separating engine contexts

[HakanKaraoglu]

Hi,

I have a method like the one below. I'm working in a queuing system and running too many rules instantaneously. I noticed a slowness during the performance. As a solution, I took it into the constructor method so that it does not create the engine every time, but this time I got an error like the following.

Like separating the engine context or is there a different solution? It works very slowly this way, unfortunately.

public class RuleEngineService : IRuleEngineService
    {
        private readonly Engine _engine;
        public RuleEngineService()
        {
            _engine = new Engine(clr => clr.AllowClr().CatchClrExceptions());
            
        }
        public Task<bool> Evulate(FeedProxy feedProxy, FeederProxy feederProxy, FeedKeywordProxy[] feedKeywords, int sourceId, string ruleExpression)
        {
            var ruleResult = false;

            var ruleFeeder = new RuleFeeder
            {
                UserName = !string.IsNullOrEmpty(feederProxy.Name) ? Asciifier.Asciify(feederProxy.Name) : string.Empty,
                Name = !string.IsNullOrEmpty(feederProxy.FullName) ? Asciifier.Asciify(feederProxy.FullName) : string.Empty,
                FollowerCount = feederProxy.FollewerCount > 0 ? feederProxy.FollewerCount : 0
            };

            var ruleFeed = new RuleFeed
            {
                Text = feedProxy.AsciifiedSearchField,
                Lang = feedProxy.Language.ToString(),
                FeedType = feedProxy.FeedType
            };

            if (feedProxy.Sentiment != null) { ruleFeed.Sentiment = feedProxy.Sentiment.Value; }
            ruleFeed.Author = !string.IsNullOrEmpty(feederProxy.Name) ? feederProxy.Name : string.Empty;
            ruleFeed.Source = sourceId;
            ruleFeed.Feeder = ruleFeeder;

            var ruleKeywords = new RuleKeywords { keywords = feedKeywords };

            ruleFeed.Keywords = ruleKeywords;

            typeof(RuleFeed).GetProperties().ToList().ForEach(x => _engine.SetValue(x.Name.ToLowerInvariant(), x.GetValue(ruleFeed)));

            _engine.Execute("String.prototype.contains = function(str) { return this.toLowerCase().indexOf(str) !== -1; };");

            JsValue result = _engine.Execute(ruleExpression).GetCompletionValue();

            if (result.IsBoolean())
            {
                ruleResult = result.AsBoolean();
            }

            return Task.FromResult(ruleResult);
        }
    }

If I create a new engine within the method rather than within the constructor method, it does not give this error, but since this creates an instance each time, there is slowness.

I get an error like this in the following section

JsValue result = _engine.Execute(ruleExpression).GetCompletionValue();

StackTrace :

at System.ThrowHelper.ThrowAddingDuplicateWithKeyArgumentException[T](T key)
  at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
  at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
  at Jint.Runtime.Environments.DeclarativeEnvironmentRecord.CreateMutableBinding(String name, Boolean canBeDeleted)
  at Jint.Engine.DeclarationBindingInstantiation(DeclarationBindingType declarationBindingType, IList`1 functionDeclarations, IList`1 variableDeclarations, FunctionInstance functionInstance, JsValue[] arguments)
  at Jint.Native.Function.ScriptFunctionInstance.Call(JsValue thisArg, JsValue[] arguments)
  at Jint.Runtime.ExpressionInterpreter.EvaluateCallExpression(CallExpression callExpression)
  at Jint.Engine.EvaluateExpression(Expression expression)
  at Jint.Runtime.StatementInterpreter.ExecuteExpressionStatement(ExpressionStatement expressionStatement)
  at Jint.Engine.ExecuteStatement(Statement statement)
  at Jint.Runtime.StatementInterpreter.ExecuteStatementList(IEnumerable`1 statementList)
  at Jint.Runtime.StatementInterpreter.ExecuteProgram(Program program)
  at Jint.Engine.Execute(Program program)
  at Jint.Engine.Execute(String source)

[lahma]

What version of Jint?

[lahma]

You probably get such an error by doing something like let x = null; x.contains('some-text');.

[HakanKaraoglu]

@lahma Thanks for your help 👍

As you said, I made a performance observation with dotTrace. My test scenario was like this. I sent 1000 messages to the rabbit queue and just run the consumer I mentioned above. And again, the number of rules for each message was 3033.

The result was as follows.

I think using prototypes is a slow thing.

[lahma]

You can register the function as CLR function like I said earlier, it'll be faster:

[Fact]
public void StringProtoFunction()
{
    var engine = new Engine();
    var containsFunction = new ClrFunctionInstance(engine, "contains", (thisObject, arguments) =>
    {
        return thisObject.AsString().IndexOf(arguments[0].AsString(), StringComparison.OrdinalIgnoreCase) != -1;
    });
    engine.String.PrototypeObject.FastAddProperty("contains", containsFunction, false, false, false);
    Assert.True(engine.Execute("'abcd'.contains('bc');").GetCompletionValue().AsBoolean());
    Assert.False(engine.Execute("'abcd'.contains('cb');").GetCompletionValue().AsBoolean());
}

Also if you have scripts that don't change that often you should parse them as Program instances and feed them to engine.

var parser = new JavaScriptParser(source);
var script = parser.ParseScript(); // reusable, parsed once
engine.Execute(script);

[HakanKaraoglu]

Thank you for your suggestions. I have another idea. To get rid of the Clr cost, I replaced the contains with includes. And I'm removing the clr method from the constructor. I know it will cost an string builder.

The final version of these performance profiles:

var engine = new Engine();
var rule = new StringBuilder(ruleExpression).Replace("contains", "includes");
props.ForEach(x => engine.SetValue(x.Name.ToLowerInvariant(), x.GetValue(ruleFeed)));
return engine.Execute(rule.ToString()).GetCompletionValue().AsBoolean();

by the way, Why is the execution method called 2 times ?

[lahma]

includes is more costly than the contains that I showed, includes is also case-sensitive. I don't know what this CLR cost is, both methods map to CLR method in Jint.

I don't know why are calling Execute twice, it's engine level public API so it should be your code in question.

[HakanKaraoglu]

I really appreciate your support. I taking the your time. But, I'm trying to understand. Like you said, I gave up on the includes prototype.
And the final code is as follows:

if (! _memCache. TryGetValue (cacheFeedKey, out List <PropertyInfo> props))
            {
                props = typeof (RuleFeed) .GetProperties (). List ();
                _memCache.Set (cacheFeedKey, props, new MemoryCacheEntryOptions {AbsoluteExpiration = DateTime.Now.AddHours (1), Priority = CacheItemPriority.Normal});
            }

var engine = new engine ();
var containsFunction = new ClrFunctionInstance (engine, "contains", (thisObject, arguments) =>
           {
                thisObject.AsString (). IndexOf (arguments [0] .AsString (), StringComparison.OrdinalIgnoreCase)! = -1;
            });
engine.String.PrototypeObject.FastAddProperty ("contains", containsFunction, false, false, false);
props.ForEach (x => engine.SetValue (x.Name.ToLowerInvariant (), x.GetValue (ruleFeed)));
return engine.Run (ruleExpression) .GetCompletionValue (). AsBoolean ();

I guess there's nothing else to do, right?

[lahma]

RuleFeed is static type, you don't need MemCache, static field works. For this specific use case you could probably reuse containsFunction instance between engines, as long as it doesn't need engine services. But I think that's pretty OK, many ways to optimize more probably but that's the gist of it.