Upgrade to Tomcat 7.0.50, working around the potential
NullPointerException by also adding dependencies to
tomcat-embedded-jasper (which is now also required for Hibernate
Validator 5.0, see commit 377953babd)
Fixes gh-245
Instead of adding active prpfiles for every one we encounter, we need to
build up a complete "default" Environment and then ask it what the active
profiles are. Implemented in ConfigFileApplicationListener.
Fixes gh-198
Main user-facing interface is still Counter/GaugeService but the
back end behind that has more options. The Default*Services write
metrics to a MetricWriter and there are some variants of that, and
also variants of MetricReader (basic read-only actions).
MetricRepository is now a combination of MetricReader, MetricWriter
and some more methods that make it a bit more repository like.
There is also a MultiMetricReader and a MultiMetricRepository for
the common case where metrics are stored in related (often open
ended) groups. Examples would be complex metrics like histograms
and "rich" metrics with averages and statistics attached (which
are both closed) and "field counters" which count the occurrences
of values of a particular named field or slot in an incoming message
(e.g. counting Twitter hastags, open ended).
In memory and redis implementations are provided for the repositories.
Generally speaking the in memory repository should be used as a
local buffer and then scheduled "exports" can be executed to copy
metric values accross to a remote repository for aggregation.
There is an Exporter interface to support this and a few implementations
dealing with different strategies for storing the results (singly or
grouped).
Codahale metrics are also supported through the MetricWriter interface.
Currently implemented through a naming convention (since Codahale has
a fixed object model this makes sense): metrics beginning with "histogram"
are Histograms, "timer" for Timers, "meter" for Meters etc.
Support for message driven metric consumption and production are provided
through a MetricWriterMessageHandler and a MessageChannelMetricWriter.
No support yet for pagination in the repositories, or for HATEOAS style
HTTP endpoints.
We get more control over the handling and in particular the registration
of the endpoint this way. It was practically impossible to disable the
AgentServlet bean when in a parent context of the management server
because of lifecyce issues - you don't know that the user wants a
separate management server until too late.
This approach also makes it possible to test with spring-test MVC
support.
Phillip Webb
Dave Syer
Rob Winch
Christian Dupuis