Managed Proxy for Connect Legacy Documentation

Consul Connect was first released as a beta feature in Consul 1.2.0. The initial release included a feature called "Managed Proxies". Managed proxies were Connect proxies where the proxy process was started, configured, and stopped by Consul. They were enabled via basic configurations within the service definition.

Managed proxies have been deprecated since Consul 1.3 and have been fully removed in Consul 1.6. Anyone using Managed Proxies should aim to change their workflow as soon as possible to avoid issues with a later upgrade.

After transitioning away from all managed proxy usage, the proxy subdirectory inside data_dir (specified in Consul config) can be deleted to remove extraneous configuration files and free up disk space.

new and known issues will not be fixed.

Deprecation Rationale

Originally managed proxies traded higher implementation complexity for an easier "getting started" user experience. After seeing how Connect was investigated and adopted during beta it became obvious that they were not the best trade off.

Managed proxies only really helped in local testing or VM-per-service based models whereas a lot of users jumped straight to containers where they are not helpful. They also add only targeted fairly basic supervisor features which meant most people would want to use something else in production for consistency with other workloads. So the high implementation cost of building robust process supervision didn't actually benefit most real use-cases.

Instead of this Connect 1.3.0 introduces the concept of sidecar service registrations which have almost all of the benefits of simpler configuration but without any of the additional process management complexity. As a result they can be used to simplify configuration in both container-based and realistic production supervisor settings.

Managed Proxy Documentation

As the managed proxy features continue to be supported for now, the rest of this page will document how they work in the interim.

Managed proxies are given a unique proxy-specific ACL token that allows read-only access to Connect information for the specific service the proxy is representing. This ACL token is more restrictive than can be currently expressed manually in an ACL policy.

The default managed proxy is a basic proxy built-in to Consul and written in Go. Having a basic built-in proxy allows Consul to have a reasonable default with performance that is good enough for most workloads. In some basic benchmarks, the service-to-service communication over the built-in proxy could sustain 5 Gbps with sub-millisecond latency. Therefore, the performance impact of even the basic built-in proxy is minimal.

Consul will be integrating with advanced proxies in the near future to support more complex configurations and higher performance. The configuration below is all for the built-in proxy.

Lifecycle

The Consul agent starts managed proxies on demand and supervises them, restarting them if they crash. The lifecycle of the proxy process is decoupled from the agent so if the agent crashes or is restarted for an upgrade, the managed proxy instances will not be stopped.

Note that this behavior while desirable in production might leave proxy processes running indefinitely if you manually stop the agent and clear its data dir during testing.

To terminate a managed proxy cleanly you need to deregister the service that requested it. If the agent is already stopped and will not be restarted again, you may choose to locate the proxy processes and kill them manually.

While in -dev mode, unless a -data-dir is explicitly set, managed proxies switch to being killed when the agent exits since it can't store state in order to re-adopt them on restart.

Minimal Configuration

Managed proxies are configured within a service definition. The simplest possible managed proxy configuration is an empty configuration. This enables the default managed proxy and starts a listener for that service:

{
  "service": {
    "name": "redis",
    "port": 6379,
    "connect": { "proxy": {} }
  }
}

The listener is started on random port within the configured Connect port range. It can be discovered using the DNS interface or Catalog API. In most cases, service-to-service communication is established by a proxy configured with upstreams (described below), which handle the discovery transparently.

Upstream Configuration

To transparently discover and establish Connect-based connections to dependencies, they must be configured with a static port on the managed proxy configuration:

{
  "service": {
    "name": "web",
    "port": 8080,
    "connect": {
      "proxy": {
        "upstreams": [
          {
            "destination_name": "redis",
            "local_bind_port": 1234
          }
        ]
      }
    }
  }
}

In the example above, "redis" is configured as an upstream with static port 1234 for service "web". When a TCP connection is established on port 1234, the proxy will find Connect-compatible "redis" services via Consul service discovery and establish a TLS connection identifying as "web".

For full details of the additional configurable options available when using the built-in proxy see the built-in proxy configuration reference.

Prepared Query Upstreams

The upstream destination may also be a prepared query. This allows complex service discovery behavior such as connecting to the nearest neighbor or filtering by tags.

For example, given a prepared query named "nearest-redis" that is configured to route to the nearest Redis instance, an upstream can be configured to route to this query. In the example below, any TCP connection to port 1234 will attempt a Connect-based connection to the nearest Redis service.

{
  "service": {
    "name": "web",
    "port": 8080,
    "connect": {
      "proxy": {
        "upstreams": [
          {
            "destination_name": "redis",
            "destination_type": "prepared_query",
            "local_bind_port": 1234
          }
        ]
      }
    }
  }
}

For full details of the additional configurable options available when using the built-in proxy see the built-in proxy configuration reference.

Custom Managed Proxy

Custom proxies can also be configured to run as a managed proxy. To configure custom proxies, specify an alternate command to execute for the proxy:

{
  "service": {
    "name": "web",
    "port": 8080,
    "connect": {
      "proxy": {
        "exec_mode": "daemon",
        "command": ["/usr/bin/my-proxy", "-flag-example"],
        "config": {
          "foo": "bar"
        }
      }
    }
  }
}

The exec_mode value specifies how the proxy is executed. The only supported value at this time is "daemon". The command is the binary and any arguments to execute. The "daemon" mode expects a proxy to run as a long-running, blocking process. It should not double-fork into the background. The custom proxy should retrieve its configuration (such as the port to run on) via the custom proxy integration APIs.

The default proxy command can be changed at an agent-global level in the agent configuration. An example in HCL format is shown below.

connect {
  proxy_defaults {
    command = ["/usr/bin/my-proxy"]
  }
}

With this configuration, all services registered without an explicit proxy command will use my-proxy instead of the default built-in proxy.

The config key is an optional opaque JSON object which will be passed through to the proxy via the proxy configuration endpoint to allow any configuration options the proxy needs to be specified. See the built-in proxy configuration reference for details of config options that can be passed when using the built-in proxy.

Managed Proxy Logs

Managed proxies have both stdout and stderr captured in log files in the agent's data_dir. They can be found in <data_dir>/proxy/logs/<proxy_service_id>-std{err,out}.log.

The built-in proxy will inherit its log level from the agent so if the agent is configured with log_level = DEBUG, a proxy it starts will also output DEBUG level logs showing service discovery, certificate and authorization information.