mentat/ffi
Grisha Kruglov b22b29679b
Basic sync support (#563) r=nalexander
* Pre: remove remnants of 'open_empty'

* Pre: Cleanup 'datoms' table after a timeline move

Since timeline move operations use a transactor, they generate a
"phantom" 'tx' and a 'txInstant' assertion. It is "phantom" in a sense
that it was never present in the 'transactions' table, and is entirely
synthetic as far as our database is concerned.
It's an implementational artifact, and we were not cleaning it up.

It becomes a problem when we start inserting transactions after a move.
Once the transactor clashes with the phantom 'tx', it will retract the
phantom 'txInstant' value, leaving the transactions log in an incorrect state.

This patch adds a test for this scenario and elects the easy way out: simply
remove the offending 'txInstant' datom.

* Part 1: Sync without support for side-effects

A "side-effect" is defined here as a mutation of a remote state as part
of the sync.

If, during a sync we determine that a remote state needs to be changed, bail out.

This generally supports different variations of "baton-passing" syncing, where clients
will succeed syncing if each change is non-conflicting.

* Part 2: Support basic "side-effects" syncing

This patch introduces a concept of a follow-up sync. If a sync generated
a "merge transaction" (a regular transaction that contains assertions
necessary for local and remote transaction logs to converge), then
this transaction needs to be uploaded in a follow-up sync.

Generated SyncReport indicates if a follow-up sync is required.

Follow-up sync itself is just a regular sync. If remote state did not change,
it will result in a simple RemoteFastForward. Otherwise, we'll continue
merging and requesting a follow-up.

Schema alterations are explicitly not supported.

As local transactions are rebased on top of remote, following changes happen:
- entids are changed into tempids, letting transactor upsert :db/unique values
- entids for retractions are changed into lookup-refs if we're confident they'll succeed
-- otherwise, retractions are dropped on the floor

* Post: use a macro for more readable tests

* Tolstoy README
2018-09-07 19:18:20 -07:00
..
src Basic sync support (#563) r=nalexander 2018-09-07 19:18:20 -07:00
Cargo.toml Add support for using sqlcipher (#737). Fixes #118 2018-06-13 08:49:40 -07:00
README.md Android SDK basic sample project and symlinked SDK Mentat binaries (#729) r=nalexander 2018-06-01 12:44:31 -07:00

Development flow for Mentat FFI

Android SDK

Android Mentat SDK is one of two first-party consumers (the other one being iOS Mentat SDK).

Binaries produced by cargo build ... are symlinked from within the SDK, and a number of target-specific libmentat_ffi.so binaries are bundled together and distributed with the SDK.

There is a build script at <mentat_root>/scripts/android_build.sh which knows how to cross-compile mentat_ffi for various Android targets.

  • ./<mentat_root>/scripts/android_build.sh - compiles for all supported targets
  • ./<mentat_root>/scripts/android_build.sh x86 - compiles for x86
  • ./<mentat_root>/scripts/android_build.sh x86 arm - compiles for x86, arm

General development flow while working on the Android SDK is:

  • (pre) compile for all targets, if you've never done so
  • make changes to mentat_ffi and/or mentat
  • re-compile mentat_ffi binaries using ./android_build.sh x86. During development it's faster to compile just for the target which matches your emulator, e.g. x86
  • make corresponding changes in the Android SDK, try them out from within the bundled sample project
  • since binaries are symlinked, no manual copy step is necessary for the Android SDK to pick up the changes

iOS SDK

TODO, contribute via issue #732.