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.
The role of a slave as a host for Factorio servers is not well reflected
in its name and has caused confusion among users. Rename slave to host
to better reflect its role as a host of Factorio servers.
The role of the master server as the party controlling every part of the
cluster is not well reflected in its name and has caused confusion among
users on several occasions. Rename master to controller to better
reflects its role.
All possible Promise rejections and exception bubbling should be handled
by either the code creating the exception or the code invoking the
operation that could fail. Treat therefore uncaught exceptions and
unhandled promise rejetions as fatal errors that log a traceback and
immedately terminate the Node.js process.
There are some corner cases with streams that cause them to not emit
finish close or end events which in turn means that code liseting for
these events directly may end up hanging forever. Use stream.finished
to detect end of streams which will handle these cases correctly.
The interface provided by Winston is unusably slow for querying large
logs. Reimplement the log querying with both forwards and backwards
line reading and a simple file based index to skip files which do not
contain any lines matching the filter.
Move the default location of the log files into a configurable logs
folder and split the written logs up by UTC date to more easily allow
deleting of old logs to be performed. The log rotation is implemented
by winston-daily-rotate-file.
The old log format will automatically be migrated to the new format and
location if the target folder for the new logs don't yet exists.
Use relative imports in lib to avoid an issue with webpack thinking
absolute imports inside @clusterio/lib are for a separate module and
giving out warnings for it being missing in package.json.
Add log query and log follow commands which allows inspection of the
combined cluster log. Past entries can be queried via the new queryLog
request. The log is stored into a single flat file for now, though the
performance of this may good enough.
Add winston based logger for master, slave, ctl, lib, and web_ui code.
Logging done from slaves and instances are sent to the master server and
tagged with the instance and/or slave it originated from. This allows
for example error messages to propagate back to the source that iniated
the action. The master server also stores the log to allow it to be
queried at a later point. For slaves a copy of the slave's log is also
stored locally.
Hornwitser