使用HttpClient時如何完全釋放連接？

Question

我使用HttpClient（ https://hc.apache.org/httpcomponents-client-4.5.x/index.html ）進行許多並行的HTTP調用。 運行一段時間后，它得到以下異常：

java.net.BindException: Address already in use: connect

我試圖關閉所有可見的內容，但是我仍然必須錯過一些東西，因為它仍然存在該錯誤。

如何正確釋放連接以避免此連接泄漏問題？

這是重現此問題的測試用例，在Windows的Java8中運行：

public void test(String url) throws Exception {
    List<Thread> threads = new ArrayList<Thread>();
    for(int t=0; t<40; t++) {
        int tt = t;
        threads.add(new Thread(() -> {
            for(int i=0; i<Integer.MAX_VALUE; i++) {
                URI metadataUri;
                try {
                    metadataUri = new URI(url);
                } catch (Exception e1) {
                    e1.printStackTrace();
                    continue;
                }

                HttpPost httpRequest = new HttpPost(metadataUri);
                httpRequest.setEntity(new ByteArrayEntity( "abc".getBytes()));
                //httpRequest.addHeader("Connection", "close");

                CloseableHttpClient httpclient = HttpClients.custom().build();
                try {
                    CloseableHttpResponse metadataResponse2 = httpclient.execute(httpRequest);
                    metadataResponse2.close();
                } catch (ClientProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    try {
                        httpRequest.completed();
                        httpRequest.releaseConnection();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    try {
                        httpclient.close();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }

                System.out.println("thread " + tt + " round " + i);
            }
        }));
    }

    for(Thread thread : threads) {
        thread.start();
    }
}

Answer 1

通常，嘗試使用resource（ 請參閱參考資料 ）應該可以解決此問題：

            try (CloseableHttpClient httpclient = HttpClients.custom().build();
                CloseableHttpResponse metadataResponse2 = httpclient.execute(httpRequest)) {
            } catch (ClientProtocolException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                httpRequest.completed();
                httpRequest.releaseConnection();

            }