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Linux command to print directory structure in the form of a tree
... /proc
|-- fd
| `-- 3 -> /proc/15589/fd
|-- fdinfo
|-- net
| |-- dev_snmp6
| |-- netfilter
| |-- rpc
| | |-- auth.rpcsec.context
| | |-- auth.rpcsec.init
| | |-- auth.unix.gid
| | |-- auth.unix.ip
| | |-- nfs4.idtoname
| | |-- nfs4.nametoid
| | |-- nfsd.export
...
通过FastCGI Cache实现服务降级 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...，架构图如下：
Degradation
实现的关键点在于通过error_page处理异常，并且完成服务降级：
limit_conn_zone $server_name zone=perserver:1m;
error_page 500 502 503 504 = @failover;
fastcgi_cache_path
/tmp
levels=1:2
keys_zone=failover:100m
i...
Rank function in MySQL
... (SELECT @curRank := 0) r
ORDER BY age;
The (SELECT @curRank := 0) part allows the variable initialization without requiring a separate SET command.
Test case:
CREATE TABLE person (id int, first_name varchar(20), age int, gender char(1));
INSERT INTO person VALUES (1, 'Bob', 25, 'M');
INSERT I...
Remove rows with all or some NAs (missing values) in data.frame
...G00000221312 0 1 2 3 2
na.omit is nicer for just removing all NA's. complete.cases allows partial selection by including only certain columns of the dataframe:
> final[complete.cases(final[ , 5:6]),]
gene hsap mmul mmus rnor cfam
2 ENSG00000199674 0 2 2 ...
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named MySQLdb
...ysql-python
When I did the above, I got the error "EnvironmentError: mysql_config not found"
To fix this, I did the below in terminal:
export PATH=$PATH:/usr/local/mysql/bin
When I reran step 1, I get a new error "error: command 'cc' failed with exit status 1"
To fix this, I did the...
What is in your .vimrc? [closed]
Vi and Vim allow for really awesome customization, typically stored inside a .vimrc file. Typical features for a programmer would be syntax highlighting, smart indenting and so on.
...
Extract a dplyr tbl column as a vector
...
This seems the most versatile method as it works identically with vectors and data.frames, i.e. it enables functions to be more agnostic.
– geotheory
Mar 14 '17 at 10:03
...
What is “Orthogonality”?
...gn, operations do not have side effects; each action (whether it's an API call, a macro invocation, or a language operation) changes just one thing without affecting others. There is one and only one way to change each property of whatever system you are controlling.
...
Having Django serve downloadable files
..._str(file_name)
response['X-Sendfile'] = smart_str(path_to_file)
# It's usually a good idea to set the 'Content-Length' header too.
# You can also set any other required headers: Cache-Control, etc.
return response
Of course, this will only work if you have control over your server, or your hostin...
How can one print a size_t variable portably using the printf family?
...on is to cast your variables to unsigned long long and use %llu to be maximally portable.
– Adam Rosenfield
Apr 13 '10 at 1:52
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