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：
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
