如何按自定义顺序处理Map/Set值中invokeAll的EntryProcessor？

Great questions about invokeAll() in distributed caching systems—let's unpack each of your concerns clearly:

The docs explicitly state that invokeAll() doesn't guarantee processing order (it can even process entries concurrently), so if you need strict custom order (like the key sequence specified in your docs), you can't rely on invokeAll()'s default behavior. Instead, you'll need to handle the ordering manually.

A straightforward approach is to iterate over your keys in the desired order and call invoke() for each entry individually. This way, you have full control over the execution sequence. Here's a quick example:

// Assume we have a predefined ordered list of keys matching your document's sequence
List<String> customOrderedKeys = Arrays.asList("key1", "key3", "key2");
Cache<String, Object> cache = ...; // Your cache instance

for (String key : customOrderedKeys) {
    if (cache.containsKey(key)) {
        cache.invoke(key, new EntryProcessor<String, Object, Object>() {
            @Override
            public Object process(MutableEntry<String, Object> entry, Object... args) {
                // Your entry processing logic here
                entry.setValue(updatedValue);
                return null;
            }
        });
    }
}

If you want some concurrency but still need logical batch ordering, you could split the ordered keys into batches, process each batch with invokeAll(), and wait for each batch to finish before moving to the next. But for strict per-entry sequence, the per-key invoke() loop is the safest bet.

Short answer: No. Even if you pass a TreeMap or TreeSet (which maintains sorted keys) to invokeAll(), the caching implementation is free to process entries in any order—including shuffling them for concurrent processing. The sorted nature of the input collection doesn't override the explicit documentation that "processing order is undefined".

The implementation might happen to iterate over the collection's entries in order, but there's no guarantee. You should never rely on this for business-critical ordering requirements.

No, that's not how the locking works. The invoke() method (and by extension, invokeAll() for individual entries) uses per-entry locking, not a global lock on all keys in the input set.

Here's what typically happens:

• For each entry in the input set, the cache attempts to acquire the lock for that specific key.
• Once the lock is acquired, the EntryProcessor runs for that entry.
• After the processor completes (successfully or with an exception), the lock for that key is released immediately.
• Different entries can be processed concurrently (as the docs note), each with their own individual locks.

This means invokeAll() doesn't hold all locks for the duration of the entire operation—locks are acquired and released per-entry, allowing for parallelism where possible.

内容的提问来源于stack exchange，提问作者dvlcis