repository state tracking stores

Adds an in-memory and a Postgres implemenation of repository
state tracking stores. The two tables added are:

1. `repositories` which contains the expected state of repositories
    in the virtual storage.
2. `storage_repositories` which contains the state of the repositories
    on the physical storages.

Cross-referencing these two makes it easier to identify outdated
repositories.

This commit implements only the stores without hooking them up to the
rest of the code.

2 files changed, 27 insertions, 0 deletions

diff --git a/internal/praefect/config/config.go b/internal/praefect/config/config.go
index 31b1b4d25..4cd10154f 100644
--- a/internal/praefect/config/config.go
+++ b/internal/praefect/config/config.go
@@ -172,6 +172,21 @@ func (c *Config) VirtualStorageNames() []string {
 	return names
 }
 
+// StorageNames returns storage names by virtual storage.
+func (c *Config) StorageNames() map[string][]string {
+	storages := make(map[string][]string, len(c.VirtualStorages))
+	for _, vs := range c.VirtualStorages {
+		nodes := make([]string, len(vs.Nodes))
+		for i, n := range vs.Nodes {
+			nodes[i] = n.Storage
+		}
+
+		storages[vs.Name] = nodes
+	}
+
+	return storages
+}
+
 // DB holds Postgres client configuration data.
 type DB struct {
 	Host                         string `toml:"host"`
diff --git a/internal/praefect/config/config_test.go b/internal/praefect/config/config_test.go
index 1ffde42ee..51c2d254c 100644
--- a/internal/praefect/config/config_test.go
+++ b/internal/praefect/config/config_test.go
@@ -336,6 +336,18 @@ func TestVirtualStorageNames(t *testing.T) {
 	require.Equal(t, []string{"praefect-1", "praefect-2"}, conf.VirtualStorageNames())
 }
 
+func TestStorageNames(t *testing.T) {
+	conf := Config{
+		VirtualStorages: []*VirtualStorage{
+			{Name: "virtual-storage-1", Nodes: []*Node{{Storage: "gitaly-1"}, {Storage: "gitaly-2"}}},
+			{Name: "virtual-storage-2", Nodes: []*Node{{Storage: "gitaly-3"}, {Storage: "gitaly-4"}}},
+		}}
+	require.Equal(t, map[string][]string{
+		"virtual-storage-1": {"gitaly-1", "gitaly-2"},
+		"virtual-storage-2": {"gitaly-3", "gitaly-4"},
+	}, conf.StorageNames())
+}
+
 func TestToPQString(t *testing.T) {
 	testCases := []struct {
 		desc string