Move all functions and classes currently available through lib/name and
libName to be under a single flat namespace in lib. This make
reorganising the lib namespace much simpler as the location of symbols
can move without breaking the consumers of lib.
The multi-entrypoint design was already problematic for the web plugin
system which couldn't effectively use it due to how webpack's shared
module system is awkward to set up with multiple entrypoints per package.
Format arguments to have nested structures start on a new line instead
of inline to make it easier to see where the structures starts and what
structure it is.
Reverse the direction of the API for sending messages from
messageDefinition.send(link, { content });
to
link.send(new MessageClass(content));
and convert all message definitions to use the JSON serialisable class
pattern and explicit registration of message handlers, along with a
end-to-end based routing of messages instead of link to link.
The experience I gained from the existing way messages were defined and
sent over links was that it was difficult to understand for people
unfamiliar with the system. The automatic registration of message
handlers ment that code was being called as if by magic from nowhere
with no easy way to discover it. The manual forwarding and rules for
what can be sent where and how obscured its working.
The use of pure JSON as both input and output from message handlers made
it tedious to work with. Data had to be manually converted between the
program representation and the over the wire format, which made handler
code unplesant to write. Particularly because the over the wire format
used snake_case while the program code uses camelCase for variables.
The idea behind the decision to do it this way was to make it more clear
which data came from the wire and which from the program, and while this
worked it didn't make message handlers any nicer to write.
The direction of the API and magic registration of message handlers also
meant that a future migration to TypeScript would be troublesome. While
it may be possible to implement, the degree of TypeScript magic required
would go starkly against the principle of keep it simple stupid.
By refactoring to using the JSON serialisable class pattern most of
these issues go away. There is no longer a need to distinguish the on
wire format of messages with the program representation because the only
place that deals with the wire format of messages are the toJSON and
fromJSON methods on the classes themselves. Message handlers will work
with proper instances of classes instead of raw data, something that
makes them easier to write, and trivial to type with TypeScript.
End-to-end routing also simplifies sending messages that need to do
mulitple hops to reach the destination. And removes the need for having
all messages be specified in plugin's info module, as they can be routed
without having to be parsed completely.
The explicit registration of message handlers is something that I
thought would be tedious boilerplate code that could be automated away.
But experience now shows it to be the opposite. Allthough dull
repetition, the purpose it serves is to link together the code in a way
that humans can easily find. With explicit registration searching the
name of the message handler in the editor will show the registration that
ties it together with the type of message it handles and the kind of
registration. With implicit registration searching the name of the
message handler turns up only the handler with no clue as to what calls
it.
Refine the state flow used in the connector abstractions to better
handle close while connecting and resuming. The new logic is to close
the connection immediately in these two states instead of continuing
trying to connect and then giving up some point later.
For the connectors the handshake state is split into connecting
and resuming, new is replaced by closed, and the closing state is turned
into a boolean flag as it's possible that closing is desired while
connecting, connected or resuming. The connecting state is not present
in the server connector because there's nothing for the server to do in
that connector state.
The timeout logic is completely removed, once a connection attempt is
started for the client it will continue to attempt to connect, attempt
to resume dropped connections and attempt reconnects until either an
authentication error occurs or the client explicitly requests to close
the connection.
A new session timeout is added to control how long to attempt to resume
the connection until it's considered dead and invalidated. This allows
stale connections to give up earlier, and swallow up less data while in
the dropped but not yet invalidated state.
For the client side sending messages while it's connecting has been
changed to throw an error instead of queuing up the message and
(possibly) sending it after the connection is established. Code
shouldn't try to send messages without knowing if the connection it's
trying to send them over is active or not.
Use lib* prefix for the modules impored from the lib package to help
distinguish them more from ordinary variables. Fix up the naming
convention for files to be consistently lowercase_underscore for
JavaScript files.
Split up codebase into the packages @clsterio/lib, @clusterio/master,
@clusterio/slave, and @clusterio/ctl using lerna to manage them. This
will allow deployment to use only the parts needed reducing install
size, and better separate the code into shared library, master, slave
and control.
Send a mapping of the plugins the master server has loaded to slaves
vice versa. Limit the plugins that may be loaded by instances to only
those that the master server has loaded.
Replace socket.io with plain WebSocket using the ws library as it
doesn't really provide any useful tools over plain WebSocket when it
comes to implementing reliable communication that works across
reconnects. The widespread browser support for WebSocket also means
it has little value to add for the web interface over WebSocket.
Remove connection and client subclasses of Link and put the connection
logic into a "connector" class. The connector deals with sending
and receiving messages, handling the connection and reconnection of lost
connections and giving sequence numbers to messages.
This move the logic of the actual connection away from the link
sub-classes, which in turn means the connection should be a lot easier
to mock in tests.
Hornwitser