Efficient synchronization mechanisms for graph databases

1 . A computing system for efficient synchronization on a graph database, the computing system comprising:

processing circuitry and memory storing instructions that, during execution, causes the processing circuitry to:

implement the graph database using at least:

a read-write node and a read-only node operating in cache memory; and

a shared storage for data persistence, wherein the shared storage stores a mapping table of the graph database;

receive an update query;

update the read-write node based on the update query;

write, using the read-write node, a set of logs corresponding to the update query to a write-ahead log (WAL) journal in the shared storage;

retrieve, using the read-only node, the set of logs corresponding to the update query from the WAL journal;

asynchronously flush the cache memory of the read-write node to the shared storage; and

after the flushing of the cache memory of the read-write node to the shared storage, update the mapping table of the graph database in the shared storage based on the update query.

2 . The computing system of claim 1 , wherein the instructions, during execution, further causes the processing circuitry to:

synchronous with the updating of the mapping table in the shared storage, write a log in the WAL journal indicating the shared storage has been updated; and

retrieve, using the read-only node, the log indicating the shared storage has been updated.

3 . The computing system of claim 2 , wherein the instructions, during execution, further causes the processing circuitry to:

update the read-only node using the retrieved set of logs corresponding to the update query; and

discard logs up to the log indicating the shared storage has been updated, including the retrieved set of logs corresponding to the update query.

4 . The computing system of claim 1 , wherein the instructions, during execution, further causes the processing circuitry to:

receive, using the read-only node, a query requesting access to a data element affected by the update of the read-write node;

update the read-only node using the retrieved set of logs corresponding to the update query; and

return, using the read-only node, a query result containing the data element.

5 . The computing system of claim 4 , wherein the instructions, during execution, further causes the processing circuitry to:

synchronous with the updating of the mapping table in the shared storage, write a log in the WAL journal indicating the shared storage has been updated;

retrieve, using the read-only node, the log indicating the shared storage has been updated; and

discard logs up to the log indicating the shared storage has been updated, including the retrieved set of logs corresponding to the update query.

6 . The computing system of claim 4 , wherein updating the read-only node using the retrieved set of logs corresponding to the update query comprises:

performing actions described in the retrieved set of logs corresponding to the update query to update a mapping of the graph database in the read-only node; and

retrieving, using the read-only node, one or more pages from the shared storage using the mapping table of the graph database in the shared storage.

7 . The computing system of claim 6 , wherein updating the read-only node using the retrieved set of logs corresponding to the update query further comprises:

if the shared storage does not contain a page described in the retrieved set of logs corresponding to the update query, creating a copy of the page in the cache memory of the read-only node.

8 . The computing system of claim 1 , wherein updating the read-write node based on the update query comprises performing a page split.

9 . The computing system of claim 1 , wherein the shared storage is an append-only shared storage.

10 . The computing system of claim 1 , wherein the graph database comprises a Bw-tree graph database.

11 . A method for efficiency synchronization on a graph database, the method comprising:

implementing the graph database using at least:

a read-write node and a read-only node operating in cache memory; and

a shared storage for data persistence, wherein the shared storage stores a mapping table of the graph database;

receiving an update query;

updating the read-write node based on the update query;

writing, using the read-write node, a set of logs corresponding to the update query to a write-ahead log (WAL) journal in the shared storage;

retrieving, using the read-only node, the set of logs corresponding to the update query from the WAL journal;

asynchronously flushing the cache memory of the read-write node to the shared storage; and

after the flushing of the cache memory of the read-write node to the shared storage, updating the mapping table of the graph database in the shared storage based on the update query.

12 . The method of claim 11 , further comprising:

synchronous with the updating of the mapping table in the shared storage, writing a log in the WAL journal indicating the shared storage has been updated; and

retrieving, using the read-only node, the log indicating the shared storage has been updated.

13 . The method of claim 12 , further comprising:

updating the read-only node using the retrieved set of logs corresponding to the update query; and

discarding logs up to the log indicating the shared storage has been updated, including the retrieved set of logs corresponding to the update query.

14 . The method of claim 11 , further comprising:

receiving, using the read-only node, a query requesting access to a data element affected by the update of the read-write node;

updating the read-only node using the retrieved set of logs corresponding to the update query; and

returning, using the read-only node, a query result containing the data element.

15 . The method of claim 14 , further comprising:

synchronous with the updating of the mapping table in the shared storage, writing a log in the WAL journal indicating the shared storage has been updated;

retrieving, using the read-only node, the log indicating the shared storage has been updated; and

discarding logs up to the log indicating the shared storage has been updated, including the retrieved set of logs corresponding to the update query.

16 . The method of claim 14 , wherein updating the read-only node using the retrieved set of logs corresponding to the update query comprises:

performing actions described in the retrieved set of logs corresponding to the update query to update a mapping of the graph database in the read-only node;

retrieving, using the read-only node, one or more pages from the shared storage using the mapping table of the graph database in the shared storage; and

if the shared storage does not contain a page described in the retrieved set of logs corresponding to the update query, creating a copy of the page in the cache memory of the read-only node.

17 . The method of claim 11 , wherein updating the read-write node based on the update query comprises performing a page split.

18 . The method of claim 11 , wherein the shared storage is an append-only shared storage.

19 . The method of claim 11 , wherein the graph database comprises a Bw-tree graph database.

20 . A method for efficiency synchronization on a Bw-tree graph database, the method comprising:

implementing the Bw-tree graph database using at least:

a read-write node and a read-only node operating in cache memory; and

an append-only shared cloud storage for data persistence;

updating the read-write node based on a received update query;

writing, using the read-write node, a set of logs corresponding to the received update query to a write-ahead log (WAL) journal in the append-only shared cloud storage;

retrieving, using the read-only node, the set of logs corresponding to the update query from the WAL journal asynchronously flushing the cache memory of the read-write node to the append-only shared cloud storage;

updating the append-only shared cloud storage based on the update query;

synchronous with the updating of the append-only shared cloud storage, writing a log in the WAL journal indicating the append-only shared cloud storage has been updated; and

synchronizing the read-only node to be consistent with the read-write node.