Milo: Use custom config caching layer

milo/appengine/common/config.go

 // Copyright 2016 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 common
 
 import (
         "fmt"
+        "time"
 
         "github.com/luci/gae/service/datastore"
         "github.com/luci/gae/service/info"
         "github.com/luci/luci-go/common/logging"
         "github.com/luci/luci-go/luci_config/server/cfgclient"
         "github.com/luci/luci-go/luci_config/server/cfgclient/textproto"
         "github.com/luci/luci-go/milo/common/config"
 
         "github.com/golang/protobuf/proto"
         "golang.org/x/net/context"
 )
 
 // Project is a LUCI project.
 type Project struct {
         // The ID of the project, as per self defined.  This is not the luci-cfg
         // name.
         ID string `gae:"$id"`
         // The luci-cfg name of the project.
         Name string
         // The Project data in protobuf binary format.
         Data []byte `gae:",noindex"`
 }
 
+// The key for the service config entity in datastore.
+const ID = "service_config"

[nodir, 2017/04/04 23:12:08]

this looks as common.ID for other packages, which is abstract. Rename to
ServiceConfigID?

[hinoka, 2017/04/05 20:45:06]

Done.

+
+// ServiceConfig is a container for the instance's service config.
+type ServiceConfig struct {
+        // ID is the datastore key.  This should be static, as there should only be
+        // one service config.
+        ID string `gae:"$id"`
+        // Revision is the revision of the config, taken from luci-config.  This is used
+        // to determine if the entry needs to be refreshed.
+        Revision string
+        // Data The binary proto of the config.

[nodir, 2017/04/04 23:12:08]

s/The/is the/ ?

[hinoka, 2017/04/05 20:45:06]

Done.

+        Data []byte `gae:",noindex"`
+        // Text is the text format of the config.  For human consumption only.
+        Text string `gae:",noindex"`
+        // LastUpdated is the time this config was last updated.
+        LastUpdated time.Time
+}
+
 // GetServiceConfig returns the service (aka global) config for the current
-// instance of Milo.
-func GetSettings(c context.Context) (*config.Settings, error) {
-        cs := cfgclient.CurrentServiceConfigSet(c)
-        msg := &config.Settings{}
-        // Our global config name is called settings.cfg.
-        err := cfgclient.Get(c, cfgclient.AsService, cs, "settings.cfg", textproto.Message(msg), nil)
-        switch err {
-        case cfgclient.ErrNoConfig:
-                // Just warn very heavily in the logs, but don't 500, instead return an
-                // empty config.
-                logging.WithError(err).Errorf(c, "settings.cfg does not exist")
-                msg.Buildbot = &config.Settings_Buildbot{}
-                err = nil
-        case nil:
-                // continue
-        default:
+// instance of Milo from the datastore.  Returns an empty config and warn heavily
+// if none is found.
+// TODO(hinoka): Use process cache to cache configs.
+func GetSettings(c context.Context) *config.Settings {
+        settings := config.Settings{
+                Buildbot: &config.Settings_Buildbot{},
+        }
+
+        msg, err := GetCurrentServiceConfig(c)
+        if err != nil {
+                // The service config does not exist, just return an empty config
+                // and complain loudly in the logs.
+                logging.WithError(err).Errorf(c,
+                        "Encountered error while loading service config, using empty config.")
+                return &settings
+        }
+
+        err = proto.Unmarshal(msg.Data, &settings)
+        if err != nil {
+                // The service config does not exist, just return an empty config

[nodir, 2017/04/04 23:12:08]

i think it does exist, but it is broken

[hinoka, 2017/04/05 20:45:06]

Done.

+                // and complain loudly in the logs.
+                logging.WithError(err).Errorf(c,
+                        "Encountered error while unmarshalling service config, using empty config.")
+                // Zero out the message just incase something got written in.
+                settings.Buildbot = &config.Settings_Buildbot{}
+                settings.Buildbucket = nil
+                settings.Swarming = nil

[nodir, 2017/04/04 23:12:08]

what if you add more fields there later? it is safer to do settings =
config.Settings{Buildbot:&config.Settings_Buildbot{}}

[hinoka, 2017/04/05 20:45:06]

Done.

+        }
+
+        return &settings
+}
+
+// GetTextSettings gets
+func GetCurrentServiceConfig(c context.Context) (*ServiceConfig, error) {
+        msg := ServiceConfig{ID: ID}
+        err := datastore.Get(c, &msg)
+        if err != nil {
                 return nil, err
         }
-        return msg, err
+        logging.Infof(c, "Loaded config entry from %s", msg.LastUpdated.Format(time.RFC3339))

[nodir, 2017/04/04 23:12:08]

this functions is going to be used a lot, sometimes multiple times in a single
http request. This will cause multiple "Loaded config entry ..." logs in a
single request.

You could remove the logging from GetCurrentServiceConfig, or you could use
https://godoc.org/github.com/luci/luci-go/common/data/caching/proccache here to
cache the config in process memory for a short period of time

[hinoka, 2017/04/05 20:45:06]

Done.

+        return &msg, nil
+}
+
+// UpdateServiceConfig fetches the service config from luci-cfg

[nodir, 2017/04/04 23:12:08]

sometimes this to refers to luci-config as luci-config and sometimes as
luci-cfg. Let's consolidate to luci-cfg

[nodir, 2017/04/04 23:27:15]

i meant let's converge on luci-config (not luci-cfg)

[hinoka, 2017/04/05 20:45:06]

Done.

+// and then stores the binary proto in datastore.

[nodir, 2017/04/04 23:12:08]

remove "binary" because it is not only binary?

[hinoka, 2017/04/05 20:45:06]

Done.

+func UpdateServiceConfig(c context.Context) error {
+        msg := ServiceConfig{ID: ID}
+        err := datastore.Get(c, &msg)
+        switch err {
+        case datastore.ErrNoSuchEntity:
+                // Might be the first time this has run.
+                logging.WithError(err).Warningf(c, "No existing service config.")
+        case nil:
+                // Continue
+        default:
+                logging.WithError(err).Errorf(c, "Could not load existing config")

[nodir, 2017/04/04 23:12:08]

general Go suggestion: handle an error only once. If you log it and return it,
the calling code may log it again => many log lines for one error. How about
return fmt.Errorf("could not load existing config: %s", err) and the calling
code can log it?

[hinoka, 2017/04/05 20:45:06]

Ok i'll just wrap it.

+                return err
+        }
+
+        logging.Infof(c, "Loaded config entry (%s) from %s", msg.Revision,
+                msg.LastUpdated.Format(time.RFC3339))
+
+        // Now, load the settings from luci-config.
+        cs := cfgclient.CurrentServiceConfigSet(c)

[nodir, 2017/04/04 23:12:08]

cfgclient is a wrapper around
https://godoc.org/github.com/luci/luci-go/common/config, but this code does not
use any of the features that the wrapper provides. Maybe use
https://godoc.org/github.com/luci/luci-go/common/config directly?

[hinoka, 2017/04/05 20:45:06]

Ah ok.  I didn't know that existed, I like that better.

edit: turns out the impl isn't currently installed in the context.  I'll punch a
hole to grab it from the backend.

+        settings := &config.Settings{}
+        meta := &cfgclient.Meta{}
+        // Our global config name is called settings.cfg.
+        err = cfgclient.Get(
+                c, cfgclient.AsService, cs, "settings.cfg", textproto.Message(settings), meta)
+        if err != nil {
+                logging.WithError(err).Errorf(c, "could not load settings.cfg from luci-cfg")
+                return err
+        }
+
+        // Check to see if we need to update
+        if msg.Revision != "" && msg.Revision == meta.Revision {

[nodir, 2017/04/04 23:12:08]

comparison and put must happen in the same transaction

[nodir, 2017/04/04 23:12:08]

!= "" seems unnecessary. The revision returned by luci-config cannot be empty

[hinoka, 2017/04/05 20:45:06]

Done.

+                logging.Infof(c, "revisions matched (%s), no need to update", msg.Revision)
+                return nil
+        }
+
+        // We do need to update.
+        msg.Text = proto.MarshalTextString(settings)
+        msg.Data, err = proto.Marshal(settings)
+        if err != nil {
+                logging.Errorf(c, "could not marshal proto into binary\n%s", msg.Text)
+                return err
+        }
+        msg.Revision = meta.Revision
+        msg.LastUpdated = time.Now().UTC()

[nodir, 2017/04/04 23:12:08]

logging the fact that revisions do not match is more important than logging that
revisions match

[hinoka, 2017/04/05 20:45:06]

Done.

+        return datastore.Put(c, &msg)
 }
 
 // UpdateProjectConfigs internal project configuration based off luci-cfg.
 // update updates Milo's configuration based off luci config.  This includes
 // scanning through all project and extract all console configs.
 func UpdateProjectConfigs(c context.Context) error {
         cfgName := info.AppID(c) + ".cfg"
 
         var (
                 configs []*config.Project
@@ skipping 92 matching lines @@
         if err != nil {
                 return nil, err
         }
         for _, cs := range p.Consoles {
                 if cs.Name == consoleName {
                         return cs, nil
                 }
         }
         return nil, fmt.Errorf("Console %s not found in project %s", consoleName, projName)
 }