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70766746f3
Preparing to point the finger at TaggedCache's mutex when the whole process freezes at rotation time. Every `sweep()` and `getKeys()` calls `noteLockHold` after releasing the mutex; `takeLockHoldPeak()` returns the longest hold since the last call and resets. A one-second hold logs a warn line naming the op and the entry count — the same one-second bar `LoadMonitor::addLoadSample` uses to flag a job. `lockHoldPeakNs_` is a mutable atomic so `getKeys() const` can note its own hold; `FullBelowCache` forwards `takeLockHoldPeak()` so the metrics layer can read either cache the same way. Nothing here depends on telemetry — this file lives in `xrpl/basics` and must not. Test pins the behaviour end to end: neither getKeys() nor sweep() records anything on an empty cache; both push the peak above zero once the cache has 200,000 entries; and takeLockHoldPeak() is destructive.
Basics
Utility functions and classes.
The module xrpl/basics should contain no dependencies on other modules.
Choosing an xrpld container.
-
std::vector- For ordered containers with most insertions or erases at the end.
-
std::deque- For ordered containers with most insertions or erases at the start or end.
-
std::list- For ordered containers with inserts and erases to the middle.
- For containers with iterators stable over insert and erase.
- Generally slower and bigger than
std::vectororstd::dequeexcept for those cases.
-
std::set- For sorted containers.
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xrpl::hash_set- Where inserts and contains need to be O(1).
- For "small" sets,
std::setmight be faster and smaller.
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xrpl::hardened_hash_set- For data sets where the key could be manipulated by an attacker in an attempt to mount an algorithmic complexity attack: see http://en.wikipedia.org/wiki/Algorithmic_complexity_attack
The following container is deprecated
std::unordered_set- Use
xrpl::hash_setinstead, which uses a better hashing algorithm. - Or use
xrpl::hardened_hash_setto prevent algorithmic complexity attacks.