ELK Logstash Grok入门指南

A Beginner’s Guide to Logstash Grok(https://logz.io/blog/logstash-grok/)

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The ability to efficiently analyze and query the data being shipped into the ELK Stack depends on the information being readable. This means that as unstructured data is being ingested into the system, it must be translated into structured message lines.

有效分析和查询送入ELK堆栈的数据的能力取决于信息的可读性。这意味着，当将非结构化数据摄取到系统中时，必须将其转换为结构化消息行。

This ungrateful but critical task is usually left to Logstash (though there are other log shippers available, see our comparison of Fluentd vs. Logstash as one example). Regardless of the data source that you define, pulling the logs and performing some magic to beautify them is necessary to ensure that they are parsed correctly before being outputted to Elasticsearch.

通常，这个忘恩负义但至关重要的任务留给Logstash（尽管还有其他日志传送器可用，请参阅我们对Fluentd与Logstash的比较作为一个示例）。无论您定义什么数据源，都必须提取日志并执行一些魔术来美化它们，以确保在将它们输出到Elasticsearch之前正确地对其进行了解析。

Data manipulation in Logstash is performed using filter plugins. This article focuses on one of the most popular and useful filter plugins – the Logstash grok filter, which is used to parse unstructured data into structured data.

Logstash中的数据操作是使用过滤器插件执行的。本文重点介绍最流行和有用的过滤器插件之一– Logstash grok过滤器，该过滤器用于将非结构化数据解析为结构化数据。

 

What is grok?

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The original term is actually pretty new — coined by Robert A. Heinlein in his 1961 book Stranger in a Strange Land — it refers to understanding something to the level one has actually immersed oneself in it. It’s an appropriate name for the grok language and Logstash grok plugin, which modify information in one format and immerse it in another (JSON, specifically). There are already a couple hundred Grok patterns for logs available.

最初的术语实际上是很新的-由罗伯特·A·海因莱因（Robert A. Heinlein）在他的1961年的《陌生的土地上的陌生人》一书中创造的–指的是理解某种东西，使人们真正沉浸于其中。这是grok语言和Logstash grok插件的合适名称，它们可以以一种格式修改信息并将其浸入另一种格式（特别是JSON）。已经有数百种用于记录的Grok模式。

Put simply, grok is a way to match a line against a regular expression, map specific parts of the line into dedicated fields, and perform actions based on this mapping.

 

How does it work?

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Put simply, grok is a way to match a line against a regular expression, map specific parts of the line into dedicated fields, and perform actions based on this mapping.

简而言之，grok是一种将行与正则表达式匹配，将行的特定部分映射到专用字段中以及根据此映射执行操作的方法。

Built-in, there are over 200 Logstash patterns for filtering items such as words, numbers, and dates in AWS, Bacula, Bro, Linux-Syslog and more. If you cannot find the pattern you need, you can write your own custom pattern. There are also options for multiple match patterns, which simplifies the writing of expressions to capture log data.

内置了超过200种Logstash模式，用于过滤AWS，Bacula，Bro，Linux-Syslog等中的单词，数字和日期等项目。如果找不到所需的模式，则可以编写自己的自定义模式。还有多个匹配模式的选项，可简化表达式的编写以捕获日志数据。

Here is the basic syntax format for a Logstash grok filter:

%{SYNTAX:SEMANTIC}

The SYNTAX will designate the pattern in the text of each log. The SEMANTIC will be the identifying mark that you actually give that syntax in your parsed logs. In other words:

SYNTAX将在每个日志的文本中指定模式。SEMANTIC将是您在解析的日志中实际赋予该语法的识别标记。换一种说法：

%{PATTERN:FieldName}

This will match the predefined pattern and map it to a specific identifying field.

这将匹配预定义的模式并将其映射到特定的标识字段。

For example, a pattern like 127.0.0.1 will match the Grok IP pattern, usually an IPv4 pattern.

例如，类似于127.0.0.1的模式将匹配Grok IP模式，通常是IPv4模式。

Grok has separate IPv4 and IPv6 patterns, but they can be filtered together with the syntax IP.

Grok具有单独的IPv4和IPv6模式，但是可以将它们与语法IP一起过滤。

This standard pattern is as follows:

IPV4 (?

假装没有统一的IP语法，您只需使用相同的语义字段名称来查找它们： 

Pretending there was no unifying IP syntax, you would simply grok both with the same semantic field name:

%{IPv4:Client IP} %{IPv6:Client IP}

Again, just use the IP syntax, unless for any reason you want to separate these respective addresses into separate fields.

同样，只需使用IP语法，除非出于任何原因要将这些各自的地址分隔到单独的字段中。

Since grok is essentially based upon a combination of regular expressions, you can also create your own custom regex-based grok filter with this pattern:

由于grok本质上是基于正则表达式的组合，因此您还可以使用以下模式创建自己的基于正则表达式的自定义grok过滤器：

(?custom pattern)

For example:

(?\d\d-\d\d-\d\d)

This grok pattern will match the regex of 22-22-22 (or any other digit) to the field name.

此grok模式将22-22-22（或任何其他数字）的正则表达式与字段名称匹配。

 

Logstash Grok Pattern Examples

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为了演示，我将使用以下应用程序日志：

To demonstrate how to get started with grokking, I’m going to use the following application log:

2016-07-11T23:56:42.000+00:00 INFO [MySecretApp.com.Transaction.Manager]:Starting transaction for session -464410bf-37bf-475a-afc0-498e0199f008

The goal I want to accomplish with a grok filter is to break down the logline into the following fields: timestamp, log level, class, and then the rest of the message.

The following grok pattern will do the job:

grok {   match => { "message" => "%{TIMESTAMP_ISO8601:timestamp} %{LOGLEVEL:log-level} \[%{DATA:class}\]:%{GREEDYDATA:message}" } }

#NOTE:GREEDYDATA is the way Logstash Grok expresses the regex .* 

Grok Data Type Conversion

By default, all SEMANTIC entries are strings, but you can flip the data type with an easy formula. The following Logstash grok example converts any syntax NUMBER identified as a semantic num into a semantic float, float:

默认情况下，所有SEMANTIC条目都是字符串，但是您可以使用简单的公式来翻转数据类型。以下Logstash grok示例将任何NUMBER标识为语义的语法num转换为语义浮点数float： 

%{NUMBER:num:float}

It’s a pretty useful tool, even though it is currently only available for conversions to float or integers int.

 这是一个非常有用的工具，即使它目前仅可用于float或转换int。

_grokparsefailure

This will try to match the incoming log to the given grok pattern. In case of a match, the log will be broken down into the specified fields, according to the defined grok patterns in the filter. In case of a mismatch, Logstash will add a tag called _grokparsefailure.

这将尝试将传入的日志与给定的grok模式匹配。如果匹配，则将根据过滤器中定义的grok模式将日志细分为指定的字段。如果不匹配，Logstash将添加一个名为的标签_grokparsefailure。

However, in our case, the filter will match and result in the following output:

{     
       "message" => "Starting transaction for session -464410bf-37bf-475a-afc0-498e0199f008",     
       "timestamp" => "2016-07-11T23:56:42.000+00:00",     
       "log-level" => "INFO",     
       "class" => "MySecretApp.com.Transaction.Manager"
}

 

The grok debugger

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A great way to get started with building your grok filters is this grok debug tool: https://grokdebug.herokuapp.com/

This tool allows you to paste your log message and gradually build the grok pattern while continuously testing the compilation. As a rule, I recommend starting with the %{GREEDYDATA:message} pattern and slowly adding more and more patterns as you proceed.

In the case of the example above, I would start with:

%{GREEDYDATA:message}

Then, to verify that the first part is working, proceed with:

%{TIMESTAMP_ISO8601:timestamp} %{GREEDYDATA:message}

 

Common Logstash grok examples

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Here are some examples that will help you to familiarize yourself with how to construct a grok filter:

Syslog

Parsing syslog messages with Grok is one of the more common demands of new users,. There are also several different kinds of log formats for syslog so keep writing your own custom grok patterns in mind. Here is one example of a common syslog parse:

grok {
   match => { "message" => "%{SYSLOGTIMESTAMP:syslog_timestamp}
%{SYSLOGHOST:syslog_hostname}
%{DATA:syslog_program}(?:\[%{POSINT:syslog_pid}\])?:
%{GREEDYDATA:syslog_message}" }
}

If you are using rsyslog, you can configure the latter to send logs to Logstash.

Apache Access logs

grok  {
      match => { "message" => "%{COMBINEDAPACHELOG}" }
   }

Elasticsearch

grok {
      match => ["message", "\[%{TIMESTAMP_ISO8601:timestamp}\]\[%{DATA:loglevel}%{SPACE}\]\[%{DATA:source}%{SPACE}\]%{SPACE}\[%{DATA:node}\]%{SPACE}\[%{DATA:index}\] %{NOTSPACE} \[%{DATA:updated-type}\]",
                "message", "\[%{TIMESTAMP_ISO8601:timestamp}\]\[%{DATA:loglevel}%{SPACE}\]\[%{DATA:source}%{SPACE}\]%{SPACE}\[%{DATA:node}\] (\[%{NOTSPACE:Index}\]\[%{NUMBER:shards}\])?%{GREEDYDATA}"
      ]
   }

 Redis

grok {
       match => ["redistimestamp", "\[%{MONTHDAY} %{MONTH} %{TIME}]",
                ["redislog", "\[%{POSINT:pid}\] %{REDISTIMESTAMP:timestamp}"], 
                ["redismonlog", "\[%{NUMBER:timestamp} \[%{INT:database} %{IP:client}:%{NUMBER:port}\] "%{WORD:command}"\s?%{GREEDYDATA:params}"]
      ]
    }

MongoDB

MONGO_LOG %{SYSLOGTIMESTAMP:timestamp} \[%{WORD:component}\] %{GREEDYDATA:message}MONGO_QUERY \{ (?<={ ).*(?= } ntoreturn:) \}MONGO_SLOWQUERY %{WORD} %{MONGO_WORDDASH:database}\.%{MONGO_WORDDASH:collection} %{WORD}: %{MONGO_QUERY:query} %{WORD}:%{NONNEGINT:ntoreturn} %{WORD}:%{NONNEGINT:ntoskip} %{WORD}:%{NONNEGINT:nscanned}.*nreturned:%{NONNEGINT:nreturned}..+ (?[0-9]+)msMONGO_WORDDASH \b[\w-]+\bMONGO3_SEVERITY \wMONGO3_COMPONENT %{WORD}|-MONGO3_LOG %{TIMESTAMP_ISO8601:timestamp} %{MONGO3_SEVERITY:severity} %{MONGO3_COMPONENT:component}%{SPACE}(?:\[%{DATA:context}\])? %{GREEDYDATA:message}

AWS

ELB_ACCESS_LOG %{TIMESTAMP_ISO8601:timestamp} %{NOTSPACE:elb} %{IP:clientip}:%{INT:clientport:int} (?:(%{IP:backendip}:?:%{INT:backendport:int})|-) %{NUMBER:request_processing_time:float} %{NUMBER:backend_processing_time:float} %{NUMBER:response_processing_time:float} %{INT:response:int} %{INT:backend_response:int} %{INT:received_bytes:int} %{INT:bytes:int} "%{ELB_REQUEST_LINE}"
CLOUDFRONT_ACCESS_LOG (?%{YEAR}-%{MONTHNUM}-%{MONTHDAY}\t%{TIME})\t%{WORD:x_edge_location}\t(?:%{NUMBER:sc_bytes:int}|-)\t%{IPORHOST:clientip}\t%{WORD:cs_method}\t%{HOSTNAME:cs_host}\t%{NOTSPACE:cs_uri_stem}\t%{NUMBER:sc_status:int}\t%{GREEDYDATA:referrer}\t%{GREEDYDATA:agent}\t%{GREEDYDATA:cs_uri_query}\t%{GREEDYDATA:cookies}\t%{WORD:x_edge_result_type}\t%{NOTSPACE:x_edge_request_id}\t%{HOSTNAME:x_host_header}\t%{URIPROTO:cs_protocol}\t%{INT:cs_bytes:int}\t%{GREEDYDATA:time_taken:float}\t%{GREEDYDATA:x_forwarded_for}\t%{GREEDYDATA:ssl_protocol}\t%{GREEDYDATA:ssl_cipher}\t%{GREEDYDATA:x_edge_response_result_type}

 

Summing it up

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Logstash grok is just one type of filter that can be applied to your logs before they are forwarded into Elasticsearch. Because it plays such a crucial part in the logging pipeline, grok is also one of the most commonly-used filters.

Logstash grok只是在将日志转发到Elasticsearch之前可以应用于您的日志的一种过滤器。由于grok在测井管道中起着至关重要的作用，因此它也是最常用的过滤器之一。 

Here is a list of some useful resources that can help you along the grokking way:

• http://grokdebug.herokuapp.com – as mentioned above, this is a useful tool for constructing and testing your grok filter on logs
• http://grokconstructor.appspot.com/ – another grok builder/tester
• https://github.com/logstash-plugins/logstash-patterns-core/tree/master/patterns – a list of Logstash-supported patterns

Happy grokking!