Martin Ritchie wrote:
2009/12/10 Rafael Schloming <rafa...@redhat.com>:
Gordon Sim wrote:
On 11/25/2009 11:06 PM, Rafael Schloming wrote:
One question I have is about how we'll provide access to alternate
syntaxes via jndi configuration and the JMS API (i.e.
createQueue(...)/createTopic(...)). I can think of a few options, e.g.
switching between syntaxes using a system/connection property. Or maybe
having some sort of meta-syntax that that would permit usage of the two
syntaxes side by side, e.g. "OLD: ...", "NEW: ...", or possibly some
combination of the two approaches.
In the case of jndi configuration, what about having a different context
factory to do the parsing? I.e. in jndi configuration files using the new
syntax you would specify something other than the existing
org.apache.qpid.jndi.PropertiesFileInitialContextFactory. That way existing
configuration will work as before with no changes, and a new format can be
parsed without any need to worry about the older format.
That doesn't deal with strings passed to createQueue()/createTopic() of
course. Perhaps there a specific 'factory' can be associated with a
connection, configured via a connection option? Where a file backed jndi
configuration is used the two different context factories could then set
different defaults for this meaning again that old config would be
unaffected and new config could ignore the old config entirely also.
Just a suggestion...
I've been thinking we should just do something like:
"ADDR: ..." gets parsed as an address (after removing the ADDR:)
"BURL: ..." gets parsed as a binding url (after removing the BURL:)
and anything not starting with ADDR: or BURL: gets parsed as one or the
other according to some default that is configurable at the connection,
context factory, and JVM levels.
--Rafael
Hi Rafi, do you have some examples of your grammar, my cold filled
head still doesn't follow why you have to start prefixing things.
What ever we do new JNDI, prefixing (which I find a tad strange) we
need to support both formats simultaneously in a single file to allow
users to migrate.
If you want to support both formats simultaneously in a single file,
then the only practical way I can think of to do that is with some sort
of meta syntax akin to prefixing. You need some way to clearly and
unambiguously figure out which parser to invoke, both for the sake of
the implementation and for the sake of the people reading the file and
trying to interpret the content.
Please refer to the attached file for an updated the grammar description
with some examples.
--Rafael
Tokens:
LBRACE: r"\{"
RBRACE: r"\}"
COLON: r":"
SEMI: r";"
SLASH: r"/"
COMMA: r","
NUMBER: r'[+-]?[0-9]*\.?[0-9]+'
ID: r'[a-zA-Z_](?:[a-zA-Z0-9_-]*[a-zA-Z0-9_])?'
STRING: r""""(?:[^\\"]|\\.)*"|'(?:[^\\']|\\.)*'"""
ESC:
r"\\[^ux]|\\x[0-9a-fA-F][0-9a-fA-F]|\\u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]"
SYM: r"[....@$^!+-]"
WSPACE: r"[ \n\r\t]+"
EOF:
Grammar:
address = name [ "/" subject ] [ ";" options ]
name = ( part | quoted )+
subject = ( part | quoted | "/" )*
quoted = STRING / ESC
part = LBRACE / RBRACE / COLON / COMMA / NUMBER / ID / SYM
options = map
map = "{" ( keyval ( "," keyval )* )? "}"
keyval = ID ":" value
value = NUMBER / STRING / ID / map / list
list = "[" ( value ( "," value )* )? "]"
Semantics:
An address identifies a source or target for messages. In its
simplest form this is just a name. In general a target address may
also be used as a source address, however not all source addresses
may be used as a target, e.g. a source might additionally have some
filtering criteria that would not be present in a target.
A subject may optionally be specified along with the name. When an
address is used as a target, any subject specified in the address is
used as the default subject of outgoing messages for that target.
When an address is used as a source, any subject specified in the
address is pattern matched against the subject of available messages
as a filter for incoming messages from that source.
The options map contains additional information about the address
including:
- policies for automatically creating, and deleting the node to
which an address refers
- policies for asserting facts about the node to which an address
refers
- extension points that can be used for sender/receiver
configuration
Mapping to 0-10 semantics:
The name is resolved to either an exchange or a queue by querying
the broker.
The subject is set as a property on the message. Additionally, if
the name refers to an exchange, the routing key is set to the
subject.
Examples:
A simple name resolves to any named node, usually a queue or a
topic:
my-queue-or-topic
A simple name with a subject will also resolve to a node, but the
presence of the subject will cause a sender using this address to
set the subject on outgoing messages, and receivers to filter based
on the subject:
my-queue-or-topic/my-subject
A subject pattern can be used and will cause filtering if used by
the receiver. If used for a sender, the literal value gets set as
the subject:
my-queue-or-topic/my-*
In all the above cases, the address is resolved to an existing node.
If you want the node to be auto-created, then you can do the
following. By default nonexistent nodes are assumed to be queues:
my-queue; {create: always}
You can customize the properties of the queue:
my-queue; {create: always, node-properties: {durable: True}}
You can create a topic instead if you want:
my-queue; {create: always, node-properties: {type: topic}}
You can assert that the address resolves to a node with particular
properties:
my-transient-topic; {assert: always, node-properties: {type: topic,
durable: False}}
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