SWI-Prolog bootstrap for the AWS Lambda provided runtime
You can build a .zip file using the docker image in this repo and your own handler scripts that is ready to be uploaded into an AWS lambda function using the provided runtime.
Write a handler/3:
%! handler(++Event:list, ++Context:list, --Response:text).
% Clearly this will complain about singleton variables
% but there is value to naming the variables here
handler(json(Event), Context, Response) :-
Response = '{"hello": "world"}'.Place it into some file like main.pl
then build your bundle like:
docker pull bkrn/prolamb:latest
# location of main.pl
cd $SOURCE_DIRECTORY
# Map your current directory (location of your SWI-prolog source code)
# into the /dist directory of the build container using volumes
docker run --rm -v $PWD:/dist bkrn/prolamb:latest
# After the build is complete you'll have a brand new bundle.zip
# archive that can be used in a lambda instance with the "provided"
# runtimeIf you're using other source files they must be in or children of $SOURCE_DIRECTORY. Otherwise they won't make it into bundle.zip.
Be sure that the handler option of your lambda is set to file.predicate. So if your entry file is main.pl and the predicate handler is handler/3 then the handler option should be main.handler.
Your handler should have an arity of three. The first two arguments, the event and context, are grounded and contain the invocation inputs. The last, the function's response, is bound to the the text type you want your function to respond with by your handler predicate.
For example a service that matches nicknames and fullnames might have a handler like:
% DOCTEST
% this example is tested in place as a part of the build pipeline
:- use_module(library(http/json)).
:- use_module(library(date)).
lambda_local_datetime(context(headers(H), _), DT) :-
member('TZ'(TimeZone), H),
member(TimeZone-TZ, ['PST'-(5 * 60 * 60)]),
I is TZ,
get_time(TS),
stamp_date_time(TS, DT, I).
names(FullName, NickName, _) :-
member(FullName-NickName, [
'Nicholas'-'Nick',
'William'-'Bob',
'William'-'Robert',
'Steven'-'Steve']).
% During the holiday season recognize additional nick names
names('Nicholas', 'Santa', Context) :-
lambda_local_datetime(Context, DT),
date_time_value(month, DT, 12),
date_time_value(day, DT, Day),
Day < 26.
% Given an event described by the JSON schema:
% {"type": "object", "properties": {"nickName": {"type": "string"}, "fullName": {"type": "string"}}}
% The response is described by the JSON schema:
% {"type": "object", "required": ["possibleNames], "properties": {"possibleNames: {"type": "array", "items":
% {"type": "object", "properties": {"fullName": {"type": "string"}, "nickName": {"type": "string"}}}}}}
handler(json(Event), Context, Response) :-
(member(fullName=FullName, Event); true),
(member(nickName=NickName, Event); true),
findall(json([fullname=FullName, nickName=NickName]),
names(FullName, NickName, Context),
Names),
atom_json_term(Response, json([possibleNames=Names]), []).
% DOCTESTThe JSON event trigger processed using http/json so that the format is as specified here https://www.swi-prolog.org/pldoc/man?section=jsonsupport - the actual schema of the JSON depends on the lambda integration. but it will always be json(_)
Request headers and variables specified in the lambda environment. Shape is context(headers([Name(Value), ...]), env([Key-Value, ...]))
Should be attached to an atom or string that is JSON formatted in the proper AWS response type schema. For example if you're using an API Gateway proxy integration Repsonse should be attached to an atom/string of the shape found here: https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#api-gateway-simple-proxy-for-lambda-output-format
Feel free to throw exceptions. If it is of the form json([errorType=Type,errorMessage=Message]) then the run time will use your literal as the error otherwise it will attempt to format your throw and use json([errorType='HandlerException',errorMessage=Message]) where format(string(Message), "~w", ThingThatWasThrown).