Subject Re: [firebird-support] Engine12 mistery
Author Ann Harrison
Post date 2016-06-15T18:19:39Z
The way I think of the Y-valve* is that the stem of the Y is the client -
whether the normal fbclient or the Java client or other language specific
clients.  The connection request goes from the client to a provider. 
Right now, the providers are Remote (which may be built into the Y-valve)
and Engine12.  Someone could create a provider that translated Firebird
requests to Oracle/PostgreSQL/MySQL or whatever and offer a provider
to a different back end.  If there's enough demand, Firebird 2.5 could be
cut back to be a provider to older versions of Firebird.

So the stem is the client and the branches are the providers.

Cheers,

Ann

* Y-valve is a nautical term.  On a boat, the head (toilet) outflow goes through
a Y-valve.  One leg takes the effluent to a holding tank, the other dumps it
overboard.  No parallel implied between what goes through the Firebird Y-valve
and the nautical term. 

On Tue, Jun 14, 2016 at 4:46 PM, fabianch@... [firebird-support] <firebird-support@yahoogroups.com> wrote:



Mark
 
Thank you, I think I am beggining to understand the concept, so the provider's have to be combined including ALWAYS Engine12 (the core FB server procedure/method that really goes to the file on disk and does the reading and writting to the DB). So the following combinations are valid:
Providers = Remote + Engine12
Providers = Loopback + Engine12
Providers = Remote  + Loopback + Engine12 (the first two in any orther)
 
And any Providers combination excluding Engine12 would not work because it is not including the component that goes to the DB file and reads/writes from /to it.
 
It seems Engine12 is not the same "type of component" as the other Providers. In the documentation it is refered as a Y valve, if I understand it correctly Engine12 is the base of the Y, while the other providers are the top left and top right of the Y, you can have any top you want, BUT YOU MUST HAVE the base always, else it does not work, correct?
 
 
Cheers,
Fabian
 
 
----- Original Message -----
Sent: Wednesday, June 15, 2016 5:32 AM
Subject: Re: [firebird-support] Engine12 mistery

On 2016-06-14 19:44, fabianch@... [firebird-support]
wrote:
> My understanding from reading the documentation is:
>
> Provider = Remote means the client is on the network, excluding
> 127.0.0.1
> Provider = Loopback means the client is actually on the same OS
> instance as the FB3 engine, and it is using the 127.0.0.1 to access
> the database to avoid the "embedded server concept" from answering
> the
> request, as it would capture the DB file and will not allow any other
> clients from remote /network source.
> Engine12 = The local server takes control of the database as if it
> was
> an embedded server, killing all future chance of accessing the DB
> from
> the network, so Engine12 is if I understand correctly the way to talk
> to the DB engine in "exclusive" mode when you want to perform
> maintenance or work on the security database.
>
> Is the above wrong?

Yes, your understanding is wrong. Engine12 **is** the component that
actually does the work with the database file. The rest is just plumbing
to connect to servers (or make fbclient connect to a local server),
select the right provider, etc.

As the release notes say:
http://www.firebirdsql.org/file/documentation/release_notes/html/en/3_0/rnfb30-engine.html

* Remote (establish network connection)
* Engine12 (main database engine)
* Loopback (force network connection to the local server for <database
name> without an explicit network protocol being supplied).

There was also talk of providing an 'Engine11' which would essentially
be a Firebird 2.5 you could use to connect to ODS 11.2 and older
database files.

Your confusion likely stems from the fact that Firebird embedded now is
fbclient + Engine12, as opposed to Firebird server + Engine12 for a
normal database server, while Firebird embedded used to be a separate
DLL/SO. BTW: In normal situations fbclient **does not** have access to
Engine12, so it only behaves as a client library.

Mark



------------------------------------
Posted by: Mark Rotteveel <mark@...>
------------------------------------

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