Running a smart contract on the blockchain network

resume

Considering that Hyperledger Fabric has several order service implementations (including Solo, Kafka and Raft), you, the developer, must understand the advantages and disadvantages of each implementation before opting for a design. As the new standard for production blockchain networks, the Raft consensus algorithm is a fault-tolerant ordering service implementation, which is easier to configure and manage than Kafka. Most importantly, Raft allows different organizations to contribute nodes to the ordering service, allowing for a more decentralized network architecture.

description

Given that there are many possible ways that nodes in a blockchain network can reach an agreement (or consensus), and that agreement is essential for a distributed computing network, it is not surprising that the debate about the most efficient consensus algorithm is often heated, and even religious. At the heart of consensus algorithms is the need to resolve a difficult, popular and distributed computing issue: how can we (computers) agree on a result (reach consensus) among a group of computers when we know that computers are unreliable ? Although there is no perfect way to solve this problem, the pattern, in fact, since 1989, has been the Paxos algorithm. The problem with Paxos is that it can take years for doctoral students to master it. Even the most brilliant engineers who try to implement this algorithm in practice find it difficult to understand and thus implement their solution.

That’s where Raft comes in. Designed as an alternative consensus algorithm for Paxos, Raft is much easier to understand and is now used in some of the most successful software projects, such as Docker. Since the launch of Hyperledger Fabric, the consensus has been designed as pluggable, and you, the developer, can choose which type of consensus your order nodes will use. Raft allows for a much easier configuration than Kafka, a more decentralized approach, as several organizations can contribute with us to the ordering service and greater tolerance to collision failures than Solo, which has a single node request. This code pattern helps you understand how to build and deploy a smart contract on a Hyperledger Fabric network running Raft and allows you to test the network’s tolerance by stopping and starting some order nodes.

When you complete this code pattern, you will understand:

How the Raft algorithm works;

How to build and execute a Raft order service with several organizations in Hyperledger Fabric;

How to send transactions and run a blockchain network using a Raft ordering service;

How to test the fault tolerance of the order service by deleting (locking) one of the order nodes.



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How to Enable Session Reliability on NetScaler in High Availability

This article describes how to enable session reliability on NetScaler in high availability.

Background

When high availability failover occurs, the ICA sessions will get disconnected. In order to avoid the ICA session disconnection on high availability failover, you can configure Session Reliability.

Points to Note

  • NetScaler appliances should be running on software version 11.1 build 49.16 or later.
  • You should not Enable or disable Session Reliability mode when the NetScaler appliances have active connections.
  • Enabling or Disabling the feature when connections are still active causes HDX Insight to stop parsing those sessions after a failover occurs and result in loss of information about the sessions.

Related:

Problem symptoms occur when all nodes in a XenMobile Server cluster are not located near to each other

XenMobile Server supports ‘active/passive’ failover between multiple sites.

It is not typically possible to configure ‘active/active’ for anything other than the access layer, comprising Citrix ADC, Public DNS records and GSLB.

A typical setup for Disaster Recovery will use two XenMobile Server clusters, one active and the other passive.

Supported SQL infrastructures include Basic AOAG (Always On Availability Groups) and Clustered SQL for High Availability.

In a Disaster Recovery scenario (either for testing or practical reasons), it is usually necessary to block or prevent device connections in to the Primary datacentre or site as one of the first steps of performing the failover. This is to prevent any further changes from being made to the configuration database for XenMobile Server.

When performing a failover to a Disaster Recovery datacentre or site, synchronise the configuration database from the Primary site to the DR site one last time, after blocking or preventing device connections in to the Primary site first. Afterwards, allow connections in to the DR site where changes can then be made to the since synchronised database.

Whilst the access layer (front end) of supported Disaster Recovery infrastructures can be configured as ‘active/active’, the different clusters of XenMobile Server nodes (back end) are intended to be ‘active/passive’.

Related:

Implementing Failover between (SG 600-35) and (S200-30)

I need a solution

As per below KB, it’s not recommend to implement failover between two different models

https://support.symantec.com/us/en/article.tech240…

but as we are planning HW refresh (600-35 ver. 6.7.2.2) proxy cluster with a new cluster (S200-30 ver. 6.7.4.3)

To achieve no downtime, we will remove the cables from old standby proxy and connect them to the new standby that has the same configuration; and so on with the active one but not in the same night

regardless the load point that is mentioned in above link, is there any “compatibility issue”, “concerns” or “recommendation” to implement HA between both of those proxies (with different model/version)?

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SOFS(Scale-Out file server) does not work with 1901 or 1902

Unable to mount a share on an scale-out-fileserver clusterresource (cluster-shared-volumes).

The below errors are seen maservice.log.

2019-02-07 03:42:04,148 ERROR [80] MountPointService: Encountered error creating mount point /mnt/maserviceshare/mnt00000004 with exception Uni.Core.Handlers.Exceptions.GlobalizedErrorException`1[Uni.Core.Contract.Results.FileCategory]: MessageId=FileShareServicePermissionDenied, DefaultTitle=, CategoryData={[FileCategory { Message = “mount error(13): Permission denied; Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)” }]}

at Uni.Appliance.Services.FileShareServices.MountPointService.MountUncToPath (System.String uncPath, Uni.Appliance.Services.FileShareServices.Interfaces.FileShareType fsType, Uni.Appliance.Services.FileShareServices.Interfaces.FileShareCredentials fsCreds, System.Boolean cacheEnabled, System.Nullable`1[T] timeout, System.Int64 mntNumber, System.String mntPoint) [0x000af] in d:buildsR4ZION-WSW-JOB1sourceUni.ApplianceServicesFileShareServicesMountPointService.cs:281

2019-02-07 03:42:04,148 INFO [80] TestRemoteFileShar: TEST( \citrix-layers.CustPrivInfo.dirlayers$, Cifs, CustPrivInfoservice, * ) FAILED MessageId=FileShareServicePermissionDenied, DefaultTitle=, CategoryData={[FileCategory { Message = “mount error(13): Permission denied; Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)” }]}

2019-02-07 03:42:04,148 INFO [80] HandlerHelper: Finished Command TestRemoteFileShareCommand->TestRemoteFileShareResult

2019-02-07 03:42:04,148 ERROR [80] HandlerHelper: ‘Application Error while processing ‘Command’ ‘TestRemoteFileShareCommand”: ‘DefaultTitle=””, MessageID=”FileShareServicePermissionDenied”, {CategoryData={[FileCategory { Message = “mount error(13): Permission denied; Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)” }]}’

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Citrix SDWAN High Availability FAQ

Q: What is the Platform and License Requirement for SDWAN High availability?

The Platform and licenses should be same for both devices which participates in HA

Q: What protocol and port numbers used by SDWAN for HA communication?

SDWAN uses Citrix Proprietary protocol for HA communication and UDP port 4980

Q: What is the default hello packet interval and Failover time?

Hello packets exchanged every 100ms and Failover is triggered after 1 second of silence period by default

Q: Which interface is used to send the Heartbeat packets?

All interfaces which is part of High Availability interface group is used for Heartbeat communication

Q: Can we add multiple interface as part of HA group?

Yes, we can add multiple interfaces as part of HA group

Q: Can we change the Hello Packet interval in configuration?

No, we cannot modify default Hello Packet interval

Q: Can we form a High Availability between 2 different subnet High Availability control IP’s?

No, High Availability IP’s should be on the same subnet as HA access interface subnet

Q: Can we do the PING test to check the communication between the appliances?

No, HA packets are initiated from the SDWAN software and PING test is not possible from CLI/SHELL

Q: What information is synchronized between SDWAN appliances?

Configuration and High Availability state is synchronized between the appliances

Q: Does VIP’s uses individual or shared VMAC address for communication?

SDWAN VIP’s uses shared MAC addresses to communication with other devices by default however this behaviour can be modified in the configuration

Q: What interfaces are monitored in SDWAN HA deployment?

All physical interfaces which is part of High Availability access interface group is monitored

Q: Does SDWAN monitor the interfaces by default for failure?.

No, By default SDWAN appliance doesn’t monitor the interfaces unless the interface is part of HA group

Q: What are all the components monitored to declare the device working state?

All HA Interfaces are monitored to determine the device health

Q: How to trigger the Force failover?

Please refer the following Citrix article https://support.citrix.com/article/CTX213510

Q: What is the recommended procedure for upgrading SDWAN High Availability setup?

Please refer the following Citrix documentation https://docs.citrix.com/en-us/netscaler-sd-wan/10/updating-upgrading/upgrade-with-vw-configuration.html

Q. How to Configure a Citrix SDWAN in high Availability mode?.

Please refer the following Citrix article https://support.citrix.com/article/CTX227522

Q: How SDWAN Failover state is detected when the device boots up first time?

1. Configuration File Date (Newer is better)

2. HA priority (Primary or Secondary)

3. MAC address (only used to break ties in the case of a misconfiguration)

Q: What happens if one of the device’s got rebooted and joined the failover pair after period of being in down state?

The new device joins the Failover pair as a secondary device unless this device is configured as Primary with “Primary Reclaim” is enabled

Q: Does SDWAN failover frequently due to stability issues

No, it’s not possible to trigger the failover frequently. SDWAN HA state doesn’t change frequently and minimum 120 seconds interval is mandatory to trigger any failover

Related:

Configure ASG Failover of transparent/explicit proxies

I need a solution

Hi All,

  Here attached our current design of proxy, and going to configure failover unit. Now we do the failover on our firewalls and proxy is connected directly to the firewalls.

  Question and challenge is : now like to use current LAN-10.1.0.1 on VIP and make active to 10.1.0.3 and standby to 10.1.0.4, also change to WAN-10.1.0.2 to VIP and make active to 10.1.0.5 and standby to 10.1.0.6, and explicit users still will use 10.1.0.1 ip and both active and standby can possible to use same certificates and we don’t really want to auto failover from proxy, we want manually failover because it is inline configured between active and standby firewalls.

for that what configuration required? below guides are not accured and no technical steps.

https://support.symantec.com/en_US/article.TECH242151.embed.html

https://www.symantec.com/connect/sites/default/files/Technical%20Brief%20Implementing%20Failover%20Services.pdf

  on the guide need to configure VIP on failover – which our case it is directly connected- and can configure 192.168.0.1 and active 192.168.0.2, standby 192.168.0.3 or can use management IPs.

Config for Primary

1. remove LAN interface IP – 10.1.0.1

2. create VIP – 10.1.0.1

3. Assign LAN interface IP – 10.1.0.3

4. remove WAN interface IP – 10.1.0.2

5. create VIP – 10.1.0.2

6. Assign WAN interface IP – 10.1.0.5

7. Failover New

– enabled

   – use existing  – 10.1.0.1 

– multicast 224.0.0.1

– master – check

Standby

. create VIP – 10.1.0.1

. Assign LAN interface IP – 10.1.0.4

. create VIP – 10.1.0.2

. Assign WAN interface IP – 10.1.0.6

. Failover New

– enabled

   – use existing  – 10.1.0.1 

– multicast 224.0.0.1

– master – check

Apply ?

 is that correct? also how to do manually failover?

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Types of Configuration Synchronized in ASG Failover

I need a solution

Hello Guys, 

Can anyone help me knowing the actual configuration that is synchronized between members of one failover group.

In other words, what are the configuration that i can configure one time on the master member(configuration sync) , and what configuration that i have to configure on both members whether before of after creating the failover group.

Thanks for you replies in advance

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