zk

package
v2.0.0-beta.1+incompat... Latest Latest
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 Go to latest Published: Mar 3, 2016 License: BSD-3-Clause Imports: 19 Imported by: 0

Documentation

Overview

Package zk emulates a "global" namespace across n zk quorums.

Index

Constants

View Source 
const (
	// PERM_DIRECTORY are default permissions for a node.
	PERM_DIRECTORY = zookeeper.PERM_ADMIN | zookeeper.PERM_CREATE | zookeeper.PERM_DELETE | zookeeper.PERM_READ | zookeeper.PERM_WRITE
	// PERM_FILE allows a zk node to emulate file behavior by disallowing child nodes.
	PERM_FILE = zookeeper.PERM_ADMIN | zookeeper.PERM_READ | zookeeper.PERM_WRITE
)
View Source 
const (
	DEFAULT_BASE_TIMEOUT = 5 * time.Second
)
View Source 
const (
	DEFAULT_MAX_RETRIES = 3
)

Variables

View Source 
var (
	// DefaultZkConfigPaths is the default list of config files to check.
	DefaultZkConfigPaths = []string{"/etc/zookeeper/zk_client.json"}
	// MagicPrefix is the Default name for the root note in the zookeeper tree.
	MagicPrefix = "zk"
)
View Source 
var (
	// This error is returned by functions that wait for a result
	// when they are interrupted.
	ErrInterrupted = errors.New("zkutil: obtaining lock was interrupted")

	// This error is returned by functions that wait for a result
	// when the timeout value is reached.
	ErrTimeout = errors.New("zkutil: obtaining lock timed out")
)
View Source 
var ErrConnectionClosed = errors.New("ZkConn: connection is closed")

ErrConnectionClosed is returned if we try to access a closed connection.

Functions

func ChildrenRecursive 

func ChildrenRecursive(zconn Conn, zkPath string) ([]string, error)

func CreateOrUpdate 

func CreateOrUpdate(zconn Conn, zkPath, value string, flags int, aclv []zookeeper.ACL, recursive bool) (pathCreated string, err error)

func CreateRecursive 

func CreateRecursive(zconn Conn, zkPath, value string, flags int, aclv []zookeeper.ACL) (pathCreated string, err error)

Create a path and any pieces required, think mkdir -p. Intermediate znodes are always created empty.

func DeleteRecursive 

func DeleteRecursive(zconn Conn, zkPath string, version int) error

func GetZkSubprocessFlags 

func GetZkSubprocessFlags() []string

GetZkSubprocessFlags returns the flags necessary to run a sub-process that would connect to the same zk servers as this process (assuming the environment of the sub-process is the same as ours)

func GuessLocalCell 

func GuessLocalCell() string

Read the cell from -zk.local-cell, or the environment ZK_CLIENT_LOCAL_CELL or guess the cell by the hostname. The letter-only prefix of the string is used as the cell name. For instance:

pa1 -> pa sjl-1 -> sjl lwc1 -> lwc

func IsDirectory 

func IsDirectory(aclv []zookeeper.ACL) bool

IsDirectory returns if this node should be treated as a directory.

func ObtainQueueLock 

func ObtainQueueLock(zconn Conn, zkPath string, wait time.Duration, interrupted <-chan struct{}) error

The lexically lowest node is the lock holder - verify that this path holds the lock. Call this queue-lock because the semantics are a hybrid. Normal zookeeper locks make assumptions about sequential numbering that don't hold when the data in a lock is modified. if the provided 'interrupted' chan is closed, we'll just stop waiting and return an interruption error

func ResolveWildcards 

func ResolveWildcards(zconn Conn, zkPaths []string) ([]string, error)

resolve paths like: /zk/nyc/vt/tablets/*/action /zk/global/vt/keyspaces/*/shards/*/action /zk/*/vt/tablets/*/action into real existing paths

If you send paths that don't contain any wildcard and don't exist, this function will return an empty array.

func ZkCellFromZkPath 

func ZkCellFromZkPath(zkPath string) (string, error)

ZkCellFromZkPath extracts the cell name from a zkPath.

func ZkKnownCells 

func ZkKnownCells() ([]string, error)

returns all the known cells, alphabetically ordered. It will include 'global' if there is a dc-specific global cell or a global cell

func ZkPathToZkAddr 

func ZkPathToZkAddr(zkPath string) (string, error)

Types

type ChangeFunc 

type ChangeFunc func(oldValue string, oldStat Stat) (newValue string, err error)

type Conn 

type Conn interface {
	Get(path string) (data string, stat Stat, err error)
	GetW(path string) (data string, stat Stat, watch <-chan zookeeper.Event, err error)

	Children(path string) (children []string, stat Stat, err error)
	ChildrenW(path string) (children []string, stat Stat, watch <-chan zookeeper.Event, err error)

	Exists(path string) (stat Stat, err error)
	ExistsW(path string) (stat Stat, watch <-chan zookeeper.Event, err error)

	Create(path, value string, flags int, aclv []zookeeper.ACL) (pathCreated string, err error)

	Set(path, value string, version int) (stat Stat, err error)

	Delete(path string, version int) (err error)

	Close() error

	RetryChange(path string, flags int, acl []zookeeper.ACL, changeFunc ChangeFunc) error

	ACL(path string) ([]zookeeper.ACL, Stat, error)
	SetACL(path string, aclv []zookeeper.ACL, version int) error
}

This interface is really close to the zookeeper connection interface. It uses the Stat interface defined here instead of the zookeeper.Stat structure for stats. Everything else is the same as in zookeeper. So refer to the zookeeper docs for the conventions used here (for instance, using -1 as version to specify any version)

type ConnCache 

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

ConnCache is a cache for Zookeeper connections which guarantees that you have at most one zookeeper connection per cell.

func NewConnCache 

func NewConnCache() *ConnCache

NewConnCache creates a new Zookeeper connection cache.

func (*ConnCache) Close 

func (cc *ConnCache) Close() error

Close closes all cached connections.

func (*ConnCache) ConnForPath 

func (cc *ConnCache) ConnForPath(zkPath string) (cn Conn, err error)

ConnForPath returns a connection for a given Zookeeper path. If no connection is cached, it creates a new one.

type ElectorTask 

type ElectorTask interface {
	Run() error
	Stop()
	// Return true if interrupted, false if it died of natural causes.
	// An interrupted task indicates that the election should stop.
	Interrupted() bool
}

ElectorTask is the interface for a task that runs essentially forever or until something bad happens. If a task must be stopped, it should be handled promptly - no second notification will be sent.

type GlobalConn 

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

func Dial 

func Dial(serverAddrs []string, recvTimeout time.Duration) (*GlobalConn, <-chan zookeeper.Event, error)

func (*GlobalConn) Children 

func (gzc *GlobalConn) Children(path string) (children []string, stat Stat, err error)

func (*GlobalConn) Close 

func (gzc *GlobalConn) Close() (err error)

func (*GlobalConn) Create 

func (gzc *GlobalConn) Create(path, value string, flags int, aclv []zookeeper.ACL) (pathCreated string, err error)

func (*GlobalConn) Delete 

func (gzc *GlobalConn) Delete(path string, version int) (err error)

func (*GlobalConn) Get 

func (gzc *GlobalConn) Get(path string) (data string, stat Stat, err error)

func (*GlobalConn) Set 

func (gzc *GlobalConn) Set(path, value string, version int) (stat Stat, err error)

type GlobalZookeeperError 

type GlobalZookeeperError string

func (GlobalZookeeperError) Error 

func (e GlobalZookeeperError) Error() string

type MetaConn 

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

func NewMetaConn 

func NewMetaConn() *MetaConn

func (*MetaConn) ACL 

func (conn *MetaConn) ACL(path string) (acl []zookeeper.ACL, stat Stat, err error)

func (*MetaConn) Children 

func (conn *MetaConn) Children(path string) (children []string, stat Stat, err error)

func (*MetaConn) ChildrenW 

func (conn *MetaConn) ChildrenW(path string) (children []string, stat Stat, watch <-chan zookeeper.Event, err error)

func (*MetaConn) Close 

func (conn *MetaConn) Close() error

func (*MetaConn) Create 

func (conn *MetaConn) Create(path, value string, flags int, aclv []zookeeper.ACL) (pathCreated string, err error)

func (*MetaConn) Delete 

func (conn *MetaConn) Delete(path string, version int) (err error)

func (*MetaConn) Exists 

func (conn *MetaConn) Exists(path string) (stat Stat, err error)

func (*MetaConn) ExistsW 

func (conn *MetaConn) ExistsW(path string) (stat Stat, watch <-chan zookeeper.Event, err error)

func (*MetaConn) Get 

func (conn *MetaConn) Get(path string) (data string, stat Stat, err error)

func (*MetaConn) GetW 

func (conn *MetaConn) GetW(path string) (data string, stat Stat, watch <-chan zookeeper.Event, err error)

func (*MetaConn) RetryChange 

func (conn *MetaConn) RetryChange(path string, flags int, acl []zookeeper.ACL, changeFunc ChangeFunc) error

func (*MetaConn) Set 

func (conn *MetaConn) Set(path, value string, version int) (stat Stat, err error)

func (*MetaConn) SetACL 

func (conn *MetaConn) SetACL(path string, aclv []zookeeper.ACL, version int) (err error)

type Stat 

type Stat interface {
	Czxid() int64
	Mzxid() int64
	CTime() time.Time
	MTime() time.Time
	Version() int
	CVersion() int
	AVersion() int
	EphemeralOwner() int64
	DataLength() int
	NumChildren() int
	Pzxid() int64
}

type ZElector 

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

ZElector stores basic state for running an election.

func CreateElection 

func CreateElection(zconn Conn, zkPath string) ZElector

CreateElection returns an initialized elector. An election is really a cycle of events. You are flip-flopping between leader and candidate. It's better to think of this as a stream of events that one needs to react to.

func (ZElector) Interrupt 

func (zm ZElector) Interrupt()

Interrupt releases a lock that's held.

func (ZElector) Lock 

func (zm ZElector) Lock() error

Lock returns nil when the lock is acquired.

func (ZElector) LockWithTimeout 

func (zm ZElector) LockWithTimeout(wait time.Duration) (err error)

LockWithTimeout returns nil when the lock is acquired. A lock is held if the file exists and you are the creator. Setting the wait to zero makes this a nonblocking lock check.

FIXME(msolo) Disallow non-super users from removing the lock?

func (*ZElector) RunTask 

func (ze *ZElector) RunTask(task ElectorTask) error

RunTask returns nil when the underlyingtask ends or the error it generated.

func (ZElector) Unlock 

func (zm ZElector) Unlock() error

Unlock returns nil if the lock was successfully released. Otherwise, it is most likely a zookeeper related error.

type ZLocker 

type ZLocker interface {
	Lock() error
	LockWithTimeout(wait time.Duration) error
	Unlock() error
	Interrupt()
}

ZLocker is an interface for a lock that can fail.

func CreateMutex 

func CreateMutex(zconn Conn, zkPath string) ZLocker

CreateMutex initializes an unacquired mutex. A mutex is released only by Unlock. You can clean up a mutex with delete, but you should be careful doing so.

type ZkConn 

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

ZkConn is a client class that implements zk.Conn using a zookeeper.Conn. The conn member variable is protected by the mutex.

func DialZk 

func DialZk(zkAddr string, baseTimeout time.Duration) (*ZkConn, <-chan zookeeper.Event, error)

Dial a ZK server and waits for connection event. Returns a ZkConn encapsulating the zookeeper.Conn, and the zookeeper session event channel to monitor the connection

The value for baseTimeout is used as a session timeout as well, and will be used to negotiate a 'good' value with the server. From reading the zookeeper source code, it has to be between 6 and 60 seconds (2x and 20x the tickTime by default, with default tick time being 3 seconds). min session time, max session time and ticktime can all be overwritten on the zookeeper server side, so these numbers may vary.

Then this baseTimeout is used to compute other related timeouts: - connect timeout is 1/3 of baseTimeout - recv timeout is 2/3 of baseTimeout minus a ping time - send timeout is 1/3 of baseTimeout - we try to send a ping a least every baseTimeout / 3

Note the baseTimeout has *nothing* to do with the time between we call Dial and the maximum time before we receive the event on the session. The library will actually try to re-connect in the background (after each timeout), and may *never* send an event if the TCP connections always fail. Use DialZkTimeout to enforce a timeout for the initial connect.

func DialZkTimeout 

func DialZkTimeout(zkAddr string, baseTimeout time.Duration, connectTimeout time.Duration) (*ZkConn, <-chan zookeeper.Event, error)

func (*ZkConn) ACL 

func (conn *ZkConn) ACL(path string) (acls []zookeeper.ACL, stat Stat, err error)

func (*ZkConn) Children 

func (conn *ZkConn) Children(path string) (children []string, stat Stat, err error)

func (*ZkConn) ChildrenW 

func (conn *ZkConn) ChildrenW(path string) (children []string, stat Stat, watch <-chan zookeeper.Event, err error)

func (*ZkConn) Close 

func (conn *ZkConn) Close() error

Close will close the connection asynchronously. It will never fail, even though closing the connection might fail in the background. Accessing this ZkConn after Close has been called will return ErrConnectionClosed.

func (*ZkConn) Create 

func (conn *ZkConn) Create(path, value string, flags int, aclv []zookeeper.ACL) (pathCreated string, err error)

func (*ZkConn) Delete 

func (conn *ZkConn) Delete(path string, version int) (err error)

func (*ZkConn) Exists 

func (conn *ZkConn) Exists(path string) (stat Stat, err error)

func (*ZkConn) ExistsW 

func (conn *ZkConn) ExistsW(path string) (stat Stat, watch <-chan zookeeper.Event, err error)

func (*ZkConn) Get 

func (conn *ZkConn) Get(path string) (data string, stat Stat, err error)

func (*ZkConn) GetW 

func (conn *ZkConn) GetW(path string) (data string, stat Stat, watch <-chan zookeeper.Event, err error)

func (*ZkConn) RetryChange 

func (conn *ZkConn) RetryChange(path string, flags int, acl []zookeeper.ACL, changeFunc ChangeFunc) error

func (*ZkConn) Set 

func (conn *ZkConn) Set(path, value string, version int) (stat Stat, err error)

func (*ZkConn) SetACL 

func (conn *ZkConn) SetACL(path string, aclv []zookeeper.ACL, version int) error

Source Files

View all Source files

Directories

Path Synopsis
Package fakezk is a pretty complete mock implementation of a Zookeper connection (see go/zk/zk.Conn).
 Package fakezk is a pretty complete mock implementation of a Zookeper connection (see go/zk/zk.Conn).

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