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Short Description
A service to reverse-proxy streams from a port at the service host to a backend service.
Full Description

stream-conductor

synopsis

This service presents a flexible stream proxy solution.
It enables the user to assign ports at the host where the service lives and have these being
transparantly proxied to a backend service.

This repository provides the service code (Python 3) as well as a Dockerfile to create the service as docker container.
A docker compose file is provided as a quick test and demo. It spins up the stream-conductor service and a
backend ssh service (based on macropin/sshd) as a demo.

use case

You have a service running at a backend server; for example a memcache service at port 2000 on address 10.1.0.1.
You cannot expose this port to the outside world, but still want it to be reachable.
If you do have an edge node that has an address that is accessible from the outside world, say at 85.12.23.34.

Running this stream-conductor at that edge node gives you the ability to quickly assign a port at this external address
and have the stream-conductor reverse proxy all traffic to your backend service.

A simple GET /createstream/9000/mybackend:2000 request will create a stream reverse proxy at 85.12.23.34:9000 to
the service at mybackend:2000.
From that point onwards, any requests at 85.12.23.34:9000 will be proxied to mybackend:2000 and any application
using 85.12.23.34:9000 would not know better.

starting the serivce

The service uses the following environment variables:

variable default description
STREAM_CONFIG_PATH /etc/nginx/stream.d/ path to store the stream definition files
NGINX_BIN /usr/sbin/nginx path to the nginx binary
STREAM_PREFIX _conductor_ prefix to the per-stream configuration files
PORT_RANGE 9000-9009 port range[^1] that is available through this service
BIND_ADDRESS 0.0.0.0 (all) addresses that the API will bind to
BIND_PORT 5000 port that the API will bind to

[^1]: The Dockerfile exposes only port 5000 and 9000-9009. If you need other ports, you will need to create your own image.

interface

The service uses a REST API that has the following options:

function example result description
status { 'version':'0.1', 'range':'range(9000-9999)' } returns the current API version and range of available ports
getstreams [ { 'listen': 9000, 'proxy_pass': 'mybackend:22' } ] get a list of current stream definitions
createstream/<port>/<backend> { 'result':'ok', 'errors':'...'} create a stream connecting a port <port> to a backend service <backend>
removestream/<port> { 'result':'ok' } remove the stream that listens at port <port>
hasstream/<port> { 'result':'false' } returns true if there is a stream created that listens at port <port>
getfreeport { 'result':'ok', 'port':9010 } returns the first available port

examples

getting the status

$ curl localhost:5000/status
{"version": "0.1", "available_ports": "range(9000, 9009)"}

creating a stream

$ curl localhost:5000/createstream/9000/streamconductor_backendssh_1.streamconductor_default:22
{"errors": "[b'2017/06/05 09:27:22 [notice] 10#10: signal process started\\n']", "result": "ok"}
$ ssh localhost -p9000
The authenticity of host '[localhost]:9000 ([::1]:9000)' can't be established.
ECDSA key fingerprint is SHA256:am/KOV40B7/LUbBRb2V2DuwJYL9mPfqq2k2ClERFR6k.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[localhost]:9000' (ECDSA) to the list of known hosts.
willem@localhost's password:

In this example, a stream is created, proxying port 9000 to the service at
streamconductor_backendssh_1.streamconductor_default:22. An ssh to that port is demonstrated to be proxied.

getting a list of streams

$ curl localhost:5000/getstreams
[{"proxy_pass": "localhost:4321", "listen": 1234}, 
{"proxy_pass": "streamconductor_backendssh_1.streamconductor_default:22", "listen": 9000}]

Here a list of all stream mappings is returned.

removing a stream

$ curl localhost:5000/removestream/9000
{"result": "ok", "errors": "[b'2017/06/05 09:34:11 [notice] 12#12: signal process started\\n']"}

This example removes the stream that listens to port 9000 from the proxy.

background

The proxy service is backed by nginx (http://nginx.org/).
A simple python program is created to manage the stream definitions and reconfigure nginx.
The python program is exposed as REST API using Flask.

NB: There is absolutely no authorization or even authentication done!

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wasperen
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