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https://issues.apache.org/jira/browse/HBASE-20679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16502047#comment-16502047
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Sean Busbey commented on HBASE-20679:
-------------------------------------
please add docs.
> Add the ability to compile JSP dynamically in Jetty
> ---------------------------------------------------
>
> Key: HBASE-20679
> URL: https://issues.apache.org/jira/browse/HBASE-20679
> Project: HBase
> Issue Type: New Feature
> Affects Versions: 2.0.0
> Reporter: Allan Yang
> Assignee: Allan Yang
> Priority: Major
> Fix For: 3.0.0
>
> Attachments: HBASE-20679.002.patch, HBASE-20679.patch
>
>
> As discussed in HBASE-20617, adding the ability to dynamically compile jsp
> enable us to do some hot fix.
> For example, several days ago, in our testing HBase-2.0 cluster,
> procedureWals were corrupted due to some unknown reasons. After restarting
> the cluster, since some procedures(AssignProcedure for example) were
> corrupted and couldn't be replayed. Some regions were stuck in RIT forever.
> We couldn't use HBCK since it haven't support AssignmentV2 yet. As a matter
> of fact, the namespace region was not online, so the master was not inited,
> we even couldn't use shell command like assign/move. But, we wrote a jsp and
> fix this issue easily. The jsp file is like this:
> {code:java}
> <%
> String action = request.getParameter("action");
> HMaster master = (HMaster)getServletContext().getAttribute(HMaster.MASTER);
> List<RegionInfo> offlineRegionsToAssign = new ArrayList<>();
> List<RegionStates.RegionStateNode> regionRITs =
> master.getAssignmentManager()
> .getRegionStates().getRegionsInTransition();
> for (RegionStates.RegionStateNode regionStateNode : regionRITs) {
> // if regionStateNode don't have a procedure attached, but meta state
> shows
> // this region is in RIT, that means the previous procedure may be
> corrupted
> // we need to create a new assignProcedure to assign them
> if (!regionStateNode.isInTransition()) {
> offlineRegionsToAssign.add(regionStateNode.getRegionInfo());
> out.println("RIT region:" + regionStateNode);
> }
> }
> // Assign offline regions. Uses round-robin.
> if ("fix".equals(action) && offlineRegionsToAssign.size() > 0) {
>
> master.getMasterProcedureExecutor().submitProcedures(master.getAssignmentManager().
> createRoundRobinAssignProcedures(offlineRegionsToAssign));
> } else {
> out.println("use ?action=fix to fix RIT regions");
> }
> %>
> {code}
> Above it is only one example we can do if we have the ability to compile jsp
> dynamically. We think it is very useful.
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