readtcp
Prototype: readtcp(hostnameip, port, sendstring, maxbytes)
Return type: string
The return value is cached.
Description: Connects to tcp port
of hostnameip
, sends sendstring
,
reads at most maxbytes
from the response and returns those.
If the send string is empty, no data are sent or received from the socket. Then the function only tests whether the TCP port is alive and returns an empty string.
Not all Unix TCP read operations respond to signals for interruption, so
poorly formed requests can block the cf-agent
process. Always test TCP
connections fully before deploying.
Arguments:
host
:string
, in the range:.*
port
:string
, in the range:.*
sendstring
:string
, in the range:.*
maxbytes
:int
, in the range:0,99999999999
Example:
body common control
{
bundlesequence => { "example" };
}
bundle agent example
{
vars:
"my80" string => readtcp("myserver.com","80","GET /index.html HTTP/1.1$(const.r)$(const.n)Host: myserver.com$(const.r)$(const.n)$(const.r)$(const.n)",20);
classes:
"server_ok" expression => regcmp("[^\n]*200 OK.*\n.*","$(my80)");
reports:
server_ok::
"Server is alive";
!server_ok::
"Server is not responding - got $(my80)";
}
Output:
R: Server is alive
Notes: Note that on some systems the timeout mechanism does not seem to successfully interrupt the waiting system calls so this might hang if you send an incorrect query string. This should not happen, but the cause has yet to be diagnosed.