didenko/pald

PALD - port allocator daemon

pald is a very simple, intentionally feature-poor local daemon aimed to keep registry of port allocations on a local system. Due to the lack of time to address security concerns pald only listens on localhost interfaces currently.

It is expected to operate on the port range of 49152-65535, as specified in Section 6 of RFC-6335. Any contiguous range of valid port numbers to be allocated can be specified in configuration.

Configuration

Configuration is read from either system-wide and user-specific config.ext files. The state of assigned services persisted in the dump file in a location for user-specific configuration file. Configuratoin file location reflects executable name.

Dump file format is undecided yet and likely will be changed in the future.

Configuration file expected to be in the TOML or othe formats as implemented by the Viper package used in pald. Here is what can be specified in the config file:

key	type	default	description
port_listen	uint16	49200	A port on which the pald process will listen for port queries and allocation requests
port_min	uint16	49201	The lowest (first) port available for allocation
port_max	uint16	49999	The highest (last) port available for allocation
dump_file	string	~/.pald/dump	The default dump file location where the service will persist the state while down

HTTP interface

All requests are available as either HTTP GET or HTTP POST, e.g.

http://localhost:49200/get?service=service-name

REPLY=`curl -d service=service-name -o - -s -f http://localhost:49200/get`
echo $?
echo $REPLY

Three URLs are currently supported (with HTTP reply codes):

action	URL	param=value
Query	/get	service=name
200 - a found port number 404 - an error message if there is no port registered with the requested service 400 - an error message in case of all other errors
Register	/set	service=name
200 - an assigned port number 412 - registration failed because no more port numbers available in the configured range 400 - an error message in case of all other errors
Delete	/del	port=number
200 - OK as a success indication (including port not found) 400 - an error message in case of all other errors

Porting to other platforms

At this time pald is only compatible with Mac OS X, but it is easy to fix. Please, add an appropriate internal\platform\specific_<platform>.go file for your platform and send me a pull request.

pald's Issues

The server does not persist the state

Make pald friendly to daemon wrappers

pald should detach I/O and fork to background on startup.

Choose a place to store configuration

Should persist the port to listen on, dynamic port range min/max, and port mappings state

pald responses should not cache in browsers

Output format

JSON or text/plain? JSON seems to be more flexible. In this case though the output would be great is processed by shell scripts as curl output, for which text/plain fits better.

Switch from GPLv3 to Apache 2.0 license

Make the HTTP server to run the registry

Per service address lists

Decide if address lists should be associated with a registered service.

Keep records' sources in the registry

default | fixed | dynamic

Daemon verbs are broken

Specifically, sudo bin/pald status panics:

panic: Unsupported Config Type ""

goroutine 1 [running]:
main.init·1()
    /Users/vlad/Code/pald/src/github.com/didenko/pald/cmd/pald/pald.go:107 +0x353
main.init()
    /Users/vlad/Code/pald/src/github.com/didenko/pald/cmd/pald/pald.go:133 +0x6a

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
    /usr/local/go/src/runtime/asm_amd64.s:2232 +0x1

Make REST API

Integrate with remote configuration stores for port assignments

Add example client code

Aware to actual ports in use

When allocating or fixing a port optionally test that the port is not in actual use on the system (platform-dependant)

Truncate to dump file's size after writing

Instead of currently truncating to zero before writing

Figure out what to do with service aliases in standard /etc/services file

Dynamic port allocations only

Fixed port assignments are scope creep for now. They complicate unnecessarily and pull the mind to complexity swamp.