On Fri, Sep 16, 2016 at 4:51 PM, Alan Griffiths <alan.griffi...@canonical.com> wrote:
On 16/09/16 02:51, Christopher James Halse Rogers wrote:
On Thu, Sep 15, 2016 at 12:11 PM, Daniel van Vugt <daniel.van.v...@canonical.com> wrote:
So actually... I now think it's OK providing the base class is named *Observer. And only some implementations would be called *Report.

I would also be happy with this; various components take an Observer (which provides a register-interested-party API), and Reports register themselves as interested parties.

1. the user of the "Report" interface is the core code - which is simply reporting something. The code reads "report->xxx()" which is clear.
2. we've had this name for years, without considering it a problem.

3. Some implementations of "Report" log, some don't - which is the behaviour that was originally intended (and what we all want).

4. I *think* the current issue is simply that we want to add support for multiple reports/observers so that code using Mir can get notifications without disabling the supplied logging/lttng options. We have existing generic "observer" code that can be used to composite reports.

In short, I agree that "Reports" are taking the "Observer" role from the pattern language, but I think the more specific name is good here and I don't follow why folks want the pain of a rename.

So, I think what's happening here is:

For some subset (including me) of the Mir team, the term “Report” has a bunch of implicit semantics, including
*) This is optional, for post-hoc human-based debugging only
*) This is *purely* observational; it might log in any number of ways, but the *only* state it's going to change is the state of some logging system. *) The calls are approximately equal to printf; relatively cheap and simple.

Which is why (1) and (2) are problematic - we *do* think that the meaning of report->xxx() is clear, and isn't a problem, but we think it means something significantly different to what you do.


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