10.3. Queue Configuration

The queueing rules are defined in a JSON file and control the number of queries that can be submitted to Presto and the quota of running queries per queue. The filename of the JSON config file should be specified in query.queue-config-file config property.

Rules that specify multiple queues will cause the query to acquire the queues’ permits sequentially. The query must acquire all queues’ permits before it starts being executed. It acquires the next queue permit only after it is accepted for execution by the previous queue. A slot for the query is reserved in all queues. The query is rejected if no slot is available in any of the queues.

Rules are processed sequentially and the first one that matches will be used. In the example configuration below, there are five queue templates. In the user.${USER} queue, ${USER} will be expanded to the name of the user that submitted the query. ${SOURCE} is also supported, which expands to the source submitting the query. The source name can be set as follows:

• CLI: use the --source option.
• JDBC: set the ApplicationName client info property on the Connection instance.

There are also five rules that define which queries go into which queues:

• The first rule makes bob an admin.
• The second rule states that all queries that come from a source that includes pipeline should first be queued in the user’s personal queue, then the pipeline queue. When a query acquires a permit from a new queue, it doesn’t release permits from previous queues until the query finishes execution.
• The last rule is a catch all, which puts all queries into the user’s personal queue.

All together these rules implement the policy that bob is an admin and all other users are subject to the follow limits:

• Users are allowed to have up to 5 queries running.
• No more than 10 pipeline queries may run at once.
• No more than 100 other queries may run at once.

{
  "queues": {
    "user.${USER}": {
      "maxConcurrent": 5,
      "maxQueued": 20
    },
    "pipeline": {
      "maxConcurrent": 10,
      "maxQueued": 100
    },
    "admin": {
      "maxConcurrent": 100,
      "maxQueued": 100
    },
    "global": {
      "maxConcurrent": 100,
      "maxQueued": 1000
    }
  },
  "rules": [
    {
      "user": "bob",
      "queues": ["admin"]
    },
    {
      "source": ".*pipeline.*",
      "queues": [
        "user.${USER}",
        "pipeline",
        "global"
      ]
    },
    {
      "queues": [
        "user.${USER}",
        "global"
      ]
    }
  ]
}