feat(sync-service): Add exclusive mode to support AWS EFS

[magnetised]

NFS filesystems, such as AWS EFS, do not support SQLite WAL mode or simultaneous access by multiple processes, due to the limitiations of NFS locking semantics.

So to support AWS EFS this pr adds a new "exclusive mode" to the shape db configuration, enabled by setting ELECTRIC_SHAPE_DB_EXCLUSIVE_MODE=true, which multiplexes all reads and writes through a single SQLite connection and configures the database with journal_mode=DELETE as recommended by the SQLite docs.

There is also a new ELECTRIC_SHAPE_DB_STORAGE_DIR configuration option which allows for hosting the shape db file in a different location from the shape data, e.g. on a non-networked filesystem.

These two options open up the possibility of an in-memory shape database, so enabling exclusive mode and setting ELECTRIC_SHAPE_DB_STORAGE_DIR=:memory: will do exactly that.

Since I was wiring up shapedb configuration, I've also added env-vars and configuration to set page cache size and durabilty (PRAGMA cache_size=... and PRAGMA synchronous=...).

Follow up work:

• Start some shape cleanup task to remove all orphaned shape data when the shape db is empty, to fix the situation when an ephemeral shape db is used alongside persistent shape data.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.18%. Comparing base (dfa6301) to head (59ba3da).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3859       +/-   ##
===========================================
+ Coverage   76.66%   87.18%   +10.52%     
===========================================
  Files          37       25       -12     
  Lines        1611     2325      +714     
  Branches      171      587      +416     
===========================================
+ Hits         1235     2027      +792     
+ Misses        375      296       -79     
- Partials        1        2        +1     

Flag	Coverage Δ
elixir	?
elixir-client	?
packages/experimental	87.73% <ø> (ø)
packages/react-hooks	86.48% <ø> (ø)
packages/start	82.83% <ø> (ø)
packages/typescript-client	92.03% <ø> (?)
packages/y-electric	56.05% <ø> (ø)
typescript	87.18% <ø> (+11.42%)	⬆️
unit-tests	87.18% <ø> (+10.52%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[netlify]

✅ Deploy Preview for electric-next ready!

Name	Link
🔨 Latest commit	986229f
🔍 Latest deploy log	https://app.netlify.com/projects/electric-next/deploys/69947fbf855dfa0008e7400e
😎 Deploy Preview	https://deploy-preview-3859--electric-next.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.