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Deploy Kong Gateway in Hybrid Mode

Prerequisites

To get started with a hybrid mode deployment, first install an instance of Kong Gateway with TLS to be your control plane (CP) node. See the installation documentation for details.

We will bring up any subsequent data plane (DP) instances in this topic.

Note: For a hybrid mode deployment on Kubernetes, see hybrid mode in the kong/charts repository.

Generate a certificate/key pair

In hybrid mode, a mutual TLS handshake (mTLS) is used for authentication so the actual private key is never transferred on the network, and communication between CP and DP nodes is secure.

Before using hybrid mode, you need a certificate/key pair. Kong Gateway provides two modes for handling certificate/key pairs:

Shared mode: (Default) Use the Kong CLI to generate a certificate/key pair, then distribute copies across nodes. The certificate/key pair is shared by both CP and DP nodes.
PKI mode: Provide certificates signed by a central certificate authority (CA). Kong validates both sides by checking if they are from the same CA. This eliminates the risks associated with transporting private keys.

Warning: If you have a TLS-aware proxy between the DP and CP nodes, you must use PKI mode and set cluster_server_name to the CP hostname in kong.conf. Do not use shared mode, as it uses a non-standard value for TLS server name indication, and this will confuse TLS-aware proxies that rely on SNI to route traffic.

For a breakdown of the properties used by these modes, see the configuration reference.

Shared mode

PKI mode

Warning: Protect the Private Key. Ensure the private key file can only be accessed by Kong nodes belonging to the cluster. If the key is compromised, you must regenerate and replace certificates and keys on all CP and DP nodes.

On an existing Kong Gateway instance, create a certificate/key pair:
```
 kong hybrid gen_cert
```
This will generate cluster.crt and cluster.key files and save them to the current directory. By default, the certificate/key pair is valid for three years, but can be adjusted with the --days option. See kong hybrid --help for more usage information.
Copy the cluster.crt and cluster.key files to the same directory on all Kong CP and DP nodes; e.g., /cluster/cluster. Set appropriate permissions on the key file so it can only be read by Kong.

Set up the control plane

Next, give the control plane node the control_plane role, and set certificate/key parameters to point at the location of your certificates and keys.

Using Docker

Using kong.conf

In your Docker container, set the following environment variables:

For shared certificate mode, use:
```
 KONG_ROLE=control_plane
 KONG_CLUSTER_CERT=/<path-to-file>/cluster.crt
 KONG_CLUSTER_CERT_KEY=/<path-to-file>/cluster.key
```
For pki certificate mode, use:
```
 KONG_ROLE=control_plane
 KONG_CLUSTER_MTLS=pki
 KONG_CLUSTER_CA_CERT=/<path-to-file>/ca-cert.pem
 KONG_CLUSTER_CERT=/<path-to-file>/control-plane.crt
 KONG_CLUSTER_CERT_KEY=/<path-to-file>/control-plane.key
```
By setting the role of the node to control_plane, this node will listen on port 0.0.0.0:8005 by default for data plane connections, and on port 0.0.0.0:8006 for telemetry data. These ports on the control plane will need to be accessible by all data planes it controls through any firewalls you may have in place.

For PKI mode, KONG_CLUSTER_CA_CERT specifies the root CA certificate for KONG_CLUSTER_CERT and KONG_CLUSTER_CERT_KEY. This certificate must be the root CA certificate and not any of an intermediate CA. Kong allows a maximum of three levels of intermediate CAs to be used between the root CA and the cluster certificate.

If you need to change the ports that the control plane listens on, set:
```
 KONG_CLUSTER_LISTEN=0.0.0.0:<port>
 KONG_CLUSTER_TELEMETRY_LISTEN=0.0.0.0:<port>
```
Next, start Kong, or reload Kong if it’s already running:
```
 kong start
```
```
 kong reload
```

Note that the control plane still needs a database to store the central configurations, although the database never needs to be accessed by data plane nodes. You may run multiple control plane nodes to provide load balancing and redundancy, as long as they all point to the same backend database.

Note: Control plane nodes cannot be used for proxying.

(Optional) Revocation checks of data plane certificates

When Kong is running hybrid mode with PKI mode, the control plane can be configured to optionally check for revocation status of the connecting data plane certificate.

The supported method is through Online Certificate Status Protocol (OCSP) responders. Issued data plane certificates must contain the Certificate Authority Information Access extension that references the URI of OCSP responder that can be reached from the control plane.

To enable OCSP checks, set the cluster_ocsp config on the control plane to one of the following values:

on: OCSP revocation check is enabled and the data plane must pass the revocation check to establish connection with the control plane. This implies that certificates without the OCSP extension or unreachable OCSP responder also prevents a connection from being established.
off: OCSP revocation check is disabled (default).
optional: OCSP revocation check will be attempted, however, if the OCSP responder URI is not found inside the data plane-provided certificate or communication with the OCSP responder failed, then data plane is still allowed through.

Note that OCSP checks are only performed on the control plane against certificates provided by incoming data plane nodes. The cluster_ocsp config has no effect on data plane nodes. cluster_oscp affects all hybrid mode connections established from a data plane to its control plane.

Install and start data planes

Now that the control plane is running, you can attach data plane nodes to it to start serving traffic.

In this step, you will give all data plane nodes the data_plane role, point them to the control plane, set certificate/key parameters to point at the location of your certificates and keys, and ensure the database is disabled.

In addition, the certificate from cluster_cert (in shared mode) or cluster_ca_cert (in pki mode) is automatically added to the trusted chain in lua_ssl_trusted_certificate.

Important: Data plane nodes receive updates from the control plane via a format similar to declarative config, therefore database has to be set to off for Kong to start up properly.

See the DP node start sequence for more information on how data plane nodes process configuration.

Using Docker

Using kong.conf

Using the Docker installation documentation, follow the instructions to:
1. Download Kong Gateway.
2. Create a Docker network.
Warning: Do not start or create a database on this node.

Bring up your data plane container with the following settings:

For shared certificate mode, use:

      Kong Gateway
    

      Kong Gateway (OSS)
    
docker run -d --name kong-dp --network=kong-net \
-e "KONG_ROLE=data_plane" \
-e "KONG_DATABASE=off" \
-e "KONG_PROXY_LISTEN=0.0.0.0:8000" \
-e "KONG_CLUSTER_CONTROL_PLANE=control-plane.<admin-hostname>.com:8005" \
-e "KONG_CLUSTER_TELEMETRY_ENDPOINT=control-plane.<admin-hostname>.com:8006" \
-e "KONG_CLUSTER_CERT=/<path-to-file>/cluster.crt" \
-e "KONG_CLUSTER_CERT_KEY=/<path-to-file>/cluster.key" \
--mount type=bind,source="$(pwd)"/cluster,target=<path-to-keys-and-certs>,readonly \
-p 8000:8000 \
kong/kong-gateway:3.4.3.18-alpine
docker run -d --name kong-dp --network=kong-net \
-e "KONG_ROLE=data_plane" \
-e "KONG_DATABASE=off" \
-e "KONG_PROXY_LISTEN=0.0.0.0:8000" \
-e "KONG_CLUSTER_CONTROL_PLANE=control-plane.<admin-hostname>.com:8005" \
-e "KONG_CLUSTER_TELEMETRY_ENDPOINT=control-plane.<admin-hostname>.com:8006" \
-e "KONG_CLUSTER_CERT=/<path-to-file>/cluster.crt" \
-e "KONG_CLUSTER_CERT_KEY=/<path-to-file>/cluster.key" \
--mount type=bind,source="$(pwd)"/cluster,target=<path-to-keys-and-certs>,readonly \
-p 8000:8000 \
kong:3.4.2-alpine

For pki certificate mode, use:

      Kong Gateway
    

      Kong Gateway (OSS)
    
docker run -d --name kong-dp --network=kong-net \
-e "KONG_ROLE=data_plane" \
-e "KONG_DATABASE=off" \
-e "KONG_PROXY_LISTEN=0.0.0.0:8000" \
-e "KONG_CLUSTER_CONTROL_PLANE=control-plane.<admin-hostname>.com:8005" \
-e "KONG_CLUSTER_TELEMETRY_ENDPOINT=control-plane.<admin-hostname>.com:8006" \
-e "KONG_CLUSTER_MTLS=pki" \
-e "KONG_CLUSTER_SERVER_NAME=control-plane.kong.yourcorp.tld" \
-e "KONG_CLUSTER_CERT=data-plane.crt" \
-e "KONG_CLUSTER_CERT_KEY=/<path-to-file>/data-plane.crt" \
-e "KONG_CLUSTER_CA_CERT=/<path-to-file>/ca-cert.pem" \
--mount type=bind,source="$(pwd)"/cluster,target=<path-to-keys-and-certs>,readonly \
-p 8000:8000 \
kong/kong-gateway:3.4.3.18-alpine
docker run -d --name kong-dp --network=kong-net \
-e "KONG_ROLE=data_plane" \
-e "KONG_DATABASE=off" \
-e "KONG_PROXY_LISTEN=0.0.0.0:8000" \
-e "KONG_CLUSTER_CONTROL_PLANE=control-plane.<admin-hostname>.com:8005" \
-e "KONG_CLUSTER_TELEMETRY_ENDPOINT=control-plane.<admin-hostname>.com:8006" \
-e "KONG_CLUSTER_MTLS=pki" \
-e "KONG_CLUSTER_SERVER_NAME=control-plane.kong.yourcorp.tld" \
-e "KONG_CLUSTER_CERT=data-plane.crt" \
-e "KONG_CLUSTER_CERT_KEY=/<path-to-file>/data-plane.crt" \
-e "KONG_CLUSTER_CA_CERT=/<path-to-file>/ca-cert.pem" \
--mount type=bind,source="$(pwd)"/cluster,target=<path-to-keys-and-certs>,readonly \
-p 8000:8000 \
kong:3.4.2-alpine

Where:

--name and --network: The tag of the Kong Gateway image that you’re using, and the Docker network it communicates on.
KONG_CLUSTER_CONTROL_PLANE: Sets the address and port of the control plane (port 8005 by default).
KONG_DATABASE: Specifies whether this node connects directly to a database.
<path-to-file> and target=<path-to-keys-and-certs>: Are the same path, pointing to the location of the cluster.key and cluster.crt files.
KONG_CLUSTER_SERVER_NAME: Specifies the SNI (Server Name Indication extension) to use for data plane connections to the control plane through TLS. When not set, data plane will use kong_clustering as the SNI.; You can also optionally use KONG_CLUSTER_TELEMETRY_SERVER_NAME to set a custom SNI for telemetry data. If not set, it defaults to KONG_CLUSTER_SERVER_NAME.
KONG_CLUSTER_TELEMETRY_ENDPOINT: Optional setting, needed for telemetry gathering. Not available in open-source deployments.

You can also choose to encrypt or disable the data plane configuration cache with some additional settings:

KONG_DATA_PLANE_CONFIG_CACHE_MODE: Optional setting for storing the config cache, defaults to unencrypted. Change this to encrypted if you want to store the data plane’s config cache in an encrypted format, or set it to off if you don’t want to use a cache. Not available in open-source deployments.
KONG_DATA_PLANE_CONFIG_CACHE_PATH: An optional custom path to the config cache. Not available in open-source deployments.

If needed, bring up any subsequent data planes using the same settings.

Verify that nodes are connected

Use the control plane’s Cluster Status API to monitor your data planes. It provides:

The name of the node
The last time the node synced with the control plane
The version of the config currently running on each data plane

To check whether the CP and DP nodes you just brought up are connected, run the following on a control plane:

Using cURL

Using HTTPie

curl -i -X GET http://localhost:8001/clustering/data-planes

The output shows all of the connected data plane instances in the cluster:

{
    "data": [
        {
            "config_hash": "a9a166c59873245db8f1a747ba9a80a7",
            "hostname": "data-plane-2",
            "id": "ed58ac85-dba6-4946-999d-e8b5071607d4",
            "ip": "192.168.10.3",
            "last_seen": 1580623199,
            "status": "connected"
        },
        {
            "config_hash": "a9a166c59873245db8f1a747ba9a80a7",
            "hostname": "data-plane-1",
            "id": "ed58ac85-dba6-4946-999d-e8b5071607d4",
            "ip": "192.168.10.4",
            "last_seen": 1580623200,
            "status": "connected"
        }
    ],
    "next": null
}

References

DP node start sequence

When set as a DP node, Kong Gateway processes configuration in the following order:

Config cache: If the file config.json.gz exists in the kong_prefix path (/usr/local/kong by default), the DP node loads it as configuration.
declarative_config exists: If there is no config cache and the declarative_config parameter is set, the DP node loads the specified file.
Empty config: If there is no config cache or declarative configuration file available, the node starts with empty configuration. In this state, it returns 404 to all requests.
Contact CP Node: In all cases, the DP node contacts the CP node to retrieve the latest configuration. If successful, it gets stored in the local config cache (config.json.gz).

Configuration reference

Use the following configuration properties to configure Kong Gateway in hybrid mode.

Parameter	Description	CP or DP
`role` Required	Determines whether the Kong Gateway instance is a control plane or a data plane. Valid values are `control_plane` or `data_plane`.	Both
`cluster_listen` Optional Default: `0.0.0.0:8005`	List of addresses and ports on which the control plane will listen for incoming data plane connections. This port is always protected with Mutual TLS (mTLS) encryption. Ignored on data plane nodes.	CP
`proxy_listen` Required	Comma-separated list of addresses and ports on which the proxy server should listen for HTTP/HTTPS traffic. Ignored on control plane nodes.	DP
`cluster_telemetry_listen` Available with Kong Gateway Enterprise subscription - Contact Sales Optional Default: `0.0.0.0:8006`	List of addresses and ports on which the control plane will listen for data plane telemetry data. This port is always protected with Mutual TLS (mTLS) encryption. Ignored on data plane nodes.	CP
`cluster_telemetry_endpoint` Available with Kong Gateway Enterprise subscription - Contact Sales Required for Enterprise deployments	The port that the data plane uses to send telemetry data to the control plane. Ignored on control plane nodes.	DP
`cluster_control_plane` Required	Address and port that the data plane nodes use to connect to the control plane. Must point to the port configured using the `cluster_listen` property on the control plane node. Ignored on control plane nodes.	DP
`cluster_mtls` Optional Default: `shared`	One of `shared` or `pki`. Indicates whether hybrid mode will use a shared certificate/key pair for CP/DP mTLS or if PKI mode will be used. See below sections for differences in mTLS modes.	Both
`data_plane_config_cache_mode` Available with Kong Gateway Enterprise subscription - Contact Sales Optional Default: `unencrypted`	Determines how the data plane configuration cache is stored. • `unencrypted`: Stores configuration without encrypting it in `config.cache.json.gz` • `encrypted`: Encrypts and stores the configuration cache in `.config.cache.jwt` (hidden file). • `off`: The data plane does not cache configuration	DP
`data_plane_config_cache_path` Available with Kong Gateway Enterprise subscription - Contact Sales Optional Default: Kong `prefix` path	Path to the data plane config cache file, for example `/tmp/kong-config-cache`. If the cache mode is `encrypted`, the filename is `.config.cache.jwt` (hidden file). If the cache mode is `unencrypted`, the filename is `config.cache.json.gz`.	DP

The following properties are used differently between shared and pki modes:

Parameter	Description	Shared Mode	PKI Mode
`cluster_cert` and `cluster_cert_key` Required	Certificate/key pair used for mTLS between CP/DP nodes.	Same between CP/DP nodes.	Unique certificate for each node, generated from the CA specified by `cluster_ca_cert`.
`cluster_ca_cert` Required in PKI mode	The trusted CA certificate file in PEM format used to verify the `cluster_cert`.	Ignored	CA certificate used to verify `cluster_cert`, same between CP/DP nodes. Required
`cluster_server_name` Required in PKI mode	The SNI presented by the DP node mTLS handshake.	Ignored	In PKI mode, the DP nodes will also verify that the Common Name (CN) or Subject Alternative Name (SAN) inside the certificate presented by CP matches the `cluster_server_name` value.
`cluster_telemetry_server_name` Available with Kong Gateway Enterprise subscription - Contact Sales	The telemetry SNI presented by the DP node mTLS handshake. If not specified, falls back on SNI set in `cluster_server_name`.	Ignored	In PKI mode, the DP nodes will also verify that the Common Name (CN) or Subject Alternative Name (SAN) inside the certificate presented by CP matches the `cluster_telemetry_server_name` value.

Next steps

Now, you can start managing the cluster using the control plane. Once all instances are set up, use the Admin API on the control plane as usual, and these changes will be synced and updated on the data plane nodes automatically within seconds.