Implement setting snapshot retention configuration on SLM lifecycles.

src/Nest/XPack/Slm/PutLifecycle/PutSnapshotLifecycleRequest.cs

@@ -35,6 +35,14 @@ public partial interface IPutSnapshotLifecycleRequest
 		/// </summary>
 		[DataMember(Name = "schedule")]
 		CronExpression Schedule { get; set; }
+
+		/// <summary>
+		/// Automatic deletion of older snapshots is an optional feature of snapshot lifecycle management. Retention is run as a cluster level task
+		/// that is not associated with a particular policy’s schedule (though the configuration of which snapshots to keep is done on a
+		/// per-policy basis).
+		/// </summary>
+		[DataMember(Name = "retention")]
+		ISnapshotRetentionConfiguration Retention { get; set; }
 	}
 
 	public partial class PutSnapshotLifecycleRequest
@@ -50,6 +58,9 @@ public partial class PutSnapshotLifecycleRequest
 
 		/// <inheritdoc />
 		public CronExpression Schedule { get; set; }
+
+		/// <inheritdoc />
+		public ISnapshotRetentionConfiguration Retention { get; set; }
 	}
 
 	public partial class PutSnapshotLifecycleDescriptor
@@ -59,6 +70,8 @@ public partial class PutSnapshotLifecycleDescriptor
 		string IPutSnapshotLifecycleRequest.Repository { get; set; }
 		CronExpression IPutSnapshotLifecycleRequest.Schedule { get; set; }
 
+		ISnapshotRetentionConfiguration IPutSnapshotLifecycleRequest.Retention { get; set; }
+
 		/// <inheritdoc cref="IPutSnapshotLifecycleRequest.Name" />
 		public PutSnapshotLifecycleDescriptor Name(string name) => Assign(name, (a, v) => a.Name = v);
 
@@ -71,5 +84,9 @@ public partial class PutSnapshotLifecycleDescriptor
 		/// <inheritdoc cref="IPutSnapshotLifecycleRequest.Config" />
 		public PutSnapshotLifecycleDescriptor Config(Func<SnapshotLifecycleConfigDescriptor, ISnapshotLifecycleConfig> selector) =>
 			Assign(selector, (a, v) => a.Config = v.InvokeOrDefault(new SnapshotLifecycleConfigDescriptor()));
+
+		/// <inheritdoc cref="IPutSnapshotLifecycleRequest.Retention" />
+		public PutSnapshotLifecycleDescriptor Retention(Func<SnapshotRetentionConfigurationDescriptor, ISnapshotRetentionConfiguration> selector) =>
+			Assign(selector, (a, v) => a.Retention = v.InvokeOrDefault(new SnapshotRetentionConfigurationDescriptor()));
 	}
 }

src/Nest/XPack/Slm/SnapshotLifecycleConfig.cs

@@ -24,7 +24,6 @@ public interface ISnapshotLifecycleConfig
 		Indices Indices { get; set; }
 	}
 
-
 	public class SnapshotLifecycleConfig : ISnapshotLifecycleConfig
 	{
 		/// <inheritdoc />

src/Nest/XPack/Slm/SnapshotLifecyclePolicy.cs

@@ -20,6 +20,9 @@ public class SnapshotLifecyclePolicy
 
 		/// <inheritdoc />
 		public CronExpression Schedule { get; set; }
+
+		/// <inheritdoc />
+		public ISnapshotRetentionConfiguration Retention { get; set; }
 	}
 
 	/// <inheritdoc />
@@ -54,5 +57,13 @@ public interface ISnapshotLifecyclePolicy
 		/// </summary>
 		[DataMember(Name = "schedule")]
 		CronExpression Schedule { get; set; }
+
+		/// <summary>
+		/// Automatic deletion of older snapshots is an optional feature of snapshot lifecycle management. Retention is run as a cluster level task
+		/// that is not associated with a particular policy’s schedule (though the configuration of which snapshots to keep is done on a
+		/// per-policy basis).
+		/// </summary>
+		[DataMember(Name = "retention")]
+		ISnapshotRetentionConfiguration Retention { get; set; }
 	}
 }

src/Nest/XPack/Slm/SnapshotRetentionConfig.cs

@@ -0,0 +1,62 @@
+using System.Runtime.Serialization;
+using Elasticsearch.Net.Utf8Json;
+
+namespace Nest
+{
+	/// <summary>
+	/// A snapshot lifecycle retention configuration
+	/// </summary>
+	[ReadAs(typeof(SnapshotRetentionConfig))]
+	[InterfaceDataContract]
+	public interface ISnapshotRetentionConfiguration
+	{
+		/// <summary>
+		/// How old a snapshot must be in order to be eligible for deletion.
+		/// </summary>
+		[DataMember(Name = "expire_after")]
+		Time ExpireAfter { get; set; }
+
+		/// <summary>
+		/// A minimum number of snapshots to keep, regardless of age.
+		/// </summary>
+		[DataMember(Name = "min_count")]
+		int? MinimumCount { get; set; }
+
+		/// <summary>
+		/// The maximum number of snapshots to keep, regardless of age. If the number of snapshots in the repository exceeds this limit, the
+		/// policy retains the most recent snapshots and deletes older snapshots.
+		/// </summary>
+		[DataMember(Name = "max_count")]
+		int? MaximumCount { get; set; }
+	}
+
+	public class SnapshotRetentionConfig : ISnapshotRetentionConfiguration
+	{
+		/// <inheritdoc />
+		public Time ExpireAfter { get; set; }
+
+		/// <inheritdoc />
+		public int? MinimumCount { get; set; }
+
+		/// <inheritdoc />
+		public int? MaximumCount { get; set; }
+	}
+
+	public class SnapshotRetentionConfigurationDescriptor : DescriptorBase<SnapshotRetentionConfigurationDescriptor, ISnapshotRetentionConfiguration>, ISnapshotRetentionConfiguration
+	{
+		Time ISnapshotRetentionConfiguration.ExpireAfter { get; set; }
+
+		int? ISnapshotRetentionConfiguration.MinimumCount { get; set; }
+
+		int? ISnapshotRetentionConfiguration.MaximumCount { get; set; }
+
+		/// <inheritdoc cref="ISnapshotRetentionConfiguration.ExpireAfter" />
+		public SnapshotRetentionConfigurationDescriptor ExpireAfter(Time time) => Assign(time, (a, v) => a.ExpireAfter = v);
+
+		/// <inheritdoc cref="ISnapshotRetentionConfiguration.MinimumCount" />
+		public SnapshotRetentionConfigurationDescriptor MinimumCount(int? count) => Assign(count, (a, v) => a.MinimumCount = v);
+
+		/// <inheritdoc cref="ISnapshotRetentionConfiguration.MaximumCount" />
+		public SnapshotRetentionConfigurationDescriptor MaximumCount(int? count) => Assign(count, (a, v) => a.MaximumCount = v);
+	}
+}

src/Tests/Tests/XPack/Slm/SlmApiTests.cs

@@ -11,7 +11,7 @@
 
 namespace Tests.XPack.Slm
 {
-	[SkipVersion("<7.4.0", "All APIs exist in Elasticsearch 7.4.0")]
+	[SkipVersion("<7.5.0", "Snapshot lifecycle retention implement in 7.5.0")]
 	public class SlmApiTests : CoordinatedIntegrationTestBase<XPackCluster>
 	{
 		private const string CreateRepositoryStep = nameof(CreateRepositoryStep);
@@ -50,6 +50,12 @@ public SlmApiTests(XPackCluster cluster, EndpointUsage usage) : base(new Coordin
 							Config = new SnapshotLifecycleConfig
 							{
 								Indices = typeof(Project)
+							},
+							Retention = new SnapshotRetentionConfig
+							{
+								ExpireAfter = "30d",
+								MinimumCount = 1,
+								MaximumCount = 5
 							}
 						},
 						(v, d) => d
@@ -58,6 +64,11 @@ public SlmApiTests(XPackCluster cluster, EndpointUsage usage) : base(new Coordin
 							.Schedule("0 0 0 1 1 ? *")
 							.Config(c => c
 								.Indices<Project>()
+							)
+							.Retention(r => r
+								.ExpireAfter("30d")
+								.MinimumCount(1)
+								.MaximumCount(5)
 							),
 						(v, c, f) => c.SnapshotLifecycleManagement.PutSnapshotLifecycle(v, f),
 						(v, c, f) => c.SnapshotLifecycleManagement.PutSnapshotLifecycleAsync(v, f),
@@ -170,6 +181,9 @@ [I] public async Task GetSnapshotLifecycleResponse() => await Assert<GetSnapshot
 			metadata.Policy.Schedule.Should().BeEquivalentTo(new CronExpression("0 0 0 1 1 ? *"));
 			metadata.Policy.Config.Should().NotBeNull();
 			metadata.Policy.Config.Indices.Should().NotBeNull().And.Be(Nest.Indices.Parse("project"));
+			metadata.Policy.Retention.ExpireAfter.Should().Be("30d");
+			metadata.Policy.Retention.MinimumCount.Should().Be(1);
+			metadata.Policy.Retention.MaximumCount.Should().Be(5);
 		});
 
 		[I] public async Task GetAllSnapshotLifecycleResponse() => await Assert<GetSnapshotLifecycleResponse>(GetAllSnapshotLifecycleStep, (v, r) =>
@@ -200,7 +214,6 @@ [I] public async Task GetSnapshotLifeCycleAfterExecuteResponse() => await Assert
 				metadata.InProgress.State.Should().NotBeNullOrWhiteSpace();
 				metadata.InProgress.StartTime.Should().BeAfter(DateTimeOffset.MinValue);
 			}
-
 		});
 
 		[I] public async Task DeleteSnapshotLifecycleResponse() => await Assert<DeleteSnapshotLifecycleResponse>(DeleteSnapshotLifecycleStep,