bzp2010 commented on code in PR #12383:
URL: https://github.com/apache/apisix/pull/12383#discussion_r2222320862
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apisix/plugins/prometheus/exporter.lua:
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@@ -310,39 +309,50 @@ function _M.stream_log(conf, ctx)
end
-local ngx_status_items = {"active", "accepted", "handled", "total",
- "reading", "writing", "waiting"}
+-- FFI definitions for nginx connection status
+-- Based on
https://github.com/nginx/nginx/blob/master/src/event/ngx_event.c#L61-L78
+ffi.cdef[[
+ typedef uint64_t ngx_atomic_uint_t;
+ extern ngx_atomic_uint_t *ngx_stat_accepted;
+ extern ngx_atomic_uint_t *ngx_stat_handled;
+ extern ngx_atomic_uint_t *ngx_stat_requests;
+ extern ngx_atomic_uint_t *ngx_stat_active;
+ extern ngx_atomic_uint_t *ngx_stat_reading;
+ extern ngx_atomic_uint_t *ngx_stat_writing;
+ extern ngx_atomic_uint_t *ngx_stat_waiting;
+]]
+
local label_values = {}
+-- Mapping of status names to FFI global variables and metrics
+local status_mapping = {
+ {name = "active", var = "ngx_stat_active"},
+ {name = "accepted", var = "ngx_stat_accepted"},
+ {name = "handled", var = "ngx_stat_handled"},
+ {name = "total", var = "ngx_stat_requests"},
+ {name = "reading", var = "ngx_stat_reading"},
+ {name = "writing", var = "ngx_stat_writing"},
+ {name = "waiting", var = "ngx_stat_waiting"},
+}
+
+-- Use FFI to get nginx status directly from global variables
local function nginx_status()
Review Comment:
@membphis
Actually, I recommend using these FFI API for data acquisition.
I confirmed from the nginx code that this data is synchronized between
workers by shared memory, so FFI API can access them.
And this mechanism is entirely LuaJIT, not nginx fake request or openresty
cosocket.
The former doesn't introduce any noise.
And when using any of the latter, no matter which one, the fetching behavior
itself causes accepted/active/handled/reading/waiting/writing metrics to
increase. waiting/writing. This is due to the fact that these mechanisms are
always requesting APIs as network sockets, and they themselves cause the
metrics to go up. This has always been a problem, and while I can understand it
and it doesn't cause serious problems, it's always been confusing.
I came up with this idea and @SkyeYoung did it independently after some
simple research, which I'm sure is not a difficult task for developers with
almost any AI LLM assistance.
These c-variables haven't changed in years, and I don't think it's going to
change nearly as much in the future (there's no need), so it's not really an
area that needs constant attention. If any future openresty/nginx breaks this
convention, our test cases can find them.
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