前言
最近根据项目需求要使用graylog收集Java异常日志，这个任务的难点在于要处理多行日志(Multiline)，对于我这个技术小白来说也是遇到了好多的坑，在此将经历多次失败之后终于成功收集的正确方式记录一下，仅供参考：)。
多行日志收集
如果您看到了这篇文章，那么graylog的基本使用，如：安装、基本配置、简单的日志收集等……这些操作对您来说应该是熟悉的了，在此就不做详细介绍了，您可参考鄙人总结的上一篇文章Graylog安装使用。
日志格式
本次我要收集的日志格式如下：
2017-12-05 13:12:41.963 [DiscoveryClient-CacheRefreshExecutor-0] ERROR com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient - Request execution error
com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused (Connection refused)
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar!/:1.19.1]
at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.sun.jersey.api.client.Client.handle(Client.java:652) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.sun.jersey.api.client.WebResource$Builder.get(WebResource.java:509) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.getApplicationsInternal(AbstractJerseyEurekaHttpClient.java:194) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.getDelta(AbstractJerseyEurekaHttpClient.java:170) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$7.execute(EurekaHttpClientDecorator.java:152) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getDelta(EurekaHttpClientDecorator.java:149) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$7.execute(EurekaHttpClientDecorator.java:152) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.execute(RedirectingEurekaHttpClient.java:89) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getDelta(EurekaHttpClientDecorator.java:149) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$7.execute(EurekaHttpClientDecorator.java:152) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:119) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getDelta(EurekaHttpClientDecorator.java:149) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$7.execute(EurekaHttpClientDecorator.java:152) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getDelta(EurekaHttpClientDecorator.java:149) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.DiscoveryClient.getAndUpdateDelta(DiscoveryClient.java:1064) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.DiscoveryClient.fetchRegistry(DiscoveryClient.java:946) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.DiscoveryClient.refreshRegistry(DiscoveryClient.java:1468) [eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.DiscoveryClient$CacheRefreshThread.run(DiscoveryClient.java:1435) [eureka-client-1.4.10.jar!/:1.4.10]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_151]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_151]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_151]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_151]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_151]
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method) ~[?:1.8.0_151]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[?:1.8.0_151]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[?:1.8.0_151]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[?:1.8.0_151]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[?:1.8.0_151]
at java.net.Socket.connect(Socket.java:589) ~[?:1.8.0_151]
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:610) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:445) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.3.jar!/:4.5.3]
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173) ~[jersey-apache-client4-1.19.1.jar!/:1.19.1]
... 29 more
2017-12-05 13:12:41.983 [DiscoveryClient-CacheRefreshExecutor-0] ERROR com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient - Request execution error
com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused (Connection refused)
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar!/:1.19.1]
at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.sun.jersey.api.client.Client.handle(Client.java:652) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.sun.jersey.api.client.WebResource$Builder.get(WebResource.java:509) ~[jersey-client-1.19.1.jar!/:1.19.1]
at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.getApplicationsInternal(AbstractJerseyEurekaHttpClient.java:194) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.getDelta(AbstractJerseyEurekaHttpClient.java:170) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$7.execute(EurekaHttpClientDecorator.java:152) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getDelta(EurekaHttpClientDecorator.java:149) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$7.execute(EurekaHttpClientDecorator.java:152) ~[eureka-client-1.4.10.jar!/:1.4.10]
at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.executeOnNewServer(RedirectingEurekaHttpClient.java:118) ~[eureka-client-1.4.10.jar!/:1.4.10]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[?:1.8.0_151]
at java.net.Socket.connect(Socket.java:589) ~[?:1.8.0_151]
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:610) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:445) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118) ~[httpclient-4.5.3.jar!/:4.5.3]
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.3.jar!/:4.5.3]
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173) ~[jersey-apache-client4-1.19.1.jar!/:1.19.1]
... 29 more
这种格式的日志是Java应用常见的ERROR日志格式，它的特点就是每条日志都是以“XXXX-XX-XX”这样的日期格式开头，那么我们在配置的时候就可以借助这一点，将所有不是以日期开头的日志都合并到上一行，这样就可以收集到每一条以日期开头的日志啦。
具体配置
以下部分的配置都是基于本文给出的日志格式进行的，如果您的日志格式与此次日志格式相近的话，稍作改动也是可以使用的。
Graylog web UI开启多行
做以下配置之前，请确保您的collector-sidecar是已经安装并且可以正常收集简单的日志。
创建新的配置文件
在graylog web界面上点击System->Collectors->Manage configurations->Create configuration”创建新的配置文件。
配置Beats output，点击“Save”保存。
配置Beats input，点击“Save”保存。
为配置打上tag。
编辑配置文件
编辑collector的配置文件：sudo vim /etc/graylog/collector-sidecar/collector_sidecar.yml
server_url: http://127.0.0.1:9000/api/
update_interval: 10
tls_skip_verify: false
send_status: true
list_log_files:
node_id: graylog-collector-sidecar
collector_id: file:/etc/graylog/collector-sidecar/collector-id
cache_path: /var/cache/graylog/collector-sidecar
log_path: /var/log/graylog/collector-sidecar
log_rotation_time: 86400
log_max_age: 604800
tags:
- multiline-log
backends:
- name: nxlog
enabled: false
binary_path: /usr/bin/nxlog
configuration_path: /etc/graylog/collector-sidecar/generated/nxlog.conf
- name: filebeat
enabled: true
binary_path: /usr/bin/filebeat
configuration_path: /etc/graylog/collector-sidecar/generated/filebeat.yml
重启collector-sidecar
执行命令：sudo systemctl restart collector-sidecar.service，也可以在graylog web UI点击“restart”按钮进行重启。
可以看到如下图所示的日志信息：
Q&A
在配置的过程中有遇到问题"Multiline match can either be 'after' or 'before', but not ' '.起初以为是在配置Beats input的时候没有选择How are matching lines combined into one event部分的选项，检查发现是有选择的。后来去看了filebeat的日志文件/var/log/graylog/collector-sidecar/filebeat_stderr.log，报出以下错误：
Exiting: error loading states for prospector 2415161850098178739: error parsing regexp: invalid escape sequence: `\d` accessing 'filebeat.prospectors.0.multiline.pattern' (source:'/etc/graylog/collector-sidecar/generated/filebeat.yml')
这个问题是配置Beats input时Start pattern of a multiline message正则表达式中有写\d造成的。
解决办法：匹配数字时不要使用\d，使用[0-9]这种形式。
配置log file path的时候可以填写多个路径，减少繁琐的工作量。
上述的配置可以收集/var/log/目录下以tomcat-、console-开头的文件夹下的error.log日志文件的内容。
参考文档
没有小伙伴共同讨论真的是一件很忧桑的事情-_-，我只能混迹于GitHub以及Graylog的官方社区提问题，很感谢大神的帮助，现在想想有些问题好低级，哎……往事不堪回首。
本篇文章中如有不正确之处，还请指正！