[GitHub] [hadoop-ozone] fapifta commented on a change in pull request #1430: HDDS-4227. Implement a 'Prepare For Upgrade' step in OM that applies all committed Ratis transactions.

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fapifta commented on a change in pull request #1430:
URL: https://github.com/apache/hadoop-ozone/pull/1430#discussion_r492702681



##########
File path: hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/OzoneManager.java
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@@ -994,6 +1005,45 @@ public static boolean omInit(OzoneConfiguration conf) throws IOException,
     }
   }
 
+  public boolean applyAllPendingTransactions()
+      throws InterruptedException, IOException {
+
+    if (!isRatisEnabled) {
+      LOG.info("Ratis not enabled. Nothing to do.");
+      return true;
+    }
+
+    String purgeConfig = omRatisServer.getServer()
+        .getProperties().get(PURGE_UPTO_SNAPSHOT_INDEX_KEY);
+    if (!Boolean.parseBoolean(purgeConfig)) {
+      throw new IllegalStateException("Cannot prepare OM for Upgrade since  " +
+          "raft.server.log.purge.upto.snapshot.index is not true");
+    }
+
+    waitForAllTxnsApplied(omRatisServer.getOmStateMachine(),
+        omRatisServer.getRaftGroup(),
+        (RaftServerProxy) omRatisServer.getServer(),
+        TimeUnit.MINUTES.toSeconds(5));

Review comment:
       Are you sure we want to add a configuration for this one? I would argue we do not need one more configurable thing to this one at least.
   prepareForUpgrade is a special startup type of OM, during which it applies all transactions that are in the raft log.
   If 5 minutes is not enough to apply all transactions in the raft log, then the process will shut down and let the user know that some of the transactions were not applied, so that the user can start the process again as a last resort, to apply further transactions. If we assume that at least a few transactions are applied sooner or later the user can get to a state where everything is applied, and if none of the transactions can be applied within 5 minutes, that sounds like a serious problem anyways, independently from the upgrade.
   
   Also in 5 minutes I would expect in all cases that the unapplied transactions can be applied, as the number of this kind of transactions should not be too much as far as I know, or if it is then the system is not healthy anyway.
   
   Can you please elaborate, why would it be useful to make this configurable?




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