THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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Status
Current state: Under DiscussionSuperseeded by KIP-699
Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
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public class FindCoordinatorRequest extends AbstractRequest {
private static final String COORDINATOR_KEY_KEY_NAME = "coordinator_key";
private static final String COORDINATOR_TYPE_KEY_NAME = "coordinator_type";
private static final String COORDINATOR_GROUPIDS_KEY_NAME = "coordinator_groupIds"
private static final Schema FIND_COORDINATOR_REQUEST_V0 = new Schema(GROUP_ID);
private static final Schema FIND_COORDINATOR_REQUEST_V1 = new Schema(
new Field("coordinator_key", STRING, "Id to use for finding the coordinator (for groups, this is the groupId, " +
"for transactional producers, this is the transactional id)"),
new Field("coordinator_type", INT8, "The type of coordinator to find (0 = group, 1 = transaction)"));
/**
* The version number is bumped to indicate that on quota violation brokers send out responses before throttling.
*/
private static final Schema FIND_COORDINATOR_REQUEST_V2 = FIND_COORDINATOR_REQUEST_V1;
private static final Schema FIND_COORDINATOR_REQUEST_V3 = new Schema(
new Field(COORDINATOR_GROUPIDS_KEY_NAME, new ArrayOf(STRING), "All the coordinator ids " +
"for this request"));
public static Schema[] schemaVersions() {
return new Schema[] {FIND_COORDINATOR_REQUEST_V0, FIND_COORDINATOR_REQUEST_V1, FIND_COORDINATOR_REQUEST_V2, FIND_COORDINATOR_REQUEST_V3};
}
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public static class Builder extends AbstractRequest.Builder<FindCoordinatorRequest> {
private final Map<String, String> groupIds; // Use to store (coordinator_key, coordinator_type) pair
private final short minVersion;
public Builder(CoordinatorType coordinatorType, String coordinatorKey) {
super(ApiKeys.FIND_COORDINATOR);
groupIds.put(coordiateType, coordinatorKey);
this.minVersion = coordinatorType == CoordinatorType.TRANSACTION ? (short) 1 : (short) 0;
}
@Override
public FindCoordinatorRequest build(short version) {
if (version < minVersion)
throw new UnsupportedVersionException("Cannot create a v" + version + " FindCoordinator request " +
"because we require features supported only in " + minVersion + " or later.");
return new FindCoordinatorRequest(coordinatorType(), coordinatorKey(), version);
}
public List<FindCoordinatorRequest> buildToList(short version){
if (version < minVersion)
throw new UnsupportedVersionException("Cannot create a v" + version + " FindCoordinator request " +
"because we require features supported only in " + minVersion + " or later.");
return Collections.singletonList(new FindCoordinatorRequest(coordinatorType, coordinatorKey, version));
}
public String coordinatorKey() {
return groupIds.keySet().stream().findFirst().get();
}
public CoordinatorType coordinatorType() {
return groupIds.get(coordinatorKey());
}
public Map groupIds(){
return groupIds;
}
}
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private final Map<String, String> groupIds; // Use to store (coordinator_key, coordinator_type) pair
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However, this KIP will change this pattern, because it introduces a batching optimization in the requests, meaning combining MANY requests into ONE request. So we need support a one-to-many backward compatible conversion for requests along with the implementation of this KIP.
This can be implemented in NetworkClient.java doSend(), in doSend(), it call builder.build() to build ONE request and send it out. What we need to do is modify this logic to something similar:
One The most tricky question is, how do we know if a higher version API has a batching optimization. Discussion is Discussions are still required and suggestions are highly encouraged, some of the possible solutions involving adding extra fields in AbstractRequest.java..
a) One solution is to let the request's builder return either ONE request or a LIST of requests. This is backward compatible. We can have a list of one single element.
For example, in FindCoordinatorRequest.java, buillder will have a new buildToList() (Should come up with a better name) method like this:
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public List<FindCoordinatorRequest> buildToList(short version) {
if (version < minVersion)
throw new UnsupportedVersionException("Cannot create a v" + version + " FindCoordinator request " +
"because we require features supported only in " + minVersion + " or later.");
return groupIds.entrySet()
.stream()
.map(x-> new FindCoordinatorRequest(x.value(), x.key(), version))
.collect(Collectors.toList());
} |
Then in NetworkClient.java/doSend(), use instanceof to check if batching has been used.
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private void doSend(ClientRequest clientRequest, boolean isInternalRequest, long now) {
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try {
NodeApiVersions versionInfo = apiVersions.get(nodeId);
short version;
// Note: if versionInfo is null, we have no server version information. This would be
// the case when sending the initial ApiVersionRequest which fetches the version
// information itself. It is also the case when discoverBrokerVersions is set to false.
if (versionInfo == null) {
version = builder.latestAllowedVersion();
if (discoverBrokerVersions && log.isTraceEnabled())
log.trace("No version information found when sending {} with correlation id {} to node {}. " +
"Assuming version {}.", clientRequest.apiKey(), clientRequest.correlationId(), nodeId, version);
} else {
version = versionInfo.latestUsableVersion(clientRequest.apiKey(), builder.oldestAllowedVersion(),
builder.latestAllowedVersion());
}
// Check if there is batching optimization, if there is, break them down and send them out one by one:
// We can use an enum to list all the batch-optimized API here.
if (builder.apiKey() == FIND_COORDINATOR){
for (AbstractRequest request: ((FindCoordinatorRequest.Builder) builder).buildToList(version)){
doSend(clientRequest, isInternalRequest, now, request);
}
} else {
doSend(clientRequest, isInternalRequest, now, builder.build(version));
}
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} |
Rejected Alternatives
- Update the batching logic in KafkaAdmin.java directly instead of modifying the structure of requests and response.
- Change the builder.build()'s return type to a Collection;