`connectionsList, err := net.ConnectionsMax("tcp4", 1000)`
when you run net.ConnectionsMax,you will find some proc is not equal with the `netstat -lptn`
The order of init function execution is dependant on the order that the
source files are passed to the compiler. This causes issues when
building under other build systems, such as bazel or buck, as they are
not guarenteed to maintain the same file order as the default go tool.
The /proc/net files are not guaranteed to be consistent, they are only
consitent on the row level. This is probably one of the reasons why
consequent read calls might return duplicate entries - the kernel is
changing the file as it is being read. In certain situations this might
lead to loop like situations - the same net entry is being returned when
reading the file as new connections are added to the kernel tcp table, i.e
there can be a lot of duplications.
This commit is trying to reduce the duplications, by fetching the contents
of the net files with a single read syscall.
Instead of encoding a JSON string of each connection (non-trivial at high
connection volumes) we can use the connTmp struct for map look-ups if we
eliminate the unused `uids` field.
Also switches to using the empty struct instead of bool for zero memory
overhead.
The goal is to improve performance of connection fetching connections across
all processes when some processes can have several hundred or thousands of file
descriptors. Right now when you have many thousands of fds the process spends
lots of time inside the syscalls from Readdir and Readlink.
The public API works as before with two new functions:
- `ConnectionsMax`
- `ConnectionsPidMax`
Each function takes an additional int argument that sets the max number of fds
read per process.
addresses a few things:
- Windows has a concept of both a network "interface" and an "adapter"
- These are almost always a one-to-one relationship, though there can be
esoteric instances where they are not.
- I believe the gopsutil NetIOCounters function should only return on a
per-interface level, since this is the behavior on linux/darwin.
Previously, the plugin was basically ignoring the actual interfaces
returned from net.Interfaces(). Instead, it was looping over the net
adapters for each interface, somewhat uselessly.
FWIW, the code for getAdapterList() doesn't exist in the Go standard lib
anymore.
closes#245
Snow Fox