From 61c0f515df4ec85d19e06659c2ede2aac611be8c Mon Sep 17 00:00:00 2001
From: hpitkeathly <hpitkeathly@thoughtmachine.net>
Date: Mon, 23 Oct 2023 15:17:13 +0100
Subject: [PATCH] add topic opts

---
 mettle/common/common.go | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/mettle/common/common.go b/mettle/common/common.go
index 8c1b1b58..4a9d436e 100644
--- a/mettle/common/common.go
+++ b/mettle/common/common.go
@@ -23,8 +23,9 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 
-	"github.com/thought-machine/please-servers/mettle/mempubsub" // Register our custom mempubsub scheme
-	// And gocloud's gcppubsub provider
+	// Register our custom pubsub schemes
+	"github.com/thought-machine/please-servers/mettle/mempubsub"
+	_ "github.com/thought-machine/please-servers/mettle/mempubsub"
 )
 
 var log = logging.MustGetLogger()
@@ -79,14 +80,37 @@ func limitBatchSize(in, size string) string {
 // MustOpenTopic opens a topic, which must have been created ahead of time.
 // Batch size and number of publishers are configurable for GCP queues only.
 func MustOpenTopic(url string, batchSize, numPublishers int) *pubsub.Topic {
-	t, err := pubsub.OpenTopic(context.Background(), url)
+	u := addTopicOpts(url, batchSize, numPublishers)
+	t, err := pubsub.OpenTopic(context.Background(), u)
 	if err != nil {
-		log.Fatalf("Failed to open topic %s: %s", url, err)
+		log.Fatalf("Failed to open topic %s: %s", u, err)
 	}
 	log.Debug("Opened topic %s", url)
 	return t
 }
 
+func addTopicOpts(in string, batchSize, numPublishers int) string {
+	u, err := url.Parse(in)
+	if err != nil {
+		// It's not clear exactly how we can even get here; url.Parse seems to pretty much never
+		// return an error. Anyway, panicking at this point shouldn't be an issue.
+		panic(err)
+	}
+	v := u.Query()
+	if batchSize > 1 {
+		v.Add("max_send_batch_size", strconv.Itoa(batchSize))
+	}
+	if numPublishers > 1 {
+		if strings.HasPrefix(in, "configurable") {
+			v.Add("num_handlers", strconv.Itoa(numPublishers))
+		} else {
+			log.Fatal("Can only set numPublishers on configurablepubsub queues")
+		}
+	}
+	u.RawQuery = v.Encode()
+	return u.String()
+}
+
 func handleSignals(cancel context.CancelFunc, s Shutdownable) {
 	ch := make(chan os.Signal, 1)
 	signal.Notify(ch, syscall.SIGHUP, syscall.SIGINT, syscall.SIGQUIT, syscall.SIGABRT, syscall.SIGTERM)