Fasthttp: Error: "too many open files" for

[sjke]

I have one very unpleasant issue with the fasthttp :
There is a "highly loaded" server that stops processing requests after 5-10 minutes (about 5000 requests per minute) with error:
Temporary error when accepting new connections: accept tcp4 IP:PORT: accept: too many open files

Tried 2 ways to start the (with standard ListenAndServe and with custom Server options (disabled Keepalive, custom timeouts and closing connection on handers) but isn't works.

```golang
func HTTPServer() {
listenAddress := strings.Join([]string{os.Getenv("SERVER_IP"), os.Getenv("SERVER_PORT")}, ":")
log.Printf("Starting server on %q", listenAddress)
go func() {
if err := server.ListenAndServe(listenAddress, CustomModelHandler); err != nil {
log.Fatalf("error in ListenAndServe: %s", err)
}
}()
}

func CustomModelHandler(ctx *server.RequestCtx) {
var customModel models.CustomModel
err := json.Unmarshal(ctx.PostBody(), &customModel)
if err != nil {
ctx.Error(err.Error(), server.StatusBadRequest)
return
}
// ....
// some actions with customModel
// ....
if updated {
ctx.SetStatusCode(server.StatusOK)
} else {
ctx.SetStatusCode(server.StatusCreated)
}

defer ctx.Request.Reset()
defer ctx.Request.SetConnectionClose()

}
`

Any ideas how to fix it?

[kirillDanshin]

ulimit -Hn 1000000; ulimit -n 1000000 before starting the service. you can also find systemd service variables that will setup this for you

[sjke]

@kirillDanshin thx, but this isn't a fix for the issue (by increasing the limits, I'm just "delaying the inevitable"). I have to understand the reason: "Why it happens" and "How can I prevent it"

[sjke]

I figured out the problem in TCPListener.
Close!

[kirillDanshin]

@sjke to be precise, you should check that your listener is correctly closing connections (if you use custom listener), decrease TTL for your keep alive connections (or disable keep-alive) and set those limits to a max number of opened connections at once.

basically, you just found a common issue, when you got 4096 opened connections and tried to open 4097th, but it can't work due to ulimits. each socket (including client-server connections) in linux are files, so to serve more connections, you'll need higher limits and always correctly handle connection close.

[savsgio]

@sjke Could you explain us exactly your error? please

[rof20004]

@savsgio Did you find a solution?

[savsgio]

No!, but @kirillDanshin has the reason, I think it's very probably the error is by the listener.

[rof20004]

@savsgio thanks for answer, but he not explained how did... sad!

[savsgio]

I think it too! :confused:

[erikdubbelboer]

@rof20004 are you having an issue with too many open files as well?

[rof20004]

@erikdubbelboer Sometimes yes, sometimes no.

My ulimit is 100000(one hundred thousand).

My test is with vegeta.

echo "GET http://localhost:8080" | vegeta attack -rate=20000 -duration=30s | vegeta report

My code is this:

package main

import (
    "fmt"
    "log"

    "github.com/buaazp/fasthttprouter"
    "github.com/valyala/fasthttp"
)

func Index(ctx *fasthttp.RequestCtx) {
    fmt.Fprint(ctx, "Welcome!\n")
}

func main() {
    router := fasthttprouter.New()
    router.GET("/", Index)
    log.Fatal(fasthttp.ListenAndServe(":8080", router.Handler))
}

[erikdubbelboer]

Running this as root on my macbook I only get:

$ echo "GET http://localhost:8080" | sudo vegeta attack -rate=20000 -duration=30s | vegeta report
Password:


Requests      [total, rate]            600000, 20000.55
Duration      [total, attack, wait]    29.999536238s, 29.999175s, 361.238µs
Latencies     [mean, 50, 95, 99, max]  256.769µs, 136.854µs, 378.63µs, 1.195158ms, 81.91395ms
Bytes In      [total, mean]            5396796, 8.99
Bytes Out     [total, mean]            0, 0.00
Success       [ratio]                  99.94%
Status Codes  [code:count]             0:356  200:599644  
Error Set:
Get http://localhost:8080: dial tcp: lookup localhost: no such host

The only error there has nothing to do with fasthttp. Could it be that you're running your test as a user that runs out of file descriptors?

[rof20004]

@erikdubbelboer Thanks, maybe my user had a limit or I not setted ulimit correctly, I tested yesterday after set ulimit to one hundred again and no errors happens.

[savsgio]

@rof20004 I recomend you to use https://github.com/fasthttp/router also.
The router is maintained by fasthttp community.

[rof20004]

@savsgio Thanks, I will use it.