REGISTRIES(2) REGISTRIES(2)
NAME
registries - access services registry
SYNOPSIS
include "registries.m";
registries := load Registries Registries->PATH;
init: fn();
Attributes: adt {
attrs: list of (string, string);
get: fn(a: self ref Attributes, attr: string): string;
set: fn(a: self ref Attributes, attr, val: string);
new: fn(attrs: list of (string, string)): ref Attributes;
};
Attached: adt {
fd: ref Sys->FD; # connection to the service
signerpkhash: string; # hash of signer's key
localuser: string; # user name here
remoteuser: string; # user name there
};
Service: adt {
addr: string; # dial this to connect to the service
attrs: ref Attributes; # service description
attach: fn(s: self ref Service, user: string,
keydir: string): ref Attached;
};
Registered: adt {
addr: string; # address where registered
reg: ref Registry; # registry where registered
fd: ref Sys->FD; # file representing registration entry
};
Registry: adt {
dir: string;
new: fn(dir: string): ref Registry;
connect: fn(svc: ref Service, user: string, keydir: string):
ref Registry;
services: fn(r: self ref Registry):
(list of ref Service, string);
find: fn(r: self ref Registry, a: list of (string, string)):
(list of ref Service, string);
register: fn(r: self ref Registry, addr: string,
attrs: ref Attributes, persist: int):
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(ref Registered, string);
unregister: fn(r: self ref Registry, addr: string): string;
};
DESCRIPTION
Registries helps access and update the contents of one or
more registry(4) servers. Each registry lists services,
each described by a set of attribute/value pairs. The
attributes need not identify the service uniquely.
Init must be called before any other function in the module.
Attributes represents a set of attribute/value pairs; a
given attribute name cannot appear more than once. It pro-
vides the following members and operations:
attrs The current value of the set, as a list of
(attr,value) tuples.
Attributes.new(attrs)
Return a new Attributes value given attrs, a list of
(attr,value) tuples.
a.get(attr)
Return the value of attr in attribute set a.
a.set(attr, value)
Set the value of attr in attribute set a.
A Service value represents a service registered in some reg-
istry. It has the following members and operations:
addr A string that represents where the service can be
reached: it is often a dial(2) address string, but
might be a name in the name space; the interpretation
is internal to Registries.
attrs The service's attributes (complete service descrip-
tion).
svc.attach(user,keydir)
Attempts to attach to the service svc, and if suc-
cessful returns an Attached value to represent the
connection; otherwise returns nil and sets the system
error string. User is the local name of the user
making the connection; if nil, the contents of
/dev/user are used by default. Keydir is the name of
a directory containing the user's certified keys for
authentication; if nil, the default is
/usr/user/keyring. If an error occurs, the return
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value is nil and the system error string contains a
diagnostic. Not all services demand authentication,
and either or both values can be nil to select suit-
able defaults. If authentication is done, the certi-
fied data determines the remote identity, not user,
which is used only to help find a suitable set of
keys and has no effect on security.
Attached holds data about an active connection to a particu-
lar service. (There can be several distinct connections to
the same Service.) It provides the following members:
fd A file descriptor that can be read and written to
exchange data with the service. The meaning of the
data depends on the service (eg, it might be a 9P
connection or a SOAP implementation). Typically an
attribute of the service description hints at the
protocol.
signerpkhash
A hexadecimal string giving the SHA-1 hash of the key
of the signer used for mutual authentication (ie, its
thumbprint); if no authentication was needed or did
not use public key methods, it is nil.
localuser
If authentication was required, the name used as the
local name for authentication; otherwise nil.
remoteuser
If authentication was required, the remote identity
for this connection; otherwise nil.
A service provider registers using one of the Registry func-
tions listed below. An active registration is represented
by a value of type Registered:
addr Location of service, as registered.
reg The registry that registered the service.
fd File descriptor open for on the service file in
registry(4) that holds the service description.
Unless the service has a non-zero persist attribute,
the service registration will be removed when this
file is closed (eg, when this Registration value is
freed by the garbage collector if there is no other
copy of fd). The file can be written as described in
registry(4) to change the some or all of current set
of attributes and/or values in the service
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description.
A Registry represents a connection to a single registry(4)
instance. It provides the following members and operations:
dir Location of the registry in the name space.
Registry.new(dir)
Return a new Registry value for the registry located
at dir in the name space; if dir is nil, the default
is /mnt/registry.
Registry.connect(svc, user, keydir)
Connect to the registry at the location determined by
the service description svc; if svc is nil, the
default is to try dial(2) to net!$registry!registry,
the symbolic name of the default registry for the
current host. (The registry might or might not be
local.) Attributes of svc determine the method used
to connect to the registry and whether authentication
is required. User and keydir provide user name and
certificate directory (see getauthinfo(8)) if authen-
tication is required; either or both can be nil to
select the defaults for the given authentication
method. On successful connection, connect returns a
Registry value that can subsequently be used to
access that registry and its services. It returns
nil on an error and sets the system error string.
reg.services()
Returns a tuple (svcs,err) where svcs is a list of
Service values, one for each service registered by
reg at time of asking. If no services are regis-
tered, both values are nil. If an error occurred,
svcs is nil but err is a diagnostic string.
reg.find(attrs)
Return a tuple (svcs,err) where svcs is a list of
Service values, one for each service registered by
reg that (at time of asking) matched all of the
attribute/value pairs in attrs. A value of "*"
matches any value. If no services matched, both val-
ues are nil. If an error occurred, svcs is nil but
err is a diagnostic string.
reg.register(addr, attrs, persist)
Attempts to register with reg a service named addr
and the given attributes attrs, and returns a tuple
(r,err) where r is a non-nil Registration value for
the entry if successful, and err is a diagnostic oth-
erwise. Persist is non-zero if the service
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registration should survive the Registration value
(connection); normally it is zero and the registry
entry vanishes when the service frees the
Registration value.
reg.unregister(addr)
Attempt to remove the registration entry at reg for
the service named addr. Only the service owner can do
so. Returns nil on success and a diagnostic other-
wise.
SEE ALSO
attrdb(2), registry(4), svc(8)
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