Sravani Revuri created HDDS-17581:
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Summary: Tracing common span helpers
Key: HDDS-17581
URL: https://issues.apache.org/jira/browse/HDDS-17581
Project: Apache Ozone
Issue Type: Sub-task
Reporter: Sravani Revuri
Assignee: rajesh
h3. Why
This is the first, common-only step of adding OpenTelemetry tracing to OM (and
later SCM and datanodes). Upcoming PRs will:
* create OM components as tracing proxies through their interfaces, such as
the request handler, client requests, the key, volume and bucket managers, and
the authorizer;
* add attributes, events and error status from inside request handling.
For that we need a few things that {{hdds-common}} doesn't have yet:
* proxies that work at startup;
* proxies whose span kind matches what the delegate does: INTERNAL for
in-process components, CLIENT for RPC clients;
* exceptions recorded in a standard way;
* small null-safe helpers for the current span;
* a test helper to assert on collected spans.
This PR adds only these building blocks. It doesn't add new spans to any
service.
h3. What
*Span helpers in {{{}TracingUtil{}}}:*
* {{createSpan(name)}} and {{createSpan(name, SpanKind)}} create a span that
is a child of the current span.
* {{recordException(span, t)}} and {{recordExceptionInCurrentSpan(t)}} record
the exception event and set the ERROR status, using the exception message as
the description.
* {{addAttributesToCurrentSpan(key, String|long|boolean)}} and
{{addEventToCurrentSpan(name, key, value)}} do nothing when there is no
recording span, and skip null values.
* New {{SpanAttributeKeys}} holds the shared attribute keys, starting with
{{{}ozone.status{}}}.
*Tracing proxies:*
* {{TraceAllMethod}} takes a {{{}SpanKind{}}}. {{@InternalSpanKind}} can now
go on a whole delegate class as well as on a method.
* Exceptions thrown by the delegate are recorded on the proxy span. Methods
missing from the delegate, and {{@SkipTracing}} methods, are called directly
instead of throwing {{{}NoSuchMethodException{}}}.
* {{createProxy(delegate, itf, conf)}} now creates INTERNAL spans. The new
{{createClientProxy(delegate, itf, conf)}} creates CLIENT spans. The existing
RPC client proxies switch to {{{}createClientProxy{}}}, so their span kind
stays CLIENT:
** the SCM block, container location, security and secret key clients, in
{{HAUtils}} and {{{}HddsServerUtil{}}};
** the OM client in {{{}RpcClient{}}}.
* New {{createProxy(delegate, itf, spanPrefix, spanKind)}} names spans
{{{}<spanPrefix>.<method>{}}}, for example {{{}KeyManagerImpl.listStatus{}}}.
It doesn't need a current span, so it can wrap objects created at service
startup when application-aware tracing is on.
*Error recording on existing spans:*
* {{executeInSpan}} and {{OzoneProtocolMessageDispatcher#processRequest}} now
use {{{}recordException{}}}. Failed spans carry the exception event and the
error message, not only the ERROR status.
*Tests:*
* New {{TestSpanCollector}} installs an in-memory span processor and has
assertion helpers.
* New tests in {{{}TestTracingUtil{}}}, {{{}TestTraceAllMethod{}}},
{{{}TestTracingAnnotations{}}}, {{TestTracingInitModes}} and
{{{}TestOzoneProtocolMessageDispatcher{}}}.
* The test tracer providers get a span processor. With OpenTelemetry 1.67, an
{{SdkTracerProvider}} without a processor returns no-op spans.
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