poorbarcode commented on code in PR #16758: URL: https://github.com/apache/pulsar/pull/16758#discussion_r935712798
########## pulsar-transaction/coordinator/src/main/java/org/apache/pulsar/transaction/coordinator/impl/TxnLogBufferedWriterMetricsStats.java: ########## @@ -0,0 +1,234 @@ +/** + * 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.pulsar.transaction.coordinator.impl; + +import io.prometheus.client.Collector; +import io.prometheus.client.CollectorRegistry; +import io.prometheus.client.Counter; +import io.prometheus.client.Histogram; +import java.io.Closeable; +import java.util.HashMap; + +/*** + * Describes the working status of the {@link TxnLogBufferedWriter}, helps users tune the thresholds of + * {@link TxnLogBufferedWriter} for best performance. + * Note-1: When batch feature is turned off, no data is logged at this. In this scenario，users can see the + * {@link org.apache.bookkeeper.mledger.ManagedLedgerMXBean}. + * Note-2: Even if enable batch feature, if a single record is too big, it still directly write to Bookie without batch, + * property {@link #pulsarBatchedLogTriggeringCountByForce} can indicate this case. But this case will not affect + * other metrics, because it would obscure the real situation. E.g. there has two record: + * [{recordsCount=512, triggerByMaxRecordCount}, {recordCount=1, triggerByTooLarge}], we should not tell the users + * that the average batch records is 256, if the users knows that there are only 256 records per batch, then users + * will try to increase {@link TxnLogBufferedWriter#batchedWriteMaxDelayInMillis} so that there is more data per + * batch to improve throughput, but that does not work. + */ +public class TxnLogBufferedWriterMetricsStats implements Closeable { + + /** + * Key is the name we used to create {@link TxnLogBufferedWriterMetricsStats}, and now there are two kinds: + * ["pulsar_txn_tc_log", "pulsar_txn_tc_batched_log"]. There can be multiple labels in each + * {@link TxnLogBufferedWriterMetricsStats}, such as The Transaction Coordinator using coordinatorId as label and + * The Transaction Pending Ack Store using subscriptionName as label. + */ + private static final HashMap<String, Collector> COLLECTOR_CACHE = new HashMap<>(); Review Comment: > Why do we need a map here? Looks like it is only used in the constructor. Yes, we need it. To build Metrics Stat, we need execute these two steps: 1. Create `Collector` and register to `CollectorRegistry`, perhaps the Collector is `Histogram` or `Counter` 2. Register labels to `Collector` and get `Collector.child`(holds by Metrics Stat). This step can also be omitted, because we can execute `collector.labels(labelValues)` to get `Collector.child`. In the Transaction log scenario, multiple Transaction Log share the same `Collector`, and each has its own `Collector.Child`, so when we build metrics stat for each Transaction Log, we call `collector.labels(labelValues)` to get the `Collector.Child`. (<strong> High light</strong>) However, the CollectorRegistry does not provide an API like this: ```java public Collector getRegistedCollector(String name); ``` and it will throw IllegalArgumentException when we registering collector with the same name more than once, see: https://github.com/prometheus/client_java/blob/1966186deaaa83aec496d88ff604a90795bad688/simpleclient/src/main/java/io/prometheus/client/CollectorRegistry.java#L49-L65 So we have to manage the registered collectors ourselves. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
