What does PoolingHttpClientConnectionManager do when there is a temporary network outage? - httpclient

Question

I am adding PoolingHttpClientConnectionManager to our Spring Boot service, which is currently using RestTemplate and CloseableHttpClient to make requests. The service is using Apache httpcomponents 4.5.
What happens if there is a temporary network outage? Do the bad connections get discarded from the pool? Or does the pool fill up with bad connections during the outage? Once the outage is over, does the pool recover on its own? Or do I need to write code to detect them and remove them from the pool?
Here is the code I have so far:
#Bean
public CloseableHttpClient closeableHttpClient() {
CloseableHttpClient client = HttpClients.custom()
.setDefaultRequestConfig(getDefaultRequestConfig())
.setConnectionManager(poolingHttpClientConnectionManager())
.setKeepAliveStrategy(getConnectionKeepAliveStrategy())
.setRetryHandler(getHttpRequestRetryHandler())
.build();
return client;
}
#Bean
public PoolingHttpClientConnectionManager poolingHttpClientConnectionManager() {
Registry<ConnectionSocketFactory> socketFactoryRegistry = getSocketFactoryRegistry();
PoolingHttpClientConnectionManager poolingConnectionManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
poolingConnectionManager.setMaxTotal(maxTotalConnections);
poolingConnectionManager.setDefaultMaxPerRoute(maxRouteConnections);
return poolingConnectionManager;
}
#Bean
public Runnable idleConnectionMonitor(PoolingHttpClientConnectionManager pool) {
return new Runnable() {
#Override
#Scheduled(fixedDelay = 20000)
public void run() {
if (pool != null) {
pool.closeExpiredConnections();
pool.closeIdleConnections(idleConnectionCloseTime, TimeUnit.MILLISECONDS);
}
}
};
}
#Bean
public TaskScheduler taskScheduler() {
ThreadPoolTaskScheduler scheduler = new ThreadPoolTaskScheduler();
scheduler.setThreadNamePrefix("idleMonitor");
scheduler.setPoolSize(idleMonitorPoolSize);
return scheduler;
}
private RequestConfig getDefaultRequestConfig() {
RequestConfig requestConfig = RequestConfig.custom()
.setConnectTimeout(establishConnectionTimeout)
.setConnectionRequestTimeout(fetchConnectionTimeout)
.setSocketTimeout(socketInactivityTimeout)
.build();
return requestConfig;
}
private Registry<ConnectionSocketFactory> getSocketFactoryRegistry() {
SSLConnectionSocketFactory socketFactory;
socketFactory = new SSLConnectionSocketFactory(getSSLContext(), new String[] { sslProtocol }, null, new DefaultHostnameVerifier());
Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder
.<ConnectionSocketFactory> create().register("https", socketFactory)
.build();
return socketFactoryRegistry;
}
private SSLContext getSSLContext() {
TrustStrategy acceptingTrustStrategy = null;
try {
KeyStore keyStore = KeyStore.getInstance(keyStoreType);
keyStore.load(new FileInputStream(new File(keyStoreFile)), keyStorePwd.toCharArray());
return new SSLContextBuilder()
.loadTrustMaterial(keyStore, acceptingTrustStrategy)
.loadKeyMaterial(keyStore, keyStorePwd.toCharArray())
.build();
} catch (KeyStoreException | IOException | NoSuchAlgorithmException | CertificateException | KeyManagementException | UnrecoverableKeyException e) {
throw new RuntimeException(e);
}
}
private ConnectionKeepAliveStrategy getConnectionKeepAliveStrategy() {
return (httpResponse, httpContext) -> {
HeaderIterator headerIterator = httpResponse.headerIterator(HTTP.CONN_KEEP_ALIVE);
HeaderElementIterator elementIterator = new BasicHeaderElementIterator(headerIterator);
while (elementIterator.hasNext()) {
HeaderElement element = elementIterator.nextElement();
String param = element.getName();
String value = element.getValue();
if (value != null && param.equalsIgnoreCase("timeout")) {
return Long.parseLong(value) * 1000; // convert to ms
}
}
return defaultKeepAliveTime;
};
}
private DefaultHttpRequestRetryHandler getHttpRequestRetryHandler() {
return new DefaultHttpRequestRetryHandler(httprequestRetryCount, false);
}

Answer 1

Those connections become invalid or "stale". If HttpClient has been configured to validate connections prior to using them to execute requests, stale connections will be detected and discarded.