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A simple web API providing MiniZinc + Gecode in a Docker container

Build & Run

docker build . -t minizinc --build-arg NUM_BUILD_JOBS=4
docker run -p 5004:80 minizinc

In the following we let the service compute the solution for the following MiniZinc problem (with parameter budget set to 10000):

int: budget;
var 0..1000: F;
var 0..400: L;
var 0..500: Z;
var 0..150: J;

constraint 13*F + 21*L + 17*Z + 100*J <= budget;

solve maximize 6*F + 10*L + 8*Z + 40*J;

Running the following:

curl -H "Content-Type: application/json" -X POST -d '{
	"problem": "int: budget;\nvar 0..1000: F;\nvar 0..400: L;\nvar 0..500: Z;\nvar 0..150: J;\n\nconstraint 13*F + 21*L + 17*Z + 100*J <= budget;\n\nsolve maximize 6*F + 10*L + 8*Z + 40*J;\n",
	"data": {"budget": "10000"},
	"args": ["--output-mode", "json", "--output-objective"],
	"timeout_ms": 10000
}' http://localhost:5004/json

Will yield:

{
	"result": "complete",
	"values": {
		"F": 0, 
		"L": 392, 
		"Z": 104, 
		"J": 0, 
		"_objective": 4752
	}, 
	"stdout": "{\n  \"F\" : 0,\n  \"L\" : 392,\n  \"Z\" : 104,\n  \"J\" : 0,\n  \"_objective\" : 4752\n}\n----------\n==========\n", 
	"stderr": "", 
	"returncode": 0, 
	"queueTimeMs": 0, 
	"computeTimeMs": 84
}

How to use

The service provides three endpoints, an echo service for a simple health check, a high-level endpoint that does some parsing and a low-level endpoint that is basically a pass-through.

Its hard-coded to 10 concurrent jobs. If more jobs arrive, they will be queued. Default timeout is 30s. You can change these values in pymznweb/server.py.

  • GET /

    Will return MiniZinc as plain text (echo service)

  • POST /json

    Call it with a JSON of the following form:

    {
    	"problem": "
    		int: budget;
    		var 0..1000: F;
    		var 0..400: L;
    		var 0..500: Z;
    		var 0..150: J;
    
    		constraint 13*F + 21*L + 17*Z + 100*J <= budget;
    
    		solve maximize 6*F + 10*L + 8*Z + 40*J;
    	",
    	"data": {
    		"budget": "10000"
    	},
    	"args": <optional command line arguments>,
    	"timeoutMs": <optional computing timeout>,
    }

    The output will be:

    {
    	"result": "complete",
    	"values": {
    		"F": 0, 
    		"L": 392, 
    		"Z": 104, 
    		"J": 0, 
    		"_objective": 4752
    	}, 
    	"stdout": "{\n  \"F\" : 0,\n  \"L\" : 392,\n  \"Z\" : 104,\n  \"J\" : 0,\n  \"_objective\" : 4752\n}\n----------\n==========\n", 
    	"stderr": "", 
    	"returncode": 0, 
    	"queueTimeMs": 0, 
    	"computeTimeMs": 84
    }

    Where result can be

    • unsat ⇨ Unsatisfyable, no solution was found
    • unbounded ⇨ Too few constraints
    • unsatOrUnbounded
    • unknown ⇨ Timed out before solution was found
    • error ⇨ Error, check the contents of stderr
    • complete ⇨ An optimal solution was found
    • found ⇨ A satisfying solution was found
  • POST /raw

    A more low-level approach. Call this endpoint with a JSON of command line args and stdin. These values will be given to MiniZinc as is.

    {
    	"args": "<command line arguments>",
    	"stdin": "<MiniZinc problem code>"
    }

    The output will be:

    {
    	"stdout": "",
    	"stderr": "",
    	"returncode": 0,
    	"queueTimeMs": 100,
    	"computeTimeMs": 20
    }

Testing

docker build . -t minizinc && docker run --rm minizinc python3 -m pytest /opt

Shell-Only

Usage example:

$ docker build . -t minizinc
$ docker run -it minizinc bash

# apt-get install -y nano
# nano army.mzn
<insert army.mzn>
# minizinc model.mzn
F = 0, L = 392, Z=104, J = 0
----------
==========

(The source code for army.mzn is available from https://github.com/MiniZinc/specialization-examples/blob/master/introduction/army/army.mzn)

Additional files included in this repository

To get minizinc to work we need some files (gecode.msc, minizinc-gecode-2.2.3.tar.gz) from the binary distribution of MiniZincIDE. (See MiniZinc/libminizinc#228)

minizinc-gecode-2.2.3.tar.gz contains the files under /MiniZincIDE-2.2.3-bundle-linux/share/minizinc/gecode of https://github.com/MiniZinc/MiniZincIDE/releases/download/2.2.3/MiniZincIDE-2.2.3-bundle-linux-x86_64.tgz. They are needed for useful execution of MiniZinc.

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Dockerfile for building minizinc with gecode from source and optionally running it as a web service

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