<div dir="ltr"><div>Re "<font size="4" face="monospace">list containing { hugeObject, expensiveObject }</font>", please look at the real API of a real library: <a href="https://www.slf4j.org/api/org/slf4j/Logger.html#debug(java.lang.String,java.lang.Object)">https://www.slf4j.org/api/org/slf4j/Logger.html#debug(java.lang.String,java.lang.Object)</a> . All these one and two args overrides were aiming to overcome the "<font size="4" face="monospace">if(isDebugLogging)</font>" boilerplate.<br></div><div>I understand that StringTemplate was not aiming to solve all the possible problems, but obviously it is not good enough for logging frameworks. Meanwhile, the C# covered the issue, maybe not so nicely, by the string template interceptors.<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, 17 Mar 2024 at 19:45, Brian Goetz <<a href="mailto:brian.goetz@oracle.com">brian.goetz@oracle.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>
<font size="4" face="monospace">It depends on how you measure "don't
care anything". Even this, which is pretty fast, still creates an
object with a list containing { hugeObject, expensiveObject }.
This is pretty cheap but not necessarily free. (It may be free if
the debug() call gets inlined.) <br>
<br>
I think for 9x% of the cases, this is entirely cheap enough; for
those cases where it is not, the old fussy technique of<br>
<br>
if (isDebugLogging)<br>
logger.debug(...)<br>
<br>
will recapture the rest. <br>
</font><br>
<div>On 3/17/2024 3:41 PM, Anatoly
Kupriyanov wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>I guess it is not fair to think about it in terms of
premature optimization. I am trying to look at it from a
logging-framework developer point of view. As a library
developer I should give the smallest overhead possible. So
library users could safely do </div>
<div><span style="font-family:monospace"> LOGGER.</span><span style="font-family:monospace">debug</span><span style="font-family:monospace">("Some thing={}, another={}",
hugeObject, expensiveObject);</span></div>
<div>and don't care about anything at all as <span style="font-family:monospace">debug</span> is usually
disabled. So the <span style="font-family:monospace">debug</span>
statement could be used even in a tight computation loop
without worries. In other words, logger devs could not assume
anything about how their framework would be used, but they
will fight for the easiest to use api with the fastest
performance.</div>
<div>The idea is that the trace is usually disabled and an app
could chew-up gigs of data, but while debugging/investigating,
the trace could be temporarily enabled and expected to degrade
performance.</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, 17 Mar 2024 at 17:36,
David Alayachew <<a href="mailto:davidalayachew@gmail.com" target="_blank">davidalayachew@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div class="gmail_default" style="font-family:monospace">Thank
you for the code example. That helps clarify your desired
behaviour.</div>
<br>
<div class="gmail_default" style="font-family:monospace">Ok,
if your intent is to have absolutely no garbage collection
whatsoever, then yes, my solution does not guarantee that.
How much the JIT will help or optimize, I cannot say.</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">That
said, a String is a "blessed type" in Java. It has a
handful of optimizations that are specific to it and it
alone. I am actually expecting that StringTemplates will
receive at least a small taste of this sort of
optimization.</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">Furthermore,
the cost of creating a StringTemplate is rarely, if ever,
the expensive part of the operation. In fact, I am certain
it is trivial, if not optimized away like you were asking.</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">I
won't presume to call this premature optimization --
perhaps your application needs require it. But if so, I
would first wait and see (or better yet, calculate!) the
performance metrics of these StringTemplates. If they fail
to meet your performance needs, then communicate your
performance needs to this mailing list, with a hard
example (and ideally metrics!) in tow.<br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, Mar 17, 2024 at
1:07 PM Anatoly Kupriyanov <<a href="mailto:kan.izh@gmail.com" target="_blank">kan.izh@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div>Classically (how it was done a decade or so ago)
the logger method would look like:</div>
<div><span style="font-family:monospace">void
debug(String template, Object arg1, Object arg2) {</span></div>
<div><span style="font-family:monospace"> if(!enabled)
return;</span></div>
<div><span style="font-family:monospace">
writeLog(interpolate(template, arg1.toString(), arg2</span><span style="font-family:monospace">.toString()</span><span style="font-family:monospace">));</span><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">}</span></div>
<div><br>
</div>
<div>That allows that if <span style="font-family:monospace">enabled==false</span>,
then it will be zero-gc, guaranteed.</div>
<div>It even used a lot of overrides with zero args, one
arg, two args to avoid ...-ellipsis array allocation.
E.g. see <a href="https://www.slf4j.org/api/org/slf4j/Logger.html" target="_blank">https://www.slf4j.org/api/org/slf4j/Logger.html</a></div>
<div><br>
</div>
<div>There is a C# hacky approach the String
Interpolation Handler ( <a href="https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/tutorials/interpolated-string-handler" target="_blank">https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/tutorials/interpolated-string-handler</a>
) to use struct (allocated on stack) and magical
isEnabled flags to cover logging effectively.</div>
<div><br>
</div>
<div>I don't see how it would be possible to use the
StringTemplate to achieve the similar effectiveness,
unless there are some good and reliable optimizations
in JIT to avoid allocations.<br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, 17 Mar 2024 at
16:41, David Alayachew <<a href="mailto:davidalayachew@gmail.com" target="_blank">davidalayachew@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div class="gmail_default" style="font-family:monospace">The cost would be no
different than evaluating a StringTemplate lazily.
Utlimately, log.debug(blah) is still a method
call, and therefore, some object is going into the
method. Whether we evaluate the StringTemplate
lazily or the Supplier<StringTemplate>
lazily is largely the same thing.</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">Or am I
misunderstanding you?<br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, Mar 17,
2024 at 12:28 PM Anatoly Kupriyanov <<a href="mailto:kan.izh@gmail.com" target="_blank">kan.izh@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">But the "() ->" thing is still a
runtime object to be allocated on the heap... or
is the JIT smart enough to always optimize it
out?<br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, 17 Mar
2024 at 16:17, David Alayachew <<a href="mailto:davidalayachew@gmail.com" target="_blank">davidalayachew@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div class="gmail_default" style="font-family:monospace">I feel like
that would be on the logging libraries to
provide, not so much the language.</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">Let's say
that your problem (as I understand it) is
like this.</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">log.debug("metrics
=
\{this.expensiveComputationThatNormallyWouldntRunUnlessYouActivateDebug()}");</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">Sounds to me
like the solution is this instead.</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">log.debug(()
-> "metrics =
\{this.expensiveComputationThatNormallyWouldntRunUnlessYouActivateDebug()}")</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">So, your
logging library just needs to add a new
overload for a
Supplier<StringTemplate>, and then
this problem is solved entirely outside of
the language. Log4J and friends are pretty
good about keeping up with new additions,
so it should not take long.<br>
</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">
I know it's a little less convenient, but
doing it this way helps keep out
complexity from the feature, and only
introduces it where necessary (and it's
only necessary at use-site).
</div>
<div class="gmail_default" style="font-family:monospace"><br>
</div>
<div class="gmail_default" style="font-family:monospace">Would this
meet your needs?<br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun,
Mar 17, 2024 at 11:15 AM Justin Spindler
<<a href="mailto:justin.spindler@gmail.com" target="_blank">justin.spindler@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">I was toying around
with the second preview of
StringTemplates and I had a question
regarding their design. I was wondering
if it had been considered for the
embedded expressions to be evaluated
lazily?
<div><br>
</div>
<div>One of the first use cases that
came to mind when I was exploring
StringTemplates is logging. That is
an extremely common case where we want
to produce a form of interpolated
value, and the current syntax
generally has the same concerns that a
formatted string would, in that the
inputs are removed from where they are
defined within the message format.
However, if the log message is below
the log level threshold you generally
don't want to incur the cost of
building the message, including
evaluating those embedded
expressions. Log libraries typically
offer a mechanism to defer evaluation
via Suppliers, but that feels like it
would be a challenge to use within
StringTemplate.</div>
<div><br>
</div>
<div>C# is an example of a language that
offers this functionality via
FormattableString, which gives a
method the ability to choose whether
or not to interpret the template or
evaluate the expressions. That allows
logging below threshold to be more or
less a no-op.</div>
<div><br>
</div>
<div><br>
</div>
</div>
</blockquote>
</div>
</blockquote>
</div>
<br clear="all">
<br>
<span class="gmail_signature_prefix">-- </span><br>
<div dir="ltr" class="gmail_signature">WBR,
Anatoly.</div>
</blockquote>
</div>
</blockquote>
</div>
<br clear="all">
<br>
<span class="gmail_signature_prefix">-- </span><br>
<div dir="ltr" class="gmail_signature">WBR, Anatoly.</div>
</blockquote>
</div>
</blockquote>
</div>
<br clear="all">
<br>
<span class="gmail_signature_prefix">-- </span><br>
<div dir="ltr" class="gmail_signature">WBR, Anatoly.</div>
</blockquote>
<br>
</div>
</blockquote></div><br clear="all"><br><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature">WBR, Anatoly.</div>