Merge lp:~chipaca/snappy/tasks into lp:~snappy-dev/snappy/snappy-moved-to-github

[John Lenton]

Tasks.

[Michael Vogt (mvo)]

Good stuff!

review: Approve

=== added file 'daemon/task.go'
--- daemon/task.go	1970-01-01 00:00:00 +0000
+++ daemon/task.go	2015-09-14 12:48:40 +0000
@@ -0,0 +1,94 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2015 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package daemon
+
+import (
+	"github.com/gorilla/mux"
+	"gopkg.in/tomb.v2"
+)
+
+// A Task encapsulates an asynchronous operation.
+type Task struct {
+	id       UUID
+	tomb     tomb.Tomb
+	metadata interface{}
+}
+
+// A task can be in one of three states
+const (
+	TaskRunning   = "running"
+	TaskSucceeded = "succeeded"
+	TaskFailed    = "failed"
+)
+
+// Metadata is the outcome of this task. If the task is still running
+// this will be nil.
+func (t *Task) Metadata() interface{} {
+	if t.tomb.Alive() {
+		return nil
+	}
+
+	return t.metadata
+}
+
+// State of the task
+func (t *Task) State() string {
+	err := t.tomb.Err()
+	switch err {
+	case tomb.ErrStillAlive:
+		return TaskRunning
+	case nil:
+		return TaskSucceeded
+	default:
+		return TaskFailed
+	}
+}
+
+// Location of the task, based on the given route.
+//
+// If the route can't build a URL for this task, returns the empty
+// string.
+func (t *Task) Location(route *mux.Route) string {
+	url, err := route.URL("uuid", t.id.String())
+	if err != nil {
+		return ""
+	}
+
+	return url.String()
+}
+
+// RunTask creates a Task for the given function and runs it.
+func RunTask(f func() interface{}) *Task {
+	id := UUID4()
+	t := &Task{id: id}
+
+	t.tomb.Go(func() error {
+		out := f()
+		t.metadata = out
+
+		if err, ok := out.(error); ok {
+			return err
+		}
+
+		return nil
+	})
+
+	return t
+}

=== added file 'daemon/task_test.go'
--- daemon/task_test.go	1970-01-01 00:00:00 +0000
+++ daemon/task_test.go	2015-09-14 12:48:40 +0000
@@ -0,0 +1,81 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2015 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package daemon
+
+import (
+	"errors"
+	"time"
+
+	"github.com/gorilla/mux"
+	"gopkg.in/check.v1"
+)
+
+type taskSuite struct{}
+
+var _ = check.Suite(&taskSuite{})
+
+func (s *taskSuite) TestTask(c *check.C) {
+	router := mux.NewRouter()
+	route := router.Handle("/xyzzy/{uuid}", nil)
+
+	ch := make(chan struct{})
+
+	t := RunTask(func() interface{} {
+		ch <- struct{}{}
+		return 42
+	})
+
+	c.Check(t.Metadata(), check.IsNil)
+	c.Check(t.State(), check.Equals, TaskRunning)
+	c.Check(t.Location(route), check.Equals, "/xyzzy/"+t.id.String())
+
+	<-ch
+
+	// let the other guy have a go, just in case
+	time.Sleep(time.Millisecond)
+
+	c.Check(t.State(), check.Equals, TaskSucceeded)
+	c.Check(t.Metadata(), check.Equals, 42)
+}
+
+func (s *taskSuite) TestFails(c *check.C) {
+	router := mux.NewRouter()
+	route := router.Handle("/xyzzy/{uuid}", nil)
+
+	ch := make(chan struct{})
+	err := errors.New("everything is broken")
+
+	t := RunTask(func() interface{} {
+		ch <- struct{}{}
+		return err
+	})
+
+	c.Check(t.Metadata(), check.IsNil)
+	c.Check(t.State(), check.Equals, TaskRunning)
+	c.Check(t.Location(route), check.Equals, "/xyzzy/"+t.id.String())
+
+	<-ch
+
+	// let the other guy have a go, just in case
+	time.Sleep(time.Millisecond)
+
+	c.Check(t.State(), check.Equals, TaskFailed)
+	c.Check(t.Metadata(), check.Equals, err)
+}

=== added file 'daemon/uuid.go'
--- daemon/uuid.go	1970-01-01 00:00:00 +0000
+++ daemon/uuid.go	2015-09-14 12:48:40 +0000
@@ -0,0 +1,52 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2015 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package daemon
+
+import (
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+// TODO: use an actual uuid package; these UUIDs actually have only
+// 126 bits free (and less entropy than that). Good enough for our use
+// case for now at least.
+
+// An UUID is a universally unique identifier
+type UUID [2]uint64
+
+var source = rand.NewSource(time.Now().UTC().UnixNano())
+
+// UUID4 are random-based UUIDs
+func UUID4() UUID {
+	return UUID{uint64(source.Int63()), uint64(source.Int63())}
+}
+
+func (u UUID) String() string {
+	m := u[0]
+	n := u[1]
+
+	return fmt.Sprintf("%08x-%04x-%04x-%04x-%012x",
+		n&0xffffffff,
+		(n>>32)&0xffff,
+		(n>>48)&0xffff,
+		m&0xffff,
+		m>>16)
+}

=== added file 'daemon/uuid_test.go'
--- daemon/uuid_test.go	1970-01-01 00:00:00 +0000
+++ daemon/uuid_test.go	2015-09-14 12:48:40 +0000
@@ -0,0 +1,42 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2015 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package daemon
+
+import (
+	"gopkg.in/check.v1"
+)
+
+type uuidSuite struct{}
+
+var _ = check.Suite(&uuidSuite{})
+
+func (s *uuidSuite) TestUUID(c *check.C) {
+	uuids := make([]UUID, 200)
+	for i := range uuids {
+		uuids[i] = UUID4()
+	}
+
+	for i := range uuids[:len(uuids)-2] {
+		c.Check(uuids[i].String(), check.Matches, `^[[:xdigit:]]{8}-[[:xdigit:]]{4}-[[:xdigit:]]{4}-[[:xdigit:]]{4}-[[:xdigit:]]{12}`, check.Commentf("format of %d wrong: %s", i, uuids[i]))
+		for j := range uuids[i+1:] {
+			c.Check(uuids[i], check.Not(check.Equals), uuids[i+j+1], check.Commentf("%d == %d", i, i+j+1))
+		}
+	}
+}