Merge pull request #14918 from manadart/3.0-dqlite-lease-store

[JUJU-1944] DB-backed lease store implementation

database/errors.go

@@ -0,0 +1,16 @@
+package database
+
+import (
+	"github.com/juju/errors"
+	"github.com/mattn/go-sqlite3"
+)
+
+// IsErrConstraintUnique returns true if the input error was
+// returned by SQLite due to violation of a unique constraint.
+func IsErrConstraintUnique(err error) bool {
+	var sqliteErr sqlite3.Error
+	if errors.As(err, &sqliteErr) && sqliteErr.ExtendedCode == sqlite3.ErrConstraintUnique {
+		return true
+	}
+	return false
+}

database/schema/controller.go

@@ -17,28 +17,46 @@ CREATE UNIQUE INDEX idx_lease_type_type
 ON lease_type (type);
 
 INSERT INTO lease_type VALUES
-    (0, 'controller'), 
-    (1, 'model' ), 
-    (2, 'application');
+    (0, 'controller'),  -- The controller running singular controller workers.
+    (1, 'model' ),      -- The controller running singular workers for a model.
+    (2, 'application'); -- The unit that holds leadership for an application.
 
-CREATE TABLE IF NOT EXISTS lease (
+CREATE TABLE lease (
     uuid            TEXT PRIMARY KEY,
     lease_type_id   INT NOT NULL,
+    model_uuid      TEXT,
     name            TEXT,
     holder          TEXT,
     start           TIMESTAMP,
     expiry          TIMESTAMP,
-    pinned          BOOLEAN,
     CONSTRAINT      fk_lease_lease_type
         FOREIGN KEY (lease_type_id)
         REFERENCES  lease_type(id)
 );
 
-CREATE UNIQUE INDEX idx_lease_type_name
-ON lease (lease_type_id, name);
+CREATE UNIQUE INDEX idx_lease_model_type_name
+ON lease (model_uuid, lease_type_id, name);
 
 CREATE INDEX idx_lease_expiry
-ON lease (expiry);`[1:]
+ON lease (expiry);
+
+CREATE TABLE lease_pin (
+    -- The presence of entries in this table for a particular lease_uuid
+    -- implies that the lease in question is pinned and cannot expire.
+    uuid       TEXT PRIMARY KEY,
+    lease_uuid TEXT,
+    entity_id  TEXT,
+    CONSTRAINT      fk_lease_pin_lease
+        FOREIGN KEY (lease_uuid)
+        REFERENCES  lease(uuid)
+);
+
+CREATE UNIQUE INDEX idx_lease_pin_lease_entity
+ON lease_pin (lease_uuid, entity_id);
+
+CREATE INDEX idx_lease_pin_lease
+ON lease_pin (lease_uuid);
+`[1:]
 
 	return strings.Split(delta, ";\n\n")
 }

worker/lease/package_test.go

@@ -1,7 +1,7 @@
 // Copyright 2015 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
-package lease_test
+package lease
 
 import (
 	"testing"
@@ -12,3 +12,7 @@ import (
 func TestPackage(t *testing.T) {
 	gc.TestingT(t)
 }
+
+type StubLogger struct{}
+
+func (StubLogger) Errorf(string, ...interface{}) {}