[大数据]Elasticsearch 日志监控方案

现在大部分公司都会选择将应用、中间件、系统等日志存储在 Elasticsearch 中，如何发现日志中的异常数据并且及时告警通知就显得十分重要。本文将会介绍两种主流的日志监控方案，分别是 Yelp 公司开源的 ElastAlert 和 Elastic 官方的商业版功能 Watcher。

如下图所示，日志数据源是一台 Nginx 服务器，在该服务器上安装 Filebeat 收集 Nginx 日志并输出到 Elasticsearch，之后会分别演示用 ElastAlert 和 Watcher 两种方案监控日志并进行告警。

部署 Nginx

安装依赖

yum install -y gcc gcc-c++ autoconf pcre pcre-devel make automake wget httpd-tools vim tree zlib-devel

下载安装包

wget http://nginx.org/download/nginx-1.14.0.tar.gz
tar -xzvf nginx-1.14.0.tar.gz

编译安装

cd nginx-1.14.0
./configure

配置 Nginx

编辑配置文件 /usr/local/nginx/conf/nginx.conf，在 Nginx 上配置一个静态网页服务。

worker_processes  1;

events {
    worker_connections  1024;
}


http {
    server {
        listen  80;
        location / {
            root html;
        }
    }
}

启动 Nginx：

sbin/nginx

访问 Nginx：

部署 Filebeat

下载并安装 Filebeat。

curl -L -O https://artifacts.elastic.co/downloads/beats/filebeat/filebeat-7.14.0-x86_64.rpm
sudo rpm -vi filebeat-7.14.0-x86_64.rpm

编辑 /etc/filebeat/filebeat.yml 配置文件，读取 Nginx 日志文件输出到 Elasticsearch 的 nginx 索引中，后缀是当前日期。

filebeat.inputs:
- type: log
  enabled: true
  paths:
    - /usr/local/nginx/logs/*.log
output.elasticsearch:
  hosts: ["192.168.1.8:9200"]
  index: "nginx-%{+yyyy.MM.dd}"
  #username: "elastic"
  #password: "changeme"
setup.ilm.enabled: false
setup.template.name: "nginx"
setup.template.pattern: "nginx-*"

启动 Filebeat：

systemctl start filebeat

ElastAlert

ElastAlert 是 Yelp 公司开源的一套用 Python 写的 Elasticsearch 告警框架，可以从 Elasticsearch 当中查询出匹配规则的数据进行告警。

ElastAlert 有以下特点：

• 支持多种匹配规则（频率、阈值、数据变化、黑白名单、变化率等）。
• 支持多种告警类型（邮件、HTTP POST、自定义脚本等）。
• 支持用户自定义规则和告警类型。
• 匹配项汇总报警，重复告警抑制，告警失败重试和过期。
• 可用性强，状态信息保存到 Elasticsearch 的索引中。
• 支持调试和审计。

部署 Elastalert

安装 Python

wget https://www.python.org/ftp/python/3.6.9/Python-3.6.9.tgz
tar -zxvf Python-3.6.9.tgz
cd Python-3.6.9
./configure
make && make install

检查 Python 版本：

python3 -V

安装依赖

yum install gcc libffi-devel python3-devel openssl-devel -y
pip3 install -U pip
pip3 install "setuptools>=11.3"

安装 Elastalert

python3 install elastalert

配置 Elastalert

克隆代码到本地：

git clone https://github.com/Yelp/elastalert.git
cd elastalert

我们可以在 ElastAlert 源码文件的根目录下找到一个叫做 config.yaml.example 的文件，修改文件名为 config.yaml：

mv config.yaml.example  config.yaml

创建存放规则的目录。

mkdir rules
cd rules

编辑 config.yaml 文件，修改主配置：

#规则存放的目录
rules_folder: rules

#运行的频率
run_every:
  minutes: 1

#ElastAlert 将缓存最近一段时间的结果，以防某些日志源不是实时的
buffer_time:
  minutes: 45

#Elasticsearch 地址
es_host: 192.168.1.8

#Elasticsearch 端口
es_port: 9200

#Elasticsearch 用户名密码（可选）
#es_username: someusername
#es_password: somepassword

#ElastAlert 元数据存储索引
writeback_index: elastalert_status

#如果警报因某种原因失败，ElastAlert将重试发送警报，直到该时间段结束
alert_time_limit:
  days: 2

创建 rules/nginx.yaml 文件，编辑 rule：

规则内容为：在 1 分钟内如果查询 nginx-* 索引的 message 字段匹配 到 error 5 次就触发告警，往指定的 URL 发送一个 HTTP POST 请求。

# Alert when the rate of events exceeds a threshold

# (Required)
# Elasticsearch host
es_host: 192.168.1.8

# (Required)
# Elasticsearch port
es_port: 9200

# (OptionaL) Connect with SSL to elasticsearch
#use_ssl: True

# (Optional) basic-auth username and password for elasticsearch
#es_username: someusername
#es_password: somepassword

# (Required)
# Rule name, must be unique
name: nginx rule

# (Required)
# Type of alert.
# the frequency rule type alerts when num_events events occur with timeframe time
type: frequency

# (Required)
# Index to search, wildcard supported
index: nginx-*

# (Required, frequency specific)
# Alert when this many documents matching the query occur within a timeframe
num_events: 5

# (Required, frequency specific)
# num_events must occur within this amount of time to trigger an alert
timeframe:
  minutes: 1

# (Required)
# A list of elasticsearch filters used for find events
# These filters are joined with AND and nested in a filtered query
# For more info: http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl.html
filter:
- term:
    message: "error"

# (Required)
# The alert is use when a match is found
alert:
- "post"

http_post_url: "https://webhook.site/2f64f4b3-8b43-488c-b2df-695136079e36"

https://webhook.site 网站提供了测试的 Webhook 接口，每个人的 URL 都是独立的，拷贝这个 URL 复制到 http_post_url 中。

ElastAlert 会把执行记录存放到一个索引中，可以方便我们审核和调试。使用以下命令创建这个索引的，默认情况下，索引名叫 elastalert_status。

root@ydt-net-es-node1:/software #elastalert-create-index
Enter Elasticsearch host: 192.168.1.8
Enter Elasticsearch port: 9200
Use SSL? t/f: f
#如果有认证输入用户名密码
Enter optional basic-auth username (or leave blank): 
Enter optional basic-auth password (or leave blank): 
Enter optional Elasticsearch URL prefix (prepends a string to the URL of every request): 
New index name? (Default elastalert_status) 
New alias name? (Default elastalert_alerts) 
Name of existing index to copy? (Default None) 
Elastic Version: 7.9.3
Reading Elastic 6 index mappings:
Reading index mapping 'es_mappings/6/silence.json'
Reading index mapping 'es_mappings/6/elastalert_status.json'
Reading index mapping 'es_mappings/6/elastalert.json'
Reading index mapping 'es_mappings/6/past_elastalert.json'
Reading index mapping 'es_mappings/6/elastalert_error.json'
New index elastalert_status created
Done!

发送 2 个请求，1 个是正确请求，1 个是错误请求。

> curl http://192.168.1.134 -I
HTTP/1.1 200 OK
Server: nginx/1.14.2
Date: Mon, 16 Aug 2021 07:28:42 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Wed, 16 Jun 2021 02:46:13 GMT
Connection: keep-alive
ETag: "60c965f5-264"
Accept-Ranges: bytes

> curl http://192.168.1.134/xxxxxx -I
HTTP/1.1 404 Not Found
Server: nginx/1.14.2
Date: Mon, 16 Aug 2021 07:28:43 GMT
Content-Type: text/html
Content-Length: 169
Connection: keep-alive

在 Kibana 上可以看到 Nginx 的日志，错误请求会在 access.log 和 error.log 各写一次，因此这里看到 3 条记录。

运行 elastalert-test-rule 命令检验配置文件是否正确并且可以看到规则匹配的次数，elastalert-test-rule 命令并不会真正触发告警。

> elastalert-test-rule rules/nginx.yaml
INFO:elastalert:Note: In debug mode, alerts will be logged to console but NOT actually sent.
            To send them but remain verbose, use --verbose instead.
Didn't get any results.
INFO:elastalert:Note: In debug mode, alerts will be logged to console but NOT actually sent.
                To send them but remain verbose, use --verbose instead.
1 rules loaded
INFO:apscheduler.scheduler:Adding job tentatively -- it will be properly scheduled when the scheduler starts
#匹配一次
INFO:elastalert:Queried rule nginx rule from 2021-08-16 15:28 CST to 2021-08-16 15:29 CST: 1 / 1 hits 

Would have written the following documents to writeback index (default is elastalert_status):

elastalert_status - {'rule_name': 'nginx rule', 'endtime': datetime.datetime(2021, 8, 16, 7, 29, 30, 422431, tzinfo=tzutc()), 'starttime': datetime.datetime(2021, 8, 16, 7, 28, 29, 822431, tzinfo=tzutc()), 'matches': 0, 'hits': 1, '@timestamp': datetime.datetime(2021, 8, 16, 7, 29, 30, 527080, tzinfo=tzutc()), 'time_taken': 0.02203655242919922}

1分钟内连续发送错误请求 5 次达到触发告警的阈值：

for i in {1..3};do curl http://192.168.1.134/xxxxxx -I;done

此时可以看到发送的告警格式。

> elastalert-test-rule rules/nginx.yaml
INFO:elastalert:Note: In debug mode, alerts will be logged to console but NOT actually sent.
            To send them but remain verbose, use --verbose instead.
Didn't get any results.
INFO:elastalert:Note: In debug mode, alerts will be logged to console but NOT actually sent.
                To send them but remain verbose, use --verbose instead.
1 rules loaded
INFO:apscheduler.scheduler:Adding job tentatively -- it will be properly scheduled when the scheduler starts
INFO:elastalert:Queried rule nginx rule from 2021-08-16 15:33 CST to 2021-08-16 15:34 CST: 5 / 5 hits
INFO:elastalert:Alert for nginx rule at 2021-08-16T07:34:26.230Z:
INFO:elastalert:nginx rule

At least 5 events occurred between 2021-08-16 15:33 CST and 2021-08-16 15:34 CST

@timestamp: 2021-08-16T07:34:26.230Z
_id: 0CDiTXsBCANUjLffFM2O
_index: nginx-2021.08.16
_type: _doc
agent: {
    "ephemeral_id": "4ee4bd89-cb8e-43fb-9331-476c229a5480",
    "hostname": "nginx-plus1",
    "id": "629442a8-34ab-40db-80a8-16e4fda8dec7",
    "name": "nginx-plus1",
    "type": "filebeat",
    "version": "7.14.0"
}
ecs: {
    "version": "1.10.0"
}
host: {
    "name": "nginx-plus1"
}
input: {
    "type": "log"
}
log: {
    "file": {
        "path": "/usr/local/nginx/logs/error.log"
    },
    "offset": 16944
}
message: 2021/08/16 15:34:22 [error] 4022#0: *40 open() "/usr/local/nginx/html/xxxxxx" failed (2: No such file or directory), client: 192.168.1.35, server: , request: "GET /xxxxxx HTTP/1.1", host: "192.168.1.134"
num_hits: 5
num_matches: 1


Would have written the following documents to writeback index (default is elastalert_status):

silence - {'exponent': 0, 'rule_name': 'nginx rule', '@timestamp': datetime.datetime(2021, 8, 16, 7, 34, 42, 866184, tzinfo=tzutc()), 'until': datetime.datetime(2021, 8, 16, 7, 35, 42, 866174, tzinfo=tzutc())}

elastalert_status - {'rule_name': 'nginx rule', 'endtime': datetime.datetime(2021, 8, 16, 7, 34, 42, 810992, tzinfo=tzutc()), 'starttime': datetime.datetime(2021, 8, 16, 7, 33, 42, 210992, tzinfo=tzutc()), 'matches': 1, 'hits': 5, '@timestamp': datetime.datetime(2021, 8, 16, 7, 34, 42, 868045, tzinfo=tzutc()), 'time_taken': 0.015259981155395508}

使用以下命令运行 elastalert，可以看到触发了告警：

> elastalert --verbose --rule rules/nginx.yaml
1 rules loaded
INFO:elastalert:Starting up
INFO:elastalert:Disabled rules are: []
INFO:elastalert:Sleeping for 59.999839 seconds
INFO:elastalert:Queried rule nginx rule from 2021-08-16 14:54 CST to 2021-08-16 15:39 CST: 7 / 7 hits
INFO:elastalert:HTTP Post alert sent.
INFO:elastalert:Ran nginx rule from 2021-08-16 14:54 CST to 2021-08-16 15:39 CST: 7 query hits (0 already seen), 1 matches, 1 alerts sent

访问 https://webhook.site 网站可以看到 ElastAlert 发送的 HTTP POST 请求。

查询 elastalert_status 索引可以看到 ElastAlert 的执行记录。

GET elastalert_status/_search
#返回结果
{
  "took" : 0,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "elastalert_status",
        "_type" : "_doc",
        "_id" : "1SDmTXsBCANUjLff0M1Q",
        "_score" : 1.0,
        "_source" : {
          "match_body" : {
            "input" : {
              "type" : "log"
            },
            "agent" : {
              "hostname" : "nginx-plus1",
              "name" : "nginx-plus1",
              "id" : "629442a8-34ab-40db-80a8-16e4fda8dec7",
              "ephemeral_id" : "4ee4bd89-cb8e-43fb-9331-476c229a5480",
              "type" : "filebeat",
              "version" : "7.14.0"
            },
            "@timestamp" : "2021-08-16T07:34:26.230Z",
            "ecs" : {
              "version" : "1.10.0"
            },
            "log" : {
              "file" : {
                "path" : "/usr/local/nginx/logs/error.log"
              },
              "offset" : 16740
            },
            "host" : {
              "name" : "nginx-plus1"
            },
            "message" : "2021/08/16 15:34:22 [error] 4022#0: *39 open() \"/usr/local/nginx/html/xxxxxx\" failed (2: No such file or directory), client: 192.168.1.35, server: , request: \"GET /xxxxxx HTTP/1.1\", host: \"192.168.1.134\"",
            "_id" : "zyDiTXsBCANUjLffFM2O",
            "_index" : "nginx-2021.08.16",
            "_type" : "_doc",
            "num_hits" : 7,
            "num_matches" : 1
          },
          "rule_name" : "nginx rule",
          "alert_info" : {
            "type" : "http_post",
            "http_post_webhook_url" : [
              "https://webhook.site/2f64f4b3-8b43-488c-b2df-695136079e36"
            ]
          },
          "alert_sent" : true,
          "alert_time" : "2021-08-16T07:39:35.185929Z",
          "match_time" : "2021-08-16T07:34:26.230Z",
          "@timestamp" : "2021-08-16T07:39:37.418536Z"
        }
      }
    ]
  }
}

Watcher

Watcher 是 Elastic 官方提供的一个对日志数据监控和报警的功能，Watcher 属于收费功能，我们可以在 License Management 中开启 30 天的试用。

Watcher 由以下 5 个部分组成：

• trigger：定义 watcher 触发的时间或者周期。
• input：定义数据的来源，可以是一个索引或者 HTTP 请求的结果等等。如果没有设置输入将为空。
• condition：定义执行 action 触发的条件。如果没有设置默认总是触发 action。
• transform（可选）：修改 watcher 的 payload。
• actions：定义执行的动作，例如 email,webhook,index,logging,slack 等等。

创建 1 个 Watcher：

• trigger：每分钟运行一次。
• input：通配符匹配 nginx-* 的索引，查询 message 字段中的 error 关键字，每次针对在过去5分钟内发生的事件来进行查询。
• condition：如果在查询结果中，匹配到 1 次，就触发 action。
• action：向指定 URL 发送一个 HTTP POST 请求。

PUT _watcher/watch/nginx-watcher
{
  "trigger": {
     "schedule" : {
      "interval" : "1m"
    }
  },
  "input": {
    "search": {
      "request": {
        "indices": [
          "nginx-*"
        ],
        "body": {
          "query": {
            "bool": {
              "must": {
                "match": {
                  "message": "error"
                }
              },
              "filter": {
                "range": {
                  "@timestamp": {
                    "from": "{{ctx.trigger.scheduled_time}}||-5m",
                    "to": "{{ctx.trigger.triggered_time}}"
                  }
                }
              }
            }
          }
        }
      }
    }
  },
  "condition": {
    "compare": {
      "ctx.payload.hits.total": {
        "gt": 0
      }
    }
  },
  "actions": {
    "my_webhook": {
      "throttle_period": "2m",
      "webhook": {
        "method": "POST",
        "url": "https://webhook.site/2f64f4b3-8b43-488c-b2df-695136079e36",
        "body": "Number of Nginx Error: {{ctx.payload.hits.total}}"
      }
    }
  }
}

查看刚刚创建的 watcher：

1分钟内连续发送 5 次错误请求。

for i in {1..3};do curl http://192.168.1.134/xxxxxx -I;done

查看 watcher 状态，可以看到触发了 action。

访问 https://webhook.site 可以看到最新的 Webhook 事件已经被触发了，而且它的 Raw Content 和我们之前定义的 body 格式是一致的。

如果我们设置的 watcher 间隔时间比较久，Elasticsearch 为了方便我们测试，提供了_execute 接口，通过执行下面命令可以立即运行一下我们的 watcher。

PUT _watcher/watch/nginx-watcher/_execute

参考资料

• https://zhuanlan.zhihu.com/p/386722918
• https://elastalert.readthedocs.io/
• https://www.elastic.co/guide/en/elasticsearch/reference/7.14/xpack-alerting.html
• https://blog.csdn.net/UbuntuTouch/article/details/106298651
• https://elasticstack.blog.csdn.net/article/details/105340379
• https://elasticstack.blog.csdn.net/article/details/103820572

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