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Let’s first look at the following code snippet: package main import ( "fmt" "os" "runtime" "time" ) func main() { runtime.GOMAXPROCS(2) a := make(map[int]int) go func() { i := 0 for { a[1] = i i++ time.Sleep(1000) } }() for { if a[1] > 1000000 { fmt.Println(a[1]) os.Exit(1) } } } After compiling and running it (assuming your machine has 2 or more cores), you will get the following error: fatal error: concurrent map read and map write goroutine 1 [running]: runtime.throw(0x10c3e05, 0x21) /usr/local/Cellar/go/1.10.3/libexec/src/runtime/panic.go:616 +0x81 fp=0xc42004bf00 sp=0xc42004bee0 pc=0x10263f1 runtime.mapaccess1_fast64(0x10a5b60, 0xc42007e180, 0x1, 0xc42008e048) /usr/local/Cellar/go/1.10.3/libexec/src/runtime/hashmap_fast.go:101 +0x197 fp=0xc42004bf28 sp=0xc42004bf00 pc=0x1008d27 main.main() /Users/yusp/test/panic3/main.go:22 +0x7c fp=0xc42004bf88 sp=0xc42004bf28 pc=0x108e28c runtime.main() /usr/local/Cellar/go/1.10.3/libexec/src/runtime/proc.go:198 +0x212 fp=0xc42004bfe0 sp=0xc42004bf88 pc=0x1027c62 runtime.goexit() /usr/local/Cellar/go/1.10.3/libexec/src/runtime/asm_amd64.s:2361 +0x1 fp=0xc42004bfe8 sp=0xc42004bfe0 pc=0x104e501 goroutine 5 [runnable]: time.Sleep(0x3e8) /usr/local/Cellar/go/1.10.3/libexec/src/runtime/time.go:102 +0x166 main.main.func1(0xc42007e180) /Users/yusp/test/panic3/main.go:18 +0x61 created by main.main /Users/yusp/test/panic3/main.go:13 +0x59 It seems straightforward; Golang’s map is not thread-safe, and concurrent read and write cause a panic. However, look at the error information on line /Users/yusp/test/panic3/main.go:18 +0x61, which points to line 18 of main.go where Sleep is called, not the actual point of concurrency issue. In a vast stack trace, it becomes even harder to locate the problem. ...

In a previous article “TiDB Source Code Reading Series (4) Overview of INSERT Statement”, we introduced the general process of the INSERT statement. Why write a separate article for INSERT? Because in TiDB, simply inserting a piece of data is the simplest and most common case. It becomes more complex when defining various behaviors within the INSERT statement, such as how to handle situations with Unique Key conflicts: Should we return an error? Ignore the current data insertion? Or overwrite existing data? Therefore, this article will continue to delve into the INSERT statement. ...

Installing HAProxy yum install haproxy is effective for CentOS 7. After installation, you can start the service using systemctl start haproxy. But don’t rush yet. Configuring HAProxy Add the following content to /etc/haproxy/haproxy.cfg. global # The content of global is generally fixed and quite understandable. log 127.0.0.1 local2 maxconn 4096 user haproxy group haproxy chroot /var/lib/haproxy daemon pidfile /var/run/haproxy.pid stats socket /var/run/haproxy.sock # Create a socket file for haproxy nbproc 40 # Start 40 processes to forward concurrently, higher versions can use nbthread, a threaded approach. defaults # This section is mostly copied, not entirely clear on the options. log global mode http option tcplog option dontlognull retries 3 option redispatch maxconn 1024 timeout connect 5000ms timeout client 50000ms timeout server 50000ms listen cdb_cluster 0.0.0.0:3030 # The actual proxy name and address for receiving services. ## cdb balance leastconn - the cluster listening on port 3030. mode tcp balance leastconn # This method is most suitable for databases; do not change. server cdb1 172.16.30.3:26257 check # Check seems to require a port for feedback status; without it, it might not work, but it doesn't matter. server cdb2 172.16.30.3:26258 check server cdb3 172.16.30.3:26259 check server cdb4 172.16.30.3:26260 check Start and Connect systemctl start haproxy to start the service. ...

Why Test TPC-C First of all, TPC-C is the de facto OLTP benchmark standard. It is a set of specifications, and any database can publish its test results under this standard, so there’s no issue of quarreling over the testing tools used. Secondly, TPC-C is closer to real-world scenarios as it includes a transaction model within it. In the flow of this transaction model, there are both high-frequency simple transaction statements and low-frequency inventory query statements. Therefore, it tests the database more comprehensively and practically. ...

Compiling Sysbench with pgsql Support CockroachDB uses the PostgreSQL protocol. If you want to use Sysbench for testing, you need to enable pg protocol support in Sysbench. Sysbench already supports the pg protocol, but it is not enabled by default during compilation. You can configure it with the following command: ./configure --with-pgsql Of course, preliminary work involves downloading the Sysbench source code and installing the necessary PostgreSQL header files required for compilation (you can use yum or sudo to install them). ...