139 lines
6.4 KiB
Plaintext
139 lines
6.4 KiB
Plaintext
---
|
|
layout: docs
|
|
page_title: Connect - Native Application Integration
|
|
sidebar_title: 'Native App Integration'
|
|
sidebar_current: docs-connect-native
|
|
description: >-
|
|
Applications can natively integrate with the Connect API to support accepting
|
|
and establishing connections to other Connect services without the overhead of
|
|
a proxy sidecar.
|
|
---
|
|
|
|
# Connect-Native App Integration
|
|
|
|
Applications can natively integrate with the Connect API to support accepting
|
|
and establishing connections to other Connect services without the overhead of a
|
|
[proxy sidecar](/docs/connect/proxies.html). This option is especially useful
|
|
for applications that may be experiencing performance issues with the proxy
|
|
sidecar deployment. This page will cover the high-level overview of
|
|
integration, registering the service, etc. For language-specific examples, see
|
|
the sidebar navigation to the left. It is also required if your service uses
|
|
relies on a dynamic set of upstream services.
|
|
|
|
Connect is just basic mutual TLS. This means that almost any application
|
|
can easily integrate with Connect. There is no custom protocol in use;
|
|
any language that supports TLS can accept and establish Connect-based
|
|
connections.
|
|
|
|
We currently provide an easy-to-use [Go integration](/docs/connect/native/go.html)
|
|
to assist with the getting the proper certificates, verifying connections,
|
|
etc. We plan to add helper libraries for other languages in the future.
|
|
However, without library support, it is still possible for any major language
|
|
to integrate with Connect.
|
|
|
|
## Overview
|
|
|
|
The primary work involved in natively integrating with Connect is
|
|
[acquiring the proper TLS certificate](/api/agent/connect.html#service-leaf-certificate),
|
|
[verifying TLS certificates](/api/agent/connect.html#certificate-authority-ca-roots),
|
|
and [authorizing inbound connections](/api/agent/connect.html#authorize).
|
|
All of this is done using the Consul HTTP APIs linked above.
|
|
|
|
An overview of the sequence is shown below. The diagram and the following
|
|
details may seem complex, but this is a _regular mutual TLS connection_ with
|
|
an API call to verify the incoming client certificate.
|
|
|
|
|
|
|
|
Details on the steps are below:
|
|
|
|
- **Service discovery** - This is normal service discovery using Consul,
|
|
a static IP, or any other mechanism. If you're using Consul DNS, the
|
|
[`<service>.connect`](/docs/agent/dns.html#connect-capable-service-lookups)
|
|
syntax to find Connect-capable endpoints for a service. After service
|
|
discovery, choose one address from the list of **service addresses**.
|
|
|
|
- **Mutual TLS** - As a client, connect to the discovered service address
|
|
over normal TLS. As part of the TLS connection, provide the
|
|
[service certificate](/api/agent/connect.html#service-leaf-certificate)
|
|
as the client certificate. Verify the remote certificate against the
|
|
[public CA roots](/api/agent/connect.html#certificate-authority-ca-roots).
|
|
As a client, if the connection is established then you've established
|
|
a Connect-based connection and there are no further steps!
|
|
|
|
- **Authorization** - As a server accepting connections, verify the client
|
|
certificate against the
|
|
[public CA roots](/api/agent/connect.html#certificate-authority-ca-roots).
|
|
After verifying the certificate, parse some basic fields from it and call
|
|
the [authorizing API](/api/agent/connect.html#authorize) against the local
|
|
agent. If this returns successfully, complete the TLS handshake and establish
|
|
the connection. If authorization fails, close the connection.
|
|
|
|
-> **A note on performance:** The only API call in the connection path is
|
|
the [authorization API](/api/agent/connect.html#authorize). The other API
|
|
calls to acquire the leaf certificate and CA roots are expected to be done
|
|
out of band and reused. The authorize API call should be called against the
|
|
local Consul agent. The agent uses locally cached
|
|
data to authorize the connection and typically responds in microseconds.
|
|
Therefore, the impact to the TLS handshake is typically microseconds.
|
|
|
|
## Updating Certificates and Certificate Roots
|
|
|
|
The leaf certificate and CA roots can be updated at any time and the
|
|
natively integrated application must react to this relatively quickly
|
|
so that new connections are not disrupted. This can be done through
|
|
Consul blocking queries (HTTP long polling) or through periodic polling.
|
|
|
|
The API calls for
|
|
[acquiring a leaf TLS certificate](/api/agent/connect.html#service-leaf-certificate)
|
|
and [reading CA roots](/api/agent/connect.html#certificate-authority-ca-roots)
|
|
both support
|
|
[blocking queries](/api/features/blocking.html). By using blocking
|
|
queries, an application can efficiently wait for an updated value. For example,
|
|
the leaf certificate API will block until the certificate is near expiration
|
|
or the signing certificates have changed and will issue and return a new
|
|
certificate.
|
|
|
|
In some languages, using blocking queries may not be simple. In that case,
|
|
we still recommend using the blocking query parameters but with a very short
|
|
`timeout` value set. Doing this is documented with
|
|
[blocking queries](/api/features/blocking.html). The low timeout will
|
|
ensure the API responds quickly. We recommend that applications poll the
|
|
certificate endpoints frequently, such as multiple times per minute.
|
|
|
|
The overhead for the blocking queries (long or periodic polling) is minimal.
|
|
The API calls are to the local agent and the local agent uses locally
|
|
cached data multiplexed over a single TCP connection to the Consul leader.
|
|
Even if a single machine has 1,000 Connect-enabled services all blocking
|
|
on certificate updates, this translates to only one TCP connection to the
|
|
Consul server.
|
|
|
|
Some language libraries such as the
|
|
[Go library](/docs/connect/native/go.html) automatically handle updating
|
|
and locally caching the certificates.
|
|
|
|
## Service Registration
|
|
|
|
Connect-native applications must tell Consul that they support Connect
|
|
natively. This enables the service to be returned as part of service
|
|
discovery for Connect-capable services, used by other Connect-native applications
|
|
and client [proxies](/docs/connect/proxies.html).
|
|
|
|
This can be specified directly in the [service definition](/docs/agent/services.html):
|
|
|
|
```json
|
|
{
|
|
"service": {
|
|
"name": "redis",
|
|
"port": 8000,
|
|
"connect": {
|
|
"native": true
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
Services that support Connect natively are still returned through the standard
|
|
service discovery mechanisms in addition to the Connect-only service discovery
|
|
mechanisms.
|