Re: [go-nuts] how to get file's current offset
On Thu, Apr 18, 2019 at 10:34:24PM +0800, sa517...@mail.ustc.edu.cn wrote:
> I want to know file's current read offset after open a file, but I can not
> found related API.
>
> f, err := os.Open("/tmp/")
> if err != nil{
> panic(err)
> }
>
> ... // some read operation
>
> // how can I get f's current read offset??
offset, err := f.Seek(0, io.SeekCurrent)
--
Valentin
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Re: [go-nuts] HTTP client request rate
On Fri, Feb 08, 2019 at 10:12:36PM +0100, Valentin Vidic wrote: > Yes, it is quite strange. I don't see it hitting any limits but > the request rate goes down. Seems it could be GC related since turning off GC gives 5x request rate with 20 gorutines: $ ./gb -duration 15s -parallel 5 http://nginx Running 5 parallel clients for 15s... Requests: 216070 Rate: 14404.7/s Bytes: 132234840 Code[200]: 216070 $ GOGC=off ./gb -duration 15s -parallel 5 http://nginx Running 5 parallel clients for 15s... Requests: 280430 Rate: 18695.3/s Bytes: 171623160 Code[200]: 280430 $ ./gb -duration 15s -parallel 20 http://nginx Running 20 parallel clients for 15s... Requests: 153903 Rate: 10260.2/s Bytes: 94188636 Code[200]: 153903 $ GOGC=off ./gb -duration 15s -parallel 20 http://nginx Running 20 parallel clients for 15s... Requests: 776554 Rate: 51770.3/s Bytes: 475251048 Code[200]: 776554 -- Valentin -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [go-nuts] HTTP client request rate
On Fri, Feb 08, 2019 at 02:30:52PM -0600, robert engels wrote: > Could be many things, but a few to think about: Yes, it is quite strange. I don't see it hitting any limits but the request rate goes down. > If you run more Go routines than you have CPUs available, and the task > is CPU bound (which may be if the url points to a local resource), > then you are going to thrash, causing worse performance. CPU does not seem to be maxed out, here is the info for 5 gorutines: CPU | sys 98% | user436% | irq 26% | idle 4222% | wait 0% | curf 2.20GHz | curscal ?% | CPL | avg13.28 | avg52.54 | avg15 1.28 | csw 186540 | intr 164257 | | numcpu48 | 541% gb 123% nginx And for 20 gorutines it looks like this: CPU | sys 132% | user970% | irq 21% | idle 3655% | wait 0% | curf 2.20GHz | curscal ?% | CPL | avg10.52 | avg51.18 | avg15 1.01 | csw 240847 | intr 203360 | | numcpu48 | 1170% gb 103% nginx > The service you are calling is not properly concurrent, so the more > simultaneously requests, the worse it performs. The server end is nginx serving a default static page, so it should be quite fast. > You are hitting network/router limits, so it is dropping packets, > causing worse performance due to TCP retries and/or smaller window > sizes. Just tried running client and server on the same host and it gives the same numbers. -- Valentin -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[go-nuts] HTTP client request rate
Hi,
Can someone help me figure out why the performance (request rate)
of this program goes down when I add more gorutines?
$ ./gb -duration 15s -parallel 5 http://nginx
Running 5 parallel clients for 15s...
Requests: 217998
Rate: 14533.2/s
Bytes: 133414776
Code[200]: 217998
$ ./gb -duration 15s -parallel 20 http://nginx
Running 20 parallel clients for 15s...
Requests: 155150
Rate: 10343.3/s
Bytes: 94951800
Code[200]: 155150
--
Valentin
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package main
import (
"flag"
"fmt"
"io"
"net"
"net/http"
"os"
"runtime"
"runtime/pprof"
"time"
)
type stats struct {
req int
err int
rerr int
bytes int
code map[int]int
}
func bench(url string, compress bool, timeout time.Duration, done chan
struct{}, result chan stats) {
s := stats{}
s.code = make(map[int]int)
transport := {
DisableCompression: !compress,
TLSHandshakeTimeout: timeout,
DialContext: ({
Timeout: timeout,
DualStack: true,
}).DialContext,
}
client := {
Transport: transport,
Timeout: timeout,
}
written := 0
buf := make([]byte, 10*1024)
LOOP:
for {
s.req++
resp, err := client.Get(url)
if err != nil {
fmt.Println(err)
s.err++
} else {
s.code[resp.StatusCode]++
for {
written, err = resp.Body.Read(buf)
s.bytes += written
if err != nil {
break
}
}
if err != nil && err != io.EOF {
fmt.Println(err)
s.rerr++
}
resp.Body.Close()
}
select {
case <-done:
break LOOP
default:
}
}
result <- s
}
func main() {
var compression = flag.Bool("compression", true, "use HTTP compression")
var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to
file")
var duration = flag.Duration("duration", 15*time.Second, "test
duration")
var memprofile = flag.String("memprofile", "", "write memory profile to
file")
var parallel = flag.Int("parallel", 20, "number of parallel client
connections")
var timeout = flag.Duration("timeout", 10*time.Second, "request
timeout")
flag.Parse()
url := flag.Arg(0)
if url == "" {
fmt.Println("No url given")
os.Exit(1)
}
if *cpuprofile != "" {
f, err := os.Create(*cpuprofile)
if err != nil {
fmt.Println("Could not create cpu profile:", err)
os.Exit(1)
}
pprof.StartCPUProfile(f)
defer pprof.StopCPUProfile()
}
done := make(chan struct{})
result := make(chan stats)
fmt.Printf("Running %d parallel clients for %v...\n", *parallel,
*duration)
for i := 0; i < *parallel; i++ {
go bench(url, *compression, *timeout, done, result)
}
time.Sleep(*duration)
close(done)
total := stats{}
total.code = make(map[int]int)
for i := 0; i < *parallel; i++ {
s := <-result
total.req += s.req
total.err += s.err
total.rerr += s.rerr
total.bytes += s.bytes
for k, v := range s.code {
total.code[k] += v
}
}
fmt.Println("Requests:", total.req)
fmt.Printf("Rate: %.1f/s\n", float64(total.req)/duration.Seconds())
fmt.Println("Bytes:", total.bytes)
if total.err > 0 {
fmt.Println("Errors:", total.err)
}
if total.rerr > 0 {
fmt.Println("Read errors:", total.rerr)
}
for k, v := range total.code {
fmt.Printf("Code[%d]: %d\n", k, v)
}
if *memprofile != "" {
f, err := os.Create(*memprofile)
if err != nil {
fmt.Println("Could not create memory profile: ", err)
}
Re: [go-nuts] Re: C++ 11 to Golang convertor
On Thu, Jan 03, 2019 at 02:46:39PM -0800, Eric Raymond wrote: > On the other hand, I believe graceful, comment-preserving C to idiomatic-Go > transpilation is almost possible. By 'almost' I mean that the tool would > pass through a small enough percentage of untranslated residuals for > corrections to be around a 5% job for a human expert. > > I've had a lot of incentive to think about this because my concerns center > around vast masses of C infrastructure code in critical network services > like NTP, DNS, etc. The security and reliability consequences of unsafe > code in that swamp are serious and it needs to be drained. Transpilation > to golang is, I think, the first realistic hope we've had of doing that > without a prohibitively high labor input. > > By possible I do not mean easy. I've scoped the job and done a design > sketch. I think my qualifications for writing such a transpiler are > exceptionally good, but it would nevertheless take me a minimum of two > years of hard work to get there. I have put put some feelers for > funding; if I get to choose my next major project after NTPsec, this would > be it. Golang compiler was converted from C to Go in some version, but I don't know if the tool used there is available somewhere. -- Valentin -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [go-nuts] How to send a POST request from http.Redirect?
On Fri, Oct 27, 2017 at 09:04:25PM -0700, hkang.sun...@gmail.com wrote:
> I have a question about sending POST request through the http.Redirect
> function.
> The following is my http handler function. In this function, I get some
> secret data and want to pass the data to the redirectURL.
> I could not use GET with query parameter because the secret data is
> explicit as a query in a GET redirect URL. So I am thinking sending the
> data in the body of a POST request.
>
> func myHandler (w http.ResponseWriter, r *HTTPRequest) {
> // process and get some secret data
> data := someValue
> http.Redirect(w, r, redirectURL, http.StatusFound)
> }
>
> I tried setting "r.Method="POST""; however it does not work.
> Could anyone help on this? Thanks. in advance.
Try if using http.StatusTemporaryRedirect instead of http.StatusFound
works better:
StatusTemporaryRedirect = 307 // RFC 7231, 6.4.7
--
Valentin
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