add max concurrency to bulk replays

Author: carderne

apps/webapp/app/env.server.ts

@@ -1939,6 +1939,8 @@ const EnvironmentSchema = z
     BULK_ACTION_BATCH_SIZE: z.coerce.number().int().default(100),
     BULK_ACTION_BATCH_DELAY_MS: z.coerce.number().int().default(200),
     BULK_ACTION_SUBBATCH_CONCURRENCY: z.coerce.number().int().default(5),
+    /// Max number of concurrent in-flight (PENDING) bulk replays per environment.
+    BULK_ACTION_MAX_CONCURRENT_REPLAYS: z.coerce.number().int().default(3),
 
     // AI Run Filter
     AI_RUN_FILTER_MODEL: z.string().optional(),

apps/webapp/app/v3/services/bulk/BulkActionV2.server.ts

@@ -53,6 +53,27 @@ export class BulkActionService extends BaseService {
     const { organizationId, projectId, environmentId, userId } = input;
     const filters = freezeRunListFilters(input.filters);
 
+    // Concurrency guard for replays
+    // The count is backed by the (environmentId, status, type) index, so it only
+    // touches this env's PENDING replays and stays cheap.
+    if (input.action === "replay") {
+      const maxConcurrentReplays = env.BULK_ACTION_MAX_CONCURRENT_REPLAYS;
+      const inFlightReplays = await this._replica.bulkActionGroup.count({
+        where: {
+          environmentId,
+          type: BulkActionType.REPLAY,
+          status: BulkActionStatus.PENDING,
+        },
+      });
+
+      if (inFlightReplays >= maxConcurrentReplays) {
+        throw new ServiceValidationError(
+          `You can only run ${maxConcurrentReplays} bulk replays at a time in this environment. Wait for an in-progress replay to finish before starting another.`,
+          429
+        );
+      }
+    }
+
     // Region is a replay-only override that re-routes the replayed runs. It's
     // stored alongside the run-list filters under a dedicated key so it isn't
     // mistaken for a `regions` selection filter when the params are parsed.

internal-packages/database/prisma/migrations/20260702120000_bulk_action_group_pending_replay_index/migration.sql

@@ -0,0 +1,5 @@
+-- Backs the per-environment concurrent-replay limit: count of PENDING REPLAY groups.
+-- Not partial (e.g. WHERE status = 'PENDING' AND type = 'REPLAY') as wouldn't be used
+-- with the bind params from prisma.
+CREATE INDEX CONCURRENTLY IF NOT EXISTS "BulkActionGroup_environmentId_status_type_idx"
+ON "BulkActionGroup" ("environmentId", "status", "type");

internal-packages/database/prisma/schema.prisma

@@ -2530,6 +2530,11 @@ model BulkActionGroup {
   // the INCLUDE/fillfactor indexes elsewhere in this schema). `migrate dev` will report
   // drift here; do NOT accept its drop/recreate — keep the hand-written migration.
   @@index([environmentId, type, dedupeKey])
+  // Backs the per-environment concurrent-replay limit (count of PENDING REPLAY groups).
+  // Plain composite (not partial) so Prisma's parameterized count reliably uses it; the
+  // migration creates it CONCURRENTLY to avoid locking writes. See migration
+  // 20260702120000_bulk_action_group_pending_replay_index.
+  @@index([environmentId, status, type])
 }
 
 enum BulkActionType {