kafka FetchSessionHandler 源码
kafka FetchSessionHandler 代码
文件路径：/clients/src/main/java/org/apache/kafka/clients/FetchSessionHandler.java
/*
* 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.kafka.clients;
import org.apache.kafka.common.TopicIdPartition;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.Uuid;
import org.apache.kafka.common.protocol.Errors;
import org.apache.kafka.common.requests.FetchMetadata;
import org.apache.kafka.common.requests.FetchRequest.PartitionData;
import org.apache.kafka.common.requests.FetchResponse;
import org.apache.kafka.common.utils.LogContext;
import org.apache.kafka.common.utils.Utils;
import org.slf4j.Logger;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import static org.apache.kafka.common.requests.FetchMetadata.INVALID_SESSION_ID;
/**
* FetchSessionHandler maintains the fetch session state for connecting to a broker.
*
* Using the protocol outlined by KIP-227, clients can create incremental fetch sessions.
* These sessions allow the client to fetch information about a set of partition over
* and over, without explicitly enumerating all the partitions in the request and the
* response.
*
* FetchSessionHandler tracks the partitions which are in the session. It also
* determines which partitions need to be included in each fetch request, and what
* the attached fetch session metadata should be for each request. The corresponding
* class on the receiving broker side is FetchManager.
*/
public class FetchSessionHandler {
private final Logger log;
private final int node;
/**
* The metadata for the next fetch request.
*/
private FetchMetadata nextMetadata = FetchMetadata.INITIAL;
public FetchSessionHandler(LogContext logContext, int node) {
this.log = logContext.logger(FetchSessionHandler.class);
this.node = node;
}
/**
* All of the partitions which exist in the fetch request session.
*/
private LinkedHashMap<TopicPartition, PartitionData> sessionPartitions =
new LinkedHashMap<>(0);
/**
* All of the topic names mapped to topic ids for topics which exist in the fetch request session.
*/
private Map<Uuid, String> sessionTopicNames = new HashMap<>(0);
public Map<Uuid, String> sessionTopicNames() {
return sessionTopicNames;
}
public static class FetchRequestData {
/**
* The partitions to send in the fetch request.
*/
private final Map<TopicPartition, PartitionData> toSend;
/**
* The partitions to send in the request's "forget" list.
*/
private final List<TopicIdPartition> toForget;
/**
* The partitions to send in the request's "forget" list if
* the version is >= 13.
*/
private final List<TopicIdPartition> toReplace;
/**
* All of the partitions which exist in the fetch request session.
*/
private final Map<TopicPartition, PartitionData> sessionPartitions;
/**
* The metadata to use in this fetch request.
*/
private final FetchMetadata metadata;
/**
* A boolean indicating whether we have a topic ID for every topic in the request so that we can send a request that
* uses topic IDs
*/
private final boolean canUseTopicIds;
FetchRequestData(Map<TopicPartition, PartitionData> toSend,
List<TopicIdPartition> toForget,
List<TopicIdPartition> toReplace,
Map<TopicPartition, PartitionData> sessionPartitions,
FetchMetadata metadata,
boolean canUseTopicIds) {
this.toSend = toSend;
this.toForget = toForget;
this.toReplace = toReplace;
this.sessionPartitions = sessionPartitions;
this.metadata = metadata;
this.canUseTopicIds = canUseTopicIds;
}
/**
* Get the set of partitions to send in this fetch request.
*/
public Map<TopicPartition, PartitionData> toSend() {
return toSend;
}
/**
* Get a list of partitions to forget in this fetch request.
*/
public List<TopicIdPartition> toForget() {
return toForget;
}
/**
* Get a list of partitions to forget in this fetch request.
*/
public List<TopicIdPartition> toReplace() {
return toReplace;
}
/**
* Get the full set of partitions involved in this fetch request.
*/
public Map<TopicPartition, PartitionData> sessionPartitions() {
return sessionPartitions;
}
public FetchMetadata metadata() {
return metadata;
}
public boolean canUseTopicIds() {
return canUseTopicIds;
}
@Override
public String toString() {
StringBuilder bld;
if (metadata.isFull()) {
bld = new StringBuilder("FullFetchRequest(toSend=(");
String prefix = "";
for (TopicPartition partition : toSend.keySet()) {
bld.append(prefix);
bld.append(partition);
prefix = ", ";
}
} else {
bld = new StringBuilder("IncrementalFetchRequest(toSend=(");
String prefix = "";
for (TopicPartition partition : toSend.keySet()) {
bld.append(prefix);
bld.append(partition);
prefix = ", ";
}
bld.append("), toForget=(");
prefix = "";
for (TopicIdPartition partition : toForget) {
bld.append(prefix);
bld.append(partition);
prefix = ", ";
}
bld.append("), toReplace=(");
prefix = "";
for (TopicIdPartition partition : toReplace) {
bld.append(prefix);
bld.append(partition);
prefix = ", ";
}
bld.append("), implied=(");
prefix = "";
for (TopicPartition partition : sessionPartitions.keySet()) {
if (!toSend.containsKey(partition)) {
bld.append(prefix);
bld.append(partition);
prefix = ", ";
}
}
}
if (canUseTopicIds) {
bld.append("), canUseTopicIds=True");
} else {
bld.append("), canUseTopicIds=False");
}
bld.append(")");
return bld.toString();
}
}
public class Builder {
/**
* The next partitions which we want to fetch.
*
* It is important to maintain the insertion order of this list by using a LinkedHashMap rather
* than a regular Map.
*
* One reason is that when dealing with FULL fetch requests, if there is not enough response
* space to return data from all partitions, the server will only return data from partitions
* early in this list.
*
* Another reason is because we make use of the list ordering to optimize the preparation of
* incremental fetch requests (see below).
*/
private LinkedHashMap<TopicPartition, PartitionData> next;
private Map<Uuid, String> topicNames;
private final boolean copySessionPartitions;
private int partitionsWithoutTopicIds = 0;
Builder() {
this.next = new LinkedHashMap<>();
this.topicNames = new HashMap<>();
this.copySessionPartitions = true;
}
Builder(int initialSize, boolean copySessionPartitions) {
this.next = new LinkedHashMap<>(initialSize);
this.topicNames = new HashMap<>();
this.copySessionPartitions = copySessionPartitions;
}
/**
* Mark that we want data from this partition in the upcoming fetch.
*/
public void add(TopicPartition topicPartition, PartitionData data) {
next.put(topicPartition, data);
// topicIds should not change between adding partitions and building, so we can use putIfAbsent
if (data.topicId.equals(Uuid.ZERO_UUID)) {
partitionsWithoutTopicIds++;
} else {
topicNames.putIfAbsent(data.topicId, topicPartition.topic());
}
}
public FetchRequestData build() {
boolean canUseTopicIds = partitionsWithoutTopicIds == 0;
if (nextMetadata.isFull()) {
if (log.isDebugEnabled()) {
log.debug("Built full fetch {} for node {} with {}.",
nextMetadata, node, topicPartitionsToLogString(next.keySet()));
}
sessionPartitions = next;
next = null;
// Only add topic IDs to the session if we are using topic IDs.
if (canUseTopicIds) {
sessionTopicNames = topicNames;
} else {
sessionTopicNames = Collections.emptyMap();
}
Map<TopicPartition, PartitionData> toSend =
Collections.unmodifiableMap(new LinkedHashMap<>(sessionPartitions));
return new FetchRequestData(toSend, Collections.emptyList(), Collections.emptyList(), toSend, nextMetadata, canUseTopicIds);
}
List<TopicIdPartition> added = new ArrayList<>();
List<TopicIdPartition> removed = new ArrayList<>();
List<TopicIdPartition> altered = new ArrayList<>();
List<TopicIdPartition> replaced = new ArrayList<>();
for (Iterator<Entry<TopicPartition, PartitionData>> iter =
sessionPartitions.entrySet().iterator(); iter.hasNext(); ) {
Entry<TopicPartition, PartitionData> entry = iter.next();
TopicPartition topicPartition = entry.getKey();
PartitionData prevData = entry.getValue();
PartitionData nextData = next.remove(topicPartition);
if (nextData != null) {
// We basically check if the new partition had the same topic ID. If not,
// we add it to the "replaced" set. If the request is version 13 or higher, the replaced
// partition will be forgotten. In any case, we will send the new partition in the request.
if (!prevData.topicId.equals(nextData.topicId)
&& !prevData.topicId.equals(Uuid.ZERO_UUID)
&& !nextData.topicId.equals(Uuid.ZERO_UUID)) {
// Re-add the replaced partition to the end of 'next'
next.put(topicPartition, nextData);
entry.setValue(nextData);
replaced.add(new TopicIdPartition(prevData.topicId, topicPartition));
} else if (!prevData.equals(nextData)) {
// Re-add the altered partition to the end of 'next'
next.put(topicPartition, nextData);
entry.setValue(nextData);
altered.add(new TopicIdPartition(nextData.topicId, topicPartition));
}
} else {
// Remove this partition from the session.
iter.remove();
// Indicate that we no longer want to listen to this partition.
removed.add(new TopicIdPartition(prevData.topicId, topicPartition));
// If we do not have this topic ID in the builder or the session, we can not use topic IDs.
if (canUseTopicIds && prevData.topicId.equals(Uuid.ZERO_UUID))
canUseTopicIds = false;
}
}
// Add any new partitions to the session.
for (Entry<TopicPartition, PartitionData> entry : next.entrySet()) {
TopicPartition topicPartition = entry.getKey();
PartitionData nextData = entry.getValue();
if (sessionPartitions.containsKey(topicPartition)) {
// In the previous loop, all the partitions which existed in both sessionPartitions
// and next were moved to the end of next, or removed from next. Therefore,
// once we hit one of them, we know there are no more unseen entries to look
// at in next.
break;
}
sessionPartitions.put(topicPartition, nextData);
added.add(new TopicIdPartition(nextData.topicId, topicPartition));
}
// Add topic IDs to session if we can use them. If an ID is inconsistent, we will handle in the receiving broker.
// If we switched from using topic IDs to not using them (or vice versa), that error will also be handled in the receiving broker.
if (canUseTopicIds) {
sessionTopicNames = topicNames;
} else {
sessionTopicNames = Collections.emptyMap();
}
if (log.isDebugEnabled()) {
log.debug("Built incremental fetch {} for node {}. Added {}, altered {}, removed {}, " +
"replaced {} out of {}", nextMetadata, node, topicIdPartitionsToLogString(added),
topicIdPartitionsToLogString(altered), topicIdPartitionsToLogString(removed),
topicIdPartitionsToLogString(replaced), topicPartitionsToLogString(sessionPartitions.keySet()));
}
Map<TopicPartition, PartitionData> toSend = Collections.unmodifiableMap(next);
Map<TopicPartition, PartitionData> curSessionPartitions = copySessionPartitions
? Collections.unmodifiableMap(new LinkedHashMap<>(sessionPartitions))
: Collections.unmodifiableMap(sessionPartitions);
next = null;
return new FetchRequestData(toSend,
Collections.unmodifiableList(removed),
Collections.unmodifiableList(replaced),
curSessionPartitions,
nextMetadata,
canUseTopicIds);
}
}
public Builder newBuilder() {
return new Builder();
}
/** A builder that allows for presizing the PartitionData hashmap, and avoiding making a
* secondary copy of the sessionPartitions, in cases where this is not necessarily.
* This builder is primarily for use by the Replica Fetcher
* @param size the initial size of the PartitionData hashmap
* @param copySessionPartitions boolean denoting whether the builder should make a deep copy of
* session partitions
*/
public Builder newBuilder(int size, boolean copySessionPartitions) {
return new Builder(size, copySessionPartitions);
}
private String topicPartitionsToLogString(Collection<TopicPartition> partitions) {
if (!log.isTraceEnabled()) {
return String.format("%d partition(s)", partitions.size());
}
return "(" + Utils.join(partitions, ", ") + ")";
}
private String topicIdPartitionsToLogString(Collection<TopicIdPartition> partitions) {
if (!log.isTraceEnabled()) {
return String.format("%d partition(s)", partitions.size());
}
return "(" + Utils.join(partitions, ", ") + ")";
}
/**
* Return missing items which are expected to be in a particular set, but which are not.
*
* @param toFind The items to look for.
* @param toSearch The set of items to search.
* @return Empty set if all items were found; some of the missing ones in a set, if not.
*/
static <T> Set<T> findMissing(Set<T> toFind, Set<T> toSearch) {
Set<T> ret = new LinkedHashSet<>();
for (T toFindItem: toFind) {
if (!toSearch.contains(toFindItem)) {
ret.add(toFindItem);
}
}
return ret;
}
/**
* Verify that a full fetch response contains all the partitions in the fetch session.
*
* @param topicPartitions The topicPartitions from the FetchResponse.
* @param ids The topic IDs from the FetchResponse.
* @param version The version of the FetchResponse.
* @return null if the full fetch response partitions are valid; human-readable problem description otherwise.
*/
String verifyFullFetchResponsePartitions(Set<TopicPartition> topicPartitions, Set<Uuid> ids, short version) {
StringBuilder bld = new StringBuilder();
Set<TopicPartition> extra =
findMissing(topicPartitions, sessionPartitions.keySet());
Set<TopicPartition> omitted =
findMissing(sessionPartitions.keySet(), topicPartitions);
Set<Uuid> extraIds = new HashSet<>();
if (version >= 13) {
extraIds = findMissing(ids, sessionTopicNames.keySet());
}
if (!omitted.isEmpty()) {
bld.append("omittedPartitions=(").append(Utils.join(omitted, ", ")).append(", ");
}
if (!extra.isEmpty()) {
bld.append("extraPartitions=(").append(Utils.join(extra, ", ")).append(", ");
}
if (!extraIds.isEmpty()) {
bld.append("extraIds=(").append(Utils.join(extraIds, ", ")).append(", ");
}
if ((!omitted.isEmpty()) || (!extra.isEmpty()) || (!extraIds.isEmpty())) {
bld.append("response=(").append(Utils.join(topicPartitions, ", ")).append(")");
return bld.toString();
}
return null;
}
/**
* Verify that the partitions in an incremental fetch response are contained in the session.
*
* @param topicPartitions The topicPartitions from the FetchResponse.
* @param ids The topic IDs from the FetchResponse.
* @param version The version of the FetchResponse.
* @return null if the incremental fetch response partitions are valid; human-readable problem description otherwise.
*/
String verifyIncrementalFetchResponsePartitions(Set<TopicPartition> topicPartitions, Set<Uuid> ids, short version) {
Set<Uuid> extraIds = new HashSet<>();
if (version >= 13) {
extraIds = findMissing(ids, sessionTopicNames.keySet());
}
Set<TopicPartition> extra =
findMissing(topicPartitions, sessionPartitions.keySet());
StringBuilder bld = new StringBuilder();
if (!extra.isEmpty())
bld.append("extraPartitions=(").append(Utils.join(extra, ", ")).append("), ");
if (!extraIds.isEmpty())
bld.append("extraIds=(").append(Utils.join(extraIds, ", ")).append("), ");
if ((!extra.isEmpty()) || (!extraIds.isEmpty())) {
bld.append("response=(").append(Utils.join(topicPartitions, ", ")).append(")");
return bld.toString();
}
return null;
}
/**
* Create a string describing the partitions in a FetchResponse.
*
* @param topicPartitions The topicPartitions from the FetchResponse.
* @return The string to log.
*/
private String responseDataToLogString(Set<TopicPartition> topicPartitions) {
if (!log.isTraceEnabled()) {
int implied = sessionPartitions.size() - topicPartitions.size();
if (implied > 0) {
return String.format(" with %d response partition(s), %d implied partition(s)",
topicPartitions.size(), implied);
} else {
return String.format(" with %d response partition(s)",
topicPartitions.size());
}
}
StringBuilder bld = new StringBuilder();
bld.append(" with response=(").
append(Utils.join(topicPartitions, ", ")).
append(")");
String prefix = ", implied=(";
String suffix = "";
for (TopicPartition partition : sessionPartitions.keySet()) {
if (!topicPartitions.contains(partition)) {
bld.append(prefix);
bld.append(partition);
prefix = ", ";
suffix = ")";
}
}
bld.append(suffix);
return bld.toString();
}
/**
* Handle the fetch response.
*
* @param response The response.
* @param version The version of the request.
* @return True if the response is well-formed; false if it can't be processed
* because of missing or unexpected partitions.
*/
public boolean handleResponse(FetchResponse response, short version) {
if (response.error() != Errors.NONE) {
log.info("Node {} was unable to process the fetch request with {}: {}.",
node, nextMetadata, response.error());
if (response.error() == Errors.FETCH_SESSION_ID_NOT_FOUND) {
nextMetadata = FetchMetadata.INITIAL;
} else {
nextMetadata = nextMetadata.nextCloseExisting();
}
return false;
}
Set<TopicPartition> topicPartitions = response.responseData(sessionTopicNames, version).keySet();
if (nextMetadata.isFull()) {
if (topicPartitions.isEmpty() && response.throttleTimeMs() > 0) {
// Normally, an empty full fetch response would be invalid. However, KIP-219
// specifies that if the broker wants to throttle the client, it will respond
// to a full fetch request with an empty response and a throttleTimeMs
// value set. We don't want to log this with a warning, since it's not an error.
// However, the empty full fetch response can't be processed, so it's still appropriate
// to return false here.
if (log.isDebugEnabled()) {
log.debug("Node {} sent a empty full fetch response to indicate that this " +
"client should be throttled for {} ms.", node, response.throttleTimeMs());
}
nextMetadata = FetchMetadata.INITIAL;
return false;
}
String problem = verifyFullFetchResponsePartitions(topicPartitions, response.topicIds(), version);
if (problem != null) {
log.info("Node {} sent an invalid full fetch response with {}", node, problem);
nextMetadata = FetchMetadata.INITIAL;
return false;
} else if (response.sessionId() == INVALID_SESSION_ID) {
if (log.isDebugEnabled())
log.debug("Node {} sent a full fetch response{}", node, responseDataToLogString(topicPartitions));
nextMetadata = FetchMetadata.INITIAL;
return true;
} else {
// The server created a new incremental fetch session.
if (log.isDebugEnabled())
log.debug("Node {} sent a full fetch response that created a new incremental " +
"fetch session {}{}", node, response.sessionId(), responseDataToLogString(topicPartitions));
nextMetadata = FetchMetadata.newIncremental(response.sessionId());
return true;
}
} else {
String problem = verifyIncrementalFetchResponsePartitions(topicPartitions, response.topicIds(), version);
if (problem != null) {
log.info("Node {} sent an invalid incremental fetch response with {}", node, problem);
nextMetadata = nextMetadata.nextCloseExisting();
return false;
} else if (response.sessionId() == INVALID_SESSION_ID) {
// The incremental fetch session was closed by the server.
if (log.isDebugEnabled())
log.debug("Node {} sent an incremental fetch response closing session {}{}",
node, nextMetadata.sessionId(), responseDataToLogString(topicPartitions));
nextMetadata = FetchMetadata.INITIAL;
return true;
} else {
// The incremental fetch session was continued by the server.
// We don't have to do anything special here to support KIP-219, since an empty incremental
// fetch request is perfectly valid.
if (log.isDebugEnabled())
log.debug("Node {} sent an incremental fetch response with throttleTimeMs = {} " +
"for session {}{}", node, response.throttleTimeMs(), response.sessionId(),
responseDataToLogString(topicPartitions));
nextMetadata = nextMetadata.nextIncremental();
return true;
}
}
}
/**
* Handle an error sending the prepared request.
*
* When a network error occurs, we close any existing fetch session on our next request,
* and try to create a new session.
*
* @param t The exception.
*/
public void handleError(Throwable t) {
log.info("Error sending fetch request {} to node {}:", nextMetadata, node, t);
nextMetadata = nextMetadata.nextCloseExisting();
}
}
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