[ 
https://issues.apache.org/jira/browse/HDDS-1843?focusedWorklogId=307712&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-307712
 ]

ASF GitHub Bot logged work on HDDS-1843:
----------------------------------------

                Author: ASF GitHub Bot
            Created on: 06/Sep/19 09:14
            Start Date: 06/Sep/19 09:14
    Worklog Time Spent: 10m 
      Work Description: nandakumar131 commented on pull request #1364: 
HDDS-1843. Undetectable corruption after restart of a datanode.
URL: https://github.com/apache/hadoop/pull/1364#discussion_r321645502
 
 

 ##########
 File path: 
hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/impl/ContainerSet.java
 ##########
 @@ -240,14 +240,46 @@ public ContainerReportsProto getContainerReport() throws 
IOException {
   }
 
   /**
-   * Builds the missing container set by taking a diff total no containers
-   * actually found and number of containers which actually got created.
+   * Builds the missing container set by taking a diff between total no
+   * containers actually found and number of containers which actually
+   * got created. It also validates the BCSID stored in the snapshot file
+   * for each container as against what is reported in containerScan.
    * This will only be called during the initialization of Datanode Service
    * when  it still not a part of any write Pipeline.
-   * @param createdContainerSet ContainerId set persisted in the Ratis snapshot
+   * @param container2BCSIDMap Map of containerId to BCSID persisted in the
+   *                           Ratis snapshot
    */
-  public void buildMissingContainerSet(Set<Long> createdContainerSet) {
-    missingContainerSet.addAll(createdContainerSet);
-    missingContainerSet.removeAll(containerMap.keySet());
+  public void buildMissingContainerSetAndValidate(
+      Map<Long, Long> container2BCSIDMap) {
+    container2BCSIDMap.entrySet().parallelStream().forEach((mapEntry) -> {
+      long id = mapEntry.getKey();
+      if (!containerMap.containsKey(id)) {
+        LOG.warn("Adding container {} to missing container set.", id);
+        missingContainerSet.add(id);
+      } else {
+        Container container = containerMap.get(id);
+        long containerBCSID = container.getBlockCommitSequenceId();
+        long snapshotBCSID = mapEntry.getValue();
+        if (containerBCSID < snapshotBCSID) {
+          LOG.warn(
+              "Marking container {} unhealthy as reported BCSID {} is smaller"
+                  + " than ratis snapshot recorded value {}", id,
+              containerBCSID, snapshotBCSID);
+          // just mark the container unhealthy. Once the DatanodeStateMachine
+          // thread starts it will send container report to SCM where these
+          // unhealthy containers would be detected
+          try {
+            container.markContainerUnhealthy();
+          } catch (StorageContainerException sce) {
+            // The container will still be marked unhealthy in memory even if
+            // exception occurs. It won't accept any new transactions and will
+            // be handled by SCM. Eve if dn restarts, it will still be detected
+            // as unheathy as its BCSID won't change.
+            LOG.info("Unable to persist unhealthy state for container {}", id);
 
 Review comment:
   This should be `LOG.error`
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 307712)
    Time Spent: 8h 50m  (was: 8h 40m)

> Undetectable corruption after restart of a datanode
> ---------------------------------------------------
>
>                 Key: HDDS-1843
>                 URL: https://issues.apache.org/jira/browse/HDDS-1843
>             Project: Hadoop Distributed Data Store
>          Issue Type: Bug
>          Components: Ozone Datanode
>    Affects Versions: 0.5.0
>            Reporter: Shashikant Banerjee
>            Assignee: Shashikant Banerjee
>            Priority: Critical
>              Labels: pull-request-available
>             Fix For: 0.5.0
>
>         Attachments: HDDS-1843.000.patch
>
>          Time Spent: 8h 50m
>  Remaining Estimate: 0h
>
> Right now, all write chunks use BufferedIO ie, sync flag is disabled by 
> default. Also, Rocks Db metadata updates are done in Rocks DB cache first at 
> Datanode. In case, there comes a situation where the buffered chunk data as 
> well as the corresponding metadata update is lost as a part of datanode 
> restart, it may lead to a situation where, it will not be possible to detect 
> the corruption (not even with container scanner) of this nature in a 
> reasonable time frame, until and unless there is a client IO failure or Recon 
> server detects it over time. In order to atleast to detect the problem, Ratis 
> snapshot on datanode should sync the rocks db file . In such a way, 
> ContainerScanner will be able to detect this.We can also add a metric around 
> sync to measure how much of a throughput loss it can incurr.
> Thanks [~msingh] for suggesting this.



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