一个轻量的数据库数据告警器
- 2022 年 5 月 26 日
本文字数:15891 字
阅读完需:约 52 分钟
「 傍晚时分,你坐在屋檐下,看着天慢慢地黑下去,心里寂寞而凄凉,感到自己的生命被剥夺了。当时我是个年轻人,但我害怕这样生活下去,衰老下去。在我看来,这是比死亡更可怕的事。--------王小波」
我的需求:
需要写一个数据库数据监控的告警小工具,要求:
非侵入式的,对监控的数据只有查询权限,没有写权限
可以对数据表的部分数据状态,数据数量进行监控告警
监控数据,告警条件等是可配置的
我需要解决的问题:
抽象告警行为,解耦告警流程构建过程
告警命中之后如何避免重复告警
可配置的部分如何从流程代码中解耦为配置
如何动态配置告警扫描计划
我是这样做的:
整体来讲,逻辑很简单,没啥技术难点,属于重复造轮子,考虑到需要解析配置文件、多数据源配置,定时任务等,所以使用 SpringBoot,利用其自动化配置,类型安全配置属性,集成简单的任务调度等优点,可以方便地的配置不同的数据源,同时将复杂配置文件中的数据注入 Bean 中,动态配置定时计划,考虑到后期扩展,用 web 的方式。
关于多数据源配置和类型安全配置属性等不是本文重点,这里不多讲。
编码思路:
一是解耦告警器类的构建和构建步骤
二是解耦告警流程,涉及的单个行为从流程解耦,对于行为可变的部分从代码解耦为配置文件。
三是对于告警缓存的处理,非侵入式需要解决重复告警,当前集成了 H2,但是没有使用,感觉有点重,所以利用
WeakHashMap
构建了一个弱键的缓存工具类来实现。
解耦告警器类的构建和构建步骤
对于告警器类的构建,涉及初始化
和告警规则生成
两部分,初始化负责告警配置文件加载解析校验,告警规则生成负责告警流程的建立。
这里可以使用默认的初始化规则,和告警解析规程,也可以使用自定义的规则。整体上编码基于构建者设计模式
,类似于Spring Security配置对象
的构建
可以使用默认的告警解析流程,调用方式
alarms.alarmStart()
或者
alarms.alarmsInit(null).alarmsRun(null);
也可以通过自定义告警解析流程,这里采用函数式编程的思想,通过行为参数化的方式,可以动态编写告警解析流程。
// 告警器初始化
alarms.alarmsInit(alarmsInit -> {
logger.info("告警器扫描时间周期cron:" + alarmsInit.getMinute());
alarmsInit.getAlarms().forEach((alarm -> {
logger.info("加载的告警器名称:" + alarm.getItemsName());
logger.info("触发器:" + alarm.getTrigger());
logger.info("动作:" + Arrays.toString(alarm.getActions()));
logger.info("告警媒介:" + Arrays.toString(alarm.getMediaType()));
logger.info("告警内容:" + alarm.getMedia());
logger.info("告警短信插表SQL:" + alarm.getMediaSql());
}));
return alarmsInit;
// 告警规则生成
}).alarmsRun(alarmsRun -> {
logger.info("告警器扫描......");
alarmsRun.getAlarms().forEach(alarm -> {
Boolean boo = Long.class.cast(jdbcTemplateOne.queryForList(alarm.getTrigger()).get(0).get("isAlarms")) == 1L ? Boolean.TRUE : Boolean.FALSE;
if (boo) {
logger.info("告警规则命中......" + alarm.getTrigger());
Arrays.stream(alarm.getActions()).forEach(sql -> {
List<Map<String, Object>> list = jdbcTemplateOne.queryForList(sql);
Object[] codes = list.stream().map((code) -> code.get("code").toString()).toArray();
Arrays.stream(alarm.getMediaType()).forEach(phone -> {
String msg = String.format(alarm.getMedia(), Arrays.toString(codes));
logger.info("告警消息生产......》》》》 content:" + msg + " phone:" + phone);
Object oldTime = cache.get(msg + phone);
if (Objects.isNull(oldTime)) {
cache.put(msg + phone, System.currentTimeMillis());
jdbcTemplateTow.execute(String.format(alarm.getMediaSql(), msg, phone, phone));
} else {
if (System.currentTimeMillis() - Long.class.cast(oldTime) > 7200000L) {
jdbcTemplateTow.execute(String.format(alarm.getMediaSql(), msg, phone, phone));
cache.put(msg + phone, System.currentTimeMillis());
} else {
logger.info("2小时内重复告警消息....不发送");
}
}
});
});
}
});
return alarmsRun;
});
解耦告警行为和流程
关于告警流程,这里结合zabbix
监控告警的配置方式,抽象出触发器,动作,告警媒介,告警消息模板,插表 sql 等行为,整个告警流程行为通过配置文件配置,在上面告警器构建中告警规则生成中整合为完整流程。
触发器(trigger):这里的触发器是一个返回 0/1 布尔值的 SQL,当为 true 时人为告警被触发,会执行动作。
动作(actions[]):动作在这里是一组返回触发告警唯一标识内容的 SQL,用于描述告警触发后的行为,返回触发告警的数据标识
告警媒介(mediaType[]): 当前告警通过短信的方式,所以这里是一组电话号码,要给哪些用户发生告警消息
告警消息模板(media):不多讲,结合上面动作获取的告警数据,生成完整告警消息
插表 sql(mediaSql): 当前发送短信的方式通过插表的方式,如过通过邮件或则短信发送调 API 的方式,就需要自定义告警规则
我们通配置文件看几个具体的场景
活动监控场景
:适用一些批量处理任务的数据,通过 where 条件判断是否有不符合预期状态的数据,有则获取这部分数据的唯一标识,生成告警消息发送。
空表校验场景
: 适用一些账期表,在某些时间会数据落表,通过 where 条件判断是否存在数据,没有则通过select 'XXX 表数据为空' as code
的方式构建告警消息,发生告警讯息
大表监控场景
: 适用部分大表在数据量达到某个峰值的时候,会影响系统性能、SQL 超时甚至部分持久化数据丢失,需要对冗余数据进行备份清理。需要提前告警.
alarms:
minute: "*/5 * * * * ?"
alarms:
# 告警策略名称
- itemsName: "活动监控 "
# SQL return isAlarms is Boolean 触发器
trigger: "select count(*) > 0 as isAlarms from 活动表 a WHERE a.CREATED_DATE > SUBDATE(NOW(),interval 1 day) AND a.CREATED_DATE < SUBDATE(NOW(), interval 1 hour) AND a.STATE ='A' AND a.SP_ID=0"
# SQL return code is String[], 动作
actions: [ "select ACTIVITY_CODE as code from 活动表 a WHERE a.CREATED_DATE > SUBDATE(NOW(),interval 1 day) AND a.CREATED_DATE < SUBDATE(NOW(), interval 1 hour) AND a.STATE ='A' AND a.SP_ID=0" ]
# MMS is String[] 告警媒介
mediaType: [ "18147405370","13147405370","12147405370"]
# MMS content 告警消息
media: "%s 活动发生异常,请排查"
# MMS install SQL 插表sql
mediaSql: "INSERT INTO 短信表 (MT_SEQ, MT_SERV_TYPE, SEND_PRIORITY, MSG_CONTENT, DEST_TERMID, SRC_TERMID, FEE_USER_TERMID, FEE_TYPE, MAKE_TIME, REQUIRE_APPLY ) VALUES (sms.ACCT_SENDSMS_SEQ.NEXTVAL,'123',2,'%s', '%s','1183111', '%s', '00',SYSDATE,0)"
- itemsName: "XXX 空表校验"
trigger: "select count(*) = 0 as isAlarms from XXX"
actions: ["select 'XXX 表数据为空' as code "]
mediaType: ['123123','3123']
media: "%s 异常信息,请排查"
mediaSql: "insert into sms(phone,content) values('%s','%s')"
- itemsName: "XXX 大表监控"
trigger: "select count(*) > 40000000 as isAlarms from XXX"
actions: ["select 'XXX 表数据量超过峰值' as code "]
mediaType: ['123123','3123']
media: "%s 异常信息,请排查"
mediaSql: "insert into sms(phone,content) values('%s','%s')"
重复告警的问题
关于重复告警的问题,集成了 H2,但是目前告警数据量小,所以没有使用,对于重复告警使用了 WeakHashMap 构建了一个弱键的缓存工具类实现。
第一告警触发后,存到缓存里,之后 2 小时内触发告警不发送告警消息,2 小时候在发送一次
Object oldTime = cache.get(msg + phone);
if (Objects.isNull(oldTime)) {
cache.put(msg + phone, System.currentTimeMillis());
jdbcTemplateTow.execute(String.format(alarm.getMediaSql(), msg, phone,phone));
} else {
if (System.currentTimeMillis() -Long.class.cast(oldTime) > 7200000L){
jdbcTemplateTow.execute(String.format(alarm.getMediaSql(), msg, phone,phone));
cache.put(msg + phone, System.currentTimeMillis());
}else {
logger.info("2小时内重复告警消息....不发送");
}
}
动态定时任务配置
通过SchedulingConfigurer
配置类实现动态配置,重配置文件获取 cron 表达式
DynamicCronSchedule.java
package com.example.alarms.alert;
import com.example.alarms.alert.dto.Alarms;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.SchedulingConfigurer;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;
import java.util.*;
import java.util.logging.Logger;
/**
* @author LiRuilong
* @Classname DynamicCronSchedule
* @Description TODO
* @Date 2022/5/16 11:31
*/
@Component
@EnableScheduling
public class DynamicCronSchedule implements SchedulingConfigurer {
private static Logger logger = Logger.getLogger("com.example.alarms.alert.DynamicCronSchedule");
@Autowired
private Alarms alarms;
@Override
public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
alarms.alarmsInit(null);
taskRegistrar.addTriggerTask(() -> {
// 自定义逻辑:
//alarms.alarmsRun(alarmsRun -> alarmsRun);
// 默认逻辑:
alarms.alarmsRun(null);
}, (triggerContext) -> {
String cron = alarms.getMinute();
logger.fine("cron expression is " + cron);
logger.fine("trigger list size is " + taskRegistrar.getTriggerTaskList().size());
CronTrigger cronTrigger = new CronTrigger(cron);
Date nextExecTime = cronTrigger.nextExecutionTime(triggerContext);
return nextExecTime;
});
}
}
全部代码
配置相关
---
server:
port: 30036
tomcat:
uri-encoding: utf-8
spring:
datasource:
one:
type: com.alibaba.druid.pool.DruidDataSource
driver-class-name: com.mysql.jdbc.Driver
username:
password:
url:
test-while-idle: true
tow:
driver-class-name: oracle.jdbc.OracleDriver
username:
password:
url:
test-while-idle: true
h2db:
type: com.alibaba.druid.pool.DruidDataSource
driver-class-name: org.h2.Driver
schema: classpath:db/schema.sql
username: sa
password: sa
url: jdbc:h2:mem:alarms
#http://本地端口/h2-console 通过项目来进行访问数据库
h2:
console:
enabled: true
alarms:
minute: "*/5 * * * * ?"
alarms:
# 告警策略名称
- itemsName: "活动监控 "
# SQL return isAlarms is Boolean 触发器
trigger: "select count(*) > 0 as isAlarms from 活动表 a WHERE a.CREATED_DATE > SUBDATE(NOW(),interval 1 day) AND a.CREATED_DATE < SUBDATE(NOW(), interval 1 hour) AND a.STATE ='A' AND a.SP_ID=0"
# SQL return code is String[], 动作
actions: [ "select ACTIVITY_CODE as code from 活动表 a WHERE a.CREATED_DATE > SUBDATE(NOW(),interval 1 day) AND a.CREATED_DATE < SUBDATE(NOW(), interval 1 hour) AND a.STATE ='A' AND a.SP_ID=0" ]
# MMS is String[] 告警媒介
mediaType: [ "18147405370","13147405370","12147405370"]
# MMS content 告警消息
media: "%s 活动发生异常,请排查"
# MMS install SQL 插表sql
mediaSql: "INSERT INTO 短信表 (MT_SEQ, MT_SERV_TYPE, SEND_PRIORITY, MSG_CONTENT, DEST_TERMID, SRC_TERMID, FEE_USER_TERMID, FEE_TYPE, MAKE_TIME, REQUIRE_APPLY ) VALUES (sms.ACCT_SENDSMS_SEQ.NEXTVAL,'123',2,'%s', '%s','1183111', '%s', '00',SYSDATE,0)"
- itemsName: "XXX 空表校验"
trigger: "select count(*) = 0 as isAlarms from XXX"
actions: ["select 'XXX 表数据为空' as code "]
mediaType: ['123123','3123']
media: "%s 异常信息,请排查"
mediaSql: "insert into sms(phone,content) values('%s','%s')"
- itemsName: "XXX 大表监控"
trigger: "select count(*) > 40000000 as isAlarms from XXX"
actions: ["select 'XXX 表数据量超过峰值' as code "]
mediaType: ['123123','3123']
media: "%s 异常信息,请排查"
mediaSql: "insert into sms(phone,content) values('%s','%s')"
package com.example.alarms.alert.config;
import com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import javax.sql.DataSource;
/**
* @author LiRuilong
* @Classname DataSourceConfig
* @Description TODO
* @Date 2022/5/10 9:59
*/
@Configuration
public class DataSourceConfig {
@Bean
@ConfigurationProperties("spring.datasource.one")
DataSource dsOne() {
return DruidDataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties("spring.datasource.tow")
DataSource dsTow() {
return DruidDataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties("spring.datasource.h2db")
DataSource dsH2db() {
return DruidDataSourceBuilder.create().build();
}
}
package com.example.alarms.alert.config;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.jdbc.core.JdbcTemplate;
import javax.sql.DataSource;
/**
* @author LiRuilong
* @Classname JdbcTemplateConfig
* @Description TODO
* @Date 2022/5/10 10:01
*/
@Configuration
public class JdbcTemplateConfig {
@Bean
JdbcTemplate jdbcTemplateOne(@Qualifier("dsOne") DataSource ds) {
return new JdbcTemplate(ds);
}
@Bean
JdbcTemplate jdbcTemplateTow(@Qualifier("dsTow") DataSource ds) {
return new JdbcTemplate(ds);
}
@Bean
JdbcTemplate jdbcTemplateH2db(@Qualifier("dsH2db") DataSource ds) {
return new JdbcTemplate(ds);
}
}
package com.example.alarms.alert;
import com.example.alarms.alert.dto.Alarms;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.SchedulingConfigurer;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;
import java.util.*;
import java.util.logging.Logger;
/**
* @author LiRuilong
* @Classname DynamicCronSchedule
* @Description TODO
* @Date 2022/5/16 11:31
*/
@Component
@EnableScheduling
public class DynamicCronSchedule implements SchedulingConfigurer {
private static Logger logger = Logger.getLogger("com.example.alarms.alert.DynamicCronSchedule");
@Autowired
private Alarms alarms;
@Override
public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
alarms.alarmsInit(null);
taskRegistrar.addTriggerTask(() -> {
// 自定义逻辑:
//alarms.alarmsRun(alarmsRun -> alarmsRun);
// 默认逻辑:
alarms.alarmsRun(null);
}, (triggerContext) -> {
String cron = alarms.getMinute();
logger.fine("cron expression is " + cron);
logger.fine("trigger list size is " + taskRegistrar.getTriggerTaskList().size());
CronTrigger cronTrigger = new CronTrigger(cron);
Date nextExecTime = cronTrigger.nextExecutionTime(triggerContext);
return nextExecTime;
});
}
}
告警 bean 相关
package com.example.alarms.alert.dto;
import java.io.Serializable;
import java.util.Arrays;
/**
* @Classname Alarm
* @Description TODO
* @Date 2022/5/13 18:12
* @Created LiRuilong
*/
public class Alarm implements Serializable {
private String itemsName;
private String trigger;
private String[] actions;
private String[] mediaType;
private String media;
private String mediaSql;
public String getItemsName() {
return itemsName;
}
public Alarm setItemsName(String itemsName) {
this.itemsName = itemsName;
return this;
}
public String[] getActions() {
return actions;
}
public Alarm setActions(String[] actions) {
this.actions = actions;
return this;
}
public String getTrigger() {
return trigger;
}
public Alarm setTrigger(String trigger) {
this.trigger = trigger;
return this;
}
public String[] getMediaType() {
return mediaType;
}
public Alarm setMediaType(String[] mediaType) {
this.mediaType = mediaType;
return this;
}
public String getMedia() {
return media;
}
public Alarm setMedia(String media) {
this.media = media;
return this;
}
public String getMediaSql() {
return mediaSql;
}
public Alarm setMediaSql(String mediaSql) {
this.mediaSql = mediaSql;
return this;
}
@Override
public String toString() {
return "Alarm{" +
"itemsName='" + itemsName + '\'' +
", actions=" + Arrays.toString(actions) +
", trigger='" + trigger + '\'' +
", mediaType=" + Arrays.toString(mediaType) +
", media='" + media + '\'' +
", mediaSql='" + mediaSql + '\'' +
'}';
}
}
package com.example.alarms.alert.dto;
import com.example.alarms.alert.WeakHashMapCache;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.function.Function;
import java.util.logging.Logger;
/**
* @author LiRuilong
* @Classname Alarms
* @Description TODO
* @Date 2022/5/13 17:23
*/
@Component
@ConfigurationProperties(prefix = "alarms")
public class Alarms {
Logger logger = Logger.getLogger("com.example.alarms.alert.dto.Alarms");
WeakHashMapCache cache = new WeakHashMapCache.Builder<String, String>(1000).build();
private String minute;
private List<Alarm> alarms;
@Autowired
@Qualifier("jdbcTemplateOne")
JdbcTemplate jdbcTemplateOne;
@Autowired
@Qualifier("jdbcTemplateTow")
JdbcTemplate jdbcTemplateTow;
public String getMinute() {
return minute;
}
public Alarms setMinute(String minute) {
this.minute = minute;
return this;
}
public List<Alarm> getAlarms() {
return alarms;
}
public Alarms setAlarms(List<Alarm> alarms) {
this.alarms = alarms;
return this;
}
/**
* @param function:
* @return: com.example.alarms.alert.dto.Alarms
* @Description 告警数据加载,默认逻辑
* @author LiRuilong
* @date 2022/5/16 11:12
**/
public Alarms alarmsInit(Function<Alarms, Alarms> function) {
if (Objects.nonNull(function)) {
return function.apply(this);
} else {
logger.info("告警器扫描时间周期cron:" + this.getMinute());
alarms.forEach((alarm -> {
logger.info("加载的告警器名称:" + alarm.getItemsName());
logger.info("触发器:" + alarm.getTrigger());
logger.info("动作:" + Arrays.toString(alarm.getActions()));
logger.info("告警媒介:" + Arrays.toString(alarm.getMediaType()));
logger.info("告警内容:" + alarm.getMedia());
logger.info("告警短信插表SQL:" + alarm.getMediaSql());
}));
return this;
}
}
/**
* @param function:
* @return: com.example.alarms.alert.dto.Alarms
* @Description 告警器执行,默认逻辑
* @author LiRuilong
* @date 2022/5/16 11:30
**/
public Alarms alarmsRun(Function<Alarms, Alarms> function) {
if (Objects.nonNull(function)) {
return function.apply(this);
} else {
logger.info("告警器扫描......");
alarms.forEach(alarm -> {
Boolean boo = Long.class.cast(jdbcTemplateOne.queryForList(alarm.getTrigger()).get(0).get("isAlarms")) == 1L ? Boolean.TRUE : Boolean.FALSE;
if (boo) {
logger.info("告警规则命中......" + alarm.getTrigger());
Arrays.stream(alarm.getActions()).forEach(sql -> {
List<Map<String, Object>> list = jdbcTemplateOne.queryForList(sql);
Object[] codes = list.stream().map((code) -> code.get("code").toString()).toArray();
Arrays.stream(alarm.getMediaType()).forEach(phone -> {
String msg = String.format(alarm.getMedia(), Arrays.toString(codes));
logger.info("告警消息生产......》》》》 content:" + msg + " phone:" + phone);
Object oldTime = cache.get(msg + phone);
if (Objects.isNull(oldTime)) {
cache.put(msg + phone, System.currentTimeMillis());
jdbcTemplateTow.execute(String.format(alarm.getMediaSql(), msg, phone,phone));
} else {
if (System.currentTimeMillis() -Long.class.cast(oldTime) > 7200000L){
jdbcTemplateTow.execute(String.format(alarm.getMediaSql(), msg, phone,phone));
cache.put(msg + phone, System.currentTimeMillis());
}else {
logger.info("2小时内重复告警消息....不发送");
}
}
});
});
}
});
return this;
}
}
public void alarmStart() {
alarmsInit(null).alarmsRun(null);
}
public static void main(String[] args) {
}
}
动态定时任务配置
package com.example.alarms.alert;
import com.example.alarms.alert.dto.Alarms;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.SchedulingConfigurer;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;
import java.util.*;
import java.util.logging.Logger;
/**
* @author LiRuilong
* @Classname DynamicCronSchedule
* @Description TODO
* @Date 2022/5/16 11:31
*/
@Component
@EnableScheduling
public class DynamicCronSchedule implements SchedulingConfigurer {
private static Logger logger = Logger.getLogger("com.example.alarms.alert.DynamicCronSchedule");
@Autowired
private Alarms alarms;
@Override
public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
alarms.alarmsInit(null);
taskRegistrar.addTriggerTask(() -> {
// 自定义逻辑:
//alarms.alarmsRun(alarmsRun -> alarmsRun);
// 默认逻辑:
alarms.alarmsRun(null);
}, (triggerContext) -> {
String cron = alarms.getMinute();
logger.fine("cron expression is " + cron);
logger.fine("trigger list size is " + taskRegistrar.getTriggerTaskList().size());
CronTrigger cronTrigger = new CronTrigger(cron);
Date nextExecTime = cronTrigger.nextExecutionTime(triggerContext);
return nextExecTime;
});
}
}
启动类
package com.example.alarms;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableScheduling;
/**
* @Description
* @author LiRuilong
* @date 2022/5/13 17:22
**/
@EnableScheduling
@SpringBootApplication
public class AlarmsApplication {
public static void main(String[] args) {
SpringApplication.run(AlarmsApplication.class, args);
}
}
弱键缓存
package com.example.alarms.alert;
import java.util.Map;
import java.util.Objects;
import java.util.WeakHashMap;
import java.util.concurrent.ConcurrentHashMap;
/**
* @Classname ConcurrentCache
* @Description TODO 一个基于WeakHashMap本地缓存(LRU)类
* @Date 2022/5/16 17:18
* @author LiRuilong
*/
public class WeakHashMapCache<K,V> {
private final int size;
private final Map<K,V> eden;
private final Map<K,V> longterm;
private WeakHashMapCache(Builder<K,V> builder){
this.size = builder.size;
this.eden = builder.eden;
this.longterm = builder.longterm;
}
public static class Builder<K,V>{
private volatile int size;
private volatile Map<K,V> eden;
private volatile Map<K,V> longterm;
public Builder(int size){
this.size = rangeCheck(size,Integer.MAX_VALUE,"缓存容器初始化容量异常");
this.eden = new ConcurrentHashMap<>(size);
this.longterm = new WeakHashMap<>(size);
}
private static int rangeCheck(int val, int i, String arg) {
if (val < 0 || val > i) {
throw new IllegalArgumentException(arg + ":" + val);
}
return val;
}
public WeakHashMapCache build(){
return new WeakHashMapCache(this);
}
}
public V get(K k){
V v = this.eden.get(k);
if (Objects.isNull(v)){
v = this.longterm.get(k);
if (Objects.nonNull(v)){
this.eden.put(k,v);
}
}
return v;
}
public void put(K k,V v){
if (this.eden.size() >= size){
this.longterm.putAll(this.eden);
this.eden.clear();
}
this.eden.put(k,v);
}
public static void main(String[] args) {
WeakHashMapCache cache = new WeakHashMapCache.Builder<String,String>(4).build();
for (int i = 0; i < 5; i++) {
cache.put(i+"",i+"");
}
System.gc();
for (int i = 0; i < 5; i++) {
System.out.println(cache.get(i + ""));
}
}
}
版权声明: 本文为 InfoQ 作者【山河已无恙】的原创文章。
原文链接:【http://xie.infoq.cn/article/eb28f448f964683c3838b4294】。
本文遵守【CC-BY 4.0】协议,转载请保留原文出处及本版权声明。
山河已无恙
CSDN博客专家,华为云云享专家,RHCE/CKA认证 2022.01.04 加入
Java 后端一枚,技术不高,前端、Shell、Python 也可以写一点.纯种屌丝,不热爱生活,热爱学习,热爱工作,喜欢一直忙,不闲着。喜欢篆刻,喜欢吃好吃的,喜欢吃饱了晒太阳。
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