THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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Tooling/Monitoring Changes
Upon implementation, we will start exposing per-client byte rate metrics metrics to JMX. Since these are new metrics there are no backward compatibility issues. These metrics will be documented prior to the release.
Client Status Code
In the current response protocol, there is no way to return the quota status back to the client. How do clients know if they are being throttled or not? One solution is to add a new field in the response that indicates the quota status. This will require us to increment the protocol version for both producer and consumer. Clients that send V0 requests will not receive the quota status flag in the response. On the client side (producer and consumer), we can have a metric that exposes whether the client was throttled during the last measured window or not.
The response protocol can define a top-level field called "isThrottled". Example:
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// Current fetch response
public static final Schema FETCH_RESPONSE_V0 = new Schema(new Field("responses", new ArrayOf(FETCH_RESPONSE_TOPIC_V0)));
// Proposed fetch response
public static final Schema FETCH_RESPONSE_V1 = new Schema(new Field("responses", new ArrayOf(FETCH_RESPONSE_TOPIC_V0)), new Field("isThrottled", INT8, "Was the request throttled or not"));
// Current produce response
public static final Schema PRODUCE_RESPONSE_V0 = new Schema(new Field("responses",
new ArrayOf(new Schema(new Field("topic", STRING),
new Field("partition_responses",
new ArrayOf(new Schema(new Field("partition",
INT32),
new Field("error_code",
INT16),
new Field("base_offset",
INT64))))))));
// Proposed produce response
public static final Schema PRODUCE_RESPONSE_V0 = new Schema(new Field("responses",
new ArrayOf(new Schema(new Field("topic", STRING),
new Field("partition_responses",
new ArrayOf(new Schema(new Field("partition",
INT32),
new Field("error_code",
INT16),
new Field("base_offset",
INT64))))))),
new Field("isThrottled", INT8, "Was the request throttled or not"));
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This work item does not block the core implementation of quotas but IMO is very useful to have.
NOTE: This was briefly discussed on the mailing list and was never concluded. One thing that we did rule out was to overload the error code field because being throttled isn't really an error and it can get really confusing.
Compatibility, Deprecation, and Migration Plan
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