Never expect the replica iterators to be sorted (#538)

cmd/litestream/generations.go

@@ -5,6 +5,7 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"sort"
 	"text/tabwriter"
 	"time"
 
@@ -90,6 +91,8 @@ func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error)
 			continue
 		}
 
+		sort.Strings(generations)
+
 		// Iterate over each generation for the replica.
 		for _, generation := range generations {
 			createdAt, updatedAt, err := r.GenerationTimeBounds(ctx, generation)

file/replica_client.go

@@ -6,7 +6,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"sort"
 
 	"github.com/benbjohnson/litestream"
 	"github.com/benbjohnson/litestream/internal"
@@ -180,8 +179,6 @@ func (c *ReplicaClient) Snapshots(ctx context.Context, generation string) (lites
 		})
 	}
 
-	sort.Sort(litestream.SnapshotInfoSlice(infos))
-
 	return litestream.NewSnapshotInfoSliceIterator(infos), nil
 }
 
@@ -297,8 +294,6 @@ func (c *ReplicaClient) WALSegments(ctx context.Context, generation string) (lit
 		})
 	}
 
-	sort.Sort(litestream.WALSegmentInfoSlice(infos))
-
 	return litestream.NewWALSegmentInfoSliceIterator(infos), nil
 }
 

replica.go

@@ -1302,10 +1302,15 @@ func (r *Replica) walSegmentMap(ctx context.Context, generation string, minIndex
 	}
 	defer itr.Close()
 
-	m := make(map[int][]int64)
+	a := []WALSegmentInfo{}
 	for itr.Next() {
-		info := itr.WALSegment()
+		a = append(a, itr.WALSegment())
+	}
 
+	sort.Sort(WALSegmentInfoSlice(a))
+
+	m := make(map[int][]int64)
+	for _, info := range a {
 		// Exit if we go past the max timestamp or index.
 		if !maxTimestamp.IsZero() && info.CreatedAt.After(maxTimestamp) {
 			break // after max timestamp, skip

replica_client.go

@@ -10,13 +10,13 @@ type ReplicaClient interface {
 	// Returns the type of client.
 	Type() string
 
-	// Returns a list of available generations.
+	// Returns a list of available generations. Order is undefined.
 	Generations(ctx context.Context) ([]string, error)
 
 	// Deletes all snapshots & WAL segments within a generation.
 	DeleteGeneration(ctx context.Context, generation string) error
 
-	// Returns an iterator of all snapshots within a generation on the replica.
+	// Returns an iterator of all snapshots within a generation on the replica. Order is undefined.
 	Snapshots(ctx context.Context, generation string) (SnapshotIterator, error)
 
 	// Writes LZ4 compressed snapshot data to the replica at a given index
@@ -31,7 +31,7 @@ type ReplicaClient interface {
 	// the snapshot does not exist.
 	SnapshotReader(ctx context.Context, generation string, index int) (io.ReadCloser, error)
 
-	// Returns an iterator of all WAL segments within a generation on the replica.
+	// Returns an iterator of all WAL segments within a generation on the replica. Order is undefined.
 	WALSegments(ctx context.Context, generation string) (WALSegmentIterator, error)
 
 	// Writes an LZ4 compressed WAL segment at a given position.

sftp/replica_client.go

@@ -8,7 +8,6 @@ import (
 	"net"
 	"os"
 	"path"
-	"sort"
 	"sync"
 	"time"
 
@@ -141,8 +140,6 @@ func (c *ReplicaClient) Generations(ctx context.Context) (_ []string, err error)
 		generations = append(generations, name)
 	}
 
-	sort.Strings(generations)
-
 	return generations, nil
 }
 
@@ -229,8 +226,6 @@ func (c *ReplicaClient) Snapshots(ctx context.Context, generation string) (_ lit
 		})
 	}
 
-	sort.Sort(litestream.SnapshotInfoSlice(infos))
-
 	return litestream.NewSnapshotInfoSliceIterator(infos), nil
 }
 
@@ -363,8 +358,6 @@ func (c *ReplicaClient) WALSegments(ctx context.Context, generation string) (_ l
 		})
 	}
 
-	sort.Sort(litestream.WALSegmentInfoSlice(infos))
-
 	return litestream.NewWALSegmentInfoSliceIterator(infos), nil
 }