I'm trying to do basically this in Go:
netstat -an | grep 2375 -c
I need to count the number of connections to the Docker daemon in my regression test for a connection leak bug. However, because I run this in multiple places in different OS (local dev box, CI, etc), I cannot rely on the "netstat" tool, so I wonder how can I do this in a more programmatic way in Go?
I looked around the net package and could not find anything that would help. There are some libraries that basically replace netstat:
https://github.com/drael/GOnetstat
https://github.com/dominikh/netstat-nat
But they are not cross-platform compliant (Mac and *nix). Any idea how can I achieve this?
In linux this info is exposed in the /proc filesystem.
Use os.Getpid and query the info in /proc/<pid>/fd. Most likely a simple count is good here, if you need more see the proc man page.
Cross platform compatibility for this kind of thing is going to be roll your own, as the ways of identifying open fd's for a process are very per platform. If you simply need to compile, and pass some tests for this on non linux platforms you can use Go's per platform support to make this a no-op on other platforms, or implement an appropriate solution.
Related
I am trying to do an assignment (from another univ's coursepage) which has a line in the starter code (Python with mininet) as
os.system("rmmod tcp_probe; modprobe tcp_probe full=1")
Popen("cat /proc/net/tcpprobe > %s" % (outfile), shell=True)
which gives an error saying that tcp_probe has been disabled.
I found out by googling that tcp_probe has been deprecated in the linux kernel. However it just asks me to 'do the same using ftrace'. I have tried searching online but could not find out how to use ftrace to achieve the same.
Any help is appreciated.
tldr;
Unfortunately, I could not find any way to get TCP tracepoints to work in Mininet, which is what ftrace would uses. The reason for this is that the mininet's /sys/kern/debug directory is empty, i.e., tracing cannot be enabled.
Options:
1. Using mininet-tracing (not recommended)
There probably is a way to get the kernel to include this, or you could use https://github.com/mininet/mininet-tracing which might get you what you need, but I have seen reports that it is slow, and has been updated 9 years ago...
2. Writing a new kernel module (I have tested this and it works)
What I found as a solution instead, was to force printing for the TCP I had in mind and then take a look at the results that way. In order to enable this, you would essentially need to extend some of TCP's behaviour and (quite possibly) reuse the TCP module you have in mind. And create a new kernel module.
Here I have provided an example that you can use. It logs socket information on each ACK. I also included a Makefile and a script to load/unload the kernel module. After you enable the module and let some traffic flow (assuming you are on a debian-based linux) you should be able to find the logs of your TCP in /var/log/kern.log.
Note:
This is a hacky way around the issue, but was good enough for my needs, and hopefully can help someone else too.
So I have a moderately complex set of requirements for my worker processes.
I want to use a the master slave topology, and a nondefault working directory.
I also want to mix both local and remote workers.
As far as I can tell from readying the --machine-file section of the documentation.
It will not let me do that.
So I am looking at the -L <file parameter
>julia -h
...
-L, --load Load immediately on all processors
...
So if I do not use the -p or --machine-file` flags, then there is initially only one processer so the all processors just mean on the only processor.
So I tried this out
start_workers.jl
addprocs([
("cluster_c4_1",:auto),
("cluster_c4_2",:auto)
],
dir="/mnt/",
topology=:master_slave
)
addprocs(
dir="/mnt/",
topology=:master_slave
)
test.jl
println("*************")
println(workers())
println("-------------")
Running it:
>julia -L start_workers.jl pl.jl
*************
[2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]
-------------
So it looks all good, got my 20 workers.
Have I done anything unreasonable? Is this the best way?
That's exactly how I'm deploying it on a HPC cluster under Torque scheduler. In fact I'm in the process of re-writing the the cluster manager to support more options when adding processes through the Torque scheduling systems in particular, so I've spent quite a bit of time looking into this.
You might also want to be aware there are various ClusterManagers, Pkg.add("ClusterManagers") that extend the ability of addprocs under a variety of environments, such as when you need to request the resources from a scheduler. It looks like passwordless ssh is possible for you, so the default cluster manager is sufficient in your case.
I don't believe there is any way of defining the extra topology and directory parameters on the command line, so your approach is correct.
Is that possible to achieve Inter process communication using any terminal or serial ports in AIX or Unix?
I would like to achieve this by using commands/scripting only where one process writes a string on terminal and another process reads same terminal and processes that string. I know that using pipe also this is possible but I do not have enough idea on that.
Also is there a way we can determine which all ports/terminals are available in AIX machine?
Or is it possible to create new terminal at run time (not the boot time) that will be used by only above two processes?
I think what you want are pty's? Or, another option would be unix domain sockets.
The answer to your first question is "no"... not really. When you write out to a tty, that output is sent out to the real device and not available to be read back.
The list of tty's on a system is: lsdev -Cctty
Creating tty's at run time is possible but not really what you want either. A tty is a child of a serial port and you can not add serial ports arbitrarily. They are real things. With AIX and Power systems, you can add devices while the system is up (hot swap) but that is getting (I'm assuming) way far off your original topic.
The basic different between a pty and a unix domain socket is a pty mimics the output and input process of a real tty in one direction. This is what telnet, rlogin, ssh, and many other daemons use when connections come in. It is easy to make ksh believe that it has a real tty by using pty's. If you don't need that, then they are added trouble that you don't need. Find a link on how to create and use a Unix domain socket and you will have what you need (or a pipe but a pipe requires a parent / child relationship which I assume you do not have).
As someone who is very new to the opensource PBX projects like Asterisk and FreeSWITCH, I am grappling with some information overload. Have read the basic FreeSWITCH docs on Wiki, but still have few questions. Since I am not very familiar with the terminology, I will try to use close approximations.
Trying to create a small/minimalistic build of FreeSWITCH, that needs to run on an rather old laptop (Celeron 1GHz, 512MB RAM, 20GB HDD, already running Debian "Wheezy"), and set it up as a 6-port GSM-SIP/Jabber gateway. So, by "small" and "minimalistic", I mean one which doesn't have modules/optional-software that is not absolutely necessary (e.g. no need for IVR announcements, or Skype integration) -- to keep memory footprint smallest, and occupy less hard-disk real-estate.
The rough idea is to have 6 GSM ports (via 'GSM-open module', similar to chan_dongle) towards public telephony network, and about 60 SIP extension, and support upto 6 calls involving GSM ports, and about 6 SIP-SIP calls (intra PBX), on this setup. I have read that the CPU overhead of GSMopen module is pretty low, so I am guessing this is possible.
Can someone confirm this to be a realistic goal?
What might be the minimum set of modules to select for minimalistic build?
For modules not chosen during initial build, can those be added later? If so, would it require me to rebuild FreeSWITCH completely, only the modules, or that everything would be built, but only configuration changes would be required to ensure that modules are loaded, and configure?
Is there any rough estimate of what might be the maximum call-rate that could be supported in such a configuration? For SIP-SIP calls? Given the underpowered processor, and little RAM (as per modern standards), I am guessing that both shall be bottlenecks, but adding RAM might still be possible (even if costly and difficult).
I have read that "hooks" can be created using Lua/Python/Java etc.. However if someone share share few examples of what-all is possible using such hooks, it would make the concept clearer. Can one hope to write an application like "missed call log" or "redirect on no answer" using these hooks?
Can someone confirm this to be a realistic goal?
Yes, this is quite realistic. You need to target as little as possible transcoding, because that's where CPU resources are needed. But even with a 1Ghz Celeron, 6 transcoded sessions seem quite realistic. But it needs testing :)
What might be the minimum set of modules to select for minimalistic build?
Just start with the default list of modules, and add gsmopen (I have no experience with gsm gateways, can't help with that part). The memory footprint is pretty low, and you may need some of those modules later.
For modules not chosen during initial build, can those be added later?
as far as I remember, Wiki describes this process. You edit modules.conf and make the specific module.
Is there any rough estimate of what might be the maximum call-rate that could be supported in such a configuration? For SIP-SIP calls? Given the underpowered processor, and little RAM (as per modern standards), I am guessing that both shall be bottlenecks, but adding RAM might still be possible (even if costly and difficult).
It really depends on complexity of your dialplan. Each context consists of a number of conditions, which are doing regexp match on channel variables. So, the more complex your dialplan is, the less CPS you get. But for a 6-channel gateway, I don't see this a problem. GSM network will be much slower than your box :)
I have read that "hooks" can be created using Lua/Python/Java etc.. However if someone share share few examples of what-all is possible using such hooks, it would make the concept clearer. Can one hope to write an application like "missed call log" or "redirect on no answer" using these hooks?
You can control every aspect of FreeSWITCH behavior with FreeSWITCH. There are even examples when the complete dialplan is re-implemented by an external program (Kazoo does that).
The simplest mode of operation is when your Lua/JS/Perl/Python script is launched from within the dialplan: then it receives a "session" object, and you can do whatever you want with the call: play sounds, bridge, forward, make a new call and bridge them together, and so on. Here in my blog there's a little practical example.
Then, you can build an external application which connects to the FS socket and monitors the events and performs actions on active calls.
Also, it can be done in the opposite direction: you run a server, and FS connects to it with its socket library.
Also, you can have an HTTP service which delivers pieces of XML configuration to FreeSWITCH, and it requests those on every call (this would be the most CPU-intensive application). This way, you can feed FS from some internal database, and build fault-tolerant systems.
I hope this helps :)
You can also find me in skype if needed.
FreeSWITCH is not really memory-hungry, and you can simply start with the default set of modules (the best is to use the prebuilt Debian packages). For example, on my 64bit machine, the FreeSWIITH process occupies only 35MB of memory.
freeswitch#vx03:~$ uname -a
Linux vx03 2.6.32-5-xen-amd64 #1 SMP Thu Nov 3 05:42:31 UTC 2011 x86_64 GNU/Linux
freeswitch#vx03:~$ ps -p 11873 v
PID TTY STAT TIME MAJFL TRS DRS RSS %MEM COMMAND
11873 ? S<l 10:29 0 0 258136 36852 2.3 /opt/freeswitch/bin/freeswitch -nc -rp -nonat -u freeswitch -g freeswitch
I will go through the rest of your questions later today
I am currently using pfiles to get the process occupying certain port in Solaris10,
but it causes problem when run parallely.
problem is pfiles can't be run parallely for the same pid.
the second one will return with error message.
pfiles: process is traced :
Is there any alternative to pfiles to get the process occupying a port in Solaris.
OR any information on OS API's to get port/process information on Solaris could help.
A workaround would be to use some lock mechanism to avoid this.
Alternatively, you might install lsof from a freeware repository and see if it supports concurrency (I think it does).
I just tested Solaris 11 Express pfiles and it doesn't seem to exhibit this issue.