[Gluster-devel] Glusterd daemon management code refactoring

[Anders Blomdell]

On 2014-12-09 16:23, Anders Blomdell wrote:
> On 2014-12-09 13:18, Krishnan Parthasarathi wrote:
>> All,
>>
>> I would like to propose refactoring of the code managing
>> various daemons in glusterd. Unlike other high(er) level proposals
>> about feature design, this one is at the implementation
>> level. Please go through the details of the proposal below
>> and share your thoughts/suggestions on the approach.
>>
>> ### Introduction
>>
>> Glusterd manages GlusterFS daemons providing services like NFS, Proactive
>> self-heal, Quota, User servicable snapshots etc. Following are some of the
>> aspects that come under daemon management.
>>
>> - Connection Management
>>   - unix domain sockets based channel for internal communication
>>   - Methods - connect, disconnect, notify
>>
>> - Process Management
>>   - pidfile to detect if the daemon is running
>>   - Environment; run-dir, svc-dir, log-dir etc.
>>   - Methods - start, stop, status, kill
>>
>> - Daemon-specific Management
>>
>> Currently, the daemon management code is fragmented and doesn't elicit the
>> structure described above. This results in further fragmentation since new
>> developers may not identify common patterns, worse even, they won't be able to
>> do anything about it.
>>
>> This proposal aims to do the following,
>>
>> - Provide an abstract data type that encapsulates what is common among daemons
>>   that are managed by glusterd.
>>
>> - 'Port' existing code to make use of the abstract type. This would help in
>>   making this change self-documented to an extent.
>>
>> - Prescribe a way to maintain per-feature daemon code separate to glusterd's
>>   common code.
>>
>> ### Abstract data types
>>
>>         struct conn_mgmt {
>>             struct rpc_clnt *rpc;
>>             int (*connect) (struct conn_mgmt *self);
>>             int (*disconnect) (struct conn_mgmt self);
>>             int (*notify) (struct conn_mgmt *self, rpc_clnt_event_t *rpc_event);
>>         }
> Great, one place to fix IPv6/IPv4 coexistence :-)
Just for cross referencing:

https://bugzilla.redhat.com/show_bug.cgi?id=1117886

> 
>>
>>         struct proc_mgmt {
>>             char svcdir[PATH_MAX];
>>             char rundir[PATH_MAX];
>>             char logdir[PATH_MAX];
>>             char pidfile[PATH_MAX];
>>             char logfile[PATH_MAX];
>>
>>             char volid[UUID_CANONICAL_FORM_LEN];
>>
>>             int (*start) (struct proc_mgmt *self, int flags);
>>             int (*stop) (struct proc_mgmt *self, int flags);
>>             int (*is_running) (struct proc_mgmt *self);
>>             int (*kill) (struct proc_mgmt *self, int flags);
>>
>>         }
>>
>> Feature authors can define data type representing their service by implementing
>> the above 'abstract' class. For e.g,
>>
>>         struct my_service {
>>             char name[PATH_MAX];
>>             /* my_service specific data members and methods */
>>
>>             /* The methods in the following structures should be implemented by
>>                respective feature authors */
>>
>>             struct conn_mgmt conn;
>>             struct proc_mgmt proc;
>>         }
>>
>> ### Code structure guidelines
>>
>> Each feature that introduces a daemon would implement the abstract data type.
>> The implementations should be in separate files named appropriately. The intent
>> is to avoid feature specific code to leak into common glusterd codebase.
>> glusterd-utils.c is testament to such practices in the past.
>>
>> For e.g,
>> [kp at trantor glusterd]$ tree
>> .
>> └── src
>>     ├── glusterd-conn-mgmt.c
>>     ├── glusterd-conn-mgmt.h
>>     ├── glusterd-proc-mgmt.c
>>     ├── glusterd-proc-mgmt.h
>>     ├── my-feature-service.c
>>     └── my-feature-service.h
>>
>> [kp at trantor glusterd]$ cat src/my-feature-service.h
>>         #include "glusterd-conn-mgmt.h"
>>         #include "glusterd-proc-mgmt.h"
>>
>> ...
>> [rest of the code elided]
>>
>> ### Bibliography
>>
>> - Object-oriented design patterns in the kernel, part 1 - http://lwn.net/Articles/444910/
>> - Object-oriented design patterns in the kernel, part 2 - http://lwn.net/Articles/446317/
>>
>>
>> thanks,
>> kp
>> _______________________________________________
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>> Gluster-devel at gluster.org
>> http://supercolony.gluster.org/mailman/listinfo/gluster-devel
>>
> 
> /Anders
> 


-- 
Anders Blomdell                  Email: anders.blomdell at control.lth.se
Department of Automatic Control
Lund University                  Phone:    +46 46 222 4625
P.O. Box 118                     Fax:      +46 46 138118
SE-221 00 Lund, Sweden