» Connect Proxies

A Connect-aware proxy enables unmodified applications to use Connect. A per-service proxy sidecar transparently handles inbound and outbound service connections, automatically wrapping and verifying TLS connections.

When a proxy is used, the actual service being proxied should only accept connections on a loopback address. This requires all external connections to be established via the Connect protocol to provide authentication and authorization.

» Proxy Service Definitions

Connect proxies are registered using regular service definitions. They can be registered both in config files or via the API just like any other service.

Additionally, to reduce the amount of boilerplate needed for a sidecar proxy, application service definitions may define inline sidecar service registrations which are an opinionated shorthand for a separate full proxy registration as described here.

To function as a Connect proxy, they must be declared as a proxy type and provide information about the service they represent.

To declare a service as a proxy, the service definition must contain the following fields:

• kind (string) must be set to connect-proxy. This declares that the service is a proxy type.

• proxy.destination_service_name (string) must be set to the service that this proxy is representing. Note that this replaces proxy_destination in versions 1.2.0 to 1.3.0.

• port (int) must be set so that other Connect services can discover the exact address for connections. address is optional if the service is being registered against an agent, since it'll inherit the node address.

Minimal Example:

{
  "name": "redis-proxy",
  "kind": "connect-proxy",
  "proxy": {
    "destination_service_name": "redis"
  },
  "port": 8181
}

With this service registered, any Connect clients searching for a Connect-capable endpoint for "redis" will find this proxy.

» Sidecar Proxy Fields

Most Connect proxies are deployed as "sidecars" which means they are co-located with a single service instance which they represent and proxy all inbound traffic to. In this case the following fields should also be set:

• proxy.destination_service_id (string: <required>) is set to the id (and not the name if they are different) of the specific service instance that is being proxied. The proxied service is assumed to be registered on the same agent although it's not strictly validated to allow for un-coordinated registrations.

• proxy.local_service_port (int: <required>) must specify the port the proxy should use to connect to the local service instance.

• proxy.local_service_address (string: "") can be set to override the IP or hostname the proxy should use to connect to the local service. Defaults to 127.0.0.1.

» Complete Configuration Example

The following is a complete example showing all the options available when registering a proxy instance.

{
  "name": "redis-proxy",
  "kind": "connect-proxy",
  "proxy": {
    "destination_service_name": "redis",
    "destination_service_id": "redis1",
    "local_service_address": "127.0.0.1",
    "local_service_port": 9090,
    "config": {},
    "upstreams": []
  },
  "port": 8181
}

» Proxy Parameters

• destination_service_name (string: <required>) - Specifies the name of the service this instance is proxying. Both side-car and centralized load-balancing proxies must specify this. It is used during service discovery to find the correct proxy instances to route to for a given service name.

• destination_service_id (string: "") - Specifies the ID of a single specific service instance that this proxy is representing. This is only valid for side-car style proxies that run on the same node. It is assumed that the service instance is registered via the same Consul agent so the ID is unique and has no node qualifier. This is useful to show in tooling which proxy instance is a side-car for which application instance and will enable fine-grained analysis of the metrics coming from the proxy.

• local_service_address (string: "") - Specifies the address a side-car proxy should attempt to connect to the local application instance on. Defaults to 127.0.0.1.

• local_service_port (int: <optional>) - Specifies the port a side-car proxy should attempt to connect to the local application instance on. Defaults to the port advertised by the service instance identified by destination_service_id if it exists otherwise it may be empty in responses.

• config (object: {}) - Specifies opaque config JSON that will be stored and returned along with the service instance from future API calls.

• upstreams (array<Upstream>: []) - Specifies the upstream services this proxy should create listeners for. The format is defined in Upstream Configuration Reference.

» Upstream Configuration Reference

The following examples show all possible upstream configuration parameters.

Note that in versions 1.2.0 to 1.3.0, managed proxy upstreams were specified inside the opaque connect.proxy.config map. The format is almost unchanged however managed proxy upstreams are now defined a level up in the connect.proxy.upstreams. The old location is deprecated and will be automatically converted into the new for an interim period before support is dropped in a future major release. The only difference in format between the upstream defintions is that the field destination_datacenter has been renamed to datacenter to reflect that it's the discovery target and not necessarily the same as the instance that will be returned in the case of a prepared query that fails over to another datacenter.

Note that snake_case is used here as it works in both config file and API registrations.

Upstreams support multiple destination types. Both examples are shown below followed by documentation for each attribute.

» Service Destination

{
  "destination_type": "service",
  "destination_name": "redis",
  "datacenter": "dc1",
  "local_bind_address": "127.0.0.1",
  "local_bind_port": 1234,
  "config": {}
},

» Prepared Query Destination

{
  "destination_type": "prepared_query",
  "destination_name": "database",
  "local_bind_address": "127.0.0.1",
  "local_bind_port": 1234,
  "config": {}
},

• destination_name (string: <required>) - Specifies the name of the service or prepared query to route connect to. The prepared query should be the name or the ID of the prepared query.
• local_bind_port (int: <required>) - Specifies the port to bind a local listener to for the application to make outbound connections to this upstream.
• local_bind_address (string: "") - Specifies the address to bind a local listener to for the application to make outbound connections to this upstream. Defaults to 127.0.0.1.
• destination_type (string: "") - Speficied the type of discovery query to use to find an instance to connect to. Valid values are service or prepared_query. Defaults to service.
• datacenter (string: "") - Specifies the datacenter to issue the discovery query too. Defaults to the local datacenter.
• config (object: {}) - Specifies opaque configuration options that will be provided to the proxy instance for this specific upstream. Can contain any valid JSON object. This might be used to configure proxy-specific features like timeouts or retries for the given upstream. See the built-in proxy configuration reference for options available when using the built-in proxy. If using Envoy as a proxy, see Envoy configuration reference

» Dynamic Upstreams

If an application requires dynamic dependencies that are only available at runtime, it must currently natively integrate with Connect. After natively integrating, the HTTP API or DNS interface can be used.