> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-fix-nav-issues.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
> Composable protocols allows more flexible configuration of TCP access to the ClickHouse server.
# Composable protocols
Overview
Composable protocols allow more flexible configuration of TCP access to the
ClickHouse server. This configuration can co-exist alongside, or replace,
conventional configuration.
Configuring composable protocols
Composable protocols can be configured in an XML configuration file. The protocols
section is denoted with `protocols` tags in the XML config file:
```xml theme={null}
```
Configuring protocol layers
You can define protocol layers using basic modules. For example, to define an
HTTP layer, you can add a new basic module to the `protocols` section:
```xml theme={null}
http
```
Modules can be configured according to:
* `plain_http` - name which can be referred to by another layer
* `type` - denotes the protocol handler which will be instantiated to process data.
It has the following set of predefined protocol handlers:
* `tcp` - native clickhouse protocol handler
* `http` - HTTP clickhouse protocol handler
* `tls` - TLS encryption layer
* `proxy1` - PROXYv1 layer
* `mysql` - MySQL compatibility protocol handler
* `postgres` - PostgreSQL compatibility protocol handler
* `prometheus` - Prometheus protocol handler
* `interserver` - clickhouse interserver handler
`gRPC` protocol handler is not implemented for `Composable protocols`
Endpoints (listening ports) are denoted by `` and optional `` tags.
For example, to configure an endpoint on the previously added HTTP layer we
could modify our configuration as follows:
```xml theme={null}
http
127.0.0.1
8123
```
If the `` tag is omitted, then the `` from the root config is
used.
Configuring layer sequences
Layers sequences are defined using the `` tag, and referencing another
module. For example, to configure a TLS layer on top of our plain\_http module
we could further modify our configuration as follows:
```xml theme={null}
http
tls
plain_http
127.0.0.1
8443
```
Attaching endpoints to layers
Endpoints can be attached to any layer. For example, we can define endpoints for
HTTP (port 8123) and HTTPS (port 8443):
```xml theme={null}
http
127.0.0.1
8123
tls
plain_http
127.0.0.1
8443
```
Defining additional endpoints
Additional endpoints can be defined by referencing any module and omitting the
`` tag. For example, we can define `another_http` endpoint for the
`plain_http` module as follows:
```xml theme={null}
http
127.0.0.1
8123
tls
plain_http
127.0.0.1
8443
plain_http
127.0.0.1
8223
```
Custom HTTP handlers per endpoint
By default, all `type=http` protocol entries share the same ``
configuration. You can override this by adding a `` tag that points
to a different configuration section. This allows each HTTP port to serve a
different set of HTTP routing rules.
For example, to run an alternative HTTP API on port 8124 with its own handlers:
```xml theme={null}
http
127.0.0.1
8123
http
127.0.0.1
8124
http_handlers_alt
/custom
predefined_query_handler
SELECT 'custom_endpoint'
```
In this example, requests to port 8123 use the standard `` rules,
while requests to port 8124 use the `` rules. If ``
is omitted, the endpoint falls back to the default ``.
The custom handlers section follows the same format as
[``](/reference/settings/server-settings/settings#http_handlers).
Changes to the custom handlers section are detected during config reload, and the
corresponding endpoint is automatically restarted.
Specifying additional layer parameters
Some modules can contain additional layer parameters. For example, the TLS layer
allows a private key (`privateKeyFile`) and certificate files (`certificateFile`)
to be specified as follows:
```xml theme={null}
http
127.0.0.1
8123
tls
plain_http
127.0.0.1
8443
another_server.key
another_server.crt
```