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/*
* Licensed 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 com.opentable.kafka.util;
import java.io.Closeable;
import java.time.Duration;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import javax.annotation.Nullable;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import com.codahale.metrics.Counting;
import com.codahale.metrics.Gauge;
import com.codahale.metrics.Histogram;
import com.codahale.metrics.Metric;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.Reservoir;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import io.github.bucket4j.Bandwidth;
import io.github.bucket4j.Bucket;
import io.github.bucket4j.Refill;
import com.opentable.concurrent.OTExecutors;
import com.opentable.metrics.graphite.MetricSets;
/**
* Class that monitors consumer groups consuming from topics; registers its metrics with a metric registry.
*
* Runs a thread that polls the Kafka broker; use {@link #start()} and {@link #stop()} to spin up and down. They are
* annotated with post-construct and pre-destroy, respectively, in order to simplify Spring integration.
*
* The metric namespace is as follows; each metric is a {@link Gauge}<{@link Long}>, and can be {@code null}.
*
*
* {@code ..{partition.%d,total}.{size,offset,lag}}
*
*
* Size is the maximum offset of the topic (this is independent of any consumer). Offset is the current offset of the
* consumer. Lag is the size minus the offset. Totals are summed across the partitions.
* NB: Since the queries for the topic sizes and consumer offsets are necessarily separate, they race; this means that
* lag can possibly be negative.
*
*
* In addition to these gauges, lag distribution {@link Histogram}s are also available as follows.
*
*
* {@code ..total.lag-distribution}
*
*
* Use an offsets supplier if you are managing your own offsets.
* Without an offsets supplier, this class will attempt to read consumer group offsets from the Kafka broker, and will
* require the partitions for which offsets are stored to match the partitions for which size information is reported.
* With an offsets supplier, this class will call it periodically. The offsets supplier's keys (partitions) must be a
* subset of the keys (also partitions) of the size information reported by the broker.
*
*
* Future work: Have alternate constructor in which you don't specify any topics, and the class uses the
* {@link OffsetMonitor} to dynamically register metrics based on the topics that the consumer group is consuming.
*
*
* Future work: Have alternate constructor in which you don't specify any groups either, and the class uses the
* {@link OffsetMonitor} to dynamically register metrics based on all consumer groups' topic consumption.
*/
@SuppressWarnings("PMD.AvoidDuplicateLiterals")
public class OffsetMetrics implements Closeable {
static final String PREFIX = "kafka.";
private static final Logger LOG = LoggerFactory.getLogger(OffsetMetrics.class);
private final Bucket logLimitBucket = Bucket
.builder()
.addLimit(Bandwidth.classic(6, Refill.greedy(1, Duration.ofMinutes(10))))
.build();
private final String metricPrefix;
private final MetricRegistry metricRegistry;
private final Collection topics;
private final Duration pollPeriod;
private final OffsetMonitor monitor;
private final boolean expectKafkaManagedOffsets;
/** Topic -> partition -> offset. */
private final Function> offsetsSupplier;
private final Map metricMap;
private final ScheduledExecutorService exec;
public static OffsetMetricsBuilder builder(
final String metricPrefix,
final MetricRegistry metricRegistry,
final String groupId,
final String brokerList
) {
return new OffsetMetricsBuilder(
metricPrefix,
metricRegistry,
groupId,
brokerList
);
}
OffsetMetrics(
final String metricPrefix,
final MetricRegistry metricRegistry,
final String groupId,
final String brokerList,
final Collection topics,
final Supplier reservoirSupplier,
final Duration pollPeriod,
@Nullable
final Function> offsetsSupplier) {
Preconditions.checkArgument(metricPrefix != null, "null metric prefix");
Preconditions.checkArgument(!topics.isEmpty(), "no topics");
Preconditions.checkArgument(!metricPrefix.contains("."), "Your prefix cannot contain a period");
this.metricPrefix = PREFIX + metricPrefix;
this.metricRegistry = metricRegistry;
this.topics = topics;
this.pollPeriod = pollPeriod;
monitor = new OffsetMonitor(groupId, brokerList);
expectKafkaManagedOffsets = offsetsSupplier == null;
if (expectKafkaManagedOffsets) {
this.offsetsSupplier = topic -> monitor.getGroupOffsets(groupId, topic);
} else {
this.offsetsSupplier = offsetsSupplier;
}
final Collection badTopics = new ArrayList<>();
final ImmutableMap.Builder builder = ImmutableMap.builder();
topics.forEach(topic -> {
final Map sizes = monitor.getTopicSizes(topic);
if (sizes.isEmpty()) {
badTopics.add(topic);
return;
}
for (final int part : sizes.keySet()) {
builder.put(partitionName(topic, part, "size"), new LongGauge());
builder.put(partitionName(topic, part, "offset"), new LongGauge());
builder.put(partitionName(topic, part, "lag"), new LongGauge());
}
builder.put(totalName(topic, "size"), new LongGauge());
builder.put(totalName(topic, "offset"), new LongGauge());
builder.put(totalName(topic, "lag"), new LongGauge());
builder.put(totalName(topic, "lag-distribution"), new Histogram(reservoirSupplier.get()));
});
if (!badTopics.isEmpty()) {
throw new IllegalArgumentException(
String.format("bad topic%s: '%s'", badTopics.size() != 1 ? "s" : "", badTopics));
}
metricMap = builder.build();
exec = Executors.newSingleThreadScheduledExecutor(
new ThreadFactoryBuilder()
.setNameFormat(String.format("%s-offset-metrics-%%d", groupId))
.build()
);
}
private String partitionName(final String topic, final int partition, final String name) {
return String.format("%s.%s.partition.%d.%s", metricPrefix, topic, partition, name);
}
private String totalName(final String topic, final String name) {
return String.format("%s.%s.total.%s", metricPrefix, topic, name);
}
@VisibleForTesting
Map getMetrics() {
return metricMap;
}
@PostConstruct
public void start() {
metricRegistry.registerAll(this::getMetrics);
exec.scheduleAtFixedRate(this::poll, 0, pollPeriod.toMillis(), TimeUnit.MILLISECONDS);
}
@SuppressWarnings("UnstableApiUsage")
@PreDestroy
public void stop() {
MetricSets.removeAll(metricRegistry, this::getMetrics);
try {
OTExecutors.shutdownAndAwaitTermination(exec, Duration.ofSeconds(5));
} catch (final InterruptedException e) {
LOG.error("worker thread shutdown interrupted", e);
Thread.currentThread().interrupt();
}
monitor.close();
}
@Override
public void close() {
stop();
}
private void poll() {
topics.forEach(topic -> {
try {
pollUnsafe(topic);
} catch (final Exception e) {
LOG.error("caught exception for topic {}", topic, e);
}
});
}
private void pollUnsafe(final String topic) {
final Map sizes = monitor.getTopicSizes(topic);
Map offsets = offsetsSupplier.apply(topic);
final Map lags;
if (offsets.isEmpty()) {
// Consumer may not be consuming this topic yet (or consumer might not exist).
// In case consumer existed previously, we set all offsets and lag to 0.
offsets = lags = sizes
.keySet()
.stream()
.collect(
Collectors.toMap(
part -> part,
part -> 0L
)
);
} else {
final Function, Boolean> test;
final String msg;
if (expectKafkaManagedOffsets) {
test = map -> sizes.keySet().equals(map.keySet());
msg = "offsets/sizes partitions do not match";
} else {
test = map -> sizes.keySet().containsAll(map.keySet());
msg = "offsets not subset of sizes";
}
if (!test.apply(offsets)) {
if (logLimitBucket.tryConsume(1)) {
LOG.warn("{} for topic {}: {}/{}", msg, topic, offsets.keySet(), sizes.keySet());
}
return;
}
final Map finalOffsets = offsets;
lags = offsets
.keySet()
.stream()
.collect(
Collectors.toMap(
part -> part,
part -> sizes.get(part) - finalOffsets.get(part)
)
);
}
// The keys of offsets is a non-empty subset of the keys of sizes, and the keys of offsets and lags are
// identical.
final Set knownParts = offsets.keySet();
final Set unknownParts = Sets.difference(sizes.keySet(), knownParts);
final Map subSizes = Maps.filterKeys(sizes, offsets::containsKey);
subSizes .forEach((part, size) -> gauge(partitionName(topic, part, "size")).set(size));
unknownParts.forEach( part -> gauge(partitionName(topic, part, "size")).set(null));
gauge(totalName(topic, "size")).set(sumValues(subSizes));
offsets .forEach((part, off) -> gauge(partitionName(topic, part, "offset")).set(off));
unknownParts.forEach( part -> gauge(partitionName(topic, part, "offset")).set(null));
gauge(totalName(topic, "offset")).set(sumValues(offsets));
lags.forEach((part, lag) -> {
gauge(partitionName(topic, part, "lag")).set(lag);
((Histogram) metricMap.get(totalName(topic, "lag-distribution"))).update(lag);
});
unknownParts.forEach(part -> gauge(partitionName(topic, part, "lag")).set(null));
gauge(totalName(topic, "lag")).set(sumValues(lags));
}
private LongGauge gauge(final String name) {
final LongGauge result = (LongGauge) metricMap.get(name);
if (result == null) {
throw new IllegalStateException("Gauge '" + name + "' not found in metricMap=" + metricMap);
}
return result;
}
private static long sumValues(final Map map) {
return map.values().stream().mapToLong(x -> x).sum();
}
@VisibleForTesting
static class LongGauge implements Gauge, Counting {
private final AtomicReference value = new AtomicReference<>();
@Override
public Long getValue() {
return value.get();
}
@Override
public long getCount() {
return Optional.ofNullable(getValue()).orElse(0L);
}
private void set(final Long value) {
this.value.set(value);
}
}
}