After downlinking and extracting the ZooKeeper package.
Create configuration file zoo.cfg in conf directory.
conf\zoo.cfg .
The content of the zoo keeper configuration file should be:
tickTime=2000
dataDir=C:\products\apache\zookeeper-3.4.6\Data
clientPort=2181
Start the zookeeper in a cmd window :
bin\zkServer.sh start
Start the client in other
bin\zkCli.sh -server 127.0.0.1:2181
Creating simple node:
I had a problem where I need explicit locking of resources in the SQL SERVER.
When sp1 run I need to prevent sp2 to run in parallel.
The stored procedures handle deferent DataBase resources so the transaction locking can’t help in this case .
I have found the following article that helped me solve the problem:
The the solution is based on the sp_getapplock command.
Exec @rc = sp_getapplock @Resource='myLock' -- the resource to be locked can be any mutex name
, @LockMode='Exclusive' -- Type of lock
, @LockOwner='Transaction' -- Transaction or Session
, @LockTimeout = 15000 -- timeout in milliseconds, 15 seconds
Committing or aborting the transaction release the lock.
allow voiding the call to sp_releaseapplock
Don’t forget to check if timeout error occurred after the sp_getapplock has returned.
I although learn from the article to use the :
set @msg= convert(varchar,getdate(), 114) + ' requesting lock'
raiserror (@msg, 0, 1) with nowait
in order to output debug strings while executing a test code.
We use Jclouds blob storage in order to manage the Blobs in our private cload swift blob storage .
The following code demonstrates creating , writing , exploring and reading from swift using jcloud SwiftBlobStore.
package com.gmuav.playwithjcloads;import java.io.IOException;import org.jclouds.ContextBuilder;import org.jclouds.blobstore.BlobStore;import org.jclouds.blobstore.BlobStoreContext;import org.jclouds.blobstore.domain.Blob;import org.jclouds.blobstore.domain.StorageMetadata;import com.google.common.base.Charsets;import com.google.common.io.ByteSource;public class PlayWithSwift {public static void main(String[] args) throws IOException {String identity = " --- ";String credential = " --- ";String containerName = "myContainer";ByteSource payload = ByteSource.wrap("This is the Data as text ".getBytes(Charsets.UTF_8));BlobStoreContext context = ContextBuilder.newBuilder("swift").credentials(identity, credential).buildView(BlobStoreContext.class);try {// Create ContainerBlobStore blobStore = context.getBlobStore();blobStore.createContainerInLocation(null, containerName);String theBlobName = "myFolder/myData";Blob blob = blobStore.blobBuilder(theBlobName).payload(payload).contentLength(payload.size()).build();blobStore.putBlob(containerName, blob);// List Containerfor (StorageMetadata nextBlob : blobStore.list()) {System.out.println("NextBlob:" + nextBlob.getName());}Blob theRetreivedBlob = blobStore.getBlob(identity, theBlobName);String theRetValue = new String (((ByteSource)theRetreivedBlob.getPayload()).read() , Charsets.UTF_8);System.out.println("The blob data " + theRetValue);} finally {context.close();}}}
References:
jclouds-examples
The sysfs allow User space kernel space simple communication .
The code
#include <linux/kobject.h>#include <linux/string.h>#include <linux/sysfs.h>#include <linux/module.h>#include <linux/init.h>/** The module demonstrats creating 2 attributes in a subdirectory of sysfs.* ls the /sys/kernel/mykobject*/static int intValue = 0;static char TxtBuffer[50];static ssize_t attr_show(struct kobject *kobj, struct kobj_attribute *attr,char *buf){if (strcmp(attr->attr.name, "TxtBuffer") == 0){return sprintf(buf, "%s\n", TxtBuffer);}if (strcmp(attr->attr.name, "intValue") == 0){return sprintf(buf, "%d\n", intValue);}return 0;}static ssize_t attr_store(struct kobject *kobj, struct kobj_attribute *attr,const char *buf, size_t count){if (strcmp(attr->attr.name, "TxtBuffer") == 0){strcpy (TxtBuffer, buf);return count;}if (strcmp(attr->attr.name, "intValue") == 0){int theTmpVar;sscanf(buf, "%du", &theTmpVar);intValue = theTmpVar;return count;}return 0;}static struct kobj_attribute intValue_attribute =__ATTR(intValue, 0666, attr_show, attr_store);static struct kobj_attribute TxtBuffer_attribute =__ATTR(TxtBuffer, 0666, attr_show, attr_store);static struct attribute *attrs[] = {&intValue_attribute.attr,&TxtBuffer_attribute.attr,NULL,};static struct attribute_group attr_group = {.attrs = attrs,.name = NULL, /* we want them in the same directory */};static struct kobject *mykobject;static int mykobject_init(void){int retval;mykobject = kobject_create_and_add("mykobject", kernel_kobj);if (!mykobject)return -ENOMEM;retval = sysfs_create_group(mykobject, &attr_group);if (retval)kobject_put(mykobject);return retval;}static void mykobject_exit(void){kobject_put(mykobject);}module_init(mykobject_init);module_exit(mykobject_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("Zvika Peer <zvikapeer@hotmail.com>");
After installing the module using insmod let test it. The module directory is :
ls /sys/kernel/
Inspecting the mykobject attributes
zvika@zvika-Linux:~/Learn/Drivers/HelloWorld$ ls /sys/kernel/mykobject
intValue TxtBuffer
Inserting Data into the attributes:
zvika@zvika-Linux:~/Learn/Drivers/HelloWorld$ sudo echo "Hello zvika" > /sys/kernel/mykobject/TxtBuffer
zvika@zvika-Linux:~/Learn/Drivers/HelloWorld$ sudo echo 164 > /sys/kernel/mykobject/intValue
Retrieving the data back from the attributes:
zvika@zvika-Linux:~/Learn/Drivers/HelloWorld$ sudo cat /sys/kernel/mykobject/intValue
164
zvika@zvika-Linux:~/Learn/Drivers/HelloWorld$ sudo cat /sys/kernel/mykobject/TxtBuffer
Hello zvika
I used the __get__ python magic method in order to implement explicit conversion of class :
The following example converts a string wrapper class into the string length:
class TheConverter:def __init__ (self):passdef __get__ (self, instance, owner):return len ( instance.mValue)class ToGetConverted:def __init__ (self ,pValue ):self.mValue = pValueLenConvertor = TheConverter()print (ToGetConverted("Hands Up").LenConvertor)if __name__ == '__main__':pass
The sample returns : 8
References:
magic words
I have found the following blog post regarding Open Stack cinder block:
laying-cinder-block-volumes-in-openstack-part-1-the-basics
Cinder allows to attach external storage volume into the cloud in addition to the instance ephemeral storage
The cinder api can be found here :
cinder api
Allows to create volumes , update volumes , delete volumes , list volume information
Handle snapshots
Last week I had design review session about Map wrapper interfaces.
The interface is part of a module that allows a programmer to switch map infrastructure implementations within its product transparently to the logic of the UI layer
Part of the proposed interface looks something like this :
The goal of the MapSurface interface is to allow adding drawing annotations on the map like routes , spots areas etc.
1.KISS:
Very simple interface allow the programmer quickly learned how to use it even without documentation and code samples .
1.Open close principle violation:
In order to add handling for new widget type for an example a closed curved etc the IMapInterface should be changed .
2.The interface does not allow me to use the created route in a surface of a map in other window .
