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https://issues.apache.org/jira/browse/HADOOP-19120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17833047#comment-17833047
]
ASF GitHub Bot commented on HADOOP-19120:
-----------------------------------------
saxenapranav commented on code in PR #6633:
URL: https://github.com/apache/hadoop/pull/6633#discussion_r1547316414
##########
hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/kac/KeepAliveCache.java:
##########
@@ -0,0 +1,317 @@
+/**
+ * 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.hadoop.fs.azurebfs.services.kac;
+
+import java.io.IOException;
+import java.io.NotSerializableException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.hadoop.classification.VisibleForTesting;
+import org.apache.http.HttpClientConnection;
+import org.apache.http.conn.routing.HttpRoute;
+
+import static
org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.DEFAULT_MAX_CONN_SYS_PROP;
+import static
org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.HTTP_MAX_CONN_SYS_PROP;
+import static
org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.KAC_CONN_TTL;
+
+/**
+ * Connection-pooling heuristics adapted from JDK's connection pooling
`KeepAliveCache`
+ * <p>
+ * Why this implementation is required in comparison to {@link
org.apache.http.impl.conn.PoolingHttpClientConnectionManager}
+ * connection-pooling:
+ * <ol>
+ * <li>PoolingHttpClientConnectionManager heuristic caches all the reusable
connections it has created.
+ * JDK's implementation only caches limited number of connections. The limit
is given by JVM system
+ * property "http.maxConnections". If there is no system-property, it defaults
to 5.</li>
+ * <li>In PoolingHttpClientConnectionManager, it expects the application to
provide `setMaxPerRoute` and `setMaxTotal`,
+ * which the implementation uses as the total number of connections it can
create. For application using ABFS, it is not
+ * feasible to provide a value in the initialisation of the connectionManager.
JDK's implementation has no cap on the
+ * number of connections it can create.</li>
+ * </ol>
+ */
+public final class KeepAliveCache
+ extends HashMap<KeepAliveCache.KeepAliveKey, KeepAliveCache.ClientVector>
+ implements Runnable {
+
+ private boolean threadShouldPause = true;
+
+ private boolean threadShouldRun = true;
+
+ private int maxConn;
+
+ private KeepAliveCache() {
+ Thread thread = new Thread(this);
+ thread.start();
+ setMaxConn();
+ }
+
+ private void setMaxConn() {
+ String sysPropMaxConn = System.getProperty(HTTP_MAX_CONN_SYS_PROP);
+ if (sysPropMaxConn == null) {
+ maxConn = DEFAULT_MAX_CONN_SYS_PROP;
+ } else {
+ maxConn = Integer.parseInt(sysPropMaxConn);
Review Comment:
If we go into implementation of Integer.parseInt(), it makes sense to not
check null as it is done internally. But, it requires developer to understand
that this will happen which may create confusion later, it is better we do
null-check on our side, and send only valid values to the external method. What
you feel @anujmodi2021.
> [ABFS]: ApacheHttpClient adaptation as network library
> ------------------------------------------------------
>
> Key: HADOOP-19120
> URL: https://issues.apache.org/jira/browse/HADOOP-19120
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/azure
> Affects Versions: 3.5.0
> Reporter: Pranav Saxena
> Assignee: Pranav Saxena
> Priority: Major
> Labels: pull-request-available
>
> Apache HttpClient is more feature-rich and flexible and gives application
> more granular control over networking parameter.
> ABFS currently relies on the JDK-net library. This library is managed by
> OpenJDK and has no performance problem. However, it limits the application's
> control over networking, and there are very few APIs and hooks exposed that
> the application can use to get metrics, choose which and when a connection
> should be reused. ApacheHttpClient will give important hooks to fetch
> important metrics and control networking parameters.
> A custom implementation of connection-pool is used. The implementation is
> adapted from the JDK8 connection pooling. Reasons for doing it:
> 1. PoolingHttpClientConnectionManager heuristic caches all the reusable
> connections it has created. JDK's implementation only caches limited number
> of connections. The limit is given by JVM system property
> "http.maxConnections". If there is no system-property, it defaults to 5.
> Connection-establishment latency increased with all the connections were
> cached. Hence, adapting the pooling heuristic of JDK netlib,
> 2. In PoolingHttpClientConnectionManager, it expects the application to
> provide `setMaxPerRoute` and `setMaxTotal`, which the implementation uses as
> the total number of connections it can create. For application using ABFS, it
> is not feasible to provide a value in the initialisation of the
> connectionManager. JDK's implementation has no cap on the number of
> connections it can have opened on a moment. Hence, adapting the pooling
> heuristic of JDK netlib,
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