HBASE-23762 Add documentation on how to enable and view tracing with …

src/main/asciidoc/_chapters/tracing.adoc

@@ -0,0 +1,57 @@
+////
+/**
+ *
+ * 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.
+ */
+////
+
+[[tracing]]
+= Tracing
+:doctype: book
+:numbered:
+:toc: left
+:icons: font
+:experimental:
+
+== Overview
+
+HBase used to depend on the HTrace project for tracing. After the Apache HTrace project moved to the Attic/retired, we decided to move to https://opentelemetry.io[OpenTelemetry] in https://issues.apache.org/jira/browse/HBASE-22120[HBASE-22120].
+
+The basic support for tracing has been done, where we added tracing for async client, rpc, region read/write/scan operation, and WAL. We use opentelemetry-api to implement the tracing support manually by code, as our code base is way too complicated to be instrumented through a java agent. But notice that you still need to attach the opentelemetry java agent to enable tracing. Please see the official site for https://opentelemetry.io/[OpenTelemetry] and the documentation for https://github.com/open-telemetry/opentelemetry-java-instrumentation[opentelemetry-java-instrumentation] for more details on how to properly configure opentelemtry instrumentation.
+
+== Usage
+
+=== Enable Tracing
+
+See this section in hbase-env.sh
+
+[source,shell]
+----
+# Uncomment to enable trace, you can change the options to use other exporters such as jaeger or
+# zipkin. See https://github.com/open-telemetry/opentelemetry-java-instrumentation on how to
+# configure exporters and other components through system properties.
+# export HBASE_TRACE_OPTS="-Dotel.resource.attributes=service.name=HBase -Dotel.traces.exporter=logging otel.metrics.exporter=none"
+----
+
+Uncomment this line to enable tracing. The default config is to output the tracing data to log. Please see the documentation for https://github.com/open-telemetry/opentelemetry-java-instrumentation[opentelemetry-java-instrumentation] for more details on how to export tracing data to other tracing system such as OTel collector, jaeger or zipkin, what does the _service.name_ mean, and how to change the sampling rate, etc.
+
+NOTE: The https://github.com/open-telemetry/opentelemetry-java/blob/v1.0.1/exporters/logging/src/main/java/io/opentelemetry/exporter/logging/LoggingSpanExporter.java[LoggingSpanExporter] uses java.util.logging(jul) for logging tracing data, and the logger is initialized in opentelemtry java agent, which seems to be ahead of our jul to slf4j bridge initialization, so it will always log the tracing data to console. We highly suggest that you use other tracing systems to collect and view tracing data instead of logging.
+
+=== Performance Impact
+
+According to the result in https://issues.apache.org/jira/browse/HBASE-25658[HBASE-25658], the performance impact is minimal. Of course the test cluster is not under heavy load, so if you find out that enabling tracing would impact the performance, try to lower the sampling rate. See documentation for configuring https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/autoconfigure/README.md#sampler[sampler] for more details.
+

src/main/asciidoc/_chapters/upgrading.adoc

@@ -638,11 +638,11 @@ The Java client API for HBase has a number of changes that break both source and
 .Tracing implementation changes
 The backing implementation of HBase's tracing features was updated from Apache HTrace 3 to HTrace 4, which includes several breaking changes. While HTrace 3 and 4 can coexist in the same runtime, they will not integrate with each other, leading to disjoint trace information.
 
-The internal changes to HBase during this upgrade were sufficient for compilation, but it has not been confirmed that there are no regressions in tracing functionality. Please consider this feature expiremental for the immediate future.
+The internal changes to HBase during this upgrade were sufficient for compilation, but it has not been confirmed that there are no regressions in tracing functionality. Please consider this feature experimental for the immediate future.
 
 If you previously relied on client side tracing integrated with HBase operations, it is recommended that you upgrade your usage to HTrace 4 as well.
 
-After the Apache HTrace project moved to the Attic/retired, the traces in HBase are left broken and unmaintained since HBase 2.0. A new project link:https://issues.apache.org/jira/browse/HBASE-22120[HBASE-22120] will replace HTrace with OpenTracing.
+After the Apache HTrace project moved to the Attic/retired, the traces in HBase are left broken and unmaintained since HBase 2.0. A new project link:https://issues.apache.org/jira/browse/HBASE-22120[HBASE-22120] will replace HTrace with OpenTelemetry. It will be shipped in 3.0.0 release. Please see the reference guide section <<tracing>> for more details.
 
 [[upgrade2.0.hfile.compatability]]
 .HFile lose forward compatability

src/main/asciidoc/book.adoc

@@ -88,6 +88,7 @@ include::_chapters/amv2.adoc[]
 include::_chapters/zookeeper.adoc[]
 include::_chapters/community.adoc[]
 include::_chapters/hbtop.adoc[]
+include::_chapters/tracing.adoc[]
 
 = Appendix