Data Matters

Today I got an "Node is not runnning!" error when test with "riak-admin status" after starting riak 0.14.2 server is about the ~/.erlang.cookie. Yet when I "ps xua |grep riak", all the riak processes were running well. I tried "riak ping", and it lefe me following error: Error when reading /home/username/.erlang.cookie: eaccesescript: exception error: no match of right hand side value I checked .erlang.cookie and found it with owner root. So I removed /home/username/.erlang.cookie, and start riak without root permission(chown should also work). Now, everything works fine.

1062 Duplicate entry 'xxxx' for key xxxx. The key is already in current mysql. In mysql slave server, try "STOP SLAVE;SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;START SLAVE;". You may also set slave_skip_errors = 1062 in my.cnf file to ignore all the 1062 errors. 1236  Got fatal error 1236 from master when reading data from binary log: 'Client requested master to start replication from impossible position' The binlog position in master mysql server is not available. Some problem of master mysql server may cause this issue. You may want change the mysql replication position to next binary log file on the master mysql server(using "change master to ..."). 126 Error 'Incorrect key file for table './db/xxx.MYI'; try to repair it' on query. The error means that index file is crashed, and you may repair it by "repair table xxx". Or you want to change mysql storage to another hard disk since the error my be induced by an disk...

Python interpreter stores the default parameter list in a dict named func_defaults meeting a "def func(a=0, b=[], c={})" statement. So there is func.func_defaults = [0, [], {}]. When we specify an object in default parameter list of a function, python interpreter will keep its reference in the list. Therefore, an object as a default parameter of a function may change if you change it. For example: def func(a = []):     a.append(0)     print a When call the function in a python IDLE, we may have: >>> func()   [0]   >>> func()   [0, 0]   >>> func()  [0, 0, 0]   >>> func([1])   [1, 0]   >>> func()  [0, 0, 0, 0] You may find some detail example at http://effbot.org/zone/default-values.htm

First, you need debconf installed by sudo apt-get -y install debconf. Then, you may install mysql-server silenly by: echo mysql-server-5.1 mysql-server/root_password password PASSWORD-STRING | sudo debconf-set-selections echo mysql-server-5.1 mysql-server/root_password_again password PASSWORD-STRING | sudo debconf-set-selections sudo apt-get -y install mysql-server All pretty simple!

Here are several examples of boto api on amazon ec2: Connect to a region: conn=boto.ec2.connect_to_region('us-west-1a') Get an instance by id: instance = conn.get_all_instances(['i-xxxxxxxx'])[0].instances[0] Run(create) an instance: conn.run_instances(image_id=u'ami-xxxxxxxx', key_name='default', security_groups=['default-group'],                   instance_type='m2.4xlarge', placement='us-west-1a') Add/remove a tag for an instance: instance.add_tag('Name','default') instance.remove_tag('Name') Reboot an instance: instance.reboot() Terminate an instance: instance.terminate() Get an ebs volume by id: volume = conn.get_all_volumes(['vol-xxxxxxxx'])[0] Attach an ebs volume to an instance: volume.attach(instance.id, '/etc/sdh') conn.attach_volume(volume.id, instance.id, '/dev/sdh')

We can use python htmllib.HTMLParser to extract link and corresponding text from html files: import urllib from formatter import * from htmllib import * formatter = AbstractFormatter(NullWriter()) class LinkParser(HTMLParser):     def __init__(self, *sub, **kw):         HTMLParser.__init__(self, *sub, **kw)         self.current_link = self.current_text = None     def handle_starttag(self, tag, method, attrs):         if tag == 'a':             for attr in attrs:                 if attr[0]=='href':                     self.current_link = attr[1]         return HTMLParser.handle_starttag(self, tag, method, attrs)     def handle_endtag(self, tag, method):         if tag ...

You may use user-defined functions with sqlalchemy. First how to create a function with sqlalchemy: cmd1 = 'DROP FUNCTION IF EXISTS `dummyfunc`' cmd2 = '''create function dummyfunc  ()   RETURNS INT   DETERMINISTIC    BEGIN     DECLARE ret INT;     SET ret = 0;     RETURN ret;    END''' metadata.bind.execute(cmd1) metadata.bind.execute(cmd2) Second, use the function you just created with func.function_name like: session.query(TestTable,func.dummyfunc()).first()   Very simple!