也可以參考看看 tornado 的 blog 範例, 他的 router 下法:

class Application(tornado.web.Application):
    def __init__(self, db):
        self.db = db
        handlers = [
            (r"/", HomeHandler),
            (r"/archive", ArchiveHandler),
            (r"/feed", FeedHandler),
            (r"/entry/([^/]+)", EntryHandler),
            (r"/compose", ComposeHandler),
            (r"/auth/create", AuthCreateHandler),
            (r"/auth/login", AuthLoginHandler),
            (r"/auth/logout", AuthLogoutHandler),
        ]

在 EntryHandler 裡, 存取 slug 就可以拿到 url 裡的我們要的 id.

class EntryHandler(BaseHandler):
    async def get(self, slug):
        entry = await self.queryone("SELECT * FROM entries WHERE slug = %s", slug)
        if not entry:
            raise tornado.web.HTTPError(404)
        self.render("entry.html", entry=entry)

如果確定是拿 /…/edit 的, 也可以設定成這樣子:

(r'/your-object/(.*)/edit', 'app.controller.ObjectEditorHandler'),

Flash 的使用方法, 真的很直覺, 程式碼也超短:
https://stackoverflow.max-everyday.com/2023/02/flask-web-server-static-file/

Tornado 對靜態檔案的說明:
https://www.tornadoweb.org/en/stable/web.html#tornado.web.StaticFileHandler

使用下面的範例, 就可以存取到靜態檔案:

import asyncio
import tornado
from tornado.web import Application
from tornado.web import StaticFileHandler

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        self.write("Hello, world")

def make_app():
    return Application([
        (r"/", MainHandler),
        (r"/content/(.*)", StaticFileHandler, {"path": "./content"}),
    ])

async def main():
    app = make_app()
    app.listen(8888)
    await asyncio.Event().wait()

if __name__ == "__main__":
    asyncio.run(main())

說明: ./content/ 輸出網頁的 /content/

使用的執行範例:
http://127.0.0.1:8888/content/static.py

有一個奇怪的坑是, 如果你在 create Application(routes, **app_settings) object 時, 所帶入的 app_settings = dict( ) 中間使用 static_path, 例如:

app_settings = dict(
    template_path=os.path.join(os.path.dirname(__file__), "templates"),
    static_path=os.path.join(os.path.dirname(__file__), "static"),

這時候, 又在 routes 裡設了 static, 例如:

handlers = [
        (r'/', MainHandler),
        (r'/static/(.*)', StaticFileHandler, {'path': "static"}),
    ]

2邊就會衝突, 原本應該正常顯示的靜態檔案都會成錯誤訊息:

Traceback (most recent call last):
  File "D:\Programs\Python\Python39-32\lib\site-packages\tornado\web.py", line 1713, in _execute
    result = await result
  File "D:\Programs\Python\Python39-32\lib\site-packages\tornado\web.py", line 2611, in get
    self.absolute_path = self.validate_absolute_path(self.root, absolute_path)
  File "D:\Programs\Python\Python39-32\lib\site-packages\tornado\web.py", line 2813, in validate_absolute_path
    raise HTTPError(404)
tornado.web.HTTPError: HTTP 404: Not Found

根目錄以下到 /static/目錄下取檔案, 並針對 404 不存在的檔案做客製化:

class MyStaticFileHandler(StaticFileHandler):
    def write_error(self, status_code, *args, **kwargs):
        my_404_page = os.path.join(options.app_root, 'template/error_404.html')
        self.set_status(status_code)
        if status_code in [404]:
            self.render(my_404_page)
        else:
            self.write("Error: %d" % status_code)

handlers = [
    (r'/', 'app.controller.HomeHandler'),
    (r'/(.*)', MyStaticFileHandler, {'path': os.path.join(app_root, 'static/')}),
]

你一定覺得很奇怪，gmail 和 yahoo 信箱就很好用了，為何要自己去架設？因為facebook Workspace 只能使用公司的 Email。

Facebook Workplace 可以將同事連結在一起，方便大家交流意見，免費進行群組對話、傳送訊息、撥打語音／視訊電話，並享有無限儲存空間。專為企業設計的實用工具。

不自己架的話，可以直接花錢買gmail for bussiness，如果想省錢就花點時間自己架了。

安裝用指令：

sudo apt-get install postfix

啟動停止 Postfix 的指令如下：

sudo /etc/init.d/postfix start #啟動 Postfix
sudo /etc/init.d/postfix stop #停止 Postfix
sudo /etc/init.d/postfix restart #重新啟動 Postfix

Postfix 主要的組態設定檔是 /etc/postfix/main.cf。
編輯 main.cf 的指令如下：

sudo vi /etc/postfix/main.cf

Postfix一些常用的指令：

# 列出目前在 Mail Queue 中的信件
mailq

# 刪除所有在 Queue 中的郵件
postsuper -d ALL

# 刪除所有正在 deferred 佇列中的郵件 ( 刪除曾經發送失敗的信 )
postsuper -d ALL deferred

# 刪除所有正在 deferred 佇列中的郵件 ( 可看出哪些信被刪除了 )
find /var/spool/postfix/deferred -type f -exec rm -vf \{\} \;

# 刪掉「三天以前」無法發出的郵件
find /var/spool/postfix/deferred -type f -mtime +3 -exec rm -f \{\} \;

# 列出目前所有無法發出的郵件
find /var/spool/postfix/deferred -type f -exec ls -l –time-style=+%Y-%m-%d_%H:%M:%S {} \;

# 刪除超過 5 天的 “defer” 佇列中的退信紀錄
find /var/spool/postfix/defer -type f -mtime +5 -exec rm -f \{\} \;

檢查為什麼無法收到信：

vi /var/log/mail.log

進入 vi 後，按大寫G，移到 end of file，訊息：

postfix/smtp[6063]: DDA94BD4E4: to=weng.32002@gmail.com, relay=gmail-smtp-in.l.google.com[74.125.24.26]:25, delay=0.88, delays=0.06/0.02/0.34/0.46, dsn=5.7.28, status=bounced (host gmail-smtp-in.l.google.com[74.125.24.26] said: 550-5.7.28 [167.172.78.3       1] Our system has detected an unusual rate of 550-5.7.28 unsolicited mail originating from your IP address. To protect our 550-5.7.28 users from spam, mail sent from your IP address has been blocked. 550-5.7.28 Please visit 550-5.7.28  https://support.google.com/mail/?p=UnsolicitedIPError to review our 550 5.7.28 Bulk Email Senders Guidelines. 31si2288714ple.177 - gsmtp (in reply to end of DATA command))

訊息被Google 擋掉。

解法，增加 TXT 到 DNS，DNS 提供網域名稱與IP位址對應的查詢，除了基本的 A、MX、CNAME、PTR、SRV 記錄外，還有一個 TXT 記錄，他可提供文字資訊給本身網域以外的來源一些額外的資訊，例如 SPF ( Sender Policy Framework )。

SPF 到底可以拿來幹嘛？

SPF 可以讓 收信端主機 根據來信中的 寄件者郵件網域，主動去寄信端所屬的DNS核對SPF記錄，當寄件者郵件網域 不同/不合法 於寄信主機網域時，可以丟棄、退信、或特別標註該封郵件。SPF 可以阻擋別人冒用你的網域寄信。

使用 dig 指令查詢網域的SPF設定，查詢資料類型請使用TXT。

dig @8.8.8.8 dropboxlike.com TXT

GMail 對被退信的說明：
https://support.google.com/mail/answer/81126?p=UnsolicitedIPError&visit_id=637161508037219534-3989246197&rd=1

為了盡可能減低郵件遭標示為垃圾郵件的機率，請設定以下驗證方式：

• 為網域發布 SPF 記錄。SPF 可防止垃圾郵件發布者假借您網域的名義寄出未經授權的郵件。
• 為郵件開啟 DKIM 簽署功能。收件伺服器會透過 DKIM 驗證網域擁有者是否確實傳送了郵件。重要資訊：Gmail 規定使用 1024 位元以上的 DKIM 金鑰。
• 為網域發布 DMARC 記錄。DMARC 可協助寄件者防止自己網域的電子郵件遭到假冒。

為了讓 SPF 和 DKIM 順利驗證郵件，郵件的「From:」標頭必須與寄件網域相符。郵件則須通過 SPF 或 DKIM 檢查才算完成驗證。

請勿在未經授權的情況下冒用其他網域或寄件者名義傳送郵件。這種做法稱為「假冒」，可能會導致 Gmail 將郵件歸類為垃圾郵件。

設好 SPF 後新的 mail.log:

postfix/smtp[6598]: 54723BD202: to=<do-no-reply@moca-shop.com>, relay=eforward3.registrar-servers.com[162.255.118.51]:25, delay=1, delays=0/0/0.82/0.2, dsn=5.1.1, status=bounced (host eforward3.registrar-servers.com[162.255.118.51] said: 554 5.1.1 <do-no-reply@moca-shop.com>: Recipient address rejected: undeliverable address: host mail-outgoing-fef.relay.svc.cluster.local[10.27.5.108] said: 554 5.7.1 <do-no-reply@moca-shop.com>: Relay access denied (in reply to RCPT TO command) (in reply to RCPT TO command))

解法：

因為DNS裡太多 MX 的欄位，刪一刪，只留下一組即可。

也可以使用 CheckTLS.com 的測試功能幫忙測試一下，填上主機上可收信的信箱，按下 Start Test 即可：
https://www.checktls.com/TestReceiver

如果 postfix 回報 Relay access denied;

那是因為 /etc/postfix/main.cf 的設定值：

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination

所以，如果不是從本機或內網或非授權的 domain name 那就會被拒絕，顯示 Relay access denied。

寄到Gmail 的信容易變「垃圾信」，所以一定要幫信建立規則（篩選器）：

最後，如果你真的問題實在太多，真心建議改用Gmail API 來寄送：

安裝教學：

《分享》Ubuntu架設mail server
http://www.shunze.info/forum/thread.php?boardid=3&threadid=2015

使用 Ubuntu 安裝郵件伺服器 (Mail Server)：Postfix + Dovecot + Openwebmail
http://jensoncc.blogspot.tw/2012/08/ubuntu-mail-serverpostfix-dovecot.html

Ubuntu Server 安裝 Postfix + pop3 imap
http://linadonis.pixnet.net/blog/post/7340997

外國人寫的也滿好的，看英文吃力很多，max心得是：很多地方看不懂就跳過就好了，重點是紅字的部份都要看懂即可：

Mark as Complete
How To Install and Configure Postfix on Ubuntu 16.04
https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-on-ubuntu-16-04

How To Set Up a Postfix E-Mail Server with Dovecot
https://www.digitalocean.com/community/tutorials/how-to-set-up-a-postfix-e-mail-server-with-dovecot

How to Install and Configure Postfix as a Send-Only SMTP Server on Ubuntu 16.04
https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-16-04

Setup mail forwarding in postfix on Ubuntu or Debian
https://www.binarytides.com/postfix-mail-forwarding-debian/

連線加密，可以用 let encrypt:

Using let’s encrypt certs with postfix
https://stackoverflow.max-everyday.com/2017/02/handling-exceptions-tornado/

letsencrypt 的 certbot 的官方說明：
https://certbot.eff.org/#ubuntuxenial-other

certbot 指令用法：

certbot --help

新的版本的 certbot 用起來更簡單：

certbot certonly --cert-name your-domain-name

Max 是使用手動模式：

certbot certonly --manual -d mail.dropboxlike.com

畫面顯示：

可以另外再開一個 terminal 連進去伺服器裡，先使用 curl http://mail.dropboxlike.com/ 來看看有沒有顯示 certbot 所需要的內容。

Max 的指令：

 ➜  html cd .well-known 
 ➜  .well-known mkdir acme-challenge
 ➜  .well-known cd acme-challenge 
 ➜  acme-challenge echo "KECpMIVxKY_-bWY_gGY3Hqqwvj-q_Pi0wy0eJdvPNsw.wxfS4hcTbJJfl1qAmLveBUuXTdcQeGE04Mvfw4Ed1NA" > KECpMIVxKY_-bWY_gGY3Hqqwvj-q_Pi0wy0eJdvPNsw

透過 echo 把內容放進檔案裡後，再回到 certbot 按下 Enter

 Press Enter to Continue
 Waiting for verification…
 Cleaning up challenges
 IMPORTANT NOTES:
 Congratulations! Your certificate and chain have been saved at:
 /etc/letsencrypt/live/mail.dropboxlike.com/fullchain.pem
 Your key file has been saved at:
 /etc/letsencrypt/live/mail.dropboxlike.com/privkey.pem
 Your cert will expire on 2020-05-01. To obtain a new or tweaked
 version of this certificate in the future, simply run certbot
 again. To non-interactively renew all of your certificates, run
 "certbot renew"
 If you like Certbot, please consider supporting our work by:
 Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
 Donating to EFF:                    https://eff.org/donate-le 

就成功拿到憑證了. ^_^

Max的參數設定 /etc/postfix/main.cf

# TLS parameters
smtpd_tls_cert_file=/etc/letsencrypt/live/mail.dropboxlike.com/fullchain.pem
smtpd_tls_key_file=/etc/letsencrypt/live/mail.dropboxlike.com/privkey.pem
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

smtp_use_tls = yes
smtp_tls_note_starttls_offer = yes

上面紅字部份是我有修改的。

將 Let’s Encrypt 申請到的 SSL 憑證用在 Postfix 上，提供 SMTP with TLS 和 smtps 服務
https://ezbox.idv.tw/63/lets-encrypt-ssl-smtp-tls-smpts/

如果有其他 user 也要用，可以加入下面這行設定值：

local_recipient_maps = proxy:unix:passwd.byname $alias_maps

完整的設定值，可以參考 /etc/postfix/main.cf.proto

除了設定  postfix 還要去設  dovecot 打開 SSL 選項，

# nano /etc/dovecot/conf.d/10-ssl.conf

找到 ssl 這行，把 no 改成 yes

ssl = yes

並且把自己的私鑰和公鑰指向檔案的路徑

ssl_key =</etc/letsencrypt/live/mail.dropboxlike.com/privkey.pem
ssl_cert =</etc/letsencrypt/live/mail.dropboxlike.com/fullchain.pem

mail server debug 用的 log:

/var/log/mail.log

必學的 2個指令：

dig  your_domain

host your_domain

一定要確定 DNS 相關設定值是正確的。

如果你遇到任何的錯誤，請先確定連線的 ip 有對應到你指定的 server

遇到：How to correct Postfix’ ‘Relay Access Denied’? 處理

Diagnostic-Code: smtp; 554 5.7.1 <max@gmail.com>: Relay access denied

you now need to authorise your local network by adding it to mynetworks. For example,

mynetworks = 192.168.1.0/24 127.0.0.0/8

測試 POP3

telnet mail.dropboxmax.com 110
Trying 128.199.124.123...
Connected to mail.dropboxmax.com.
Escape character is '^]'.
+OK Dovecot ready.
USER max
-ERR [AUTH] Plaintext authentication disallowed on non-secure (SSL/TLS) connections.

centos dsn client 的設定值放在 /etc/resolv.conf 檔案裡，設定範例：

nameserver 8.8.8.8

上面的做法，在ubuntu 裡已過時，需要改用這個解法：

在 /etc/network/interfaces 檔裡，加入下面這一行就可以指定 DNS Server 了

dns-nameservers 8.8.8.8 168.95.192.1

滿奇怪的，這個設定檔好像需要內縮，沒有內縮，我使用 reboot 後，dns 設定值沒有被修改，內縮後reboot 即可取到正確的 DNS 設定。

import socket
  (hostname, aliaslist, ipaddrlist) = socket.gethostbyname_ex(socket.gethostname())

Error message:

socket.gaierror: [Errno 8] nodename nor servname provided, or not known

真的滿奇怪的，只好改從 netifaces 來拿 ip

python 取得 ip address 的方法
https://stackoverflow.max-everyday.com/2017/02/python-netifaces/

 /**
 * 對字符串md5加密
 *
 * @param str
 * @return
 */
 public String getMD5(String str) {
 String ret = null;
 try {
 // 生成一個MD5加密計算摘要
 MessageDigest md = MessageDigest.getInstance("MD5");
 // 計算md5函數
 md.update(str.getBytes());
 // digest()最後確定返回md5 hash值，返回值為8為字符串。因為md5 hash值是16位的hex值，實際上就是8位的字符
 // BigInteger函數則將8位的字符串轉換成16位hex值，用字符串來表示；得到字符串形式的hash值
 ret = new BigInteger(1, md.digest()).toString(16);
 } catch (Exception e) {
 //throw new SpeedException("MD5加密出現錯誤");
 e.printStackTrace();
 }
 return ret;
 }

java.math.BigInteger.toString(int radix)方法實例

java.math.BigInteger.toString(int radix) 返回此BigInteger在給定的基數的字符串表示形式。如果基數是從Character.MIN_RADIX到Character.MAX_RADIX包容的範圍內，它會默認為10(因為Integer.toString的情況下)。

聲明

以下是java.math.BigInteger.toString()方法的聲明

public String toString(int radix)

參數

radix – 該字符串表示形式的基數

返回值

此方法返回此BigInteger在給定的基數的字符串表示形式。

BigInteger(byte[] val)
BigInteger的大小为val的顺序拼接结果

byte[] val = new byte[]{0x11,0x22,0x33};
BigInteger bigInteger = new BigInteger(val);
System.out.println(bigInteger.toString(16)); //16进制输出 , 结果 : 112233

BigInteger(String val, int radix)
得到大小为val , 以 radix 为基数的 BigInteger

BigInteger bigInteger = new BigInteger("1F", 16);
System.out.println(bigInteger.toString(16));//输出结果 1f
System.out.println(bigInteger.toString(10));//输出结果 31

String s1 = "126656864e144ad88d7ff96badd2f68b"; // 16进制数
BigInteger b = new BigInteger(s1,16);           // 16进制转成大数类型    
String s2 = b.toString(16);                     // 大数类型转成16进制

上列的範例輸入結果：

s1: 126656864e144ad88d7ff96badd2f68b
s2: 126656864e144ad88d7ff96badd2f68b

如果前2碼修改為00，則：

s1: 006656864e144ad88d7ff96badd2f68b
s2: 6656864e144ad88d7ff96badd2f68b

所以，最上面的例子，前面要補滿0 才不會出錯。

備份：

— 備份某個資料庫

mysqldump -u root -p db_name > backup.sql;

— 備份所有資料庫

mysqldump -u root -p --all-databases > backup.sql;

附註：備所有資料庫，遇到 database 版本不同時，會有問題，例如 mysql 5.6 到 5.7 會造成系統預設的欄位長度不符的錯誤。

備份用的 shell script:

#!/bin/sh 
pw='your-password'
mysqldump --all-databases --add-drop-table -h 127.0.0.1 -u root -p$pw > your-backup-file.sql
bzip2 -f your-backup-file.sql

bz2 壓縮：

bzip2 -z FileName

bz2 解壓縮：
bzip2 -d FileName.bz2

還原：

mysql -u root -p < backup.sql

如果出現 no database selected 是因為 backup.sql 裡沒有包括了 create database 的指令，只有去 drop table. 所以要在一還原的地方指定好要被貼回來的 database name:

mysql DATABASE_NAME -u root -p < backup.sql

進階一點的備份：

MySQL 自動備份 Shell Script
https://stackoverflow.max-everyday.com/2018/01/mysql-shell-script/

https://github.com/tornadoweb/tornado/issues/1046

完整版Source code:
http://tornado-doc-chs.readthedocs.io/en/latest/_modules/tornado/web.html

class StaticFileHandler(RequestHandler):

Alright this time I found the actual solution:

            # Note: only return HTTP 206 if less than the entire range has been
            # requested. Not only is this semantically correct, but Chrome
            # refuses to play audio if it gets an HTTP 206 in response to
            # ``Range: bytes=0-``.

This note applies to audio only, chrome will play video that begins be returning a 206.

    @asynchronous
    @gen.coroutine
    def get(self, path, include_body=True):
        #Assume that path is correct, validation will be handeled elsewhere
        self.absolute_path = os.path.abspath(path)
        self.path = self.absolute_path
        if self.absolute_path is None:
            return

        self.modified = self.get_modified_time()
        self.set_headers()

        if self.should_return_304():
            self.set_status(304)
            return

        request_range = None
        range_header = self.request.headers.get("Range")
        if range_header:
            # As per RFC 2616 14.16, if an invalid Range header is specified,
            # the request will be treated as if the header didn't exist.
            request_range = httputil._parse_request_range(range_header)

        if request_range:
            start, end = request_range
            size = self.get_content_size()
            if (start is not None and start >= size) or end == 0:
                # As per RFC 2616 14.35.1, a range is not satisfiable only: if
                # the first requested byte is equal to or greater than the
                # content, or when a suffix with length 0 is specified
                self.set_status(416)  # Range Not Satisfiable
                self.set_header("Content-Type", "text/plain")
                self.set_header("Content-Range", "bytes */%s" % (size, ))
                return
            if start is not None and start < 0:
                start += size
            if end is not None and end > size:
                # Clients sometimes blindly use a large range to limit their
                # download size; cap the endpoint at the actual file size.
                end = size

            self.set_status(206)  # Partial Content
            self.set_header("Content-Range",
                            httputil._get_content_range(start, end, size))
        else:
            start = end = None

        content = self.get_content(self.absolute_path, start, end)

        for chunk in content:
            self.write(chunk)
            yield gen.Task(self.flush)
        self.finish()

related:
HTTP STATUS: 206 PARTIAL CONTENT AND RANGE REQUESTS
https://benramsey.com/blog/2008/05/206-partial-content-and-range-requests/

File “zipextimporter.pyc”, line 98, in load_module
ImportError: MemoryLoadLibrary failed loading netifaces.pyd

錯誤畫面載圖：

發生的原因是 py2exe 無法透過 data_files 參數，或 includes 或 packages 這些參數把 netifaces.pyd 打包進去。

由於 py2exe for python 2.7 已經沒有在維護，不建議繼續使用，所以改用python 3 + py2exe 新版，或 pyinstaller + python 2.7.

全部改寫成 python 3 太累，太多 code 要重測，所以切換到 pyinstaller 比較快。

要開始／結束 ActionMode 是用：

Whenever you are creating/starting ActionMode Create by

mMode = startActionMode(....);

To Dismiss it use following Syntax

if (mMode != null) 
 {
     mMode.finish();
 }

from:
http://stackoverflow.com/questions/11158957/how-to-close-an-actionmode-menu-programmatically-on-honeycomb

這要寫的有效率，似乎滿難的。

發現把某一個 function 加入 @gen.coroutine，主程式遇到這一個 function 自動變成 muti-thread .. @_@;

相關文章：

Tornado – getting return value from IOLoop.add_callback()
http://stackoverflow.com/questions/33742023/tornado-getting-return-value-from-ioloop-add-callback

I’m not sure what the difference is between the following two functions:

 IOLoop.add_callback(callback, *args, **kwargs) 

AND

IOLoop.spawn_callback(callback, *args, **kwargs)

You can’t get a return value, at least not in the way you’re thinking of. Your callback can’t even run until the function that called spawn_callback (i.e. on_message) returns. Just do whatever you want to do when that callback finishes in the callback itself (or pass it another callback to invoke with its result).

stack_context is an error-handling mechanism for callback-oriented code. It doesn’t let you handle exceptions in the calling function, but it does let you establish an error handler in the calling function that will “follow” the code even through a chain of multiple add_callback calls. This turned out to be confusing as often as it helped, so now that coroutines are available I recommend using coroutines as much as possible and when you do need to fall back to raw callbacks, use spawn_callback instead of add_callback and put your try/except handler in the callback itself.

https://huangxiaohen2738.gitbooks.io/tornado-tcp-program/content/chapter2-2.html

2.2 ioloop的回调函数

1.IOLoop.add_callback(callback, args, *kwargs)

这个函数是最简单的，在ioloop开启后执行的回调函数callback，args和*kwargs都是这个回调函数的参数。一般我们的server都是单进程单线程的，即使是多线程，那么这个函数也是安全的。

8.IOLoop.spawn_callback(callback, args, *kwargs)

这个函数也是去执行一个回调函数，但是和上面说过的其他callback不同，它和回调者的栈上下文没有关联，因此呢，他比较时候去做一些独立的功能回调。

Tornado Execution Order Spawn callback
http://stackoverflow.com/questions/38696131/tornado-execution-order-spawn-callback

No, in fact you’re guaranteed that all the functions are spawned before any of them starts running, because first does not yield between spawning func and spawning func2. You can verify this yourself by testing your code:

from tornado import gen, ioloop

@gen.coroutine
def func():
    print('func started')
    yield gen.moment
    print('func done')


@gen.coroutine
def func2():
    print('func2 started')
    yield gen.moment
    print('func2 done')


@gen.coroutine
def first():
    for i in range(2):
        ioloop.IOLoop.current().spawn_callback(func)

    ioloop.IOLoop.current().spawn_callback(func2)
    yield gen.sleep(1)

ioloop.IOLoop.current().run_sync(first)

It prints:

func started
func started
func2 started
func done
func done
func2 done

See, func2 begins before the coroutines running func complete.

To accomplish what you want:

@gen.coroutine
def first():
    yield [func() for i in range(2)]
    ioloop.IOLoop.current().spawn_callback(func2)

This prints:

func started
func started
func done
func done
func2 started
func2 done

If you want first to wait for func2 to finish before it exits, then:

@gen.coroutine
def first():
    yield [func() for i in range(2)]
    yield func2()

For more info on calling coroutines from coroutines, see my Refactoring Tornado Coroutines.

官方文件：

http://www.tornadoweb.org/en/stable/ioloop.html

Running in the background

PeriodicCallback is not normally used with coroutines. Instead, a coroutine can contain a while True: loop and use tornado.gen.sleep:

@gen.coroutine
def minute_loop():
    while True:
        yield do_something()
        yield gen.sleep(60)

# Coroutines that loop forever are generally started with
# spawn_callback().
IOLoop.current().spawn_callback(minute_loop)

Sometimes a more complicated loop may be desirable. For example, the previous loop runs every 60+N seconds, where N is the running time of do_something(). To run exactly every 60 seconds, use the interleaving pattern from above:

@gen.coroutine
def minute_loop2():
    while True:
        nxt = gen.sleep(60)   # Start the clock.
        yield do_something()  # Run while the clock is ticking.
        yield nxt             # Wait for the timer to run out.