On Tuesday 16 March 2010 01:34:52 Andrey Semashev wrote:
On 03/15/2010 11:47 PM, Steven Watanabe wrote:
AMDG
Vladimir Prus wrote:
There's another thing about component/severity logging that I have apparently forgot about -- filtering. It is surely necessary to change filtered components dynamically -- either while the application is running, or between runs, therefore lambda expression that compares to a fixed string will not be enough -- we need a lookup in a map. It's not obvious to me how to form a lambda expression to do a lookup in a map using the library, e.g. something like:
enabled_components.count(attr<string>("Component"))
So I wonder:
1. What is the actual syntax to do this inside lambda expression.
There is no simple syntax for it. (The lambda functionality is rather crippled compared to a real lambda library.) You could probably do it with boost::bind and the satisfies function. Also, this by itself would be dangerous, since filters need to be thread safe.
In my view, the filter should be replaced on update. You can have the map of components or whatever, and the filter pointing to them. On update you create a new map and a new filter, and set it to the core/sinks. No additional locking required, no special syntax, everything's safe and clean. Same goes for formatters.
What about performance? If I have 100 components, copying map on each update seems not too good. Locking is probably better. - Volodya