[GitHub] nifi issue #1646: NIFI-3668: Fix purging expired replicate requests.

[ijokarumawak <gi...@git.apache.org>]

Github user ijokarumawak commented on the issue:

    https://github.com/apache/nifi/pull/1646
  
    @markap14 Would you review this fix since you originally worked on NIFI-3636.
    I've reproduced the issue with following test method which sends lots of S2S client requests concurrently against a NiFi cluster. The issue was reproducible before this patch and confirmed it's addressed by this patch:
    
    ```java
        @Test
        public void test() throws Exception {
            final ExecutorService executors = Executors.newFixedThreadPool(100);
            final AtomicInteger processed = new AtomicInteger();
            final AtomicInteger error = new AtomicInteger();
            for (int i = 0; i < 1000; i++) {
                executors.submit(() -> {
                    try (final SiteToSiteClient client = new SiteToSiteClient.Builder()
                            .transportProtocol(SiteToSiteTransportProtocol.HTTP)
                            .url("http://localhost:9011/nifi/")
                            .portName("input")
                            .build()) {
    
                        final Transaction transaction = client.createTransaction(TransferDirection.SEND);
                        transaction.send("test".getBytes(), new HashMap<>());
                        transaction.confirm();
                        transaction.complete();
                        processed.incrementAndGet();
    
                    } catch (Exception e) {
                        logger.error("ERR!", e);
                        error.incrementAndGet();
                    }
                });
            }
            executors.shutdown();
            executors.awaitTermination(1, TimeUnit.DAYS);
            logger.warn("processed={}, err={}", new Object[]{processed.get(), error.get()});
        }
    ```
    
    On Mac OS X Sierra, I had to increase file descriptor limit to make above test works by creating limit.maxfiles.plist and limit.maxproc.plist as described in these web pages:
    - https://www.chrissearle.org/2016/10/01/too-many-open-files-on-osx-macos/
    - https://superuser.com/questions/830149/os-x-yosemite-too-many-files-open
    
    I hope the fix still preserve the performance gain in clustered environment that have been added by NIFI-3636. Thanks!


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