Duration.MAX_VALUE

Fri Sep 5 18:57:40 UTC 2025

As promised, Kurt and I have examined some of the uses of our Durations.MAX
constant. This is a summary of what we see in a random sample of 30 out of
about 700 usages in Google's (giant) codebase.

First, about half of the usages specifically concern deadlines. Many of
them involve a method that sets an RPC deadline and where it is explicitly
documented that you should use Durations.MAX to mean no deadline (or
equivalently, infinite deadline).

Several other usages concern deadline-adjacent concepts such as
time-to-live or cache expiration delay.

A number of usages specifically compare a Duration against Durations.MAX to
recognize the "infinite duration" value.

One usage uses our internal Sleeper interface to do
sleeper.sleep(Durations.MAX), for an indefinite sleep (until interrupted).

In a couple of places, there is a maximum allowed Duration for some
operation, and a user-supplied Duration value is capped by this maximum.
When no maximum is needed, the cap is Durations.MAX. This is similar to the
"sentinel" use case I mentioned earlier.

One case is using Durations.MAX in a test, to ensure that a function works
correctly for all Duration values including the largest one. It is testing
a Kotlin extension function that allows you to write e.g. 5.minutes:

    val n = Durations.MAX.toMinutes()

    assertThat(n.minutes).isEqualTo(Duration.ofMinutes(n))

    assertFailsWith<ArithmeticException> { (n + 1).minutes }

In summary, I think the most interesting use cases fall into these
categories:

   -

   to express an effectively-infinite Duration, possibly accompanied by
   special-case logic to optimize the exact value Durations.MAX;
   -

   to express the absence of an optional cap on a user-supplied Duration
   value;
   -

   to test that code works correctly even with extreme Duration values.

Of these, the first is potentially fragile because of the overflow problems
we discussed. The other two seem unproblematic, though.

On Thu, 4 Sept 2025 at 15:02, Éamonn McManus <emcmanus at google.com> wrote:

> Two typical use cases:
>
> // 1. Sentinel
> Duration min = Duration.MAX;
> for (var foo : something()) {
>   if (foo.duration().compareTo(min) < 0) {
>     min = foo.duration();
>   }
> }
>
> // 2. "Forever"
> void frob(Optional<Duration> optionalTimeout) {
>   Duration timeout = optionalTimeout.orElse(Duration.MAX);
>   Instant start = Instant.now();
>   boolean done = false;
>   while (!done && startTime.until(Instant.now()).compareTo(timeout) < 0)
> {...}
> }
>
> The second case illustrates why this is potentially a bit delicate. You
> better not write this:
>
> void frob(Optional<Duration> optionalTimeout) {
>   Duration timeout = optionalTimeout.orElse(Duration.MAX);
>   Instant deadline = Instant.now().plus(timeout); // oops
>   boolean done = false;
>   while (!done && Instant.now().isBefore(deadline)) {...}
> }
>
> Like Kevin, I am skeptical about Duration.MIN. If it means the most
> negative Duration, that is just Duration.MAX.negated(); and if it means the
> smallest positive Duration, that is just Duration.ofNanos(1).
>
> On Wed, 3 Sept 2025 at 18:32, Roger Riggs <roger.riggs at oracle.com> wrote:
>
>> Hi,
>>
>> I'd be interested in the range of use cases for Duration.MAX or MIN.
>>
>> But for deadlines, I think the code should compute the deadline from a
>> Duration of its choice based on the use.
>> Maybe there is a use for Duration.REALLY_BIG or _SMALL, but that ignores
>> information about the particular use that is relevant. Its just sloppy code
>> that doesn't bother to express how long is long enough to meet operational
>> parameters.
>>
>> YMMV, Roger
>>
>> On 9/3/25 8:21 PM, Kurt Alfred Kluever wrote:
>>
>> Duration.MIN is a whole 'nother bag of worms, because Durations are
>> signed (they can be positive or negative...or zero). Internally we also
>> have Durations.MIN, but it's not public ... and along with it, I left
>> myself a helpful note about naming:
>>
>>   /** The minimum supported {@code Duration}, approximately -292 billion
>> years. */
>>   // Note: before making this constant public, consider that "MIN" might
>> not be a great name (not
>>   //       everyone knows that Durations can be negative!).
>>   static final Duration MIN = Duration.ofSeconds(Long.MIN_VALUE);
>>
>> This reminds me of Double.MIN_VALUE (which is the smallest _positive_
>> double value) --- we've seen Double.MIN_VALUE misused so much that we
>> introduced Doubles.MIN_POSITIVE_VALUE as a more descriptive alias. A large
>> percent of Double.MIN_VALUE users actually want the smallest possible
>> negative value, aka -Double.MAX_VALUE.
>>
>> If we introduce Duration.MIN, I hope it would not be Duration.ofNanos(1),
>> but rather Duration.ofSeconds(Long.MIN_VALUE).
>>
>> On Wed, Sep 3, 2025 at 7:59 PM ecki <ecki at zusammenkunft.net> wrote:
>>
>>> If you ask me, I don’t find it very useful, It won’t work for
>>> arithmetrics, even the APIs would have a hard time using it (how do you
>>> express the deadline) and APIs with a timeout parameter do have a good
>>> reason for it, better pick “possible” values for better self healing and
>>> unstuck of systems. In fact I would err on the smaller side in combination
>>> with expecting spurious wakeups.
>>>
>>> BTW, when you introduce MIN as well, maybe also think about min
>>> precision, min delta or such. Will it always be 1 nano?
>>>
>>> Gruß,
>>> Bernd
>>> --
>>> https://bernd.eckenfels.net
>>> ------------------------------
>>> *Von:* core-libs-dev <core-libs-dev-retn at openjdk.org> im Auftrag von
>>> Pavel Rappo <pavel.rappo at gmail.com>
>>> *Gesendet:* Donnerstag, September 4, 2025 12:41 AM
>>> *An:* Kurt Alfred Kluever <kak at google.com>
>>> *Cc:* Stephen Colebourne <scolebourne at joda.org>; core-libs-dev <
>>> core-libs-dev at openjdk.org>
>>> *Betreff:* Re: Duration.MAX_VALUE
>>>
>>> This is useful; thanks. It would be good to see more of your data.
>>>
>>> My use case is also duration which practically means **forever**. I
>>> pass it to methods that accept timeouts, and expect these methods to
>>> correctly interpret it.
>>>
>>> One example of a practical interpretation is
>>> java.util.concurrent.TimeUnit.convert(Duration). This method never
>>> overflows; instead, it caps at Long.MAX_VALUE nanoseconds, which is
>>> roughly 292 years.
>>>
>>> Would I be okay, if the proposed duration didn't reflect **forever**
>>> but instead reflected **long enough**? I think so. But it still
>>> somehow feels wrong to make it less than maximum representable value.
>>>
>>> Personally, I'm not interested in calendar arithmetic, that is, in
>>> adding or subtracting durations. Others might be, and that's okay and
>>> needs to be factored in. For better or worse, java.time made a choice
>>> to be unforgiving in regard to overflow and is very upfront about it.
>>> It's not only proposed Duration.MAX. The same thing happens if you try
>>> this
>>>
>>> Instant.MAX.toEpochMilli()
>>>
>>> I guess my point is that doing calendar arithmetic on an unknown value
>>> is probably wrong. Doing it on a known huge/edge-case value is surely
>>> wrong. So back to your data. I would be interested to see what
>>> triggers overflows for your Durations.MAX.
>>>
>>> On Wed, Sep 3, 2025 at 8:45 PM Kurt Alfred Kluever <kak at google.com>
>>> wrote:
>>> >
>>> > Hi all,
>>> >
>>> > Internally at Google, we've had a Durations.MAX constant exposed for
>>> the past 7 years. It now has about 700 usages across our depot, which I can
>>> try to categorize (at a future date).
>>> >
>>> > While I haven't performed that analysis yet, I think exposing this
>>> constant was a bit of a mistake. People seem to want to use MAX to mean
>>> "forever" (often in regards to an RPC deadline). This works fine as long as
>>> every single layer that touches the deadline is very careful about
>>> overflow. The only reasonable thing you can do with MAX is compareTo() and
>>> equals(). Attempting to do any simple math operation (e.g., now+deadline)
>>> is going to explode. Additionally, decomposing Duration.MAX explodes for
>>> any sub-second precision (e.g., toMillis()).
>>> >
>>> > As we dug into this, another proposal came up which was something like
>>> Durations.VERY_LONG. This duration would be longer than any reasonable
>>> finite duration but not long enough to cause an overflow when added to any
>>> reasonable time. E.g., a million years would probably satisfy both
>>> criteria. This would mean math operations and decompositions won't explode
>>> (well, microseconds and nanoseconds still would), and it could safely be
>>> used as a relative timeout.
>>> >
>>> > As I mentioned above, I'd be happy to try to categorize a sample of
>>> our 700 existing usages if folks think that would be useful for this
>>> proposal.
>>> >
>>> > Thanks,
>>> >
>>> > -Kurt Alfred Kluever (on behalf of Google's Java and Kotlin Ecosystem
>>> team)
>>> >
>>> > On Wed, Sep 3, 2025 at 1:53 PM Pavel Rappo <pavel.rappo at gmail.com>
>>> wrote:
>>> >>
>>> >> If I understood you correctly, you think we should also add
>>> >> Duration.MIN. If so, what use case do you envision for it? Or we add
>>> >> if purely for symmetry with Instant?
>>> >>
>>> >> On Wed, Sep 3, 2025 at 6:43 PM Pavel Rappo <pavel.rappo at gmail.com>
>>> wrote:
>>> >> >
>>> >> > On Wed, Sep 3, 2025 at 6:06 PM Stephen Colebourne <
>>> scolebourne at joda.org> wrote:
>>> >> > >
>>> >> > > Hmm, yes. Not sure why that didn't get added in Java 8!
>>> >> > > The constants would be MAX/MIN as per classes like Instant.
>>> >> > > Stephen
>>> >> >
>>> >> > I thought that naming could be tricky :) The public constant
>>> >> > Duration.ZERO and the public method isZero() are already there.
>>> >> > However, it does not preclude us from naming a new constant MAX.
>>> >
>>> >
>>> >
>>> > --
>>> > kak
>>>
>>>
>>
>> --
>> kak
>>
>>
>>
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