[HTRACE-214] De-globalize Tracer.java

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0
• Fix Version/s: 4.0
• Component/s: api, core

Environment

release-notes: local-file-span-receiver.path configuration key changed to local.file.span.receiver.path for consistency
local-file-span-receiver.capacity configuration key changed to local.file.span.receiver.capacity for consistency
Default package for searching for SpanReceivers and Samplers was changed from org.apache.htrace.impl to org.apache.htrace.core.
TracerId is now configured with %

{tname}

and similar, instead of ${tname}
(to match the C client and make things easier when passing configuration through the shell.

• Target Version/s: 4.0
• Assignee: Colin McCabe
• Reporter: Colin McCabe
• Created: 17/Jul/15 04:05
• Updated: 14/Oct/15 01:01
• Resolved: 25/Aug/15 02:18

Description

De-globalize Tracer.java.

Currently, Tracer is a Singleton managed by TracerHolder. Instead, Tracer objects should be created by each process or library that needs to use HTrace. This enables a few things:

• When the Tracer object is created, we can give it a name. Then we can use this name in the "process id" of all spans created by that tracer, rather than trying to scrape the JVM name using "questionable" methods.

• SpanReceivers can be shared between multiple Tracer objects in the same process. The span receivers are reference counted. This should eliminate the "double tracing" issues we have had when tracing client libraries inside processes which also want tracing.

• Tracers can be closed by calling Tracer#close. If the Tracer being closed is the last tracer in the process, it will close all the span receivers.

• We will have a TracerFactory that takes care of the details of creating the right span receivers based on the configuration. This removes some boilerplate that is currently needed to enable HTrace in an application or library. We can also make SpanReceiverFactory package-private since it will no longer need to be publicly visible.

Issue Links

• relates to: HTRACE-230 Make TracerBuilder like all other Builders; an internal rather than adjacent class