[milo] Add BuildSummary and common models.

milo/appengine/common/model/build_summary.go

Index: milo/appengine/common/model/build_summary.go
diff --git a/milo/appengine/common/model/build_summary.go b/milo/appengine/common/model/build_summary.go
new file mode 100644
index 0000000000000000000000000000000000000000..c394155a7efe638c992f08dfbf1517e7b2301106
--- /dev/null
+++ b/milo/appengine/common/model/build_summary.go
@@ -0,0 +1,65 @@
+// Copyright 2017 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package model
+
+import (
+	"time"
+
+	"github.com/luci/gae/service/datastore"
+)
+
+// BuildSummary is a datastore model which is used for displaying

[Ryan Tseng, 2017/06/17 00:44:28]

s/displaying/storing summarized data for/

[iannucci, 2017/06/17 01:30:04]

Done.

+// backend-agnostic views (i.e. builders, console). It contains only data that:
+//   * is necessary to render these simplified views
+//   * is present in all implementations (buildbot, buildbucket)
+//
+// This entity will live as a child of the various implementation's
+// representations of a build (e.g. buildbotBuild). It has various 'tag' fields
+// so that it can be queried by the various backend-agnostic views.
+type BuildSummary struct {
+	// _id for a BuildSummary is always 1

[Ryan Tseng, 2017/06/17 00:44:28]

Why? What is this for?

[iannucci, 2017/06/17 01:30:04]

This is part of the key that luci/gae will generate. Basically they key will
always be `*BuildKey/"BuildSummary",1` now.

+	_ int64 `gae:"$id,1"`
+
+	// BuildKey will always point to the "real" build, i.e. a buildbotBuild or
+	// a buildbucketBuild. It is always the parent key for the BuildSummary.
+	BuildKey *datastore.Key `gae:"$parent"`
+
+	// Global identifier for the builder that this Build belongs to, i.e.:
+	//   "buildbot/<mastername>/<buildername>"
+	//   "buildbucket/<bucketname>/<buildername>"
+	BuilderID string
+
+	// KnownConsoleHash is used for backfilling and must always equal
+	//   sha256(sorted(ConsoleEpochs.keys())

[Ryan Tseng, 2017/06/17 00:44:28]

Is this a binary representation (instead of a hex representation?) If so then
note it here.

I think this being a string and then using the hex representation would be
easier to wrangle with.

[iannucci, 2017/06/17 01:30:04]

I tend to prefer the raw representation (since it's 50% smaller). It's meant to
be opaque anyway :)

+	KnownConsoleHash []byte
+
+	// ConsoleEpochs is used for backfilling, and is a series of cmpbin tuples:
+	//   (console_name[str], recorded_epoch[int])

[Ryan Tseng, 2017/06/17 00:44:28]

// When a new console definition appears, this determines if the build needs to
be updated.

[iannucci, 2017/06/17 01:30:04]

Done.

+	ConsoleEpochs [][]byte
+
+	// ConsoleTags contains query tags for the console view. These are cmpbin
+	// tuples which look like:
+	//   (console_name[str], sort_criteria[tuple], sort_values[tuple])

[Ryan Tseng, 2017/06/17 00:44:28]

Explain sort_criteria[tuple] and sort_values[tuple]

[iannucci, 2017/06/17 01:30:04]

Done.

+	ConsoleTags [][]byte
+
+	// Created is the time when the Build was first created. Due to pending
+	// queues, this may be substantially before Summary.Start.
+	Created time.Time
+
+	// Summary summarizes relevant bits about the overall build.
+	Summary Summary
+
+	// CurrentStep summarizes relevant bits about the currently running step (if
+	// any). Only expected to be set if !Summary.Status.Terminal().
+	CurrentStep Summary
+
+	// Manifests is a list of links to source manifests that this build reported.
+	Manifests []ManifestLink
+
+	// Patches is the list of patches which are associated with this build.
+	// We reserve the multi-patch case for advanced (multi-repo) tryjobs...
+	// Typically there will only be one patch associated with a build.
+	Patches []PatchInfo
+}