[jira] [Resolved] (IGNITE-16284) In-depth CC related spanner research

["Alexander Lapin (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IGNITE-16284?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alexander Lapin resolved IGNITE-16284.
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    Resolution: Fixed

> In-depth CC related spanner research
> ------------------------------------
>
>                 Key: IGNITE-16284
>                 URL: https://issues.apache.org/jira/browse/IGNITE-16284
>             Project: Ignite
>          Issue Type: Task
>            Reporter: Alexander Lapin
>            Assignee: Alexander Lapin
>            Priority: Major
>              Labels: ignite-3
>         Attachments: Spanner (2).png, Spanner (4).png
>
>
> Let's read, understand and discuss the following spanner specific docs
> [https://static.googleusercontent.com/media/research.google.com/en//archive/spanner-osdi2012.pdf]
> [https://blog.the-pans.com/notes-on-the-spanner/]
> [https://www.microsoft.com/en-us/research/wp-content/uploads/2013/09/DC-col51-Sep13-1.pdf]
> Let's read, understand and discuss the following spanner specific docs
> [https://static.googleusercontent.com/media/research.google.com/en//archive/spanner-osdi2012.pdf]
> [https://blog.the-pans.com/notes-on-the-spanner/]
> [https://www.microsoft.com/en-us/research/wp-content/uploads/2013/09/DC-col51-Sep13-1.pdf]
> h2. Research results
> Spanner is Google’s scalable, multi-version, globally-distributed, and synchronously-replicated database. From the transaction's point of view Spanner is a system that guarantees external consistency and provides lock-free read-only and pessimistic read-write transactions. It worth mentioning that Spanner widely uses TrueTime with corresponding commit Wait logic. Bellow there’s a detail explanation of how read-write and read-only transactions are work in Spanner.
> h4. Read-Write Transactions
> For transactions that involve multiple Paxos groups, Spanner uses the two-phase commit protocol with long-held locks to guarantee that read-write transactions provide external consistency.
> The client buffers the write operations that occur in a transaction until it is ready to commit. At commit time, it chooses a leader of one of the Paxos groups to act as the transaction coordinator and sends a prepare message with the buffered writes and the identity of the coordinator to the leaders of the other participant groups. Each participant leader then acquires writes locks and performs the specified operations before responding to the coordinator with the status of its mini-transaction.
> The client also issues reads within read-write transactions to the leader replica of the relevant group, which acquires read locks and reads the most recent data. One of the other limitations of two-phase commit highlighted in the previous lecture is its proneness to deadlocks. Spanner uses the wound-wait locking rule to avoid deadlocks when reading data.
>  
> !Spanner (2).png|width=666,height=611!
> h4. Read-Only Transactions
> Spanner makes two optimizations to achieve greater performance in read-only transactions:
>  # It does not hold locks or use the two-phase commit protocol to serve requests.
>  # It allows reads from replicas.
> In order to guarantee external consistency through snapshot isolation Spanner keeps multiple versions of an object—each version labelled with a timestamp representing what transaction produced it. Snapshot isolation enforces that a read-only transaction will only see the versions of a record that have a timestamp less than its assigned transaction timestamp i.e. a snapshot of what the record was before the transaction started. To prevent reading stale data from non-majority replicas, each replica maintains a _safe time_ property, which is the maximum timestamp at which it is up to date. Paxos leaders send writes to followers in timestamp order and the safe time represents the most recent timestamp a replica has seen.
>  
> !Spanner (4).png|width=676,height=520!
>  



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