When deploying the code, a 500 error occurred
However, neither the error log of www-error.log defined under php-fpm nor the error log defined by nginx shows anything
You can use the following method
strace $(pidof’php-fpm’|sed’s/\([0-9]*\)/-p \1/g’) -e write -e read -s 1024
Use strace to monitor the read and write function calls of the fpm process
You can see errors like this
Wrong password or no permission when connecting to mysql
Just do the corresponding processing
When a 406 error occurs, it means that it is a client error, and the client cannot parse the content returned by the server
Generally, in the accept header sent by the client, the allowed type is set, but the server does not return in this format
Accept represents the type of data that the sender (client) wants to accept.
If the type specified by accept is inconsistent with the content-type returned by the response, a 406, not acceptable error will occur
Modify the server to return in the specified format
Or modify the client to accept the format of the server
Use github.com/emersion/go-smtp to send notification email content through smtp
After adding the content of the html code, it will be displayed as it is in some mailboxes, and it is not displayed as html. The reason is that the Content-Type is not added.
tools/smtp.go
package tools
import (
"encoding/base64"
"github.com/emersion/go-sasl"
"github.com/emersion/go-smtp"
"strings"
)
func SendSmtp(server string, from string, password string, to []string, subject string, body string) error {
auth := sasl.NewPlainClient("", from, password)
subjectBase := base64.StdEncoding.EncodeToString([]byte(subject))
msg := strings.NewReader(
"From: " + from + "\r\n" +
"To: " + strings.Join(to, ",") + "\r\n" +
"Subject: =?UTF-8?B?" + subjectBase + "?=\r\n" +
"Content-Type: text/html; charset=UTF-8" +
"\r\n\r\n" +
body + "\r\n")
err := smtp.SendMail(server, auth, from, to, msg)
if err != nil {
return err
}
return nil
}
Test case
tools/smtp_test.go
package tools
import "testing"
func TestSendSmtp(t *testing.T) {
body := "<a href=''>hello</a>"
SendSmtp("smtp.sina.cn:25", "[email protected]", "xxxxx", []string{"[email protected]"}, "123456", body)
}
The current code is located under the tools package, that is, under the tools/ directory. When executing the test case, use the following command
go test tools/smtp.go tools/smtp_test.go
There is a tag in the content, and the result can be displayed normally in a connected form
Also note that my subject is base64 encoded
Subject: =?UTF-8?B?” + subjectBase + “?=\r\n
So that the subject part is not garbled, =?UTF-8?B? This is a fixed format in the mail protocol, for example, the following content, the middle part is the content after base64
=?UTF-8?B?5LiA5Y+35bqXNOWRqOW5tOW6hu+8jDEwMDDkuIfku7bng63plIA=?=
When a property or method is called on nil, a null pointer will be reported
Especially the structure pointer, this problem is very easy to occur, the following is the test code
package tools import "fmt" func MyTest() { type MConn struct { Name string } var conn * MConn var conn2 MConn conn3 := new (MConn) conn4 := & MConn{} fmt.Printf("%v,%v,%v,%v" , conn, conn2, conn3, conn4) }
Return separately
<nil>,{},&{},&{}
When a structure pointer variable var conn *MConn is declared, but it is not initialized and the property is called directly, it will appear
panic: runtime error: invalid memory address or nil pointer dereference
Because conn is nil at this time, it is a null pointer
A null operation must be performed, if conn != nil {}
Of course, we sometimes do not make such an obvious error, but when we cooperate with map, this error may occur unintentionally.
var mMap map[ string ]* MConn m1: = mMap[ " name " ] m1.Name = " qqq "
In this code map, when the key element does not exist, the zero value of value is returned, which happens to be *MConn. The zero value is nil, and an error will also be reported.
So the map has to be judged here
var mMap map[ string ]* MConn m1, ok: = mMap[ " name " ] if ok { m1.Name = " qqq " }
When the same file code is modified by the local branch and the remote branch, a file conflict will occur when the code of the remote branch is pulled
This error occurs Please commit your changes or stash them before you merge.
You can store the current content first, and git stash can store the current content in the stack
git stash and then git pull the new code
Then put out the content stored in the stack, git stash pop
git stash list can view the list in the temporary storage stack
When tcp performs a three-way handshake, the first step is that the client sends a syn request, the server returns syn+sck, and the client responds to sck
When the syn request times out, tcp will timeout retransmission, and the number of retransmissions can be viewed here cat /proc/sys/net/ipv4/tcp_syn_retries
You can see that the number of retransmissions is 6
Each timeout time is 1 second, 2 seconds, 4 seconds, 8 seconds, 16 seconds, 32 seconds
Use telnet to test a non-existent ip and port
telnet 222.222.222.222 80
Use tcpdump to view the retransmission phenomenon
tcpdump -i any port 88
It can be seen that after the first connection failed, it was retransmitted 6 times
The interval time is 1 second, 2 seconds, 4 seconds, 8 seconds, 16 seconds, 32 seconds
When nginx is not configured to support webocket, but the domain name has been configured, such as: ws://gofly.sopans.com/ws_visitor
Direct js connection will return a 400 error
You need to add these three headers under the nginx location block to upgrade the http connection to a websocket connection
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection “Upgrade”;
For example, I open source customer gofly in
server{ listen 80 ; server_name gofly.sopans.com; access_log /var/log/nginx/ gofly.sopans.com.access.log main; client_max_body_size 10M; location /static { root /var/www/html/go- fly; } location / { proxy_pass http://127.0.0.1:8081; proxy_http_version 1.1 ; proxy_set_header X-Real- IP $remote_addr; proxy_set_header Upgrade $http_upgrade; proxy_set_header Connection "upgrade" ; } }
It is recommended that there is only one entry file for main.go under the golang main package
When there are other go files, and functions are defined in other go files
This function is called in the main.go entry file, go run main.go is executed, it will prompt undefined
If you have to do this, then all files must be added when go run, otherwise only the main.go file will be loaded by default
Only files in the non-main package will be automatically loaded through dependencies. So you need to enter multiple files as parameters
Should use go run a.go b.go c.go or go run *.go to run, compile the same
Download the compressed package that matches your own system version
https://sourceforge.net/projects/mingw-w64/files/mingw-w64/
I am 64 bit, download this version
After decompressing directly, put the bin directory into the PATH environment variable.
If you are using goland ide development
To restart goland, if it still doesn’t work, use the system’s own cli window first
The principle of group by is
First divide the data into groups according to the grouping field,
Then perform specific aggregation operations in each group
The limitations of ONLY_FULL_GROUP_BY mode are:
SELECT list is not in GROUP BY clause and contains nonaggregated column
In the columns of the select query, there are fields that are not in the group by clause, and there are fields that are not aggregate functions
After group by, all fields and attributes are the attributes of this group
Among the attributes of a group, only if the maximum/minimum/average/total is known, this aggregated attribute is meaningful
The attributes of each individual group member are meaningless
That’s why this restriction appears
When executing a specified function of go test, the report: testing: warning: no tests to run
For example go test -v -run Mytest
The test file name must be this _test suffix
xxxx_test.go
If it is not designated to run by correspondence, then the test function must start with Test
For example, the following file can
package tools import ( " fmt " " testing " ) func TestMytest(t * testing.T) { Mytest() } func Mytest() { m: = make(map[ string ] string ) m[ " a " ] = " b " m2: = make(map[ string ] interface {}) m2[ " a " ] = " b " test(m2) a: = " aaa " test2(a) } func test(t map[ string ] interface {}) { fmt.Printf( " %T " , t) } func test2(t interface {}) { fmt.Printf( " %T " , t) }
There are two ways of execution
go test -v test_test.go
go test -v -run Mytest
Empty interface{}
Can store any type of data
But when working with slices and maps, pay attention
[]interface{} or map[string]interface{}
May make this mistake cannot use (type []string) as type []interface {}
You cannot convert []T to []interface, nor can you convert map[string]T to map[string]interface{}
The Go language specification does not allow this because the two types do not have the same representation in memory.
Need to define separately []interface{} map[string]interface{}
Copy the element you want to convert to the above type
For example, the following error:
