Generating short ID for prebuilds

dannykopping · dannykopping · commit 9d5c6633de70 · 2025-02-14T12:17:07.000Z
Also dropped unnecessary CASTs

Signed-off-by: Danny Kopping &lt;danny@coder.com&gt;
diff --git a/coderd/database/queries.sql.go b/coderd/database/queries.sql.go
diff --git a/coderd/database/queries/prebuilds.sql b/coderd/database/queries/prebuilds.sql
@@ -38,25 +38,25 @@ WITH
 							  GROUP BY wpb.template_version_id, wpb.transition)
 SELECT t.template_id,
 	   t.template_version_id,
-	   t.using_active_version     AS is_active,
-	   CAST(COALESCE(MAX(CASE WHEN p.template_version_id = t.template_version_id THEN p.ids END),
-					 '') AS TEXT) AS running_prebuild_ids,
-	   CAST(COALESCE(MAX(CASE WHEN t.using_active_version THEN p.count ELSE 0 END),
-					 0) AS INT)   AS actual,     -- running prebuilds for active version
-	   CAST(COALESCE(MAX(CASE WHEN t.using_active_version THEN t.desired_instances ELSE 0 END),
-					 0) AS INT)   AS desired,    -- we only care about the active version's desired instances
-	   CAST(COALESCE(MAX(CASE
-							 WHEN p.template_version_id = t.template_version_id AND t.using_active_version = false
-								 THEN p.count END),
-					 0) AS INT)   AS extraneous, -- running prebuilds for inactive version
-	   CAST(COALESCE(MAX(CASE WHEN pip.transition = 'start'::workspace_transition THEN pip.count ELSE 0 END),
-					 0) AS INT)   AS starting,
-	   CAST(COALESCE(MAX(CASE WHEN pip.transition = 'stop'::workspace_transition THEN pip.count ELSE 0 END),
-					 0) AS INT)   AS stopping,   -- not strictly needed, since prebuilds should never be left if a "stopped" state, but useful to know
-	   CAST(COALESCE(MAX(CASE WHEN pip.transition = 'delete'::workspace_transition THEN pip.count ELSE 0 END),
-					 0) AS INT)   AS deleting,
-	   t.deleted                  AS template_deleted,
-	   t.deprecated               AS template_deprecated
+	   t.using_active_version AS is_active,
+	   COALESCE(MAX(CASE WHEN p.template_version_id = t.template_version_id THEN p.ids END),
+				'')::text     AS running_prebuild_ids,
+	   COALESCE(MAX(CASE WHEN t.using_active_version THEN p.count ELSE 0 END),
+				0)::int       AS actual,     -- running prebuilds for active version
+	   COALESCE(MAX(CASE WHEN t.using_active_version THEN t.desired_instances ELSE 0 END),
+				0)::int       AS desired,    -- we only care about the active version's desired instances
+	   COALESCE(MAX(CASE
+						WHEN p.template_version_id = t.template_version_id AND t.using_active_version = false
+							THEN p.count END),
+				0)::int       AS extraneous, -- running prebuilds for inactive version
+	   COALESCE(MAX(CASE WHEN pip.transition = 'start'::workspace_transition THEN pip.count ELSE 0 END),
+				0)::int       AS starting,
+	   COALESCE(MAX(CASE WHEN pip.transition = 'stop'::workspace_transition THEN pip.count ELSE 0 END),
+				0)::int       AS stopping,   -- not strictly needed, since prebuilds should never be left if a "stopped" state, but useful to know
+	   COALESCE(MAX(CASE WHEN pip.transition = 'delete'::workspace_transition THEN pip.count ELSE 0 END),
+				0)::int       AS deleting,
+	   t.deleted              AS template_deleted,
+	   t.deprecated           AS template_deprecated
 FROM templates_with_prebuilds t
 		 LEFT JOIN running_prebuilds p ON p.template_version_id = t.template_version_id
 		 LEFT JOIN prebuilds_in_progress pip ON pip.template_version_id = t.template_version_id
diff --git a/coderd/prebuilds/controller.go b/coderd/prebuilds/controller.go
@@ -2,6 +2,8 @@ package prebuilds
 
 import (
 	"context"
+	"crypto/rand"
+	"encoding/base32"
 	"fmt"
 	"github.com/coder/coder/v2/coderd/audit"
 	"github.com/coder/coder/v2/coderd/database/dbtime"
@@ -279,7 +281,10 @@ func (c Controller) reconcileTemplate(ctx context.Context, template database.Tem
 }
 
 func (c Controller) createPrebuild(ctx context.Context, db database.Store, prebuildID uuid.UUID, template database.Template) error {
-	name := fmt.Sprintf("prebuild-%s", prebuildID)
+	name, err := generateName()
+	if err != nil {
+		return xerrors.Errorf("failed to generate unique prebuild ID: %w", err)
+	}
 
 	now := dbtime.Now()
 	// Workspaces are created without any versions.
@@ -355,3 +360,21 @@ func (c Controller) provision(ctx context.Context, db database.Store, prebuildID
 func (c Controller) Stop() {
 	c.closeCh <- struct{}{}
 }
+
+// generateName generates a 20-byte prebuild name which should safe to use without truncation in most situations.
+// UUIDs may be too long for a resource name in cloud providers (since this ID will be used in the prebuild's name).
+//
+// We're generating a 9-byte suffix (72 bits of entry):
+// 1 - e^(-1e9^2 / (2 * 2^72)) = ~0.01% likelihood of collision in 1 billion IDs.
+// See https://en.wikipedia.org/wiki/Birthday_attack.
+func generateName() (string, error) {
+	b := make([]byte, 9)
+
+	_, err := rand.Read(b)
+	if err != nil {
+		return "", err
+	}
+
+	// Encode the bytes to Base32 (A-Z2-7), strip any '=' padding
+	return fmt.Sprintf("prebuild-%s", base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(b)), nil
+}
