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/*
* Copyright 2023 Responsive Computing, Inc.
*
* 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 dev.responsive.kafka.internal.metrics;
import static dev.responsive.kafka.internal.metrics.TopicMetrics.END_OFFSET;
import static dev.responsive.kafka.internal.metrics.TopicMetrics.END_OFFSET_DESCRIPTION;
import dev.responsive.kafka.internal.clients.ResponsiveConsumer;
import dev.responsive.kafka.internal.utils.Constants;
import java.time.Duration;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.function.Consumer;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import org.apache.kafka.clients.admin.Admin;
import org.apache.kafka.clients.admin.ListOffsetsResult.ListOffsetsResultInfo;
import org.apache.kafka.clients.admin.OffsetSpec;
import org.apache.kafka.common.MetricName;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.metrics.Gauge;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This class polls the current end offset of the topic partitions assigned locally and
* publishes the values as a metric. It gets the set of assigned partitions by listening
* on ResponsiveConsumer. This class should not be assumed to be thread-safe by callers.
* Internally, it runs asynchronous poller tasks and synchronizes access to its own shared
* state.
*/
public class EndOffsetsPoller {
private static final Logger LOG = LoggerFactory.getLogger(EndOffsetsPoller.class);
private static final int ADMIN_RECREATE_THRESHOLD = 3;
private final Map threadIdToMetrics = new HashMap<>();
private final ResponsiveMetrics metrics;
private final Map configs;
private final Factories factories;
private final ScheduledExecutorService executor;
private Poller poller = null;
public EndOffsetsPoller(
final Map configs,
final ResponsiveMetrics metrics,
final Factories factories
) {
this(
configs,
metrics,
Executors.newSingleThreadScheduledExecutor(r -> {
final var t = new Thread(r);
t.setDaemon(true);
t.setName("responsive-end-offsets-poller");
return t;
}),
factories
);
}
public EndOffsetsPoller(
final Map configs,
final ResponsiveMetrics metrics,
final ScheduledExecutorService executor,
final Factories factories
) {
// TODO: does admin client get only committed offsets?
this.configs = Map.copyOf(Objects.requireNonNull(configs));
this.metrics = Objects.requireNonNull(metrics);
this.executor = Objects.requireNonNull(executor);
this.factories = Objects.requireNonNull(factories);
}
public synchronized Listener addForThread(final String threadId) {
LOG.debug("Adding end offset metrics for thread {}", threadId);
final var tm = new Listener(threadId, metrics, this::removeForThread);
if (threadIdToMetrics.containsKey(threadId)) {
final var msg = String.format("End offset poller already has metrics for %s", threadId);
final var err = new RuntimeException(msg);
LOG.error(msg, err);
throw err;
}
if (threadIdToMetrics.isEmpty()) {
initPoller();
}
threadIdToMetrics.put(threadId, tm);
return tm;
}
private synchronized void removeForThread(final String threadId) {
LOG.debug("Removing end offset metrics for thread {}", threadId);
final Listener tm = threadIdToMetrics.remove(threadId);
if (tm != null) {
if (threadIdToMetrics.isEmpty()) {
stopPoller();
}
} else {
LOG.warn("No metrics found for thread {}", threadId);
}
}
private synchronized Collection getThreadMetrics() {
return List.copyOf(threadIdToMetrics.values());
}
private void initPoller() {
LOG.info("Initializing end offsets poller");
if (poller != null) {
throw new IllegalStateException("Poller was already initialized");
}
poller = new Poller(
() -> factories.createAdminClient(configs),
executor,
this::getThreadMetrics
);
}
private void stopPoller() {
LOG.info("Stopping end offsets poller");
try {
poller.stop();
} catch (final RuntimeException e) {
LOG.warn("Poller stop returned an unexpected error. It will be ignored, and the poller "
+ "task + admin client might be leaked.", e);
}
poller = null;
}
private static class Poller {
private Admin adminClient;
private int failuresWithoutReinit = 0;
private final Supplier adminSupplier;
private final ScheduledFuture future;
private final ScheduledExecutorService executor;
private final Supplier> threadMetricsSupplier;
private Poller(
final Supplier adminClientSupplier,
final ScheduledExecutorService executor,
final Supplier> threadMetricsSupplier
) {
this.adminSupplier = adminClientSupplier;
this.executor = executor;
this.threadMetricsSupplier = threadMetricsSupplier;
init();
this.future = executor.scheduleAtFixedRate(this::pollEndOffsets, 0, 30, TimeUnit.SECONDS);
}
private void stop() {
future.cancel(true);
executor.schedule(this::close, 0, TimeUnit.SECONDS);
}
private void init() {
adminClient = adminSupplier.get();
failuresWithoutReinit = 0;
}
private void close() {
adminClient.close(Duration.ofNanos(0));
}
private void maybeReinit() {
if (failuresWithoutReinit >= ADMIN_RECREATE_THRESHOLD) {
LOG.info("reinitializing admin client");
close();
init();
}
}
private void doPollEndOffsets() {
LOG.info("Polling end offsets");
maybeReinit();
final var partitions = new HashMap();
final Collection threadMetrics = threadMetricsSupplier.get();
for (final var tm : threadMetrics) {
for (final var tp : tm.endOffsets.keySet()) {
partitions.put(tp, OffsetSpec.latest());
}
}
final var result = adminClient.listOffsets(partitions);
final Map endOffsets;
try {
endOffsets = result.all()
.get(Constants.BLOCKING_TIMEOUT_VALUE, Constants.BLOCKING_TIMEOUT_UNIT);
} catch (final InterruptedException | ExecutionException | TimeoutException e) {
throw new RuntimeException(e);
}
threadMetrics.forEach(tm -> tm.update(endOffsets));
failuresWithoutReinit = 0;
LOG.info("Finished updating end offsets");
}
private void pollEndOffsets() {
try {
doPollEndOffsets();
} catch (final RuntimeException e) {
LOG.error("error polling end offsets. will retry at next poll interval", e);
failuresWithoutReinit += 1;
}
}
}
public static class Listener implements ResponsiveConsumer.Listener {
private final String threadId;
private final Map endOffsets = new ConcurrentHashMap<>();
private final Logger log;
private final ResponsiveMetrics metrics;
private final Consumer onClose;
private Listener(
final String threadId,
final ResponsiveMetrics metrics,
final Consumer onClose
) {
this.threadId = threadId;
this.metrics = metrics;
this.onClose = onClose;
log = LoggerFactory.getLogger(EndOffsetsPoller.class.getName() + "." + threadId);
}
@Override
public void onPartitionsLost(final Collection lost) {
// For now, we can just delegate to #onPartitionsRevoked here since we're just
// cleaning up partitions we no longer own, but these callbacks are semantically
// distinct and may need individual implementations if more sophisticated metrics
// are ever introduced
onPartitionsRevoked(lost);
}
@Override
public void onPartitionsRevoked(final Collection revoked) {
for (final var p : revoked) {
metrics.removeMetric(endOffsetMetric(p));
endOffsets.remove(p);
}
}
@Override
public void onPartitionsAssigned(final Collection assigned) {
for (final var p : assigned) {
endOffsets.put(p, -1L);
metrics.addMetric(
endOffsetMetric(p),
(Gauge) (config, now) -> endOffsets.getOrDefault(p, -1L)
);
}
}
private void update(final Map newEndOffsets) {
for (final var entry : newEndOffsets.entrySet()) {
endOffsets.computeIfPresent(entry.getKey(), (k, v) -> entry.getValue().offset());
}
if (log.isDebugEnabled()) {
log.debug("Updated end offsets to [{}].",
endOffsets.entrySet().stream()
.map(tp -> "(" + tp.getKey() + ": " + tp.getValue() + ")")
.collect(Collectors.joining(", "))
);
}
}
public void close() {
log.info("Cleaning up offset metrics");
for (final TopicPartition p : endOffsets.keySet()) {
metrics.removeMetric(endOffsetMetric(p));
}
onClose.accept(threadId);
}
private MetricName endOffsetMetric(final TopicPartition topicPartition) {
return metrics.metricName(
END_OFFSET,
END_OFFSET_DESCRIPTION,
metrics.topicLevelMetric(TopicMetrics.TOPIC_METRIC_GROUP, threadId, topicPartition)
);
}
}
@FunctionalInterface
public interface Factories {
Admin createAdminClient(final Map configs);
}
}
