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https://issues.apache.org/jira/browse/RATIS-498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16803556#comment-16803556
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Hanisha Koneru edited comment on RATIS-498 at 3/28/19 3:21 AM:
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Thank you [~szetszwo] for the review.
{quote}When a server is installing snapshot, how should it resply appendEntries
requests? It seems the server should reject any appendEntries requests until
installSnapshot completes.
For the example after #8, when N2 sends appendEntries, N3 should ignore the
request and reply (AppendEntriesReplyProto) the nextIndex 100 (since it has
installed snapshot 100). Then, it would work.
{quote}
Agree. Updated the patch to check if snapshot installation is going on in
AppendEntries. Also checking that the first append entry index is greater than
the latest snapshot index.
{quote}Also, when a leader requests notifyInstallSnapshot at index n, the
follower could install any snapshots with index >= n. The follower should
install the latest available snapshot. After the installation has completed,
the follower reply (either notifyInstallSnapshot or appendEntries) with the new
index.
{quote}
Yes, we do return the installed snapshot index and not the index n which was
notified to the follower. This is returned as "snapshotIndex" in
InstallSnapshotReplyProto.
was (Author: hanishakoneru):
{quote}When a server is installing snapshot, how should it resply appendEntries
requests? It seems the server should reject any appendEntries requests until
installSnapshot completes.
For the example after #8, when N2 sends appendEntries, N3 should ignore the
request and reply (AppendEntriesReplyProto) the nextIndex 100 (since it has
installed snapshot 100). Then, it would work.
{quote}
Agree. Updated the patch to check if snapshot installation is going on in
AppendEntries. Also checking that the first append entry index is greater than
the latest snapshot index.
{quote}Also, when a leader requests notifyInstallSnapshot at index n, the
follower could install any snapshots with index >= n. The follower should
install the latest available snapshot. After the installation has completed,
the follower reply (either notifyInstallSnapshot or appendEntries) with the new
index.
{quote}
Yes, we do return the installed snapshot index and not the index n which was
notified to the follower. This is returned as "snapshotIndex" in
InstallSnapshotReplyProto.
> Notify Follower to Install Snapshot through state machine
> ---------------------------------------------------------
>
> Key: RATIS-498
> URL: https://issues.apache.org/jira/browse/RATIS-498
> Project: Ratis
> Issue Type: New Feature
> Components: server
> Reporter: Hanisha Koneru
> Assignee: Hanisha Koneru
> Priority: Major
> Attachments: RATIS-498.000.patch, RATIS-498.001.patch,
> RATIS-498.002.patch, RATIS-498.003.patch, RATIS-498.004.patch,
> RATIS-498.005.patch, RATIS-498.006.patch
>
>
> When a lagging Follower wants to catch up with the Leader, and the Leader
> only has logs with start index greater than the Followers's last log index,
> then the leader sends an InstallSnapshotRequest to the the Follower.
> The aim of this Jira is to allow State Machine to decouple snapshot
> installation from the Ratis server. When Leader does not have the logs to get
> the Follower up to speed, it should notify the Follower to install a snapshot
> (if install snapshot through Log Appender is disabled). The Follower in turn
> notifies its state machine that a snapshot is required to catch up with the
> leader.
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