[MonetDB-users] Introducing the Merovingian: a MonetDB 5 database keeper
Hi all,
I'd like to bring a little program to your attention that may or may not be useful to you: merovingian.
Merovingian is meant as end-user program to start and stop one or more MonetDB databases. The program allows itself to be naturally used into start and stop scripts, as well as manual use from the console. It is aimed at MonetDB5/SQL users.
In short, merovingian performs two basic tasks: 1. handle connections from clients and redirect those connections to the appropriate mserver process, and 2. start an mserver process in case it is not running (any more). Currently, an appropriate mserver process is defined by the database a client requests for. Since each mserver process only serves one database, multiple mserver processes are necessary to deal with multiple databases. Because merovingian can start mserver processes on demand, it has the potential to (attempt to) restart an mserver after it has crashed.
Since merovingian will (currently only) start mserver processes, output of those processes might get confusing, especially when multiple servers are started. Also, interacting with them is non-trivial. For this reason, merovingian starts mserver processes as daemon processes in the background and catches their outputs to display it in a log-like fashion. Distinction is made between messages and errors. Not surprisingly both outputs can be written to a logfile on disk or just outputted to the console. An example output on the console would look like this:
% merovingian demo MSG merovingian[30160]: Merovingian 0.3 starting ... MSG mserver5[30162]: executing 'bin/mserver5' for database 'demo' MSG merovingian[30160]: monitoring dbfarm var/MonetDB5/dbfarm MSG merovingian[30160]: listening for connections on pegasus.ins.cwi.nl:50000 MSG merovingian[30160]: starting database 'demo' ERR mserver5[30162]: #warning: please don't forget to set your vault key! ERR mserver5[30162]: #(see etc/monetdb5.conf) MSG mserver5[30162]: # MonetDB server v5.1.0, based on kernel v1.19.0 MSG mserver5[30162]: # Serving database 'demo' MSG mserver5[30162]: # Compiled for x86_64-pc-linux-gnu/64bit with 64bit OIDs dynamically linked MSG mserver5[30162]: # Copyright (c) 1993-2007 CWI, all rights reserved MSG mserver5[30162]: # Visit http://monetdb.cwi.nl/ for further information MSG mserver5[30162]: # Listening for connection requests on mapi:monetdb://127.0.0.1:50001/
In this example merovingian was requested to start database demo upfront, without waiting for a client to ask for it. Without the demo argument, merovingian waits for connections that ask for a database and starts it at that time. An arbitrary number of databases can be given as "pre-start" arguments. Pre-starting databases can be important when clients are used that do not request for a specific database. In such case, the client is redirected to the first database that is running at that moment.
Please look at the Merovingian section in the etc/monetdb5.conf file for more options for merovingian. The section is still small, but it might grow.
Merovingian is available in the development branch (CVS head) of the MonetDB5 repository. Feedback is welcome.
Are you presenting something similar to the famous Mgardian (I do not know if this is the correct name, but at least I know it starts with a "M").
Regards, Romulo
Hi all,
I'd like to bring a little program to your attention that may or may not be useful to you: merovingian.
Merovingian is meant as end-user program to start and stop one or more MonetDB databases. The program allows itself to be naturally used into start and stop scripts, as well as manual use from the console. It is aimed at MonetDB5/SQL users.
In short, merovingian performs two basic tasks:
- handle connections from clients and redirect those connections to the appropriate mserver process, and
- start an mserver process in case it is not running (any more).
Currently, an appropriate mserver process is defined by the database a client requests for. Since each mserver process only serves one database, multiple mserver processes are necessary to deal with multiple databases. Because merovingian can start mserver processes on demand, it has the potential to (attempt to) restart an mserver after it has crashed.
Since merovingian will (currently only) start mserver processes, output of those processes might get confusing, especially when multiple servers are started. Also, interacting with them is non-trivial. For this reason, merovingian starts mserver processes as daemon processes in the background and catches their outputs to display it in a log-like fashion. Distinction is made between messages and errors. Not surprisingly both outputs can be written to a logfile on disk or just outputted to the console. An example output on the console would look like this:
% merovingian demo MSG merovingian[30160]: Merovingian 0.3 starting ... MSG mserver5[30162]: executing 'bin/mserver5' for database 'demo' MSG merovingian[30160]: monitoring dbfarm var/MonetDB5/dbfarm MSG merovingian[30160]: listening for connections on pegasus.ins.cwi.nl:50000 MSG merovingian[30160]: starting database 'demo' ERR mserver5[30162]: #warning: please don't forget to set your vault key! ERR mserver5[30162]: #(see etc/monetdb5.conf) MSG mserver5[30162]: # MonetDB server v5.1.0, based on kernel v1.19.0 MSG mserver5[30162]: # Serving database 'demo' MSG mserver5[30162]: # Compiled for x86_64-pc-linux-gnu/64bit with 64bit OIDs dynamically linked MSG mserver5[30162]: # Copyright (c) 1993-2007 CWI, all rights reserved MSG mserver5[30162]: # Visit http://monetdb.cwi.nl/ for further information MSG mserver5[30162]: # Listening for connection requests on mapi:monetdb://127.0.0.1:50001/
In this example merovingian was requested to start database demo upfront, without waiting for a client to ask for it. Without the demo argument, merovingian waits for connections that ask for a database and starts it at that time. An arbitrary number of databases can be given as "pre-start" arguments. Pre-starting databases can be important when clients are used that do not request for a specific database. In such case, the client is redirected to the first database that is running at that moment.
Please look at the Merovingian section in the etc/monetdb5.conf file for more options for merovingian. The section is still small, but it might grow.
Merovingian is available in the development branch (CVS head) of the MonetDB5 repository. Feedback is welcome.
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On 21-07-2007 22:17:37 +0200, R.A.Goncalves@cwi.nl wrote:
Are you presenting something similar to the famous Mgardian (I do not know if this is the correct name, but at least I know it starts with a "M").
AFAICT the Mguardian has never been (properly) implemented. You can see Merovingian as an implementation of part of the ideas behind Mguardian.
Fabian Groffen wrote:
On 21-07-2007 22:17:37 +0200, R.A.Goncalves@cwi.nl wrote:
Are you presenting something similar to the famous Mgardian (I do not know if this is the correct name, but at least I know it starts with a "M").
AFAICT the Mguardian has never been (properly) implemented. You can see Merovingian as an implementation of part of the ideas behind Mguardian.
yes. The Mguardian originally was intended to handle watching over resources, e.g. running out of disk space, fail-overs, and managing checkpoint/recoveries. In the light of our overall goal for self-management remove the abundance of tools and knobs to tune a DB for any user.
It would be nice if Mero 'hunts' for peers, forming a P2P network to reach any database.
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participants (3)
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Fabian Groffen -
Martin Kersten -
R.A.Goncalves＠cwi.nl