# 解析CSV格式日志
本文档介绍在解析Syslog或者其他文本格式时，针对数据中以特殊字符分隔的格式如何进行解析。
#### 解析正常形式的CSV格式日志
原始日志：
```
{
"program":"access",
"severity":6,
"priority":14,
"facility":1,
"content":"198.51.100.1|10/Jun/2019:11:32:16 +0800|example.com|GET /zf/11874.html HTTP/1.1|200|0.077|6404|198.51.100.10:8001|200|0.060|https://example.com/s?q=%25%24%23%40%21&from=wy878378&uc_param_str=dnntnwvepffrgibijbprsvdsei|-|Mozilla/5.0 (Linux; Android 9; HWI-AL00 Build/HUAWEIHWI-A00) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Mobile Safari/537.36|-|-"
}
```
背景需求：
1. 当program字段值为access时，对字段content做一次PSV（pipe分隔的解析），然后丢弃content字段。
2. 将request: GET /zf/11874.html HTTP/1.1字段拆分为request_method、http_version以及request。
3. http_referer做URL解码。
4. time做格式化。
解决方案：
1. 如果program字段值是access，则通过e_psv函数解析content内容，并删除原始字段content。
   ```
   e_if(e_search("program==access"), e_compose(e_psv("content", "remote_addr, time_local,host,request,status,request_time,body_bytes_sent,upstream_addr,upstream_status, upstream_response_time,http_referer,http_x_forwarded_for,http_user_agent,session_id,guid", restrict=True), e_drop_fields("content")))
   ```
   返回的日志为：
   ```
   {
   "severity": 6,
   "remote_addr": "198.51.100.1",
   "request": "GET /zf/11874.html HTTP/1.1",
   "upstream_addr": "198.51.100.10:8001",
   "body_bytes_sent": 6404,
   "session_id": "-",
   "program": "access",
   "priority": 14,
   "http_user_agent": "Mozilla/5.0 (Linux; Android 9; HWI-AL00 Build/HUAWEIHWI-A00) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Mobile Safari/537.36",
   "upstream_status": 200,
   "request_time": "0.077",
   "http_referer": "https://example.com/s?q=%3A%2F%3A&from=wy878378&uc_param_str=dnntnwvepffrgibijbprsvdsei",
   "upstream_response_time": "0.060",
   "host": "example.com",
   "http_x_forwarded_for": "-",
   "guid": "-",
   "facility": 1,
   "time_local": "10/Jun/2019:11:32:16 +0800",
   "status": 200
   }
   ```
   
2. 使用e_regex函数将request字段解析成request_method、request、http_version。
   ```
   e_regex("request",r"^(?P<request_method>\w+) (?P<request>.+) (?P<http_version>\w+/[\d\.]+)$")
   ```
   返回的日志为：
   ```
   "request": "GET /zf/11874.html HTTP/1.1",
   "request_method": "GET",
   "http_version": "HTTP/1.1"
   ```
   
3. 对http_referer做URL解码。
   ```
   e_set("http",url_decoding(v("http_referer")))
   ```
   返回的日志为：
   ```
   "http": "https://example.com/s?q=:/:&from=wy878378&uc_param_str=dnntnwvepffrgibijbprsvdsei",
   ```
   
4. 综上解决方案具体如下：
   ```
   e_if(e_search("program==access"), e_compose(e_psv("content", "remote_addr, time_local,host,request,status,request_time,body_bytes_sent,upstream_addr,upstream_status, upstream_response_time,http_referer,http_x_forwarded_for,http_user_agent,session_id,guid", restrict=True), e_drop_fields("content")))
   e_regex("request",r"^(?P<request_method>\w+) (?P<request>.+) (?P<http_version>\w+/[\d\.]+)$")
   e_set("http",url_decoding(v("http_referer")))
   ```
   
输出的日志：
```
{
"severity": 6,
"remote_addr": "198.51.100.1",
"request": "GET /zf/11874.html HTTP/1.1",
"upstream_addr": "198.51.100.10:8001",
"body_bytes_sent": 6404,
"session_id": "-",
"http_version": "HTTP/1.1",
"program": "access",
"request_method": "GET",
"priority": 14,
"http_user_agent": "Mozilla/5.0 (Linux; Android 9; HWI-AL00 Build/HUAWEIHWI-A00) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Mobile Safari/537.36",
"upstream_status": 200,
"request_time": "0.077",
"http_referer": "https://example.com/s?q=%3A%2F%3A&from=wy878378&uc_param_str=dnntnwvepffrgibijbprsvdsei",
" upstream_response_time": "0.060",
"host": "example.com",
"http_x_forwarded_for": "-",
"guid": "-",
"http": "https://example.com/s?q=:/:&from=wy878378&uc_param_str=dnntnwvepffrgibijbprsvdsei",
"facility": 1,
" time_local": "10/Jun/2019:11:32:16 +0800",
"status": 200
}
```
#### 解析非正常形式的CSV格式日志
如下日志格式存在一条异常日志信息，用户想对content进行解析。
- 原始日志
  ```
  {
      "content":"192.168.0.1|07/Aug/2019:11:10:37 +0800|www.learn.example.com|GET /index/htsw/?ad=5|8|6|11| HTTP/1.1|200|6.729|14559|192.168.0.1:8001|200|6.716|-|-|Mozilla/5.0 (Linux; Android 4.1.1; Nexus 7 Build/JRO03D))||"
  }
  ```
  
- 解决方案 在content中的GET /index/htsw/?ad=5\|8\|6\|11\| HTTP/1.1，如果使用e_csv解析不出正确的字段，需要先把这一块提取出来，然后在content中把这块内容替换成空。
  ```
  e_regex("content", r"[^\|]+\|[^\|]+\|[^\|]+\|(?P<request>(.+)HTTP/\d.\d)")
  e_set("content", regex_replace(v("content"), r"([^\|]+\|[^\|]+\|[^\|]+)\|((.+)HTTP/\d.\d)\|(.+)",replace= r"\1||\4"))
  e_psv("content", "remote_addr,time_local,host,status,request_time,body_bytes_sent,upstream_addr,upstream_status, upstream_response_time,http_referer,http_x_forwarded_for,http_user_agent,session_id,guid", restrict=True)
  ```
  
- 输出日志
  ```
  {
  "request": "GET /index/htsw/?ad=5|8|6|11| HTTP/1.1",
  "remote_addr": "192.168.0.1",
  "upstream_addr": 14559,
  "body_bytes_sent": "6.729",
  "time_local": "07/Aug/2019:11:10:37 +0800",
  "session_id": "Mozilla/5.0 (Linux; Android 4.1.1; Nexus 7 Build/JRO03D))",
  "content": "192.168.0.1|07/Aug/2019:11:10:37 +0800|www.learn.example.com||200|6.729|14559|192.168.0.1:8001|200|6.716|-|-|Mozilla/5.0 (Linux; Android 4.1.1; Nexus 7 Build/JRO03D))||",
  "http_user_agent": "-",
  "upstream_status": "192.168.0.1:8001",
  "request_time": 200,
  "http_referer": "6.716",
  " upstream_response_time": 200,
  "host": "www.learn.example.com",
  "http_x_forwarded_for": "-",
  "guid": "",
  "status": ""
  }
  ```