[jira] [Commented] (OAK-4803) Simplify the client side of the cold standby

["Andrei Dulceanu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-4803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15492953#comment-15492953 ] 

Andrei Dulceanu commented on OAK-4803:
--------------------------------------

@frm, here are some of my observations regarding the patch:

# When looking at {{StandbyClient}} and {{StandbyServer}} I find it a little bit odd that the former doesn't have a {{FileStore}}, while the latter has. IMHO having a {{FileStore}} reference in the client would make sense and would also help reading the code, as it is much clearer from the beginning who owns what.
# Along the same lines, IMHO it would make sense to reverse the relationship between {{StandbyClient}} and {{StandbySync}} since it looks more natural to have a client which wants to perform a sync as opposed to have a sync which will create a client, assign it a file store and then execute the sync. For example, replacing the line
{code:java}
StandbyClient cl = newStandbyClient(secondary);
{code}
with this line
{code:java}
StandbySync cl = newStandbyClient(secondary);
{code}
seems a little bit confusing to me.
# One minor change in {{StandbySync.run()}}, to allow the state to actually enter {{STATUS_STARTING}}:
{code:java}
state = STATUS_STARTING;
        synchronized (sync) {
            if (active) {
                return;
            }
            state = STATUS_RUNNING;
            active = true;
        }
{code}
# another minor change in {{StandbySyncExecution}}: rename {{copySegmentFromPrimary}} to {{copySegmentHierarchyFromPrimary}} or any other explanatory method name, since this method does a BFS starting with the initial segment to fetch from server.

/cc [~marett]

> Simplify the client side of the cold standby
> --------------------------------------------
>
>                 Key: OAK-4803
>                 URL: https://issues.apache.org/jira/browse/OAK-4803
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: segment-tar
>            Reporter: Francesco Mari
>            Assignee: Francesco Mari
>             Fix For: Segment Tar 0.0.12
>
>         Attachments: OAK-4803-01.patch
>
>
> The implementation of the cold standby client is overly and unnecessarily complicated. It would be way clearer to separate the client code in two major components: a simple client responsible for sending messages to and receive responses from the standby server, and the synchronization algorithm used to read data from the server and to save read data in the local {{FileStore}}.
> Moreover, the client simple client could be further modularised by encapsulating request encoding, response decoding and message handling into their own Netty handlers.



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