[HDDS-9674] Read from non-datanode host does not consider topology

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.4.0
• Component/s: SCM
• Labels: pull-request-available
• Target Version/s: 1.4.0
• Assignee: Attila Doroszlai
• Reporter: Attila Doroszlai
• Created: 11/Nov/23 15:45
• Updated: 28/Nov/23 14:22
• Resolved: 28/Nov/23 14:22

Description

https://github.com/apache/ozone/blob/0c7ae8007ddb4725e10668299613668ef9ad19a7/hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/server/SCMBlockProtocolServer.java#L338-L360

  public List<DatanodeDetails> sortDatanodes(List<String> nodes,
      String clientMachine) {
    boolean auditSuccess = true;
    try {
      NodeManager nodeManager = scm.getScmNodeManager();
      Node client = null;
      List<DatanodeDetails> possibleClients =
          nodeManager.getNodesByAddress(clientMachine);
      if (possibleClients.size() > 0) {
        client = possibleClients.get(0);
      }
      List<Node> nodeList = new ArrayList();
      nodes.stream().forEach(uuid -> {
        DatanodeDetails node = nodeManager.getNodeByUuid(uuid);
        if (node != null) {
          nodeList.add(node);
        }
      });
      List<? extends Node> sortedNodeList = scm.getClusterMap()
          .sortByDistanceCost(client, nodeList, nodes.size());
      List<DatanodeDetails> ret = new ArrayList<>();
      sortedNodeList.stream().forEach(node -> ret.add((DatanodeDetails)node));
      return ret;

Client's node (place in the topology) is looked up via SCMNodeManager.getNodesByAddress. But SCMNodeManager only knows about datanodes. If the request comes from a host which does not run Ozone Datanode, then read will not be topology-aware. While read cannot be host-local in this case, it still could benefit from being rack-local.

Examples where such non-datanode hosts may occur:

• edge nodes
• dedicated metadata nodes
• Docker/Kubernetes containers running only one service

Issue Links

• is related to: HDDS-9343 Shift sortDatanodes logic to OM
• is related to: HDDS-9651 Restore random selection of datanode when reading RATIS objects
• links to: GitHub Pull Request #5610