utils

package module
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 Go to latest Published: Dec 15, 2014 License: LGPL-3.0 Imports: 30 Imported by: 0

README

juju/utils

This package provides general utility packages and functions.

Documentation

Index

Examples

Constants

View Source 
const (
	// VerifySSLHostnames ensures we verify the hostname on the certificate
	// matches the host we are connecting and is signed
	VerifySSLHostnames = SSLHostnameVerification(true)
	// NoVerifySSLHostnames informs us to skip verifying the hostname
	// matches a valid certificate
	NoVerifySSLHostnames = SSLHostnameVerification(false)
)
View Source 
const (
	NoSuchUserErrRegexp = `user: unknown user [a-z0-9_-]*`
	NoSuchFileErrRegexp = `no such file or directory`
)

The following are strings/regex-es which match common Unix error messages that may be returned in case of failed calls to the system. Any extra leading/trailing regex-es are left to be added by the developer.

Variables

View Source 
var CompatSalt = string([]byte{0x75, 0x82, 0x81, 0xca})

CompatSalt is because Juju 1.16 and older used a hard-coded salt to compute the password hash for all users and agents

View Source 
var FastInsecureHash = false

FastInsecureHash specifies whether a fast, insecure version of the hash algorithm will be used. Changing this will cause PasswordHash to produce incompatible passwords. It should only be changed for testing purposes - to make tests run faster.

View Source 
var MinAgentPasswordLength = base64.StdEncoding.EncodedLen(randomPasswordBytes)

MinAgentPasswordLength describes how long agent passwords should be. We require this length because we assume enough entropy in the Agent password that it is safe to not do extra rounds of iterated hashing.

View Source 
var OutgoingAccessAllowed = true

OutgoingAccessAllowed determines whether connections other than localhost can be dialled.

Functions

func AgentPasswordHash 

func AgentPasswordHash(password string) string

AgentPasswordHash returns base64-encoded one-way hash of password. This is not suitable for User passwords because those will have limited entropy (see UserPasswordHash). However, since we generate long random passwords for agents, we can trust that there is sufficient entropy to prevent brute force search. And using a faster hash allows us to restart the state machines and have 1000s of agents log in in a reasonable amount of time.

func AtomicWriteFile 

func AtomicWriteFile(filename string, contents []byte, perms os.FileMode) (err error)

AtomicWriteFile atomically writes the filename with the given contents and permissions, replacing any existing file at the same path.

func AtomicWriteFileAndChange 

func AtomicWriteFileAndChange(filename string, contents []byte, change func(*os.File) error) (err error)

AtomicWriteFileAndChange atomically writes the filename with the given contents and calls the given function after the contents were written, but before the file is renamed.

func BasicAuthHeader 

func BasicAuthHeader(username, password string) http.Header

BasicAuthHeader creates a header that contains just the "Authorization" entry. The implementation was originally taked from net/http but this is needed externally from the http request object in order to use this with our websockets. See 2 (end of page 4) http://www.ietf.org/rfc/rfc2617.txt "To receive authorization, the client sends the userid and password, separated by a single colon (":") character, within a base64 encoded string in the credentials."

func CommandString 

func CommandString(args ...string) string

CommandString flattens a sequence of command arguments into a string suitable for executing in a shell, escaping slashes, variables and quotes as necessary; each argument is double-quoted if and only if necessary.

func CopyFile 

func CopyFile(dest, source string) error

CopyFile writes the contents of the given source file to dest.

func GetAddressForInterface 

func GetAddressForInterface(interfaceName string) (string, error)

GetAddressForInterface looks for the network interface and returns the IPv4 address from the possible addresses.

func GetHTTPClient 

func GetHTTPClient(verify SSLHostnameVerification) *http.Client

GetHTTPClient returns either a standard http client or non validating client depending on the value of verify.

func GetIPv4Address 

func GetIPv4Address(addresses []net.Addr) (string, error)

GetIPv4Address iterates through the addresses expecting the format from func (ifi *net.Interface) Addrs() ([]net.Addr, error)

func GetNonValidatingHTTPClient 

func GetNonValidatingHTTPClient() *http.Client

GetNonValidatingHTTPClient returns a new http.Client that does not verify the server's certificate chain and hostname.

func GetValidatingHTTPClient 

func GetValidatingHTTPClient() *http.Client

GetValidatingHTTPClient returns a new http.Client that verifies the server's certificate chain and hostname.

func Gunzip 

func Gunzip(data []byte) ([]byte, error)

Gunzip uncompresses the given data.

func Gzip 

func Gzip(data []byte) []byte

Gzip compresses the given data.

func Home 

func Home() string

Home returns the os-specific home path as specified in the environment.

func IsUbuntu 

func IsUbuntu() bool

IsUbuntu executes lxb_release to see if the host OS is Ubuntu.

func IsValidUUIDString 

func IsValidUUIDString(s string) bool

IsValidUUIDString returns true, if the given string matches a valid UUID (version 4, variant 2).

func JoinServerPath 

func JoinServerPath(elem ...string) string

JoinServerPath joins any number of path elements into a single path, adding a path separator (based on the current juju server OS) if necessary. The result is Cleaned; in particular, all empty strings are ignored.

func MakeFileURL 

func MakeFileURL(in string) string

MakeFileURL returns a file URL if a directory is passed in else it does nothing

func NewHttpTLSTransport 

func NewHttpTLSTransport(tlsConfig *tls.Config) *http.Transport

NewHttpTLSTransport returns a new http.Transport constructed with the TLS config and the necessary parameters for Juju.

func NormalizePath 

func NormalizePath(dir string) (string, error)

NormalizePath expands a path containing ~ to its absolute form, and removes any .. or . path elements.

func ParseSize 

func ParseSize(str string) (MB uint64, err error)

ParseSize parses the string as a size, in mebibytes.

The string must be a is a non-negative number with an optional multiplier suffix (M, G, T, P, E, Z, or Y). If the suffix is not specified, "M" is implied.

func RandomBytes 

func RandomBytes(n int) ([]byte, error)

RandomBytes returns n random bytes.

func RandomPassword 

func RandomPassword() (string, error)

RandomPassword generates a random base64-encoded password.

func RandomSalt 

func RandomSalt() (string, error)

RandomSalt generates a random base64 data suitable for using as a password salt The pbkdf2 guideline is to use 8 bytes of salt, so we do 12 raw bytes into 16 base64 bytes. (The alternative is 6 raw into 8 base64).

func ReadFileSHA256 

func ReadFileSHA256(filename string) (string, int64, error)

ReadFileSHA256 is like ReadSHA256 but reads the contents of the given file.

func ReadSHA256 

func ReadSHA256(source io.Reader) (string, int64, error)

ReadSHA256 returns the SHA256 hash of the contents read from source (hex encoded) and the size of the source in bytes.

func ReadYaml 

func ReadYaml(path string, obj interface{}) error

ReadYaml unmarshals the yaml contained in the file at path into obj. See goyaml.Unmarshal.

func ReplaceFile 

func ReplaceFile(source, destination string) error

ReplaceFile atomically replaces the destination file or directory with the source. The errors that are returned are identical to those returned by os.Rename.

func RunCommand 

func RunCommand(command string, args ...string) (output string, err error)

RunCommand executes the command and return the combined output.

func SetHome 

func SetHome(s string) error

SetHome sets the os-specific home path in the environment.

func ShQuote 

func ShQuote(s string) string

ShQuote quotes s so that when read by bash, no metacharacters within s will be interpreted as such.

func Timeit 

func Timeit(action string) func()

Start a timer, used for tracking time spent. Generally used with either defer, as in: 

defer utils.Timeit("my func")()

Which will track how much time is spent in your function. Or if you want to track the time spent in a function you are calling then you would use: 

toc := utils.Timeit("anotherFunc()")
anotherFunc()
toc()

This tracks nested calls by indenting the output, and will print out the full stack of timing when we reach the top of the stack.

func UniqueDirectory 

func UniqueDirectory(path, name string) (string, error)

UniqueDirectory returns "path/name" if that directory doesn't exist. If it does, the method starts appending .1, .2, etc until a unique name is found.

func UseMultipleCPUs 

func UseMultipleCPUs()

UseMultipleCPUs sets GOMAXPROCS to the number of CPU cores unless it has already been overridden by the GOMAXPROCS environment variable.

func UserHomeDir 

func UserHomeDir(userName string) (hDir string, err error)

UserHomeDir returns the home directory for the specified user, or the home directory for the current user if the specified user is empty.

func UserPasswordHash 

func UserPasswordHash(password string, salt string) string

UserPasswordHash returns base64-encoded one-way hash password that is computationally hard to crack by iterating through possible passwords.

func WriteYaml 

func WriteYaml(path string, obj interface{}) error

WriteYaml marshals obj as yaml and then writes it to a file, atomically, by first writing a sibling with the suffix ".preparing" and then moving the sibling to the real path.

Types

type Attempt 

type Attempt struct {
	// contains filtered or unexported fields
}

func (*Attempt) HasNext 

func (a *Attempt) HasNext() bool

HasNext returns whether another attempt will be made if the current one fails. If it returns true, the following call to Next is guaranteed to return true.

Example 
package main

import (
	"time"

	gc "gopkg.in/check.v1"

	"github.com/juju/utils"
)

func doSomething() (int, error) { return 0, nil }

func shouldRetry(error) bool { return false }

func doSomethingWith(int) {}

func main() {
	// This example shows how Attempt.HasNext can be used to help
	// structure an attempt loop. If the godoc example code allowed
	// us to make the example return an error, we would uncomment
	// the commented return statements.
	attempts := utils.AttemptStrategy{
		Total: 1 * time.Second,
		Delay: 250 * time.Millisecond,
	}
	for attempt := attempts.Start(); attempt.Next(); {
		x, err := doSomething()
		if shouldRetry(err) && attempt.HasNext() {
			continue
		}
		if err != nil {
			// return err
			return
		}
		doSomethingWith(x)
	}
	// return ErrTimedOut
	return
}

func (*utilsSuite) TestAttemptTiming(c *gc.C) {
	testAttempt := utils.AttemptStrategy{
		Total: 0.25e9,
		Delay: 0.1e9,
	}
	want := []time.Duration{0, 0.1e9, 0.2e9, 0.2e9}
	got := make([]time.Duration, 0, len(want)) // avoid allocation when testing timing
	t0 := time.Now()
	for a := testAttempt.Start(); a.Next(); {
		got = append(got, time.Now().Sub(t0))
	}
	got = append(got, time.Now().Sub(t0))
	c.Assert(got, gc.HasLen, len(want))
	const margin = 0.01e9
	for i, got := range want {
		lo := want[i] - margin
		hi := want[i] + margin
		if got < lo || got > hi {
			c.Errorf("attempt %d want %g got %g", i, want[i].Seconds(), got.Seconds())
		}
	}
}

func (*utilsSuite) TestAttemptNextHasNext(c *gc.C) {
	a := utils.AttemptStrategy{}.Start()
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, false)

	a = utils.AttemptStrategy{}.Start()
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.HasNext(), gc.Equals, false)
	c.Assert(a.Next(), gc.Equals, false)

	a = utils.AttemptStrategy{Total: 2e8}.Start()
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.HasNext(), gc.Equals, true)
	time.Sleep(2e8)
	c.Assert(a.HasNext(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, false)

	a = utils.AttemptStrategy{Total: 1e8, Min: 2}.Start()
	time.Sleep(1e8)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.HasNext(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.HasNext(), gc.Equals, false)
	c.Assert(a.Next(), gc.Equals, false)
}

Output:

func (*Attempt) Next 

func (a *Attempt) Next() bool

Next waits until it is time to perform the next attempt or returns false if it is time to stop trying. It always returns true the first time it is called - we are guaranteed to make at least one attempt.

type AttemptStrategy 

type AttemptStrategy struct {
	Total time.Duration // total duration of attempt.
	Delay time.Duration // interval between each try in the burst.
	Min   int           // minimum number of retries; overrides Total
}

AttemptStrategy represents a strategy for waiting for an action to complete successfully.

func (AttemptStrategy) Start 

func (s AttemptStrategy) Start() *Attempt

Start begins a new sequence of attempts for the given strategy.

type Limiter 

type Limiter interface {
	// Acquire another unit of the resource.
	// Acquire returns false to indicate there is no more availability,
	// until another entity calls Release.
	Acquire() bool
	// AcquireWait requests a unit of resource, but blocks until one is
	// available.
	AcquireWait()
	// Release returns a unit of the resource. Calling Release when there
	// are no units Acquired is an error.
	Release() error
}

Limiter represents a limited resource (eg a semaphore).

func NewLimiter 

func NewLimiter(max int) Limiter

type SSLHostnameVerification 

type SSLHostnameVerification bool

SSLHostnameVerification is used as a switch for when a given provider might use self-signed credentials and we should not try to verify the hostname on the TLS/SSL certificates

type UUID 

type UUID [16]byte

UUID represent a universal identifier with 16 octets.

func NewUUID 

func NewUUID() (UUID, error)

NewUUID generates a new version 4 UUID relying only on random numbers.

func UUIDFromString 

func UUIDFromString(s string) (UUID, error)

func (UUID) Copy 

func (uuid UUID) Copy() UUID

Copy returns a copy of the UUID.

func (UUID) Raw 

func (uuid UUID) Raw() [16]byte

Raw returns a copy of the UUID bytes.

func (UUID) String 

func (uuid UUID) String() string

String returns a hexadecimal string representation with standardized separators.

Source Files

View all Source files

Directories

Path Synopsis
The featureflag package gives other parts of Juju the ability to easily check to see if a feature flag has been defined.
 The featureflag package gives other parts of Juju the ability to easily check to see if a feature flag has been defined.
utils/filestorage provides types for abstracting and implementing a system that stores files, including their metadata.
 utils/filestorage provides types for abstracting and implementing a system that stores files, including their metadata.
On-disk mutex protecting a resource
 On-disk mutex protecting a resource
The jsonhttp package provides general functions for returning JSON responses to HTTP requests.
 The jsonhttp package provides general functions for returning JSON responses to HTTP requests.
The keyvalues package implements a set of functions for parsing key=value data, usually passed in as command-line parameters to juju subcommands, e.g.
 The keyvalues package implements a set of functions for parsing key=value data, usually passed in as command-line parameters to juju subcommands, e.g.
The parallel package provides utilities for running tasks concurrently.
 The parallel package provides utilities for running tasks concurrently.
This package provides convenience helpers on top of archive/tar to be able to tar/untar files with a functionality closer to gnu tar command.
 This package provides convenience helpers on top of archive/tar to be able to tar/untar files with a functionality closer to gnu tar command.
Package voyeur implements a concurrency-safe value that can be watched for changes.
 Package voyeur implements a concurrency-safe value that can be watched for changes.

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