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https://issues.apache.org/jira/browse/FLINK-10423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16648174#comment-16648174
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ASF GitHub Bot commented on FLINK-10423:
----------------------------------------
StefanRRichter commented on a change in pull request #6814:
[FLINK-10423][rocksdb][metrics] rocksdb native metrics monitor
URL: https://github.com/apache/flink/pull/6814#discussion_r224860246
##########
File path:
flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBNativeMetricMonitor.java
##########
@@ -0,0 +1,154 @@
+/*
+ * 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.flink.contrib.streaming.state;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.core.fs.CloseableRegistry;
+import org.apache.flink.metrics.Gauge;
+import org.apache.flink.metrics.MetricGroup;
+import org.apache.flink.metrics.View;
+import org.apache.flink.util.FlinkRuntimeException;
+import org.apache.flink.util.IOUtils;
+import org.apache.flink.util.ResourceGuard;
+
+import org.rocksdb.ColumnFamilyHandle;
+import org.rocksdb.RocksDB;
+import org.rocksdb.RocksDBException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nonnull;
+
+import java.io.Closeable;
+import java.io.IOException;
+
+/**
+ * A monitor which pull {{@link RocksDB}} native metrics
+ * and forwards them to Flink's metric group. All metrics are
+ * unsigned longs and are reported at the column family level.
+ */
+@Internal
+public class RocksDBNativeMetricMonitor implements Closeable {
+
+ private final CloseableRegistry registeredGauges;
+
+ private final RocksDB db;
+
+ private final ResourceGuard.Lease lease;
+
+ private final RocksDBNativeMetricOptions options;
+
+ private final MetricGroup metricGroup;
+
+ RocksDBNativeMetricMonitor(
+ @Nonnull RocksDB db,
+ @Nonnull ResourceGuard guard,
+ @Nonnull RocksDBNativeMetricOptions options,
+ @Nonnull MetricGroup metricGroup
+ ) throws IOException {
+ this.db = db;
+ this.lease = guard.acquireResource();
+ this.options = options;
+ this.metricGroup = metricGroup;
+
+ this.registeredGauges = new CloseableRegistry();
+ }
+
+ /**
+ * Register gauges to pull native metrics for the column family.
+ * @param columnFamilyName group name for the new gauges
+ * @param handle native handle to the column family
+ */
+ void registerColumnFamily(String columnFamilyName, ColumnFamilyHandle
handle) {
+ try {
+ MetricGroup group =
metricGroup.addGroup(columnFamilyName);
+
+ for (String property : options.getProperties()) {
+ RocksDBNativeMetricView gauge = new
RocksDBNativeMetricView(
+ property,
+ handle,
+ db
+ );
+
+ group.gauge(property, gauge);
+ registeredGauges.registerCloseable(gauge);
+ }
+ } catch (IOException e) {
+ throw new FlinkRuntimeException("Unable to register
native metrics with RocksDB", e);
+ }
+ }
+
+ @Override
+ public void close() {
+ IOUtils.closeQuietly(registeredGauges);
+ IOUtils.closeQuietly(lease);
+ }
+
+ static class RocksDBNativeMetricView implements Gauge<String>, View,
Closeable {
+ private static final Logger LOG =
LoggerFactory.getLogger(RocksDBNativeMetricView.class);
+
+ private final String property;
+
+ private final ColumnFamilyHandle handle;
+
+ private final RocksDB db;
+
+ private volatile boolean open;
+
+ private long value;
+
+ private RocksDBNativeMetricView(
+ @Nonnull String property,
+ @Nonnull ColumnFamilyHandle handle,
+ @Nonnull RocksDB db
+ ) {
+ this.property = property;
+ this.handle = handle;
+ this.db = db;
+ this.open = true;
+ }
+
+ @Override
+ public String getValue() {
+ return Long.toUnsignedString(value);
+ }
+
+ @Override
+ public void update() {
+ if (open) {
Review comment:
The important point is that no metrics access is pending against RocksDB
after the db is closed.
Option 1, you can ensure that by requesting a lease in the metrics thread
before accessing db and releasing it right after the access. The request will
fail if db was released in the meantime.
Option 2, you have a lifecycle management in place that lets you decouple
the metrics that access RocksDB from the metrics thread and also ensures that
the thread is not in a pending request against the db and will do no more
requests in the future. Then you can decouple/close the metrics as first thing
in dispose(), you know that no more access is pending, and you can safely close
the db. In this case there is even no more need to use a lease. The use case
for lease is more for pending threads that could still access db and have a
lifecycle that is outside of your control. Those threads must get a lease
before working with db and release when they are done.
I suggest to prefer option 2 over 1 if you can. The current use of the lease
is inconsequent and does actually not solve the problem. Either you need to
request/release all the time, or there should be no need to use a lease at all.
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> Forward RocksDB native metrics to Flink metrics reporter
> ---------------------------------------------------------
>
> Key: FLINK-10423
> URL: https://issues.apache.org/jira/browse/FLINK-10423
> Project: Flink
> Issue Type: New Feature
> Components: Metrics, State Backends, Checkpointing
> Reporter: Seth Wiesman
> Assignee: Seth Wiesman
> Priority: Major
> Labels: pull-request-available
>
> RocksDB contains a number of metrics at the column family level about current
> memory usage, open memtables, etc that would be useful to users wishing
> greater insight what rocksdb is doing. This work is inspired heavily by the
> comments on this rocksdb issue thread
> (https://github.com/facebook/rocksdb/issues/3216#issuecomment-348779233)
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