if not specified in HOCON, set AppVersion to executing assembly version

src/core/Akka.Cluster.Tests/ClusterConfigSpec.cs

@@ -8,6 +8,7 @@
 using System;
 using System.Collections.Immutable;
 using Akka.Actor;
+using Akka.Configuration;
 using Akka.Dispatch;
 using Akka.Remote;
 using Akka.TestKit;
@@ -46,7 +47,9 @@ public void Clustering_must_be_able_to_parse_generic_cluster_config_elements()
             settings.MinNrOfMembers.Should().Be(1);
             settings.MinNrOfMembersOfRole.Should().Equal(ImmutableDictionary<string, int>.Empty);
             settings.Roles.Should().BeEquivalentTo(ImmutableHashSet<string>.Empty);
-            settings.AppVersion.Should().Be(AppVersion.Zero);
+
+            var appVersion = AppVersion.AppVersionFromAssemblyVersion();
+            settings.AppVersion.Should().Be(appVersion);
             settings.UseDispatcher.Should().Be(Dispatchers.InternalDispatcherId);
             settings.GossipDifferentViewProbability.Should().Be(0.8);
             settings.ReduceGossipDifferentViewProbability.Should().Be(400);
@@ -67,5 +70,16 @@ public void Clustering_must_be_able_to_parse_generic_cluster_config_elements()
             settings.VerboseGossipReceivedLogging.Should().BeFalse();
             settings.RunCoordinatedShutdownWhenDown.Should().BeTrue();
         }
+
+        /// <summary>
+        /// To verify that overriding AppVersion from HOCON works
+        /// </summary>
+        [Fact]
+        public void Clustering_should_parse_nondefault_AppVersion()
+        {
+            Config config = "akka.cluster.app-version = \"0.0.0\"";
+            var settings = new ClusterSettings(config.WithFallback(Sys.Settings.Config), Sys.Name);
+            settings.AppVersion.Should().Be(AppVersion.Zero);
+        }
     }
 }

src/core/Akka.Cluster/ClusterSettings.cs

@@ -9,6 +9,7 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
+using System.Reflection;
 using Akka.Actor;
 using Akka.Configuration;
 using Akka.Dispatch;
@@ -69,6 +70,7 @@ public ClusterSettings(Config config, string systemName)
 
             Roles = clusterConfig.GetStringList("roles", new string[] { }).ToImmutableHashSet();
             AppVersion = Util.AppVersion.Create(clusterConfig.GetString("app-version"));
+
             MinNrOfMembers = clusterConfig.GetInt("min-nr-of-members", 0);
 
             _useDispatcher = clusterConfig.GetString("use-dispatcher", null);

src/core/Akka.Cluster/Configuration/Cluster.conf

@@ -92,7 +92,16 @@ akka {
     # It has support for https://github.com/dwijnand/sbt-dynver format with `+` or
     # `-` separator. The number of commits from the tag is handled as a numeric part.
     # For example `1.0.0+3-73475dce26` is less than `1.0.10+10-ed316bd024` (3 < 10).
-    app-version = "0.0.0"
+    #
+    # DEFAULT: by default the app-version will default to the entry assembly's version,
+    # i.e. the assembly of the executable running `Program.cs`
+    # 
+    # Values can be "assembly-version" or a version string as defined above, i.e.
+    # app-version = "1.0.0"
+    # app-version = "1.1-beta1"
+    # app-version = "1"
+    # app-version = "1.1"
+    app-version = assembly-version 
 
 	# Run the coordinated shutdown from phase 'cluster-shutdown' when the cluster
     # is shutdown for other reasons than when leaving, e.g. when downing. This

src/core/Akka/Util/AppVersion.cs

@@ -8,7 +8,9 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reflection;
 using System.Runtime.CompilerServices;
+using Akka.Configuration;
 using Newtonsoft.Json;
 
 namespace Akka.Util
@@ -32,20 +34,50 @@ namespace Akka.Util
     public class AppVersion : IComparable<AppVersion>, IEquatable<AppVersion>
     {
         public static readonly AppVersion Zero = new AppVersion("0.0.0");
+
+        // made internal for testing purposes
+        internal const string AssemblyVersionMarker = "assembly-version";
         private const int Undefined = 0;
 
-        private int[] numbers = Array.Empty<int>();
-        private string rest = "";
+        private int[] _numbers = Array.Empty<int>();
+        private string _rest = "";
 
         [JsonConstructor]
         internal AppVersion(string version)
         {
-            this.Version = version;
+            Version = version;
         }
 
         public static AppVersion Create(string version)
         {
-            var v = new AppVersion(version);
+            // check to see if we're going to use the assembly-version
+            if (version.Equals(AssemblyVersionMarker, StringComparison.InvariantCultureIgnoreCase))
+            {
+                return AppVersionFromAssemblyVersion();
+            }
+
+            var v2 = new AppVersion(version);
+            return v2.Parse();
+        }
+
+        /// <summary>
+        /// INTERNAL API
+        /// </summary>
+        /// <remarks>
+        /// Internal for testing purposes only.
+        /// </remarks>
+        internal static AppVersion AppVersionFromAssemblyVersion()
+        {
+            // user hasn't specified AppVersion in HOCON
+            // try looking it up via assembly
+            var entryAssembly = Assembly.GetEntryAssembly();
+
+            // if the entryAssembly is null (which can happen when we're called from unmanaged code)
+            // then fall back to the executing assembly for the version number.
+            var targetAssembly = entryAssembly ?? Assembly.GetExecutingAssembly();
+
+            var name = targetAssembly.GetName();
+            var v = new AppVersion($"{name.Version.Major}.{name.Version.Minor}.{name.Version.Build}");
             return v.Parse();
         }
 
@@ -110,7 +142,7 @@ private AppVersion Parse()
                 }
             }
 
-            if (numbers.Length == 0)
+            if (_numbers.Length == 0)
             {
                 var nbrs = new int[4];
                 var segments = Version.Split('.');
@@ -168,8 +200,8 @@ private AppVersion Parse()
                     throw new ArgumentOutOfRangeException($"Only 3 digits separated with '.' are supported. [{Version}]");
                 }
 
-                this.rest = rst;
-                this.numbers = nbrs;
+                this._rest = rst;
+                this._numbers = nbrs;
             }
             return this;
         }
@@ -183,24 +215,24 @@ public int CompareTo(AppVersion other)
                 Parse();
                 other.Parse();
                 var diff = 0;
-                diff = numbers[0] - other.numbers[0];
+                diff = _numbers[0] - other._numbers[0];
                 if (diff == 0)
                 {
-                    diff = numbers[1] - other.numbers[1];
+                    diff = _numbers[1] - other._numbers[1];
                     if (diff == 0)
                     {
-                        diff = numbers[2] - other.numbers[2];
+                        diff = _numbers[2] - other._numbers[2];
                         if (diff == 0)
                         {
-                            diff = numbers[3] - other.numbers[3];
+                            diff = _numbers[3] - other._numbers[3];
                             if (diff == 0)
                             {
-                                if (rest == "" && other.rest != "")
+                                if (_rest == "" && other._rest != "")
                                     diff = 1;
-                                if (other.rest == "" && rest != "")
+                                if (other._rest == "" && _rest != "")
                                     diff = -1;
                                 else
-                                    diff = rest.CompareTo(other.rest);
+                                    diff = _rest.CompareTo(other._rest);
                             }
                         }
                     }
@@ -235,11 +267,11 @@ public override int GetHashCode()
         {
             Parse();
             var hashCode = 13;
-            hashCode = (hashCode * 397) ^ numbers[0];
-            hashCode = (hashCode * 397) ^ numbers[1];
-            hashCode = (hashCode * 397) ^ numbers[2];
-            hashCode = (hashCode * 397) ^ numbers[3];
-            hashCode = (hashCode * 397) ^ rest.GetHashCode();
+            hashCode = (hashCode * 397) ^ _numbers[0];
+            hashCode = (hashCode * 397) ^ _numbers[1];
+            hashCode = (hashCode * 397) ^ _numbers[2];
+            hashCode = (hashCode * 397) ^ _numbers[3];
+            hashCode = (hashCode * 397) ^ _rest.GetHashCode();
             return hashCode;
         }