Rorschach is a Node.js module for high-level interaction with ZooKeeper. Currently it provides all the basic ZooKeeper operations. Refer to the Rorschach API doc below. And in a mean time more recipes will be added.
Rorschach is meant to provide functionality similar to Apache Curator. It was started as implementation of distributed locking recipe and most of algorithms are taken from Curator sources.
While Curator is a ZooKeeper Keeper, Rorschach is a ZooKeeper Watchman.
npm install rorschach --save
'use strict';
var Rorschach = require('rorschach');
var zookeeper = require('node-zookeeper-client');
var ACL = Rorschach.ACL;
var CreateMode = Rorschach.CreateMode;
var Event = Rorschach.Event;
var Lock = Rorschach.Lock;
var ReadWriteLock = Rorschach.ReadWriteLock;
var client = new Rorschach('127.0.0.1:2181');
client.on('connected', doTheWork);
client.on('error', onerror);
function doTheWork() {
client
.create()
.withMode(CreateMode.EPHEMERAL)
.withACL(ACL.READ_ACL_UNSAFE)
.forPath('/a', /*afterCreate(err, path)*/);
client
.create()
.withProtection()
.creatingParentsIfNeeded()
.forPath('/my/cool/znode/foo/bar', /*afterCreate(err, path)*/);
client
.delete()
.deleteChildrenIfNeeded()
.guaranteed()
.forPath('/my/cool/znode', /*afterDelete(err)*/);
client
.getData()
.usingWatcher(function watcher(event) {
if (event.getType() === Event.NODE_DELETED) {
// handle deleted
}
else if (event.getType() === Event.NODE_DATA_CHANGED) {
// handle data change
}
else {
console.warn('Wow, really?');
}
})
.forPath('/some/path', /*afterGetData(err, data, stat)*/);
var lock = new Lock(client, '/my/znodes/locks/myResource');
lock.acquire(500, function afterAcquire(err) {
// handle error
// do the work with `myResource`
lock.release(/*callback(err)*/);
});
var rwLock = new ReadWriteLock(client, '/my/znodes/locks/anotherResource');
rwLock.writeLock().acquire(1000, function afterWriteAcquire(err) {
// handle error
// update `anotherResource`
rwLock.writeLock().release(/*callback(err)*/);
});
}
function onerror(err) {
console.warn('[Error: %d]: %s', err.getCode(), err.stack);
}
Main class and, better to add, namespace.
For convenience, following node-zookeeper-client classes & constants were referenced by Rorschach:
ACLCreateModeEventExceptionIdPermissionStateSo you can use them like following:
function watcher(event) {
if (event.getType() === Rorschach.Event.NODE_DELETED) {
console.log('At last...');
}
}
Create instance.
Arguments
String ZooKeeper connection stringObject Options:
Object|RetryPolicy RetryPolicy instance or optionsObject ZooKeeper client optionsconnectedfunction onConnected() { }
Emitted when connection to ZooKeeper server is established.
connectionStateChangedfunction onStateChanged(state) {
if (state === Rorschach.ConnectionState.CONNECTED || state === Rorschach.ConnectionState.RECONNECTED) {
console.info('Let\'s rock!');
}
/* else if ... */
}
Emitted whenever ZooKeeper client connection state changes. The only argument is state which is one of ConnectionStates.
errorfunction onerror(err) {
/* whatTheFussIsGoingOn(err); */
}
Currently, this event is emitted only when some operation fails in retry loop. It is emitted only if error event listener is added to Rorschach instance - to save user from Unhandled 'error' event.
Close connection to ZooKeeper.
Arguments
function Callback functionCreateBuilder create()Instantiate create operation builder.
Returns
CreateBuilder Builder instanceDeleteBuilder delete()Instantiate delete operation builder.
Returns
DeleteBuilder Builder instanceExistsBuilder exists()Instantiate exists operation builder.
Returns
ExistsBuilder Builder instanceGetACLBuilder getACL()Instantiate get ACL builder.
Returns
GetACLBuilder Builder instanceGetChildrenBuilder getChildren()Instantiate get children builder.
Returns
GetChildrenBuilder Builder instanceGetDataBuilder getData()Instantiate get data builder.
Returns
GetDataBuilder Builder instanceSetACLBuilder setACL()Instantiate set ACL builder.
Returns
SetACLBuilder Builder instanceSetDataBuilder setData()Instantiate set data builder.
Returns
SetDataBuilder Builder instanceRepresents high-level connection state.
ConnectionState CONNECTEDConnected state. Emitted only once for each Rorschach instance.
ConnectionState READ_ONLYConnected in read-only mode.
ConnectionState RECONNECTEDConnection was re-established.
ConnectionState SUSPENDEDConnection was lost, but we're waiting to re-connect.
ConnectionState LOSTConnection was lost. Bye-bye, white pony.
Return "connected" state.
Utility functions.
Delete children for given path and maybe given znode.
Arguments
Client ZooKeeper clientString Node pathBoolean Delete node itself Default: falsefunction Callback function: (err)String join(args...)Join paths.
Arguments
String PathsReturns
StringCreate path and parent nodes if needed.
Arguments
Client ZooKeeper clientStringBooleanArray.<ACL>function Callback function: (err)Retry policy controls behavior of Rorschach in case of operational errors.
Instantiate policy.
Arguments
Object Options:
Number Max number of attemptsArray.<String>|function Error codes or error validation functionNumber DEFAULT_MAX_ATTEMPTSDefault number of operation attempts.
Array.<Number> DEFAULT_RETRYABLE_ERRORSDefault codes of errors allowing re-try in case of no. of attempts < maxRetries.
Boolean isRetryable(err)Check if error is retryable.
Arguments
Error|Exception ZooKeeper client errorReturns
BooleanCreate request builder.
CreateBuilder creatingParentsIfNeeded()If path create operation will receive NO_NODE error then builder will make an attempt to create parent nodes.
Returns
CreateBuilderExecute create op.
Arguments
String Path to znodeBuffer ZNode data to set Default: nullfunction Callback function: (executionError, path)CreateBuilder withACL(acls)Set ACLs.
Arguments
Array.<ACL>Returns
CreateBuilderCreateBuilder withMode(mode)Set create mode.
Arguments
Number CreateModeReturns
CreateBuilderCreateBuilder withProtection()See this page for explanation.
Returns
CreateBuilderDelete request builder.
DeleteBuilder deleteChildrenIfNeeded()If delete operation receives NOT_EMPTY error then make an attempt to delete child nodes.
Returns
DeleteBuilderExecute delete.
Arguments
String Node pathfunction Callback function: (err)DeleteBuilder guaranteed()Mark delete op. as guaranteed.
Returns
DeleteBuilderDeleteBuilder withVersion(version)Set node version to delete.
Arguments
NumberReturns
DeleteBuilderExists request builder.
Execute exists().
Arguments
String Node pathfunction Callback function: (executionError, exists, stat)ExistsBuilder usingWatcher(watcher)Add watcher to operation request.
Arguments
function Watch function: (event)Returns
ExistsBuilderGet ACL request builder.
Execute getACL().
Arguments
String Node pathfunction Callback function: (executionError, acls, stat)Get children request builder.
Execute getChildren().
Arguments
String Node pathfunction Callback function: (executionError, data, stat)GetChildrenBuilder usingWatcher(watcher)Add watcher to operation request.
Arguments
function Watch function: (event)Returns
GetChildrenBuilderGet data request builder.
Execute getData().
Arguments
String Node pathfunction Callback function: (executionError, data, stat)GetDataBuilder usingWatcher(watcher)Add watcher to operation request.
Arguments
function Watch function: (event)Returns
GetDataBuilderSet ACL request builder.
Execute setACL().
Arguments
String Node pathArray.<ACL> ACLsfunction Callback function: (executionError, stat)SetACLBuilder withVersion(version)Set node ACL version (number of changes of ACL).
It's not the same as node version (number of data changes).
Arguments
NumberReturns
SetACLBuilderSet data request builder.
Execute setData().
Arguments
String Node pathBuffer Data to setfunction Callback function: (executionError, stat)SetDataBuilder withVersion(version)Set node version.
Arguments
NumberReturns
SetDataBuilderLeader election recipe implementation.
Leader election participant.
Arguments
Rorschach Rorschach instanceString Election pathString Participant iderrorfunction onerror(err) {
// do smth. with error
}
Emitted when some background operation fails. You must always set listener for this event.
isLeaderfunction leaderListener() {
// start tasks for which leader is responsible
}
Emitted when leadership is obtained.
notLeaderfunction notLeaderListener() {
// stop tasks for which leader is responsible
}
Emitted when leadership is lost.
Rorschach clientRef. to client.
String pathZooKeeper path where participants' nodes exist.
String idId of participant. It's kept in node.
Boolean hasLeadership()Check if our node is leader.
Returns
BooleanStart taking part in election process.
Arguments
function Callback function: (err)Leave the game for youngz.
Arguments
function Callback function: (err)Distributed re-entrant lock.
Distributed lock implementation
Arguments
Rorschach Rorschach instanceString Base lock pathString Ephemeral node nameLockDriver Lock utilities Default: new LockDriver()String LOCK_NAMEDefault lock node name.
Rorschach clientKeep ref to client as all the low-level operations are done through it.
String basePathBase path should be valid ZooKeeper path.
String lockNameNode name.
LockDriver driverLock driver.
String lockPathSequence node name (set when acquired).
Number maxLeasesNumber of max leases.
Number acquiresNumber of acquires.
Acquire a lock.
Arguments
Number Time to wait for (milliseconds).function Callback function: (err)Destroy lock i.e. remove node and set acquires counter to zero.
Arguments
function Optional callback functionBoolean isOwner()Check lock is owned by process.
Returns
BooleanRelease the lock.
Arguments
function Callback function: (err)Lock setMaxLeases(maxLeases)Set max leases.
Arguments
Number Max # of participants holding the lock at one timeReturns
Lock Instance is returned for chainingReaders-writer lock implementation.
Initialize read and write mutexes.
Arguments
Rorschach Rorschach instanceString Base lock pathString READ_LOCK_NAMERead lock node name.
string WRITE_LOCK_NAMEWrite lock node name.
Lock writeMutexWrite mutex.
Lock readMutexRead mutex.
Lock readLock()Return read mutex.
Returns
Lock Read lockLock writeLock()Return write mutex.
Returns
Lock Write lockError which serves a wrapper to actual ZooKeeper client error. It is returned by operation builders in case of failure.
Error originalOriginal error instance.
String operationOperation type: create, remove, etc.
Array operationArgsArguments passed to original ZK client method.
Number getCode()Defined only if original error is instance of Exception. Returns error code of
original error.
See CHANGELOG.md.
InterProcessSemaphoreV2;InterProcessSemaphoreMutex;InterProcessMultiLock;See LICENSE.md.
FAQs
Curator-like framework for ZooKeeper
The npm package rorschach receives a total of 26 weekly downloads. As such, rorschach popularity was classified as not popular.
We found that rorschach demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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