token-server: Warmup some local caches in /_ah/warmup.

tokenserver/appengine/impl/certchecker/warmup.go

 // 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 certchecker
 
 import (
         "golang.org/x/net/context"
 
+        "github.com/luci/luci-go/common/logging"
         "github.com/luci/luci-go/server/warmup"
+        "github.com/luci/luci-go/tokenserver/appengine/impl/certconfig"
 )
 
 func init() {
         warmup.Register("tokenserver/appengine/impl/certchecker", func(c context.Context) error {
-                // TODO
+                names, err := certconfig.ListCAs(c)
+                if err != nil {
+                        return err
+                }
+                for _, cn := range names {
+                        logging.Infof(c, "Warming up %q", cn)
+                        checker, err := GetCertChecker(c, cn)
+                        if err == nil {
+                                _, err = checker.GetCA(c)
+                        }
+                        if err != nil {
+                                logging.WithError(err).Warningf(c, "Failed to warm up %q", cn)

[nodir, 2017/03/29 21:45:06]

why it doesn't return err in this case but returns it @L19?

[Vadim Sh., 2017/03/29 21:49:30]

Because we don't want to do "return err" here, before checking all CAs, and I
didn't want to bother with MultiErrror handling :) Errors in warmup are not
really important.

[Vadim Sh., 2017/03/29 23:46:00]

Added MultiError.

+                        }
+                }
                 return nil
         })
 }