When using the SQLite`cache`, must I ensure the machine is a primary?

[kentcdodds]

Discussed in #1038

^{Originally posted by warronbebster September 4, 2025}
I've followed the caching docs and when I run it in production, I get Disk I/O SQLite errors:

2025-09-04T19:33:55Z app[784049ef491948] iad [info]level=INFO msg="fuse: write(): wal error: read only replica"
error setting cache: challenge:mallorca-championships-presented-by-ecotrans-group-2025-served-2025 Error: disk I/O error
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at Object.set (file:///myapp/app/utils/cache.server.ts:154:16)
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at getFreshValue (file:///myapp/node_modules/@epic-web/cachified/src/getFreshValue.ts:65:19)
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at cachified (file:///myapp/node_modules/@epic-web/cachified/src/cachified.ts:94:17)
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at getChallenge (file:///myapp/app/utils/challenge.server.ts:32:18)
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at getTournamentContextMain (file:///myapp/app/utils/tournament-context.server.ts:60:18)
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at loader$9 (file:///myapp/app/routes/tournaments+/$slug+/$tour+/index.tsx:38:9)
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at callRouteHandler (file:///myapp/node_modules/react-router/dist/development/chunk-5UALIXAM.mjs:509:16)
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at commonRoute.loader (file:///myapp/node_modules/react-router/dist/development/chunk-5UALIXAM.mjs:658:19)
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at file:///myapp/node_modules/react-router/dist/development/chunk-PVWAREVJ.mjs:4259:19
2025-09-04T19:33:55Z app[784049ef491948] iad [info]    at callLoaderOrAction (file:///myapp/node_modules/react-router/dist/development/chunk-PVWAREVJ.mjs:4311:16) {
2025-09-04T19:33:55Z app[784049ef491948] iad [info]  code: 'ERR_SQLITE_ERROR',
2025-09-04T19:33:55Z app[784049ef491948] iad [info]  errcode: 778,
2025-09-04T19:33:55Z app[784049ef491948] iad [info]  errstr: 'disk I/O error'
2025-09-04T19:33:55Z app[784049ef491948] iad [info]}

To use the SQLite cache, do we have to first use ensurePrimary() before saving to it? If so, can the docs be updated to reflect that?

[kentcdodds]

I mistakenly removed this in 120022b