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// Copyright 2015 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//go:build !windows && !freebsd
// +build !windows,!freebsd
// Package limits provides routines to check and enforce certain resource
// limits on the Cloud SQL client proxy process.
package limits
import (
"fmt"
"syscall"
"github.com/GoogleCloudPlatform/cloudsql-proxy/logging"
)
var (
// For overriding in unittests.
syscallGetrlimit = syscall.Getrlimit
syscallSetrlimit = syscall.Setrlimit
)
// Each connection handled by the proxy requires two file descriptors, one
// for the local end of the connection and one for the remote. So, the proxy
// process should be able to open at least 8K file descriptors if it is to
// handle 4K connections to one instance.
const ExpectedFDs = 8500
// SetupFDLimits ensures that the process running the Cloud SQL proxy can have
// at least wantFDs number of open file descriptors. It returns an error if it
// cannot ensure the same.
func SetupFDLimits(wantFDs uint64) error {
rlim := &syscall.Rlimit{}
if err := syscallGetrlimit(syscall.RLIMIT_NOFILE, rlim); err != nil {
return fmt.Errorf("failed to read rlimit for max file descriptors: %v", err)
}
if rlim.Cur >= wantFDs {
logging.Verbosef("current FDs rlimit set to %d, wanted limit is %d. Nothing to do here.", rlim.Cur, wantFDs)
return nil
}
// Linux man page:
// The soft limit is the value that the kernel enforces for the corre‐
// sponding resource. The hard limit acts as a ceiling for the soft limit:
// an unprivileged process may set only its soft limit to a value in the
// range from 0 up to the hard limit, and (irreversibly) lower its hard
// limit. A privileged process (under Linux: one with the CAP_SYS_RESOURCE
// capability in the initial user namespace) may make arbitrary changes to
// either limit value.
if rlim.Max < wantFDs {
// When the hard limit is less than what is requested, let's just give it a
// shot, and if we fail, we fallback and try just setting the softlimit.
rlim2 := &syscall.Rlimit{}
rlim2.Max = wantFDs
rlim2.Cur = wantFDs
if err := syscallSetrlimit(syscall.RLIMIT_NOFILE, rlim2); err == nil {
logging.Verbosef("Rlimits for file descriptors set to {Current = %v, Max = %v}", rlim2.Cur, rlim2.Max)
return nil
}
}
rlim.Cur = wantFDs
if err := syscallSetrlimit(syscall.RLIMIT_NOFILE, rlim); err != nil {
return fmt.Errorf(
`failed to set rlimit {Current = %v, Max = %v} for max file
descriptors. The hard limit on file descriptors (4096) is lower than the
requested rlimit. The proxy will only be able to handle ~2048
connections. To hide this message, please request a limit within the available range.`,
rlim.Cur,
rlim.Max,
)
}
logging.Verbosef("Rlimits for file descriptors set to {Current = %v, Max = %v}", rlim.Cur, rlim.Max)
return nil
}
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