In order to support this in Ambassador Edge Stack, you'll need to set use_proxy_protocol to true; this is not the default since the PROXY protocol is not compatible with HTTP.

xff_num_trusted_hops

The value of xff_num_trusted_hops indicates the number of trusted proxies in front of Ambassador Edge Stack. The default setting is 0 which tells Envoy to use the immediate downstream connection's IP address as the trusted client address. The trusted client address is used to populate the remote_address field used for rate limiting and can affect which IP address Envoy will set as X-Envoy-External-Address.

xff_num_trusted_hops behavior is determined by the value of use_remote_address (which defaults to true in Ambassador Edge Stack).

• If use_remote_address is false and xff_num_trusted_hops is set to a value N that is greater than zero, the trusted client address is the (N+1)th address from the right end of XFF. (If the XFF contains fewer than N+1 addresses, Envoy falls back to using the immediate downstream connection’s source address as a trusted client address.)

• If use_remote_address is true and xff_num_trusted_hops is set to a value N that is greater than zero, the trusted client address is the Nth address from the right end of XFF. (If the XFF contains fewer than N addresses, Envoy falls back to using the immediate downstream connection’s source address as a trusted client address.)

Refer to Envoy's documentation for some detailed examples of this interaction.

NOTE: This value is not dynamically configurable in Envoy. A restart is required changing the value of xff_num_trusted_hops for Envoy to respect the change.