Github user ppadma commented on a diff in the pull request:
https://github.com/apache/drill/pull/928#discussion_r136491684
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/work/foreman/rm/QueryQueue.java
---
@@ -0,0 +1,129 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.exec.work.foreman.rm;
+
+import org.apache.drill.exec.proto.UserBitShared.QueryId;
+
+/**
+ * Interface which defines a queue implementation for query queues.
+ * Implementations can queue locally, queue distributed, or do
+ * nothing at all.
+ * <p>
+ * A queue can report itself as enabled or disabled. When enabled,
+ * all queries must obtain a lease prior to starting execution. The
+ * lease must be released at the completion of execution.
+ */
+
+public interface QueryQueue {
+
+ /**
+ * The opaque lease returned once a query is admitted
+ * for execution.
+ */
+
+ public interface QueueLease {
+ long queryMemoryPerNode();
+
+ /**
+ * Release a query lease obtained from {@link #queue(QueryId,
double))}.
+ * Should be called by the per-query resource manager.
+ *
+ * @param lease the lease to be released.
+ */
+
+ void release();
+
+ String queueName();
+ };
+
+ /**
+ * Exception thrown if a query exceeds the configured wait time
+ * in the query queue.
+ */
+
+ @SuppressWarnings("serial")
+ public class QueueTimeoutException extends Exception {
+
+ private QueryId queryId;
+ private String queueName;
+ private int timeoutMs;
+
+ public QueueTimeoutException(QueryId queryId, String queueName, int
timeoutMs) {
+ super( String.format(
+ "Query timed out of the %s queue after %d ms.",
+ queueName, timeoutMs ));
+ this.queryId = queryId;
+ this.queueName = queueName;
+ this.timeoutMs = timeoutMs;
+ }
+
+ public QueryId queryId() { return queryId; }
+ public String queueName() { return queueName; }
+ public int timeoutMs() { return timeoutMs; }
+ }
+
+ /**
+ * Exception thrown for all non-timeout error conditions.
+ */
+
+ @SuppressWarnings("serial")
+ public class QueryQueueException extends Exception {
+ QueryQueueException(String msg, Exception e) {
+ super(msg, e);
+ }
+ }
+
+ void setMemoryPerNode(long memoryPerNode);
+
+ /**
+ * Return the amount of memory per node when creating a EXPLAIN
+ * query plan. Plans to be executed should get the query memory from
+ * the lease, as the lease may adjust the default amount on a per-query
+ * basis. This means that the memory used to execute the query may
+ * differ from the amount shown in an EXPLAIN plan.
+ *
+ * @return assumed memory per node, in bytes, to use when creating
+ * an EXPLAIN plan
+ */
+
+ long getDefaultMemoryPerNode(double cost);
+
+ /**
+ * Determine if the queue is enabled.
+ * @return true if the query is enabled, false otherwise.
+ */
+
+ boolean enabled();
+
+ /**
+ * Queue a query. The method returns only when the query is admitted for
+ * execution. As a result, the calling thread may block up to the
configured
--- End diff --
we should have a upper bound on how many such queries can wait for
execution.
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