Incremental work on scheduling activities

Elsa.sln

@@ -80,6 +80,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Serialization", "src\c
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Scripting.Liquid", "src\scripting\Elsa.Scripting.Liquid\Elsa.Scripting.Liquid.csproj", "{A7473430-F228-4534-AEA5-AA8D80E09364}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "modules", "modules", "{5BA4A8FA-F7F4-45B3-AEC8-8886D35AAC79}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Modules.Quartz", "src\modules\Elsa.Modules.Quartz\Elsa.Modules.Quartz.csproj", "{7D5A49B4-9A9B-496E-803B-DEB85B2C3132}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -170,6 +174,10 @@ Global
 		{A7473430-F228-4534-AEA5-AA8D80E09364}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A7473430-F228-4534-AEA5-AA8D80E09364}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{A7473430-F228-4534-AEA5-AA8D80E09364}.Release|Any CPU.Build.0 = Release|Any CPU
+		{7D5A49B4-9A9B-496E-803B-DEB85B2C3132}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{7D5A49B4-9A9B-496E-803B-DEB85B2C3132}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{7D5A49B4-9A9B-496E-803B-DEB85B2C3132}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{7D5A49B4-9A9B-496E-803B-DEB85B2C3132}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{155227F0-A33B-40AA-A4B4-06F813EB921B} = {61017E64-6D00-49CB-9E81-5002DC8F7D5F}
@@ -205,5 +213,7 @@ Global
 		{820016B7-01CD-4032-8239-6A4E53F1A352} = {9F8AE7FB-E5F9-4DCB-9CF8-0362B3D18DAA}
 		{55F9B33D-5FAF-4355-97EF-445C93208E85} = {C6658DE0-2B2F-47F0-BB61-2CA66D435C09}
 		{A7473430-F228-4534-AEA5-AA8D80E09364} = {2633B8B9-4AEC-4A54-8832-1C940B54E041}
+		{5BA4A8FA-F7F4-45B3-AEC8-8886D35AAC79} = {61017E64-6D00-49CB-9E81-5002DC8F7D5F}
+		{7D5A49B4-9A9B-496E-803B-DEB85B2C3132} = {5BA4A8FA-F7F4-45B3-AEC8-8886D35AAC79}
 	EndGlobalSection
 EndGlobal

src/activities/Elsa.Activities.Http/HttpTrigger.cs

@@ -2,13 +2,12 @@
 using System.Linq;
 using System.Net.Http;
 using Elsa.Attributes;
-using Elsa.Contracts;
 using Elsa.Management.Models;
 using Elsa.Models;
 
 namespace Elsa.Activities.Http;
 
-public class HttpTrigger : Trigger
+public class HttpTrigger : TriggerActivity
 {
     [Input] public Input<string> Path { get; set; } = default!;
 
@@ -20,32 +19,14 @@ public class HttpTrigger : Trigger
 
     [Output] public Output<HttpRequestModel>? Result { get; set; }
 
-    protected override IEnumerable<object> GetHashInputs(TriggerIndexingContext context)
+    protected override IEnumerable<object> GetHashInputs(TriggerIndexingContext context) => GetHashInputs(context.ExpressionExecutionContext);
+    protected override void Execute(ActivityExecutionContext context) => context.SetBookmarks(GetHashInputs(context.ExpressionExecutionContext));
+
+    private IEnumerable<object> GetHashInputs(ExpressionExecutionContext context)
     {
-        var path = context.ExpressionExecutionContext.Get(Path);
-        var methods = context.ExpressionExecutionContext.Get(SupportedMethods);
+        // Generate a bookmark hash for path and selected methods.
+        var path = context.Get(Path);
+        var methods = context.Get(SupportedMethods);
         return methods!.Select(x => (path!.ToLowerInvariant(), x.ToLowerInvariant())).Cast<object>().ToArray();
     }
-
-    protected override void Execute(ActivityExecutionContext context)
-    {
-        var bookmarks = CreateBookmarks(context).ToList();
-        context.SetBookmarks(bookmarks);
-    }
-
-    private IEnumerable<Bookmark> CreateBookmarks(ActivityExecutionContext context)
-    {
-        var path = context.Get(Path)!;
-        var methods = context.Get(SupportedMethods)!;
-        var hasher = context.GetRequiredService<IHasher>();
-        var identityGenerator = context.GetRequiredService<IIdentityGenerator>();
-
-        foreach (var method in methods)
-        {
-            var hashInput = (path.ToLowerInvariant(), method.ToLowerInvariant());
-            var hash = hasher.Hash(hashInput);
-            var bookmarkId = identityGenerator.GenerateId();
-            yield return new Bookmark(bookmarkId, NodeType, hash, Id, context.Id);
-        }
-    }
 }

src/activities/Elsa.Activities.Scheduling/Contracts/IJob.cs

@@ -0,0 +1,10 @@
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Elsa.Activities.Scheduling.Contracts;
+
+public interface IJob
+{
+    string JobId { get; }
+    Task ExecuteAsync(CancellationToken cancellationToken);
+}

src/activities/Elsa.Activities.Scheduling/Contracts/IJobScheduler.cs

@@ -0,0 +1,9 @@
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Elsa.Activities.Scheduling.Contracts;
+
+public interface IJobScheduler
+{
+    Task ScheduleAsync(IJob job, ISchedule schedule, CancellationToken cancellationToken = default);
+}

src/activities/Elsa.Activities.Scheduling/Contracts/ISchedule.cs

@@ -0,0 +1,5 @@
+namespace Elsa.Activities.Scheduling.Contracts;
+
+public interface ISchedule
+{
+}

src/activities/Elsa.Activities.Scheduling/Elsa.Activities.Scheduling.csproj

@@ -10,4 +10,8 @@
       <ProjectReference Include="..\..\core\Elsa.Core\Elsa.Core.csproj" />
     </ItemGroup>
 
+    <ItemGroup>
+      <Folder Include="Services" />
+    </ItemGroup>
+
 </Project>

src/activities/Elsa.Activities.Scheduling/Jobs/ResumeWorkflowJob.cs

@@ -0,0 +1,27 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Elsa.Activities.Scheduling.Contracts;
+
+namespace Elsa.Activities.Scheduling.Jobs;
+
+public class ResumeWorkflowJob : IJob
+{
+    public ResumeWorkflowJob()
+    {
+    }
+
+    public ResumeWorkflowJob(string workflowInstanceId, string activityId)
+    {
+        WorkflowInstanceId = workflowInstanceId;
+        ActivityId = activityId;
+    }
+
+    public string JobId => $"workflow-instance:{WorkflowInstanceId}-{ActivityId}";
+    public string WorkflowInstanceId { get; init; } = default!;
+    public string ActivityId { get; init; } = default!;
+
+    public Task ExecuteAsync(CancellationToken cancellationToken)
+    {
+        throw new System.NotImplementedException();
+    }
+}

src/activities/Elsa.Activities.Scheduling/Jobs/RunWorkflowJob.cs

@@ -0,0 +1,27 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Elsa.Activities.Scheduling.Contracts;
+using Elsa.Models;
+
+namespace Elsa.Activities.Scheduling.Jobs;
+
+public class RunWorkflowJob : IJob
+{
+    public RunWorkflowJob()
+    {
+    }
+    
+    public RunWorkflowJob(WorkflowIdentity workflowIdentity)
+    {
+        WorkflowIdentity = workflowIdentity;
+    }
+
+    public string JobId => $"workflow:{WorkflowIdentity.DefinitionId}";
+    public WorkflowIdentity WorkflowIdentity { get; init; } = default!;
+    
+
+    public Task ExecuteAsync(CancellationToken cancellationToken)
+    {
+        throw new System.NotImplementedException();
+    }
+}

src/activities/Elsa.Activities.Scheduling/Schedules/CronSchedule.cs

@@ -0,0 +1,8 @@
+using Elsa.Activities.Scheduling.Contracts;
+
+namespace Elsa.Activities.Scheduling.Schedules;
+
+public class CronSchedule : ISchedule
+{
+    public string CronExpression { get; set; } = default!;
+}

src/activities/Elsa.Activities.Scheduling/Schedules/RecurringSchedule.cs

@@ -0,0 +1,10 @@
+using System;
+using Elsa.Activities.Scheduling.Contracts;
+
+namespace Elsa.Activities.Scheduling.Schedules;
+
+public class RecurringSchedule : ISchedule
+{
+    public DateTime StartAt { get; set; }
+    public TimeSpan Interval { get; set; }
+}

src/activities/Elsa.Activities.Scheduling/Schedules/SpecificInstantSchedule.cs

@@ -0,0 +1,9 @@
+using System;
+using Elsa.Activities.Scheduling.Contracts;
+
+namespace Elsa.Activities.Scheduling.Schedules;
+
+public class SpecificInstantSchedule : ISchedule
+{
+    public DateTime DateTime { get; set; }
+}

src/activities/Elsa.Activities.Scheduling/Timer.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using Elsa.Attributes;
+using Elsa.Contracts;
 using Elsa.Models;
 
 namespace Elsa.Activities.Scheduling;
@@ -7,4 +9,12 @@ namespace Elsa.Activities.Scheduling;
 public class Timer : Trigger
 {
     [Input] public Input<TimeSpan> Interval { get; set; } = default!;
+
+    protected override IEnumerable<object> GetHashInputs(TriggerIndexingContext context)
+    {
+        var interval = context.ExpressionExecutionContext.Get(Interval);
+        var clock = context.ExpressionExecutionContext.GetRequiredService<ISystemClock>();
+        var executeAt = clock.UtcNow.Add(interval);
+        return new object[] { executeAt, interval };
+    }
 }

src/core/Elsa.Core/Contracts/ITrigger.cs

@@ -4,6 +4,5 @@ namespace Elsa.Contracts;
 
 public interface ITrigger : INode
 {
-    string TriggerType { get; set; }
     ValueTask<IEnumerable<object>> GetHashInputsAsync(TriggerIndexingContext context, CancellationToken cancellationToken = default);
 }

src/core/Elsa.Core/Models/ActivityExecutionContext.cs

@@ -47,18 +47,35 @@ public class ActivityExecutionContext
             ScheduleActivity(activity, completionCallback);
     }
 
+    public void SetBookmarks(IEnumerable<object> hashInputs, IDictionary<string, object?>? data = default, ExecuteActivityDelegate? callback = default)
+    {
+        foreach (var hashInput in hashInputs)
+            SetBookmark(hashInput, data, callback);
+    }
+
     public void SetBookmarks(IEnumerable<Bookmark> bookmarks) => _bookmarks.AddRange(bookmarks);
     public void SetBookmark(Bookmark bookmark) => _bookmarks.Add(bookmark);
 
-    public void SetBookmark(string? hash, IDictionary<string, object?>? data = default, ExecuteActivityDelegate? callback = default) =>
+    public void SetBookmark(object? hashInput, IDictionary<string, object?>? data = default, ExecuteActivityDelegate? callback = default)
+    {
+        var hasher = GetRequiredService<IHasher>();
+        var hash = hashInput != null ? hasher.Hash(hashInput) : default;
+        SetBookmark(hash, data, callback);
+    }
+
+    public void SetBookmark(string? hash, IDictionary<string, object?>? data = default, ExecuteActivityDelegate? callback = default)
+    {
+        var identityGenerator = GetRequiredService<IIdentityGenerator>();
+
         SetBookmark(new Bookmark(
-            Guid.NewGuid().ToString(),
+            identityGenerator.GenerateId(),
             Activity.NodeType,
             hash,
             Activity.Id,
             Id,
             data ?? new Dictionary<string, object?>(),
             callback?.Method.Name));
+    }
 
     public T? GetProperty<T>(string key) => Properties.TryGetValue(key, out var value) ? (T?)value : default;
     public void SetProperty<T>(string key, T value) => Properties[key] = value;

src/core/Elsa.Core/Models/ExpressionExecutionContext.cs

@@ -1,9 +1,14 @@
+using Microsoft.Extensions.DependencyInjection;
+
 namespace Elsa.Models;
 
 public class ExpressionExecutionContext
 {
-    public ExpressionExecutionContext(Register register, ExpressionExecutionContext? parentContext)
+    private readonly IServiceProvider _serviceProvider;
+
+    public ExpressionExecutionContext(IServiceProvider serviceProvider, Register register, ExpressionExecutionContext? parentContext)
     {
+        _serviceProvider = serviceProvider;
         Register = register;
         ParentContext = parentContext;
     }
@@ -31,5 +36,6 @@ public class ExpressionExecutionContext
         Set(output.LocationReference, convertedValue);
     }
 
+    public T GetRequiredService<T>() where T : notnull => _serviceProvider.GetRequiredService<T>();
     private RegisterLocation? GetLocationInternal(RegisterLocationReference locationReference) => Register.TryGetLocation(locationReference.Id, out var location) ? location : ParentContext?.GetLocationInternal(locationReference);
 }

src/core/Elsa.Core/Models/Trigger.cs

@@ -1,22 +1,16 @@
 using Elsa.Contracts;
+using Elsa.Helpers;
 
 namespace Elsa.Models;
 
-public class Trigger : Activity, ITrigger
+public class Trigger : ITrigger
 {
-    protected Trigger()
-    {
-    }
+    protected Trigger() => NodeType = TypeNameHelper.GenerateTypeName(GetType());
+    protected Trigger(string triggerType) => NodeType = triggerType;
 
-    protected Trigger(string triggerType) : base(triggerType)
-    {
-    }
-
-    public string TriggerType
-    {
-        get => NodeType;
-        set => NodeType = value;
-    }
+    public string Id { get; set; } = default!;
+    public string NodeType { get; set; }
+    public IDictionary<string, object> Metadata { get; set; } = new Dictionary<string, object>();
 
     public virtual ValueTask<IEnumerable<object>> GetHashInputsAsync(TriggerIndexingContext context, CancellationToken cancellationToken = default)
     {

src/core/Elsa.Core/Models/TriggerActivity.cs

@@ -0,0 +1,28 @@
+using Elsa.Contracts;
+
+namespace Elsa.Models;
+
+public class TriggerActivity : Activity, ITrigger
+{
+    protected TriggerActivity()
+    {
+    }
+
+    protected TriggerActivity(string triggerType) : base(triggerType)
+    {
+    }
+
+    public string TriggerType
+    {
+        get => NodeType;
+        set => NodeType = value;
+    }
+
+    public virtual ValueTask<IEnumerable<object>> GetHashInputsAsync(TriggerIndexingContext context, CancellationToken cancellationToken = default)
+    {
+        var hashes = GetHashInputs(context);
+        return ValueTask.FromResult(hashes);
+    }
+
+    protected virtual IEnumerable<object> GetHashInputs(TriggerIndexingContext context) => Enumerable.Empty<object>();
+}

src/core/Elsa.Core/Services/ActivityInvoker.cs

@@ -6,10 +6,12 @@ namespace Elsa.Services;
 public class ActivityInvoker : IActivityInvoker
 {
     private readonly IActivityExecutionPipeline _pipeline;
+    private readonly IServiceProvider _serviceProvider;
 
-    public ActivityInvoker(IActivityExecutionPipeline pipeline)
+    public ActivityInvoker(IActivityExecutionPipeline pipeline, IServiceProvider serviceProvider)
     {
         _pipeline = pipeline;
+        _serviceProvider = serviceProvider;
     }
 
     public async Task InvokeAsync(
@@ -25,7 +27,7 @@ public class ActivityInvoker : IActivityInvoker
 
         // Setup an activity execution context.
         var register = new Register();
-        var expressionExecutionContext = new ExpressionExecutionContext(register, parentActivityExecutionContext?.ExpressionExecutionContext);
+        var expressionExecutionContext = new ExpressionExecutionContext(_serviceProvider, register, parentActivityExecutionContext?.ExpressionExecutionContext);
         var activityExecutionContext = new ActivityExecutionContext(workflowExecutionContext, parentActivityExecutionContext, expressionExecutionContext, activity, cancellationToken);
 
         // Declare locations.

src/core/Elsa.Core/Services/WorkflowStateSerializer.cs

@@ -9,6 +9,13 @@ namespace Elsa.Services;
 
 public class WorkflowStateSerializer : IWorkflowStateSerializer
 {
+    private readonly IServiceProvider _serviceProvider;
+
+    public WorkflowStateSerializer(IServiceProvider serviceProvider)
+    {
+        _serviceProvider = serviceProvider;
+    }
+    
     public WorkflowState ReadState(WorkflowExecutionContext workflowExecutionContext)
     {
         var state = new WorkflowState
@@ -119,7 +126,7 @@ public class WorkflowStateSerializer : IWorkflowStateSerializer
         {
             var activity = workflowExecutionContext.FindActivityById(activityExecutionContextState.ScheduledActivityId);
             var register = new Register(activityExecutionContextState.Register.Locations);
-            var expressionExecutionContext = new ExpressionExecutionContext(register, default);
+            var expressionExecutionContext = new ExpressionExecutionContext(_serviceProvider, register, default);
             var properties = activityExecutionContextState.Properties;
             var activityExecutionContext = new ActivityExecutionContext(workflowExecutionContext, default, expressionExecutionContext, activity, workflowExecutionContext.CancellationToken)
             {

src/core/Elsa.Management/Services/TriggerDescriber.cs

@@ -45,9 +45,9 @@ public class TriggerDescriber : ITriggerDescriber
             InputProperties = DescribeInputProperties(inputProperties).ToList(),
             Constructor = context =>
             {
-                var activity = _activityFactory.Create(triggerType, context);
-                activity.TriggerType = fullTypeName;
-                return activity;
+                var trigger = _activityFactory.Create(triggerType, context);
+                trigger.NodeType = fullTypeName;
+                return trigger;
             }
         };
 

src/modules/Elsa.Modules.Quartz/Contracts/IElsaJobSerializer.cs

@@ -0,0 +1,10 @@
+using Elsa.Activities.Scheduling.Contracts;
+using IElsaJob = Elsa.Activities.Scheduling.Contracts.IJob;
+
+namespace Elsa.Modules.Quartz.Contracts;
+
+public interface IElsaJobSerializer
+{
+    string Serialize(IJob job);
+    T Deserialize<T>(string json) where T : IElsaJob;
+}

src/modules/Elsa.Modules.Quartz/Elsa.Modules.Quartz.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Quartz" Version="3.3.3" />
+        <PackageReference Include="Quartz.Extensions.DependencyInjection" Version="3.3.3" />
+        <PackageReference Include="Quartz.Extensions.Hosting" Version="3.3.3" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\..\activities\Elsa.Activities.Scheduling\Elsa.Activities.Scheduling.csproj" />
+    </ItemGroup>
+
+</Project>

src/modules/Elsa.Modules.Quartz/Extensions/ServiceCollectionExtensions.cs

@@ -0,0 +1,74 @@
+using Elsa.Activities.Scheduling.Contracts;
+using Elsa.Activities.Scheduling.Jobs;
+using Elsa.Modules.Quartz.Contracts;
+using Elsa.Modules.Quartz.Jobs;
+using Elsa.Modules.Quartz.Services;
+using Microsoft.Extensions.DependencyInjection;
+using Quartz;
+using IElsaJob = Elsa.Activities.Scheduling.Contracts.IJob;
+
+namespace Elsa.Modules.Quartz.Extensions;
+
+public static class ServiceCollectionExtensions
+{
+    /// <summary>
+    /// This will register both Quartz as well as Elsa-specific services and jobs.
+    /// If you prefer to register Quartz yourself, use <see cref="ConfigureQuartzModule"/>
+    /// </summary>
+    public static IServiceCollection AddQuartzModule(
+        this IServiceCollection services,
+        Action<QuartzOptions>? configureQuartzOptions = default,
+        Action<IServiceCollectionQuartzConfigurator>? configureQuartz = default,
+        Action<QuartzHostedServiceOptions>? configureQuartzHostedService = default)
+    {
+        if (configureQuartzOptions != null)
+            services.Configure(configureQuartzOptions);
+
+        return services
+            .AddQuartz(configure =>
+            {
+                ConfigureQuartz(configure, configureQuartz);
+                ConfigureQuartzModule(services, configure);
+            })
+            .AddQuartzHostedService(options => ConfigureQuartzHostedService(options, configureQuartzHostedService));
+    }
+
+    /// <summary>
+    /// This will register Elsa-specific services and jobs, but will **not** register Quartz itself. To register Quartz, you need to do so yourself, or use <see cref="AddQuartzModule"/> to register & configure Quartz for Elsa.
+    /// </summary>
+    public static IServiceCollection ConfigureQuartzModule(this IServiceCollection services, IServiceCollectionQuartzConfigurator quartz)
+    {
+        services
+            .AddSingleton<IElsaJobSerializer, ElsaJobSerializer>()
+            .AddSingleton<IJobScheduler, QuartzJobScheduler>();
+        
+        quartz.AddElsaJobs();
+
+        return services;
+    }
+
+    private static IServiceCollectionQuartzConfigurator AddElsaJobs(this IServiceCollectionQuartzConfigurator quartz)
+    {
+        quartz.AddJob<RunWorkflowJob>();
+
+        return quartz;
+    }
+
+    private static void ConfigureQuartzHostedService(QuartzHostedServiceOptions options, Action<QuartzHostedServiceOptions>? configureQuartzHostedService)
+    {
+        options.WaitForJobsToComplete = true;
+        configureQuartzHostedService?.Invoke(options);
+    }
+
+    private static IServiceCollectionQuartzConfigurator AddJob<TJob>(this IServiceCollectionQuartzConfigurator quartz) where TJob : IElsaJob =>
+        quartz.AddJob<QuartzJob<RunWorkflowJob>>(job => job.StoreDurably().WithIdentity(nameof(RunWorkflowJob)));
+
+    private static void ConfigureQuartz(IServiceCollectionQuartzConfigurator quartz, Action<IServiceCollectionQuartzConfigurator>? configureQuartz)
+    {
+        quartz.UseMicrosoftDependencyInjectionJobFactory();
+        quartz.AddJob<QuartzJob<RunWorkflowJob>>(job => job.StoreDurably().WithIdentity(nameof(RunWorkflowJob)));
+        quartz.UseSimpleTypeLoader();
+        quartz.UseInMemoryStore();
+        configureQuartz?.Invoke(quartz);
+    }
+}

src/modules/Elsa.Modules.Quartz/Jobs/QuartzJob.cs

@@ -0,0 +1,25 @@
+using Elsa.Modules.Quartz.Contracts;
+using Elsa.Modules.Quartz.Services;
+using Quartz;
+using IElsaJob = Elsa.Activities.Scheduling.Contracts.IJob;
+
+namespace Elsa.Modules.Quartz.Jobs;
+
+/// <summary>
+/// A generic Quartz job that executes Elsa scheduled jobs.
+/// </summary>
+/// <typeparam name="TElsaJob"></typeparam>
+public class QuartzJob<TElsaJob> : IJob where TElsaJob : IElsaJob
+{
+    private readonly IElsaJobSerializer _elsaJobSerializer;
+
+    public QuartzJob(IElsaJobSerializer elsaJobSerializer) => _elsaJobSerializer = elsaJobSerializer;
+
+    public async Task Execute(IJobExecutionContext context)
+    {
+        var json = context.MergedJobDataMap.GetString(QuartzJobScheduler.JobDataKey)!;
+        var elsaJob = _elsaJobSerializer.Deserialize<TElsaJob>(json);
+        
+        await elsaJob.ExecuteAsync(context.CancellationToken);
+    }
+}

src/modules/Elsa.Modules.Quartz/Services/ElsaJobSerializer.cs

@@ -0,0 +1,23 @@
+using System.Text.Json;
+using Elsa.Activities.Scheduling.Contracts;
+using Elsa.Modules.Quartz.Contracts;
+using IElsaJob = Elsa.Activities.Scheduling.Contracts.IJob;
+
+namespace Elsa.Modules.Quartz.Services;
+
+public class ElsaJobSerializer : IElsaJobSerializer
+{
+    public string Serialize(IJob job)
+    {
+        var serializerOptions = CreateSerializerOptions();
+        return JsonSerializer.Serialize(job, serializerOptions);
+    }
+
+    public T Deserialize<T>(string json) where T : IElsaJob
+    {
+        var serializerOptions = CreateSerializerOptions();
+        return JsonSerializer.Deserialize<T>(json, serializerOptions)!;
+    }
+
+    private JsonSerializerOptions CreateSerializerOptions() => new();
+}

src/modules/Elsa.Modules.Quartz/Services/QuartzJobScheduler.cs

@@ -0,0 +1,77 @@
+using Elsa.Activities.Scheduling.Schedules;
+using Elsa.Modules.Quartz.Contracts;
+using Elsa.Modules.Quartz.Jobs;
+using Microsoft.Extensions.Logging;
+using Quartz;
+using IElsaJobScheduler = Elsa.Activities.Scheduling.Contracts.IJobScheduler;
+using IElsaJob = Elsa.Activities.Scheduling.Contracts.IJob;
+using IElsaSchedule = Elsa.Activities.Scheduling.Contracts.ISchedule;
+
+namespace Elsa.Modules.Quartz.Services;
+
+public class QuartzJobScheduler : IElsaJobScheduler
+{
+    public const string JobDataKey = "ElsaJob";
+    private readonly IElsaJobSerializer _elsaJobSerializer;
+    private readonly ISchedulerFactory _schedulerFactory;
+    private readonly ILogger _logger;
+
+    public QuartzJobScheduler(IElsaJobSerializer elsaJobSerializer, ISchedulerFactory schedulerFactory, ILogger<QuartzJobScheduler> logger)
+    {
+        _elsaJobSerializer = elsaJobSerializer;
+        _schedulerFactory = schedulerFactory;
+        _logger = logger;
+    }
+
+    public async Task ScheduleAsync(IElsaJob job, IElsaSchedule schedule, CancellationToken cancellationToken = default)
+    {
+        var quartzTrigger = CreateTrigger(job, schedule);
+        await ScheduleJob(quartzTrigger, cancellationToken);
+    }
+    
+    private async Task ScheduleJob(ITrigger trigger, CancellationToken cancellationToken)
+    {
+        var scheduler = await _schedulerFactory.GetScheduler(cancellationToken);
+        
+        try
+        {
+            await scheduler.ScheduleJob(trigger, cancellationToken);
+        }
+        catch (SchedulerException e)
+        {
+            _logger.LogWarning(e, "Failed to schedule trigger {TriggerKey}", trigger.Key.ToString());
+        }
+    }
+
+    private ITrigger CreateTrigger(IElsaJob job, IElsaSchedule schedule)
+    {
+        var jobName = job.GetType().Name;
+        var json = _elsaJobSerializer.Serialize(job);
+        var builder = TriggerBuilder.Create().ForJob(jobName).WithIdentity(job.JobId).UsingJobData(JobDataKey, json);
+
+        switch (schedule)
+        {
+            case RecurringSchedule recurringSchedule:
+            {
+                builder.StartAt(recurringSchedule.StartAt);
+                builder.WithSimpleSchedule(x => x.WithInterval(recurringSchedule.Interval).RepeatForever());
+                break;
+            }
+            case CronSchedule cronSchedule:
+            {
+                builder.WithCronSchedule(cronSchedule.CronExpression);
+                break;
+            }
+            case SpecificInstantSchedule specificInstantSchedule:
+            {
+                builder.StartAt(specificInstantSchedule.DateTime);
+                break;
+            }
+
+            default:
+                throw new NotSupportedException($"Schedule of type {schedule.GetType()} is not supported. But if you create an issue, we'll make this logic extensible & replaceable :)");
+        }
+
+        return builder.Build();
+    }
+}

src/runtime/Elsa.Runtime/Services/TriggerIndexer.cs

@@ -17,6 +17,7 @@ public class TriggerIndexer : ITriggerIndexer
     private readonly IWorkflowRegistry _workflowRegistry;
     private readonly IExpressionEvaluator _expressionEvaluator;
     private readonly ICommandSender _mediator;
+    private readonly IServiceProvider _serviceProvider;
     private readonly IHasher _hasher;
     private readonly ILogger _logger;
 
@@ -24,12 +25,14 @@ public class TriggerIndexer : ITriggerIndexer
         IWorkflowRegistry workflowRegistry,
         IExpressionEvaluator expressionEvaluator,
         ICommandSender mediator,
+        IServiceProvider serviceProvider,
         IHasher hasher,
         ILogger<TriggerIndexer> logger)
     {
         _workflowRegistry = workflowRegistry;
         _expressionEvaluator = expressionEvaluator;
         _mediator = mediator;
+        _serviceProvider = serviceProvider;
         _hasher = hasher;
         _logger = logger;
     }
@@ -79,7 +82,7 @@ public class TriggerIndexer : ITriggerIndexer
         var inputs = trigger.GetInputs();
         var assignedInputs = inputs.Where(x => x.LocationReference != null!).ToList();
         var register = context.GetOrCreateRegister(trigger);
-        var expressionExecutionContext = new ExpressionExecutionContext(register, default);
+        var expressionExecutionContext = new ExpressionExecutionContext(_serviceProvider, register, default);
 
         // Evaluate trigger inputs.
         foreach (var input in assignedInputs)
@@ -121,9 +124,9 @@ public class TriggerIndexer : ITriggerIndexer
         }
         catch (Exception e)
         {
-            _logger.LogWarning( e, "Failed to get hash inputs");
+            _logger.LogWarning(e, "Failed to get hash inputs");
         }
 
-        return Array.Empty<object>() ;
+        return Array.Empty<object>();
     }
 }

src/samples/aspnet/Elsa.Samples.Web1/Elsa.Samples.Web1.csproj

@@ -7,8 +7,10 @@
 
     <ItemGroup>
       <ProjectReference Include="..\..\..\activities\Elsa.Activities.Http\Elsa.Activities.Http.csproj" />
+      <ProjectReference Include="..\..\..\activities\Elsa.Activities.Scheduling\Elsa.Activities.Scheduling.csproj" />
       <ProjectReference Include="..\..\..\api\Elsa.Api\Elsa.Api.csproj" />
       <ProjectReference Include="..\..\..\core\Elsa\Elsa.csproj" />
+      <ProjectReference Include="..\..\..\modules\Elsa.Modules.Quartz\Elsa.Modules.Quartz.csproj" />
       <ProjectReference Include="..\..\..\persistence\Elsa.Persistence.EntityFrameworkCore.Sqlite\Elsa.Persistence.EntityFrameworkCore.Sqlite.csproj" />
       <ProjectReference Include="..\..\..\runtime\Elsa.Runtime.ProtoActor\Elsa.Runtime.ProtoActor.csproj" />
       <ProjectReference Include="..\..\..\scripting\Elsa.Scripting.Liquid\Elsa.Scripting.Liquid.csproj" />

src/samples/aspnet/Elsa.Samples.Web1/Program.cs

@@ -2,12 +2,14 @@ using Elsa.Activities.Console;
 using Elsa.Activities.ControlFlow;
 using Elsa.Activities.Http;
 using Elsa.Activities.Http.Extensions;
+using Elsa.Activities.Scheduling;
 using Elsa.Activities.Workflows;
 using Elsa.Api.Extensions;
 using Elsa.Extensions;
 using Elsa.Management.Contracts;
 using Elsa.Management.Extensions;
 using Elsa.Mediator.Extensions;
+using Elsa.Modules.Quartz.Extensions;
 using Elsa.Persistence.EntityFrameworkCore.Extensions;
 using Elsa.Persistence.EntityFrameworkCore.Sqlite;
 using Elsa.Persistence.Middleware.WorkflowExecution;
@@ -52,17 +54,22 @@ services
     .AddActivity<ReadLine>()
     .AddActivity<If>()
     .AddActivity<HttpTrigger>()
-    .AddActivity<Flowchart>();
+    .AddActivity<Flowchart>()
+    ;
 
 // Register available triggers.
 services
-    .AddTrigger<HttpTrigger>();
+    .AddTrigger<HttpTrigger>()
+    .AddTrigger<Timer>();
 
 // Register scripting languages.
 services
     .AddJavaScriptExpressions()
     .AddLiquidExpressions();
 
+// Register modules.
+services.AddQuartzModule(); // Provides a scheduler implementation for Timer activities.
+
 // Configure middleware pipeline.
 var app = builder.Build();
 var serviceProvider = app.Services;