Management HTTP API sometimes returns an empty array for the owner_pid_details property of the queue info

[anadale]

Describe the bug

The queues/{vhost}/{queue} resource returns an empty array ([ ]) for the owner_pid_details property of exclusive queue instead of null or expected object.

Reproduction steps

1. Create an exclusive queue. In my case it was created by the MassTransit library when I request non-durable, exclusive queue
2. Query queue information through Management HTTP API
3. Inspect the owner_pid_details field

Expected behavior

owner_pid_details field is expected to be null or an object.

Additional context

Here is the JSON returned by the management API:

{
  "consumer_details" : [ {
    "arguments" : { },
    "channel_details" : {
      "connection_name" : "10.129.0.17:60602 -> 10.2.131.29:5672",
      "name" : "10.129.0.17:60602 -> 10.2.131.29:5672 (1)",
      "node" : "rabbit@rabbitmq-2.rabbitmq-headless.rabbitmq.svc.cluster.local",
      "number" : 1,
      "peer_host" : "10.129.0.17",
      "peer_port" : 60602,
      "user" : "xxx"
    },
    "ack_required" : true,
    "active" : true,
    "activity_status" : "up",
    "consumer_tag" : "amq.ctag-wqD8mlw7JhyPJcLcqpbomQ",
    "exclusive" : false,
    "prefetch_count" : 16,
    "queue" : {
      "name" : "api67fbcc998wfl7l_XxxXxxApi_endpoint_yryyyyrpriu9rgbebdxeypj7r4",
      "vhost" : "xxx"
    }
  } ],
  "arguments" : {
    "x-expires" : 60000
  },
  "auto_delete" : false,
  "backing_queue_status" : {
    "avg_ack_egress_rate" : 3.4424719169470355E-101,
    "avg_ack_ingress_rate" : 3.4424719169470355E-101,
    "avg_egress_rate" : 3.4424719169470355E-101,
    "avg_ingress_rate" : 3.4424719169470355E-101,
    "delta" : [ "delta", "undefined", 0, 0, "undefined" ],
    "len" : 0,
    "mode" : "default",
    "next_deliver_seq_id" : 115,
    "next_seq_id" : 115,
    "num_pending_acks" : 0,
    "num_unconfirmed" : 0,
    "q1" : 0,
    "q2" : 0,
    "q3" : 0,
    "q4" : 0,
    "target_ram_count" : "infinity",
    "version" : 1
  },
  "consumer_capacity" : 1.0,
  "consumer_utilisation" : 1.0,
  "consumers" : 1,
  "deliveries" : [ ],
  "durable" : false,
  "effective_policy_definition" : { },
  "exclusive" : true,
  "exclusive_consumer_tag" : null,
  "garbage_collection" : {
    "fullsweep_after" : 65535,
    "max_heap_size" : 0,
    "min_bin_vheap_size" : 46422,
    "min_heap_size" : 233,
    "minor_gcs" : 1731
  },
  "head_message_timestamp" : null,
  "idle_since" : "2026-03-13T13:38:29.134+00:00",
  "incoming" : [ ],
  "memory" : 9088,
  "message_bytes" : 0,
  "message_bytes_paged_out" : 0,
  "message_bytes_persistent" : 0,
  "message_bytes_ram" : 0,
  "message_bytes_ready" : 0,
  "message_bytes_unacknowledged" : 0,
  "message_stats" : {
    "ack" : 115,
    "ack_details" : {
      "rate" : 0.0
    },
    "deliver" : 115,
    "deliver_details" : {
      "rate" : 0.0
    },
    "deliver_get" : 115,
    "deliver_get_details" : {
      "rate" : 0.0
    },
    "deliver_no_ack" : 0,
    "deliver_no_ack_details" : {
      "rate" : 0.0
    },
    "get" : 0,
    "get_details" : {
      "rate" : 0.0
    },
    "get_empty" : 0,
    "get_empty_details" : {
      "rate" : 0.0
    },
    "get_no_ack" : 0,
    "get_no_ack_details" : {
      "rate" : 0.0
    },
    "publish" : 115,
    "publish_details" : {
      "rate" : 0.0
    },
    "redeliver" : 0,
    "redeliver_details" : {
      "rate" : 0.0
    }
  },
  "messages" : 0,
  "messages_details" : {
    "rate" : 0.0
  },
  "messages_paged_out" : 0,
  "messages_persistent" : 0,
  "messages_ram" : 0,
  "messages_ready" : 0,
  "messages_ready_details" : {
    "rate" : 0.0
  },
  "messages_ready_ram" : 0,
  "messages_unacknowledged" : 0,
  "messages_unacknowledged_details" : {
    "rate" : 0.0
  },
  "messages_unacknowledged_ram" : 0,
  "name" : "api67fbcc998wfl7l_XxxXxxApi_endpoint_yryyyyrpriu9rgbebdxeypj7r4",
  "node" : "rabbit@rabbitmq-2.rabbitmq-headless.rabbitmq.svc.cluster.local",
  "operator_policy" : null,
  "owner_pid_details" : [ ],
  "policy" : null,
  "recoverable_slaves" : null,
  "reductions" : 1075279,
  "reductions_details" : {
    "rate" : 0.0
  },
  "single_active_consumer_tag" : null,
  "state" : "running",
  "type" : "classic",
  "vhost" : "xxx"
}

[michaelklishin]

Because an empty proplist in Erlang is an empty JSON list. A lot of these were addressed over the years.

@anadale you haven't shared the version you run and we do not guess in this community, so you are welcome to investigate and fix this one on your own. Here is an example of a similar fix in a different place #12797