Compatibility breaks in Embulk v0.9

[Dai Mikurube]

Hi,

Thank you for joining this Embulk-announce mailing list. This is the
first e-mail delivered!

We'll be releasing Embulk v0.9 in a couple of months, which expects
some compatibility breaks from the v0.8 series. Some existing plugins
may not work in v0.9. Let me summarize the expected breaks here, and
ask a favor of you to give your feedbacks for us on the expected
compatibility breaks.


<< tl;dr for Users >>

The biggest change is that Embulk v0.9 would expect Java 8. Embulk
core would be tested only in Java 8 (and possibly Java 9 in addition
sooner or later... *hopefully*). Plugins compiled with Java 8 features
are welcome then!

Next, we stop providing embulk.gem from v0.9. If you are using
embulk.gem and/or require 'embulk' from Ruby, please see and comment
in: https://github.com/embulk/embulk/issues/628 and/or
https://github.com/embulk/embulk/issues/766

Then, please try Embulk v0.8.36 soon with the plugins and the usages
which you actually operate. You'd see some warning messages like below
on your console (stderr) if your usage expects compatibility breaks.

===== Example warning message =====
[WARN] Plugin uses deprecated constructor of
org.embulk.spi.time.TimestampFormatter.
[WARN] Report plugins in your config at:
https://github.com/embulk/embulk/issues/***
===== Example warning message =====

If you see such warning messages, please report in the GitHub Issues
URL in your case. We'd provide how to workaround, notify the developer
of the plugin, or reconsider the breakage then.


<< for Plugin Developers >>

v0.9 would introduce 6 types of plugin SPI incompatibilities as of
now. They are related with JRuby which we're removing from Embulk's
deeply-tightened dependencies in v0.9. Some of them are related with
Timestamps which have been unnecessarily depending on JRuby.


1. Some constructors of TimestampParser and TimestampFormatter
https://github.com/embulk/embulk/issues/745

It could be the most impactful on plugins. TimestampParser and
TimestampFormatter have been constructed with JRuby instances, but the
constructors will be removed in v0.9. The GitHub Issue above describes
how to workaround this incompatibility.


2. AbstractDynamicColumnSetter#setRubyObject
https://github.com/embulk/embulk/issues/799

We expect no plugins are calling this method directly. Ruby's
PageBuilder had been calling it inside Embulk core, but the part is
now replaced to pure-Ruby implementation. Please ping us if your
plugin is calling the method directly.


3. RubyValueApi
https://github.com/embulk/embulk/issues/802

We expect no plugins are using this class directly. It had been a
static utility class to convert internal MessagePack values and JRuby
values inside Embulk core, but the part is now replaced to pure-Ruby
implementation. Please ping us if your plugin is using this class
directly.


4. Timestamp#getRubyTime or Timestamp.fromRubyTime
https://github.com/embulk/embulk/issues/820

We expect no plugins are using these methods directly. The methods had
been used to convert Embulk Timestamps and JRuby's time objects inside
Embulk core, but the part is now replaced to pure-Ruby implementation.
Please ping us if your plugin is calling the methods directly.


5. Some constructors of PagePrinter
https://github.com/embulk/embulk/issues/827

We expect no plugins are using PagePrinter. The class had been used
from embedded StdoutOutputPlugin. StdoutOutputPlugin now calls
PagePrinter's new constructor.


6. TimestampFormat: newFormatter and newParser
https://github.com/embulk/embulk/issues/828

We expect no plugins are using these methods to create
TimestampFormatter and/or TimestampParser. They have been @Deprecated
for a long time since v0.6.14.

--
Dai MIKURUBE
dmik...@treasure-data.com