Question about the new Metrics stats interface

[freak82]

Hi there,

I'm developing an ATS plugin for our company and I need few statistic counters in the plugin.
According to this page, I should use the new APIs from Metrics.h for this purpose. Correct me if I misunderstood the Note.

I glanced over the functionality in the Metrics.h and checked its usage inside the ATS core. I think, I understood how to use it.

// define the counter
ts::Metrics::Counter::AtomicType *counter_name;
...
// create/register the counter
counter_name = ts::Metrics::Counter::createPtr("the-name-of-the-counter");
...
// use the counter
ts::Metrics::Counter::increment(counter_name);

However, I'm wondering about the future binary compatibility.
So far, all of the other APIs are C functions and opaque types/pointers to hide the actual implementation.
However, this new functionality exposes lots of implementation details in the header file along with the Metrics data member.
Now if I use this functionality and for example:

• my plugin is built against ATS version 10
• ATS version 12 introduces some changes in the Metrics functionality which change the implementation of some of the inline functions and/or the data members of Metrics.
  It seems to me, that In the above scenario the plugin may experience some UB (Undefined Behavior) effects if run along ATS version 12.

Did I misunderstood something?
Or there is no guarantee for binary compatibility between the ATS versions and I should always rebuild the plugins against the currently used ATS version?

[bryancall]

We require rebuilding plugins for new major version releases of ATS.

[zwoop]

The common use case, using these APIs rather than the old APIs in ts.h (which also uses the new Metrics under the hood) would be

auto  id1  = ts::Metrics::Counter::create(name);
auto  id2  = ts::Metrics::Gauge::create(name);

If you want the pointer, you can get it from the id, e.g.

auto ptr1 = ts::Metrics::Counter::lookup(id1, nullptr);
auto ptr2 = ts::Metrics::Gauge::lookup(id2, nullptr);

or, you can also create them directly with createPtr() as above, e.g.

auto  ptr1 = ts::Metrics::Counter::createPtr(name);
auto  ptr2 = ts::Metrics::Gauge::createPtr(name);

Note that the lookup() functionalities requires locking around the lookup tables etc., so are not a good idea to do in critical code. The ID can be used to access the metric directly though, without locks, such as

static auto &instance = ts::Metrics::instance();

instance[id1].increment();
instance[id2].decrement(5);

[freak82]

Thank you all for the clarifications.