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5d401f1e1b
* Added query logging for prometheus. Options added: 1) active.queries.filepath: Filename where queries will be recorded 2) active.queries.filesize: Size of the file where queries will be recorded. Functionality added: All active queries are now logged in a file. If prometheus crashes unexpectedly, these queries are also printed out on stdout in the rerun. Queries are written concurrently to an mmaped file, and removed once they are done. Their positions in the file are reused. They are written in json format. However, due to dynamic nature of application, the json has an extra comma after the last query, and is missing an ending ']'. There may also null bytes in the tail of file. Signed-off-by: Advait Bhatwadekar <advait123@ymail.com>
118 lines
3.6 KiB
Go
118 lines
3.6 KiB
Go
// Copyright 2011 Evan Shaw. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file defines the common package interface and contains a little bit of
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// factored out logic.
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// Package mmap allows mapping files into memory. It tries to provide a simple, reasonably portable interface,
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// but doesn't go out of its way to abstract away every little platform detail.
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// This specifically means:
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// * forked processes may or may not inherit mappings
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// * a file's timestamp may or may not be updated by writes through mappings
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// * specifying a size larger than the file's actual size can increase the file's size
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// * If the mapped file is being modified by another process while your program's running, don't expect consistent results between platforms
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package mmap
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import (
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"errors"
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"os"
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"reflect"
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"unsafe"
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)
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const (
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// RDONLY maps the memory read-only.
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// Attempts to write to the MMap object will result in undefined behavior.
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RDONLY = 0
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// RDWR maps the memory as read-write. Writes to the MMap object will update the
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// underlying file.
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RDWR = 1 << iota
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// COPY maps the memory as copy-on-write. Writes to the MMap object will affect
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// memory, but the underlying file will remain unchanged.
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COPY
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// If EXEC is set, the mapped memory is marked as executable.
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EXEC
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)
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const (
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// If the ANON flag is set, the mapped memory will not be backed by a file.
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ANON = 1 << iota
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)
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// MMap represents a file mapped into memory.
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type MMap []byte
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// Map maps an entire file into memory.
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// If ANON is set in flags, f is ignored.
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func Map(f *os.File, prot, flags int) (MMap, error) {
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return MapRegion(f, -1, prot, flags, 0)
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}
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// MapRegion maps part of a file into memory.
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// The offset parameter must be a multiple of the system's page size.
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// If length < 0, the entire file will be mapped.
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// If ANON is set in flags, f is ignored.
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func MapRegion(f *os.File, length int, prot, flags int, offset int64) (MMap, error) {
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if offset%int64(os.Getpagesize()) != 0 {
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return nil, errors.New("offset parameter must be a multiple of the system's page size")
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}
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var fd uintptr
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if flags&ANON == 0 {
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fd = uintptr(f.Fd())
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if length < 0 {
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fi, err := f.Stat()
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if err != nil {
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return nil, err
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}
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length = int(fi.Size())
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}
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} else {
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if length <= 0 {
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return nil, errors.New("anonymous mapping requires non-zero length")
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}
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fd = ^uintptr(0)
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}
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return mmap(length, uintptr(prot), uintptr(flags), fd, offset)
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}
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func (m *MMap) header() *reflect.SliceHeader {
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return (*reflect.SliceHeader)(unsafe.Pointer(m))
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}
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func (m *MMap) addrLen() (uintptr, uintptr) {
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header := m.header()
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return header.Data, uintptr(header.Len)
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}
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// Lock keeps the mapped region in physical memory, ensuring that it will not be
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// swapped out.
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func (m MMap) Lock() error {
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return m.lock()
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}
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// Unlock reverses the effect of Lock, allowing the mapped region to potentially
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// be swapped out.
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// If m is already unlocked, aan error will result.
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func (m MMap) Unlock() error {
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return m.unlock()
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}
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// Flush synchronizes the mapping's contents to the file's contents on disk.
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func (m MMap) Flush() error {
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return m.flush()
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}
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// Unmap deletes the memory mapped region, flushes any remaining changes, and sets
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// m to nil.
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// Trying to read or write any remaining references to m after Unmap is called will
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// result in undefined behavior.
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// Unmap should only be called on the slice value that was originally returned from
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// a call to Map. Calling Unmap on a derived slice may cause errors.
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func (m *MMap) Unmap() error {
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err := m.unmap()
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*m = nil
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return err
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}
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