Milo: Add ?limit= support to builders

milo/appengine/settings/settings.go

Index: milo/appengine/settings/settings.go
diff --git a/milo/appengine/settings/settings.go b/milo/appengine/settings/settings.go
index 82148f8869a3ef93e69f2f92d3cdd43352368049..ae5e30aa2b163858d7cdd22d6af5ba3cc662416a 100644
--- a/milo/appengine/settings/settings.go
+++ b/milo/appengine/settings/settings.go
@@ -9,10 +9,12 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"strconv"
 
 	ds "github.com/luci/gae/service/datastore"
 	"github.com/luci/luci-go/milo/api/resp"
 	"github.com/luci/luci-go/milo/appengine/model"
+	"github.com/luci/luci-go/milo/common/miloerror"
 	"github.com/luci/luci-go/server/auth"
 	"github.com/luci/luci-go/server/auth/identity"
 	"github.com/luci/luci-go/server/auth/xsrf"
@@ -149,3 +151,26 @@ func getSettings(c context.Context, r *http.Request) (*resp.Settings, error) {
 
 	return result, nil
 }
+
+// GetLimit extracts the "limit" http param from the request, or returns "-1"
+// implying no limit was specified.
+func GetLimit(r *http.Request) (int, error) {

[nodir, 2016/10/28 07:17:54]

why this is in settings package? what does limit query string parameter have to
do with settings?

[hinoka, 2016/10/28 19:47:30]

Technically nothing, i'm using the settings package as sort of a "misc" or
"utils" package, since it has to be imported everywhere anyways.  I could split
it out, but I feel like theres too many top-level packages already, and that
would only complicate things.

[nodir, 2016/10/28 19:52:51]

Perhaps this needs some refactoring. Go does not encourage misc/utils packages.

[hinoka, 2016/10/28 19:53:42]

The alternative would be copypasta code...?

+	sLimit := r.FormValue("limit")

[nodir, 2016/10/28 07:17:54]

can you also fall back to "numBuilds"? this is what buildbucket builder view
uses because buildbot uses it

[hinoka, 2016/10/28 19:47:30]

Done.

+	if sLimit == "" {
+		return -1, nil
+	}
+	limit, err := strconv.Atoi(sLimit)
+	if err != nil {
+		return -1, &miloerror.Error{
+			Message: fmt.Sprintf("limit parameter value %q is not a number: %s", sLimit, err),
+			Code:    http.StatusBadRequest,
+		}
+	}
+	if limit < 0 {
+		return -1, &miloerror.Error{
+			Message: fmt.Sprintf("limit parameter value %q is less than 0", sLimit),
+			Code:    http.StatusBadRequest,
+		}
+	}
+	return limit, nil
+}