Include both index and shard ID in allocation messages

The shardId in AllocationCommand is the 0-based ID for the shard. It
needs to be combined with the index name to make sense in both error and
explanation messages. This PR ensures that is the case for both
CancelAllocationCommand and MoveAllocationCommand. Other commands are
already doing the same thing.

server/src/main/java/org/elasticsearch/cluster/routing/allocation/command/CancelAllocationCommand.java

@@ -136,11 +136,13 @@ public RerouteExplanation execute(RoutingAllocation allocation, boolean explain)
                     allocation.decision(
                         Decision.NO,
                         "cancel_allocation_command",
-                        "can't cancel " + shardId + ", failed to find it on node " + discoNode
+                        "can't cancel [" + index + "][" + shardId + "], failed to find it on node " + discoNode
                     )
                 );
             }
-            throw new IllegalArgumentException("[cancel_allocation] can't cancel " + shardId + ", failed to find it on node " + discoNode);
+            throw new IllegalArgumentException(
+                "[cancel_allocation] can't cancel [" + index + "][" + shardId + "], failed to find it on node " + discoNode
+            );
         }
         if (shardRouting.primary() && allowPrimary == false) {
             if ((shardRouting.initializing() && shardRouting.relocatingNodeId() != null) == false) {
@@ -151,19 +153,23 @@ public RerouteExplanation execute(RoutingAllocation allocation, boolean explain)
                         allocation.decision(
                             Decision.NO,
                             "cancel_allocation_command",
-                            "can't cancel "
+                            "can't cancel ["
+                                + index
+                                + "]["
                                 + shardId
-                                + " on node "
+                                + "] on node "
                                 + discoNode
                                 + ", shard is primary and "
                                 + shardRouting.state().name().toLowerCase(Locale.ROOT)
                         )
                     );
                 }
                 throw new IllegalArgumentException(
-                    "[cancel_allocation] can't cancel "
+                    "[cancel_allocation] can't cancel ["
+                        + index
+                        + "]["
                         + shardId
-                        + " on node "
+                        + "] on node "
                         + discoNode
                         + ", shard is primary and "
                         + shardRouting.state().name().toLowerCase(Locale.ROOT)
@@ -178,7 +184,7 @@ public RerouteExplanation execute(RoutingAllocation allocation, boolean explain)
             allocation.decision(
                 Decision.YES,
                 "cancel_allocation_command",
-                "shard " + shardId + " on node " + discoNode + " can be cancelled"
+                "shard [" + index + "][" + shardId + "] on node " + discoNode + " can be cancelled"
             )
         );
     }

server/src/main/java/org/elasticsearch/cluster/routing/allocation/command/MoveAllocationCommand.java

@@ -141,11 +141,21 @@ public RerouteExplanation execute(RoutingAllocation allocation, boolean explain)
                 if (explain) {
                     return new RerouteExplanation(
                         this,
-                        allocation.decision(Decision.NO, "move_allocation_command", "shard " + shardId + " has not been started")
+                        allocation.decision(
+                            Decision.NO,
+                            "move_allocation_command",
+                            "shard [" + index + "][" + shardId + "] has not been started"
+                        )
                     );
                 }
                 throw new IllegalArgumentException(
-                    "[move_allocation] can't move " + shardId + ", shard is not started (state = " + shardRouting.state() + "]"
+                    "[move_allocation] can't move ["
+                        + index
+                        + "]["
+                        + shardId
+                        + "], shard is not started (state = "
+                        + shardRouting.state()
+                        + "]"
                 );
             }
 
@@ -155,9 +165,11 @@ public RerouteExplanation execute(RoutingAllocation allocation, boolean explain)
                     return new RerouteExplanation(this, decision);
                 }
                 throw new IllegalArgumentException(
-                    "[move_allocation] can't move "
+                    "[move_allocation] can't move ["
+                        + index
+                        + "]["
                         + shardId
-                        + ", from "
+                        + "], from "
                         + fromDiscoNode
                         + ", to "
                         + toDiscoNode
@@ -182,10 +194,12 @@ public RerouteExplanation execute(RoutingAllocation allocation, boolean explain)
             if (explain) {
                 return new RerouteExplanation(
                     this,
-                    allocation.decision(Decision.NO, "move_allocation_command", "shard " + shardId + " not found")
+                    allocation.decision(Decision.NO, "move_allocation_command", "shard [" + index + "][" + shardId + "] not found")
                 );
             }
-            throw new IllegalArgumentException("[move_allocation] can't move " + shardId + ", failed to find it on node " + fromDiscoNode);
+            throw new IllegalArgumentException(
+                "[move_allocation] can't move [" + index + "][" + shardId + "], failed to find it on node " + fromDiscoNode
+            );
         }
         return new RerouteExplanation(this, decision);
     }