Commit 0654a713 authored by Marcin Siodelski's avatar Marcin Siodelski
Browse files

[5317] Updated Developer's Guide.

parent d913e9a7
......@@ -154,39 +154,21 @@ or HTTPS connection):
- @ref isc::config::CommandMgr::openCommandSocket that passes structure defined
in the configuration file. Currently only two parameters are supported: socket-type
(which must contain value 'unix') and socket-name (which contains unix path for
the named socket to be created). This method calls @ref
isc::config::CommandSocketFactory::create method, which parses the parameters
and instantiates one object from a class derived from @ref isc::config::CommandSocket.
Again, currently only UNIX type is supported, but the factory
class is expected to be extended to cover additional types.
the named socket to be created).
- @ref isc::config::CommandMgr::closeCommandSocket() - it is used to close the
socket. It calls close method on the @ref isc::config::CommandSocket object, if
one exists. In particular, for UNIX socket, it also deletes the file after socket
was closed.
@section ctrlSocketConnections Accepting connections
Control Channel is connection oriented communication. In that sense it is
different than all other communications supported so far in Kea. To facilitate
connections, several mechanisms were implemented. Intially a single UNIX socket
it opened (see @c isc::config::UnixCommandSocket in
src/lib/config/ Its @ref
isc::config::UnixCommandSocket::receiveHandler callback method is
installed in @ref isc::dhcp::IfaceMgr to process incoming connections. When the
select call in @ref isc::dhcp::IfaceMgr::receive4 indicates that there is some data to be
processed, this callback calls accept, which creates a new socket for handling
this particular incoming connection. Once the socket descriptor is known, a new
instance of @ref isc::config::ConnectionSocket is created to represent that
socket (and the whole ongoing connection). It installs another callback
(@ref isc::config::ConnectionSocket::receiveHandler that calls
(@ref isc::config::CommandMgr::commandReader) that will process incoming
data or will close the socket when necessary. CommandReader reads data from
incoming socket and attempts to parse it as JSON structures. If successful,
it calls isc::config::CommandMgr::processCommand(), serializes the structure
returned and attempts to send it back.
@todo Currently commands and responses up to 64KB are supported. It was deemed
sufficient for the current needs, but in the future we may need to extend
it to handle bigger structures.
The @ref isc::config::CommandMgr is implemented using boost ASIO and uses
asynchronous calls to accept new connections and receive commands from the
controlling clients. ASIO uses IO service object to run asynchronous calls.
Thus, before the server can use the @ref isc::dhcp::CommandMgr it must
provide it with a common instance of the @ref isc::asiolink::IOService
object using @ref isc::dhcp::CommandMgr::setIOService. The server's
main loop must contain calls to @ref isc::asiolink::IOService::run or
@ref isc::asiolink::IOService::poll or their variants to invoke Command
Manager's handlers as required for processing control requests.
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