当有30个或更多并发请求时，我会收到类似"无法创建子事件循环/无法打开新选择器/打开的文件太多"的错误。。。如何解决上述错误？我做错什么了吗？我使用的是Spring引导和Java cassandra驱动程序下面是连接文件：
public class Connection {
public static Session getConnection() {
final Cluster cluster = Cluster.builder().addContactPoint(ConnectionBean.getCASSANDRA_DB_IP())
.withQueryOptions(new QueryOptions().setConsistencyLevel(ConsistencyLevel.LOCAL_ONE))
.withCredentials(ConnectionBean.getCASSANDRA_USER(), ConnectionBean.getCASSANDRA_PASSWORD())
.withPoolingOptions(poolingOptions)
.build();
final Session session = cluster.connect(ConnectionBean.getCASSANDRA_DB_NAME());
return session;
}
}
下面是我在连接文件中使用的ConnectionBean文件：
public class ConnectionBean {
public static String CASSANDRA_DB_IP;
public static String CASSANDRA_DB_NAME;
public static String CASSANDRA_USER;
public static String CASSANDRA_PASSWORD;
public ConnectionBean() {
}
public ConnectionBean(String CASSANDRA_DB_IP,String CASSANDRA_DB_NAME,String CASSANDRA_USER,String CASSANDRA_PASSWORD) {
this.CASSANDRA_DB_IP=CASSANDRA_DB_IP;
this.CASSANDRA_DB_NAME=CASSANDRA_DB_NAME;
this.CASSANDRA_USER=CASSANDRA_USER;
this.CASSANDRA_PASSWORD=CASSANDRA_PASSWORD;
}
public static String getCASSANDRA_DB_IP() {
return CASSANDRA_DB_IP;
}
public static void setCASSANDRA_DB_IP(String cASSANDRA_DB_IP) {
CASSANDRA_DB_IP = cASSANDRA_DB_IP;
}
public static String getCASSANDRA_DB_NAME() {
return CASSANDRA_DB_NAME;
}
public static void setCASSANDRA_DB_NAME(String cASSANDRA_DB_NAME) {
CASSANDRA_DB_NAME = cASSANDRA_DB_NAME;
}
public static String getCASSANDRA_USER() {
return CASSANDRA_USER;
}
public static void setCASSANDRA_USER(String cASSANDRA_USER) {
CASSANDRA_USER = cASSANDRA_USER;
}
public static String getCASSANDRA_PASSWORD() {
return CASSANDRA_PASSWORD;
}
public static void setCASSANDRA_PASSWORD(String cASSANDRA_PASSWORD) {
CASSANDRA_PASSWORD = cASSANDRA_PASSWORD;
}
}
下面是初始化ConnectionBean变量的类：
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
private static final String LOGIN_PROCESSING_URL = "/login";
private static final String LOGIN_FAILURE_URL = "/login?error";
private static final String LOGIN_URL = "/login";
@Autowired
private BCryptPasswordEncoder bCryptPasswordEncoder;
@Autowired
private DataSource dataSource;
@Value("${spring.queries.users-query}")
private String usersQuery;
@Value("${spring.queries.roles-query}")
private String rolesQuery;
@Value("${CASSANDRA_DB_IP}")
public String CASSANDRA_DB_IP;
@Value("${CASSANDRA_DB_NAME}")
public String CASSANDRA_DB_NAME;
@Value("${CASSANDRA_USER}")
public String CASSANDRA_USER;
@Value("${CASSANDRA_PASSWORD}")
public String CASSANDRA_PASSWORD;
@Override
protected void configure(AuthenticationManagerBuilder auth) throws Exception {
ConnectionBean cb = new ConnectionBean(CASSANDRA_DB_IP, CASSANDRA_DB_NAME, CASSANDRA_USER, CASSANDRA_PASSWORD);
auth.jdbcAuthentication().usersByUsernameQuery(usersQuery).authoritiesByUsernameQuery(rolesQuery)
.dataSource(dataSource).passwordEncoder(bCryptPasswordEncoder);
}
@Override
protected void configure(HttpSecurity http) throws Exception {
// Not using Spring CSRF here to be able to use plain HTML for the login page
http.csrf().disable()
// Register our CustomRequestCache, that saves unauthorized access attempts, so
// the user is redirected after login.
.requestCache().requestCache(new CustomRequestCache())
// Restrict access to our application.
.and().authorizeRequests()
// Allow all flow internal requests.
.requestMatchers(SecurityUtils::isFrameworkInternalRequest).permitAll()
// Allow all requests by logged in users.
.anyRequest().authenticated()
// Configure the login page.
.and().formLogin().loginPage(LOGIN_URL).permitAll().loginProcessingUrl(LOGIN_PROCESSING_URL)
.failureUrl(LOGIN_FAILURE_URL)
// Register the success handler that redirects users to the page they last tried
// to access
.successHandler(new SavedRequestAwareAuthenticationSuccessHandler())
// Configure logout
.and().logout().logoutSuccessUrl(LOGOUT_SUCCESS_URL);
}
/**
* Allows access to static resources, bypassing Spring security.
*/
@Override
public void configure(WebSecurity web) throws Exception {
web.ignoring().antMatchers(
// Vaadin Flow static resources
"/VAADIN/**",
// the standard favicon URI
"/favicon.ico",
// web application manifest
"/manifest.json", "/sw.js", "/offline-page.html",
// icons and images
"/icons/**", "/images/**",
// (development mode) static resources
"/frontend/**",
// (development mode) webjars
"/webjars/**",
// (development mode) H2 debugging console
"/h2-console/**",
// (production mode) static resources
"/frontend-es5/**", "/frontend-es6/**");
}
}
最后，下面是我查询cassandra数据的类：
public class getData {
Session session;
public getData(){
session = Connection.getConnection();
getDataTable();
}
private void getDataTable() {
try {
String query = "SELECT * FROM tableName";
ResultSet rs = session.execute(query);
for (Row row : rs) {
/*Do some stuff here using row*/
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
如果为每个请求调用getConnection()，则每次都要创建一个新的Cluster实例。
不鼓励这样做，因为在客户端和每个Cluster实例的C*节点之间会创建一个连接，而对于每个Session，则会为每个C*节点创建至少一个连接的连接池。
如果在请求完成后没有关闭Cluster实例，则这些连接将保持打开状态。在多次请求之后，您将打开太多的连接，以至于您的操作系统中的文件描述符将用完。
要解决此问题，请仅创建一个Cluster和Session实例，并在请求之间重用它。在使用Cassandra:的DataStax驱动程序时，4条简单规则概述了此策略
- 每个(物理(集群使用一个集群实例(每个应用程序生存期(
- 每个密钥空间最多使用一个会话，或者使用单个会话并在查询中明确指定密钥空间