Zombie telnet process pile up while using spawn with Expect - linux

Question

I intend to make a telnet connection with a network device using Expect, and it involves sending commands to the device multiple times and also rebooting the device as well. I thereby need to make the telnet connection again and again.
proc dputs {msg} {
if {[info exists ::debug] && $::debug} {
puts $msg
}
}
proc open_telnet_session {} {
set sResult FAIL
set prompt "(\r|\n|\r\n).*?(#|%|>|\\\$) $"
#set prompt "#|%|>|\\\$ $"
set timeout 60
if {$::tcl_platform(platform) eq "windows"} {
spawn {c:\Dinesh\telnet_32bit.exe} $::device_ip
} else {
spawn telnet $::device_ip
}
set ::device_ip $spawn_id
expect {
timeout {puts "Timeout happened while spawning telnet session";return $sResult}
eof {puts "EOF happened while spawning telnet session";return $sResult}
"login: $" {send "$::device_uname\r";exp_continue}
"password: $" {send "$::device_pwd\r";exp_continue}
-re $prompt
}
set sResult PASS
return $sResult
}
proc send_cmd_to_device {cmd} {
set timeout 180
dputs "cmd : $cmd"
set sResult FAIL
set prompt "(\r|\n|\r\n).*?(#|%|>|\\\$) $"
set ::spawn_id $::device_ip
if {[catch {send "$cmd\r"} errorMsg]} {
puts "Failed to send the commands..."
puts "Reason : $errorMsg"
return $sResult
}
expect {
timeout {puts "Timeout happened while sending commands to telnet session";return 0}
eof {puts "EOF happened while sending commands to telnet session";return 1}
"invalid token" {puts "Invalid token error from device";exp_continue}
"$cmd" { dputs "\n\n matching the cmd\n\n";set ::actual_cmd_match 1;exp_continue}
-re $prompt {
if {$::actual_cmd_match} {
dputs "\n\n final prompt match \n\n"
set ::actual_cmd_match 0
set sResult PASS
} else {
dputs "\n\n still waiting for prompt match \n\n"
exp_continue
}
}
}
return $sResult
}
proc close_telnet_session {} {
set sResult FAIL
set ::spawn_id $::device_ip
#This will send 'Ctrl+]' to close the telnet connection gracefully
if {[catch {send "\x1d"} errorMsg]} {
puts "Failed to send the commands..."
puts "Reason : $errorMsg"
return $sResult
}
expect {
timeout {return $sResult}
eof {return $sResult}
-nocase "telnet>"
}
if {[catch {send "quit\r"}]} {
puts "Failed to send the commands..."
puts "Reason : $errorMsg"
return $sResult
}
expect {
timeout {return $sResult}
eof {set sResult PASS}
}
return $sResult
}
Even though I am closing the connection gracefully, I can still see the process running in the task manager (in Windows 7). (Same case with Linux as well, telnet process shows up as <defunct> process).
If I run the script overnight and say I have to open the telnet connection about thousands of time (as my script involves rebooting the device multiple times and thus the management connection will be lost), it will end up reducing the performance.
This will lead to memory leak or failure in resource allocation when this happens continuously.
After searching a lot, I end up with exp_close and exp_wait.
# Killing the process in Windows...
exec taskkill /pid $telnet_process_id
exp_close -i $::device_id
exp_wait -i $::device_id; # This becomes a blocking call..
With the above code, exp_wait is keep on waiting and it is getting blocked in there.
To avoid the same, I have used -nowait flag as well, but still no use. It is returning immediately and the process still stays in the process chart.
What should be the optimal way to handle this issue?

Answer 1

In my experience, spawned process connections are usually terminated with a call to close. Is expect on windows different than expect on *nix in that regard?