[GitHub] [hbase] bharathv commented on a change in pull request #1020: HBASE-23653 Expose content of meta table in web ui

[GitBox <gi...@apache.org>]

bharathv commented on a change in pull request #1020: HBASE-23653 Expose content of meta table in web ui
URL: https://github.com/apache/hbase/pull/1020#discussion_r365477170
 
 

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 File path: hbase-server/src/main/java/org/apache/hadoop/hbase/master/webapp/MetaBrowser.java
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+/*
+ * 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.hbase.master.webapp;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLDecoder;
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.stream.Collectors;
+import javax.servlet.http.HttpServletRequest;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.lang3.builder.ToStringBuilder;
+import org.apache.commons.lang3.builder.ToStringStyle;
+import org.apache.hadoop.hbase.CompareOperator;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.client.AsyncConnection;
+import org.apache.hadoop.hbase.client.AsyncTable;
+import org.apache.hadoop.hbase.client.Scan;
+import org.apache.hadoop.hbase.client.ScanResultConsumer;
+import org.apache.hadoop.hbase.filter.Filter;
+import org.apache.hadoop.hbase.filter.FilterList;
+import org.apache.hadoop.hbase.filter.PrefixFilter;
+import org.apache.hadoop.hbase.filter.SingleColumnValueFilter;
+import org.apache.hadoop.hbase.master.RegionState;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.hbase.thirdparty.com.google.common.util.concurrent.ThreadFactoryBuilder;
+import org.apache.hbase.thirdparty.io.netty.handler.codec.http.QueryStringEncoder;
+
+/**
+ * A support class for the "Meta Entries" section in
+ * {@code resources/hbase-webapps/master/table.jsp}.
+ */
+@InterfaceAudience.Private
+public class MetaBrowser implements Iterable<RegionReplicaInfo> {
+  private static final Logger logger = LoggerFactory.getLogger(MetaBrowser.class);
+
+  public static final String NAME_PARAM = "name";
+  public static final String SCAN_LIMIT_PARAM = "scan_limit";
+  public static final String SCAN_REGION_STATE_PARAM = "scan_region_state";
+  public static final String SCAN_START_PARAM = "scan_start";
+  public static final String SCAN_TABLE_PARAM = "scan_table";
+
+  public static final int SCAN_LIMIT_DEFAULT = 10;
+  public static final int SCAN_LIMIT_MAX = 10_000;
+
+  private final AsyncConnection connection;
+  private final HttpServletRequest request;
+  private final ExecutorService pool;
+  private final List<String> errorMessages;
+  private final String name;
+  private final Integer scanLimit;
+  private final RegionState.State scanRegionState;
+  private final byte[] scanStart;
+  private final TableName scanTable;
+
+  public MetaBrowser(final AsyncConnection connection, final HttpServletRequest request) {
+    this.connection = connection;
+    this.request = request;
+    this.pool = buildThreadPool();
+    this.errorMessages = new LinkedList<>();
+    this.name = resolveName(request);
+    this.scanLimit = resolveScanLimit(request);
+    this.scanRegionState = resolveScanRegionState(request);
+    this.scanStart = resolveScanStart(request);
+    this.scanTable = resolveScanTable(request);
+  }
+
+  public List<String> getErrorMessages() {
+    return errorMessages;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public Integer getScanLimit() {
+    return scanLimit;
+  }
+
+  public byte[] getScanStart() {
+    return scanStart;
+  }
+
+  public RegionState.State getScanRegionState() {
+    return scanRegionState;
+  }
+
+  public TableName getScanTable() {
+    return scanTable;
+  }
+
+  @Override
+  public Iterator<RegionReplicaInfo> iterator() {
+    return limitIterator();
+  }
+
+  public LimitIterator<RegionReplicaInfo> limitIterator() {
+    logger.debug("initiating meta scan, {}", this);
+
+    final AsyncTable<ScanResultConsumer> asyncTable =
+      connection.getTable(TableName.META_TABLE_NAME, pool);
+    // TODO: buffering the entire result set seems unnecessary.
+    final List<RegionReplicaInfo> results = asyncTable.scanAll(buildScan()).join()
+      .stream()
+      .map(RegionReplicaInfo::from)
+      .flatMap(Collection::stream)
+      .collect(Collectors.toList());
+    return new LimitIterator<>(
+      results.iterator(), Optional.ofNullable(scanLimit).orElse(SCAN_LIMIT_DEFAULT));
+  }
+
+  @Override
+  public String toString() {
+    return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
+      .append("scanStart", scanStart)
+      .append("scanLimit", scanLimit)
+      .append("scanTable", scanTable)
+      .append("scanRegionState", scanRegionState)
+      .toString();
+  }
+
+  private static ExecutorService buildThreadPool() {
+    return Executors.newSingleThreadExecutor(new ThreadFactoryBuilder()
+      .setNameFormat("MetaBrowser-%d")
+      .setDaemon(true)
+      .setUncaughtExceptionHandler(
+        (thread, throwable) -> logger.info("Error in worker thread, {}", throwable.getMessage()))
+      .build());
+  }
+
+  private static String resolveName(final HttpServletRequest request) {
+    return Optional.ofNullable(request)
+      .map(req -> req.getParameter(NAME_PARAM))
+      .filter(StringUtils::isNotBlank)
+      .map(MetaBrowser::urlDecode)
+      .orElse(null);
+  }
+
+  private Integer resolveScanLimit(final HttpServletRequest request) {
+    final Optional<String> requestValueStr = Optional.ofNullable(request)
+      .map(req -> req.getParameter(SCAN_LIMIT_PARAM))
+      .filter(StringUtils::isNotBlank);
+    if (!requestValueStr.isPresent()) { return null; }
+
+    final Integer requestValue = requestValueStr
+      .flatMap(MetaBrowser::tryParseInt)
+      .orElse(null);
+    if (requestValue == null) {
+      errorMessages.add(buildScanLimitMalformedErrorMessage(requestValueStr.get()));
+      return null;
+    }
+    if (requestValue <= 0) {
+      errorMessages.add(buildScanLimitLTEZero(requestValue));
+      return SCAN_LIMIT_DEFAULT;
+    }
+
+    final int truncatedValue = Math.min(requestValue, SCAN_LIMIT_MAX);
+    if (requestValue != truncatedValue) {
+      errorMessages.add(buildScanLimitExceededErrorMessage(requestValue));
+    }
+    return truncatedValue;
+  }
+
+  private RegionState.State resolveScanRegionState(final HttpServletRequest request) {
+    final Optional<String> requestValueStr = Optional.ofNullable(request)
+      .map(req -> req.getParameter(SCAN_REGION_STATE_PARAM))
+      .filter(StringUtils::isNotBlank)
+      .map(MetaBrowser::urlDecode);
+    if (!requestValueStr.isPresent()) { return null; }
+
+    final RegionState.State requestValue = requestValueStr
+      .flatMap(val -> tryValueOf(RegionState.State.class, val))
+      .orElse(null);
+    if (requestValue == null) {
+      errorMessages.add(buildScanRegionStateMalformedErrorMessage(requestValueStr.get()));
+      return null;
+    }
+    return requestValue;
+  }
+
+  private static byte[] resolveScanStart(final HttpServletRequest request) {
+    return Optional.ofNullable(request)
+      .map(req -> req.getParameter(SCAN_START_PARAM))
+      .filter(StringUtils::isNotBlank)
+      .map(MetaBrowser::urlDecode)
+      .map(Bytes::toBytesBinary)
+      .orElse(null);
+  }
+
+  private static TableName resolveScanTable(final HttpServletRequest request) {
+    return Optional.ofNullable(request)
+      .map(req -> req.getParameter(SCAN_TABLE_PARAM))
+      .filter(StringUtils::isNotBlank)
+      .map(MetaBrowser::urlDecode)
+      .map(TableName::valueOf)
+      .orElse(null);
+  }
+
+  private static Filter buildTableFilter(final TableName tableName) {
+    return new PrefixFilter(tableName.toBytes());
+  }
+
+  private static Filter buildScanRegionStateFilter(final RegionState.State state) {
+    return new SingleColumnValueFilter(
+      HConstants.CATALOG_FAMILY,
+      HConstants.TABLE_STATE_QUALIFIER,
+      CompareOperator.EQUAL,
+      // use the same serialization strategy as found in MetaTableAccessor#addRegionStateToPut
+      Bytes.toBytes(state.name()));
+  }
+
+  private Optional<Filter> buildScanFilter() {
+    if (scanTable == null && scanRegionState == null) {
+      return Optional.empty();
+    }
+
+    final List<Filter> filters = new ArrayList<>(2);
+    Optional.ofNullable(scanTable)
+      .map(MetaBrowser::buildTableFilter)
+      .ifPresent(filters::add);
+    Optional.ofNullable(scanRegionState)
+      .map(MetaBrowser::buildScanRegionStateFilter)
+      .ifPresent(filters::add);
+
+    if (filters.size() == 1) {
+      return Optional.of(filters.get(0));
+    }
+
+    return Optional.of(new FilterList(FilterList.Operator.MUST_PASS_ALL, filters));
+  }
+
+  private Scan buildScan() {
+    final Scan metaScan = new Scan()
+      .addFamily(HConstants.CATALOG_FAMILY)
+      .readVersions(1)
+      .setLimit(Optional.ofNullable(scanLimit).orElse(SCAN_LIMIT_DEFAULT) + 1);
+    Optional.ofNullable(scanStart)
+      .ifPresent(startRow -> metaScan.withStartRow(startRow, false));
+    buildScanFilter().ifPresent(metaScan::setFilter);
+    return metaScan;
+  }
+
+  private <T> void maybeAddParam(final QueryStringEncoder encoder, final String paramName,
 
 Review comment:
   nit: I think this could use a javadoc.

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