前陣子發現一直想注冊但被別人注冊了的一個域名快要過期了，就想著寫個腳本跑在電腦上，每分鐘檢查一次域名狀態，一旦域名被正式刪除，就發封郵件通知我，這樣就不用頻繁手動檢查域名狀態了。
寫腳本時發現一個有趣的現象，使用whois命令查詢域名狀態時，它給我返回了兩組信息，而且這兩組信息的域名狀態竟然是不一致的，讓人非常好奇，所以特意了解了一下whois的機制，記錄在這里。
$ whois $DOMAIN | grep "Domain Status"Domain Status: pendingDelete https://icann.org/epp#redemptionPeriod
Domain Status: pendingDelete https://icann.org/epp#ok
在whois返回的兩組信息中，第一組來自注冊局（Registry，如VeriSign），第二組來自注冊商（Registrar，如阿里云），注冊商通常擁有比注冊局更加詳細的域名信息。whois會執行遞歸查詢：首先從注冊局查詢域名信息，注冊局返回的信息中包含注冊商的whois服務器，然后再向注冊商查詢域名信息。調用whois命令時加上--verbose參數可以觀察到這個過程：
$ whois $DOMAIN --verbose | grep -E "Using server|Registrar WHOIS Server"
Using server whois.verisign-grs.com.Registrar WHOIS Server: whois.paycenter.com.cn
Using server whois.paycenter.com.cn.
Registrar WHOIS Server: whois.paycenter.com.cn
那么問題來了：注冊商whois服務器是從注冊局查詢得來的，那注冊局whois服務器是從哪里來的呢？答案是硬編碼。whois命令源碼中包含一個tld_serv_list文件，里面包含各頂級域名的注冊局whois服務器，以下是該文件的節選：
...
.com VERISIGN whois.verisign-grs.com.za.net whois.za.net
.net VERISIGN whois.verisign-grs.com.eu.org whois.eu.org
.za.org whois.za.org
.org whois.pir.org.edu whois.educause.edu
.gov whois.dotgov.gov
.int whois.iana.org
.mil NONE
...
既然whois信息保存在不止一個地方，那么由于數據同步的延遲，有時信息不一致也就不足為奇了，那到底該以哪邊為準呢？就域名狀態而言，應當以注冊局的信息為準，https://lookup.icann.org/en/faq里面提供了各字段的數據源，以下是摘錄：
| Result Label | Description | Source |
|---|---|---|
| Domain Information | ||
| Name | The name of the domain name which was entered into the lookup tool. | Registry |
| Internationalized Domain Name | The non-ASCII character name of the domain name which was entered into the lookup tool, if applicable. | Registry |
| Registry Domain ID | Registry-unique identifier for a domain name. | Registry |
| Domain Status | The status of a domain name registration. Every domain has at least one status code, but they can also have more than one status code. See EPP Status Codes for more info. | Registry |
| Nameservers | Information regarding the domain name’s DNS nameservers. To include nameserver unicode name and IP addresses, where applicable. | Registry |
| Dates | ||
| Dates | Multiple dates may be displayed in the “Dates” section and can include the date when the domain name registration was created, expires, and updated, as applicable. | Registry/Registrar |
| Contact Information | ||
| Registrant, Administrative, Technical, and Billing Contact Information | The contact information of the registrant, administrative, technical, and billing contacts will appear in this section, where applicable. | Registrar |
| Registrar Information | ||
| Name | The name of the registrar sponsoring the domain name’s registration. | Registrar |
| IANA ID | The registrar’s IANA ID from the IANA’s Registrar ID registry (https://www.iana.org/assignments/registrar-ids/registrar-ids.xhtml) | Registry |
| Abuse contact email | The abuse contact email address of the registrar. | Registrar |
| Abuse contact phone | The abuse contact telephone number of the registrar. | Registrar |
| … |
我關心的是域名狀態這個信息，為了防止從注冊商那里獲取到過時的數據，可以使用-h選項指定只從注冊局獲取數據：
$ whois $DOMAIN -h whois.verisign-grs.com --verbose | grep -E "Using server|Domain Status"
Using server whois.verisign-grs.com.Domain Status: ok https://icann.org/epp#redemptionPeriod
后來又改用js，在js中使用whois模塊時也有類似的問題，需要指定server參數和follow參數來防止對注冊商服務器進行查詢：
whois.lookup(domain, { server: "whois.verisign-grs.com", follow: 0 }, (err, data) => {if (err) return reject(err);let statusLines = data.split("\n").filter(line => /Domain Status/i.test(line)).map(line => {const match = line.match(/Domain Status:\s+(\w+)/i);return match ? match[1] : "";}).sort().join("\n");if (statusLines === "") {statusLines = "(empty)";}resolve(statusLines);
});
不過最終的結局是仍然沒能注冊上這個域名，今天早上醒來，發現域名已經被人注冊了，域名狀態在半夜兩點多發生了變化，從pendingDelete狀態直接變更為了ok。這個域名就是我名字的全拼，有9個字母，不知道有啥稀罕的┑(￣Д ￣)┍
