ref: 75c92428225428c8fde2d015f010e608a0b12f1d
dir: purgatorio/man/2/registries
.TH REGISTRIES 2
.SH NAME
registries \- access services registry
.SH SYNOPSIS
.EX
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):
(ref Registered, string);
unregister: fn(r: self ref Registry, addr: string): string;
};
.EE
.SH DESCRIPTION
.B Registries
helps access and update the contents of one or more
.I registry (4)
servers.
Each registry lists services, each described by a set of attribute/value pairs.
The attributes need not identify the service uniquely.
.PP
.B Init
must be called before any other function in the module.
.PP
.B Attributes
represents a set of attribute/value pairs;
a given attribute name cannot appear more than once.
It provides the following members and operations:
.TF attrs
.PD
.TP
.B attrs
The current value of the set, as a list of
.BI ( attr , value )
tuples.
.TP
.BI Attributes.new( attrs )
Return a new
.B Attributes
value given
.IR attrs ,
a list of
.BI ( attr , value )
tuples.
.TP
.IB a .get( attr )
Return the value of
.I attr
in attribute set
.IR a .
.TP
.IB a .set( attr\fB,\fP\ value )
Set the
.I value
of
.I attr
in attribute set
.IR a .
.PP
A
.B Service
value represents a service registered in some registry.
It has the following members and operations:
.TF attrs
.PD
.TP
.B addr
A string that represents where the service can be reached: it is often a
.IR dial (2)
address string, but might be a name in the name space; the interpretation is internal to
.BR Registries .
.TP
.B attrs
The service's attributes (complete service description).
.TP
.IB svc .attach( user , keydir )
Attempts to attach to the service
.IR svc ,
and if successful returns an
.B Attached
value to represent the connection;
otherwise returns nil and sets the system error string.
.I User
is the local name of the user making the connection; if nil, the contents of
.B /dev/user
are used by default.
.I Keydir
is the name of a directory containing the
.IR user 's
certified keys for authentication; if nil, the default is
.BI /usr/ user /keyring.
If an error occurs, the return 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 suitable defaults.
If authentication is done, the certified data determines the remote identity, not
.IR user ,
which is used only to help find a suitable set of keys and has no effect on security.
.PP
.B Attached
holds data about an active connection to a particular service.
(There can be several distinct connections to the same
.BR Service .)
It provides the following members:
.TF attrs
.PD
.TP
.B 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.
.TP
.B 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.
.TP
.B localuser
If authentication was required, the name used as the local name for authentication;
otherwise nil.
.TP
.B remoteuser
If authentication was required, the remote identity for this connection; otherwise nil.
.PP
A service provider registers using one of the
.B Registry
functions listed below.
An active registration is represented by a value of type
.BR Registered :
.TF attrs
.PD
.TP
.B addr
Location of service, as registered.
.TP
.B reg
The registry that registered the service.
.TP
.B fd
File descriptor open for on the service file in
.IR registry (4)
that holds the service description.
Unless the service has a non-zero
.B persist
attribute, the service registration will be removed when this file is closed
(eg, when this
.B Registration
value is freed by the garbage collector if there is no other copy of
.BR fd ).
The file can be written as described in
.IR registry (4)
to change the some or all of current set of attributes and/or values
in the service description.
.PP
A
.B Registry
represents a connection to a single
.IR registry (4)
instance.
It provides the following members and operations:
.TF attrs
.PD
.TP
.B dir
Location of the registry in the name space.
.TP
.BI Registry.new( dir )
Return a new
.B Registry
value for the registry located at
.I dir
in the name space; if
.I dir
is nil, the default is
.BR /mnt/registry .
.TP
.BI Registry.connect( svc\fB,\fP\ user\fB,\fP\ keydir )
Connect to the registry at the location determined by the service description
.IR svc ;
if
.I svc
is nil, the default is to try
.IR dial (2)
to
.BR net!$registry!registry ,
the symbolic name of the default registry for the current host.
(The registry might or might not be local.)
Attributes of
.I svc
determine the method used to connect to the registry and whether authentication is required.
.I User
and
.I keydir
provide user name and certificate directory (see
.IR getauthinfo (8))
if authentication is required; either or both can be nil to select the defaults for the given authentication method.
On successful connection,
.B connect
returns a
.B 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.
.TP
.IB reg ".services()"
Returns a tuple
.BI ( svcs , err )
where
.I svcs
is a list of
.B Service
values, one for each service registered by
.I reg
at time of asking.
If no services are registered, both values are nil.
If an error occurred,
.I svcs
is nil but
.I err
is a diagnostic string.
.TP
.IB reg .find( attrs )
Return a tuple
.BI ( svcs , err )
where
.I svcs
is a list of
.B Service
values, one for each service registered by
.I reg
that (at time of asking) matched all of the attribute/value pairs in
.IR attrs .
A value of
.B \&"*"
matches any value.
If no services matched, both values are nil.
If an error occurred,
.I svcs
is nil but
.I err
is a diagnostic string.
.TP
.IB reg .register( addr\fB,\fP\ attrs\fB,\fP\ persist )
Attempts to register with
.I reg
a service named
.I addr
and the given attributes
.IR attrs ,
and returns a tuple
.BI ( r , err )
where
.I r
is a non-nil
.B Registration
value for the entry if successful, and
.I err
is a diagnostic otherwise.
.I Persist
is non-zero if the service registration should survive the
.B Registration
value (connection); normally it is zero and the registry entry vanishes when
the service frees the
.B Registration
value.
.TP
.IB reg .unregister( addr )
Attempt to remove the registration entry at
.I reg
for the service named
.IR addr .
Only the service owner can do so.
Returns nil on success and a diagnostic otherwise.
.SH SEE ALSO
.IR attrdb (2),
.IR registry (4),
.IR svc (8)