Remote Access to a Midas experiment: Difference between revisions

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mserver provides remote access to any MIDAS client. It is needed when one or more of the MIDAS clients for an experiment are running on a different host. In this case, an mserver client must be started on the host where the experiment resides.
{{Pagelinks}}


For example, if there is no mserver client is running on host dasdevpc2, then an attempt to run a client on dasdevpc2 from a remote computer (isdaq01) will result in an error message:
As Midas supports remote [[Frontend Operation|frontend(s)]], the method to connect the frontend to the backend is through a daemon '''[[mserver]]''' providing the necessary interface at the backend computer for accepting the frontend connection. This client requesting connection to a particular Midas experiment, will have to provide arguments such as:
* The backend node name to which it wants to connect
* The name of the Midas experiment to connect
* The port through which it wants to connect (optional)


[bnmr@isdaq01 ~/online]$ odb -e t2kgas -h dasdevpc2
Cannot connect to remote host
Undesired nodes can be prevented from connecting to the backend by using the -a argument of the Midas server ('''[[mserver|mserver]]'''). This can provide mserver with a list of clients nodes allowed to connect to any experiment on this backend node.
If an mserver client is now started on host dasdevpc2,


[suz@dasdevpc2 ~]$ mserver -D
[[Category:Experiment]] [[Category:Frontend]]
mserver started interactively
Becoming a daemon...
Now one can connect to the remote experiment :
 
[bnmr@isdaq01 ~/online]$ odb -e t2kgas -h dasdevpc2
[dasdevpc2:t2kgas:S]/>quit
The mserver utility usually runs in the background and doesn't need to be modified. In the case where debugging is required, the mserver can be started with the -d flag which will write an entry for each transaction to a log file /tmp/mserver.log . The log entry contains the time stamp and RPC call request.
More than one mserver can be started on a system, provided they use different tcp ports. This is useful if, for example, different versions of MIDAS are in use on a single host at the same time. To start a version of mserver on a different port, use the -p argument, e.g. mserver -p XXXX -D
To connect a client to this version of mserver, use the format "hostname:port", e.g.
 
  fe_test -h lin08:7066 -e expt
 
mserver arguments
 
Arguments
[-h ] : help
[-s ] : Single process server
[-t ] : Multi thread server
[-m ] : Multi process server (default)
[-p ] : Port number; listen for connections on non-default tcp port
[-d ] : Write debug info to /tmp/mserver.log
[-D ] : Become a Daemon

Latest revision as of 14:03, 8 July 2015


As Midas supports remote frontend(s), the method to connect the frontend to the backend is through a daemon mserver providing the necessary interface at the backend computer for accepting the frontend connection. This client requesting connection to a particular Midas experiment, will have to provide arguments such as:

  • The backend node name to which it wants to connect
  • The name of the Midas experiment to connect
  • The port through which it wants to connect (optional)


Undesired nodes can be prevented from connecting to the backend by using the -a argument of the Midas server (mserver). This can provide mserver with a list of clients nodes allowed to connect to any experiment on this backend node.

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