tablevc

tablevc - Table versin control

Small library to keep synchronized a table of records between two different sites, one of the sites designed as the central server. Typescript powered.

The gist

Given a record type

interface TstRecordType {
    _id: Id;
    name: string;
    when: Date;
    amount: number;
    children: Id[];
    isTrue: boolean;
}

create a local table instance (by default powered by a memory map):

const serverTable = await createVersionedTable<TstRecordType>();
await serverTable.addRecord('TEST1', testRecord1);
await serverTable.addRecord('TEST2', testRecord2);

some time later a client requests the contents of the table

async function handleClientRequest() {
    const records = await serverTable.getRecords()
    return {records, commitId: serverTable.lastCommitId()}
}

whilst on the client

async function initializeTable(): VersionedTable<TstRecordType> {
    const {records, commitId} = await requestTableData();
    saveLastCommonCommitId(commitId);
    const localTable = await createVersionedTable({
      initialData: {
        commitId,
        idExtract: (record: TstRecordType) => record._id,
        data: records
      }
    });
}

somewhere else on the client

async function changeAmount(id, amount) {
    await localTable.changeRecord(
        id,
        {amount}
    );
    pushChanges(localTable.getHistoryDelta(
        getLastCommonCommitId(commitId)
    )).then().catch();
}

the idea being you apply changes locally, and the synchronization back is handled within pushChanges.

In general compatible record level changes (e.g. different fields updated concurrently) work as expected. When a conflict arises, in general the server version will emerge victorious. For example if locally I change record A but on the server record A has been deleted, the result once the branches are reconciled is that the deletion stays.