Running a build at a runtime with a RocksDB database fails

[kriszyp]

When the nextjs plugin runs a build, nextjs spawns a new process to do the SSG build, and that process can try to access the database which fails because RocksDB does not support multi-process access. The error is:

Error: IO error: While lock file: /user.../hdb/database/system/LOCK: Resource temporarily unavailable opening database

We can look into trying to run nextjs builds in worker thread (reproduce the command line execution). Or the alternate resolution to that is probably to implement HarperFast/rocksdb-js#490 and then implement support for falling back to read-only mode in Harper, so that nextjs can do the build.

[dawsontoth]

Hit this with a create-harper Next.js template. A minimal, common trigger worth noting: a top-level import 'harper' in a Next.js server module (which the README currently recommends — see #51).

import 'harper' opens the database as a module-load side effect, and Next evaluates server modules during the build (page-data/config collection) — even for export const dynamic = 'force-dynamic' routes. So the build subprocess opens the DB and collides with the running instance's lock:

Error: Failed to collect configuration for /dogs/[id]
  [cause]: Error: IO error: While lock file: .../database/data/LOCK: Resource temporarily unavailable opening database

Because actual data access in these apps happens only at request time (server actions / dynamic render), not importing harper at module scope — and using the injected tables global directly — sidesteps the lock entirely: the build no longer opens the DB, and requests still work. That's a viable interim workaround for template/app authors while the read-only-during-build fix here is pursued.

Versions: @harperfast/nextjs 2.2.1, next 16.2.11, harper 5.1.22, Node 24.