There is 'gas' in Ethereum and Bitcoin doesn't support loop at all, I am curious how does Hyperledger Fabric avoid infinite loop?
Hyperledger Fabric does not use gas, but it does address the halting problem by setting a timeout for chaincode execution. The chaincode container will be killed if the transaction does not execute within the configured timeout as specified by the chaincode.executetimeout property.
It appears there is no mechanism to stop infinite loops. There is an open issue in github, https://github.com/hyperledger-archives/fabric/issues/2232 so its possible that it is coming.
Hyperledger Fabric is not intended to be a public blockchain and smart contracts are not intended to be uploaded by any user. They are intended to be developed by an internal team and tested these scenarios.
Related
I have a test Hyperledger Fabric environment using docker and caliper.
I have installed the fabric from https://github.com/hyperledger/fabric.
I want to reuse the started test network in fabcar folder, but using networkDown.sh to stop the network and start it again is very time consuming.
Is there a way to reset the fabric blockchain to its first state or genesis block without recreating it, so I can run a new Caliper test on it?
No, there is no supported way of resetting a channel on peers and orderers to genesis blocks. However, you may create a new channel if that helps.
I am deploying my nodejs application in google cloud app engine but it is giving error
This request caused a new process to be started for your application, and thus caused your application code to be loaded for the first time.
This request may thus take longer and use more CPU than a typical request for your application. -- when making request.
I had also saw some stackoverflow answers, but they didn't worked for me.
my app.yaml have this config
runtime: nodejs10
Can anyone help me out
You could add the following to your app.yaml:
inbound_services:
- warmup
And then implement a handler that will catch all warmup requests, so that your application doesn't get the full load. The full explanation is given here. Another detailed post about this topic can be found here.
Additionally you can also add automatic scaling options. You can play a bit with those to find the optimum for your application. Especially the latency related variables are important. Good to note that they can be set in a standard GAE environment.
automatic_scaling:
min_idle_instances: automatic
max_idle_instances: automatic
min_pending_latency: automatic
max_pending_latency: automatic
More scaling options can be found here.
The "request caused a new process to be started" notification usually occurred when there is no warm up request present in your application.
Can you try to implement a health check handler that only returns a ready status when the application is warmed up. This will allow your service to not receive traffic until it is ready.
Warning: Legacy health checks using the /_ah/health path are now
deprecated, and you should migrate to use split health checks.
Here you can find Split health checks for Nodejs
Liveness checks
Liveness checks confirm that the VM and the Docker container are
running. Instances that are deemed unhealthy are restarted.
path: "/liveness_check"
check_interval_sec: 30
timeout_sec: 4
failure_threshold: 2
success_threshold: 2
Readiness checks
Readiness checks confirm that an instance can accept incoming
requests. Instances that don't pass the readiness check are not added
to the pool of available instances.
path: "/readiness_check"
check_interval_sec: 5
timeout_sec: 4
failure_threshold: 2
success_threshold: 2
app_start_timeout_sec: 300
Edit
For App Engine Standard, which doesn't afford you that flexibility, hardware and software failures that cause early termination or frequent restarts can occur without prior warning. link
App Engine attempts to keep manual and basic scaling instances running
indefinitely. However, at this time there is no guaranteed uptime for
manual and basic scaling instances. Hardware and software failures
that cause early termination or frequent restarts can occur without
prior warning and can take considerable time to resolve; thus, you
should construct your application in a way that tolerates these
failures.
Here are some good strategies for avoiding downtime due to instance
restarts:
Reduce the amount of time it takes for your instances restart or for
new ones to start.
For long-running computations, periodically create
checkpoints so that you can resume from that state.
Your app should be "stateless" so that nothing is stored on the instance.
Use queues for performing asynchronous task execution.
If you configure your instances to manual scaling: Use load balancing across > multiple instances. Configure more instances than required to handle normal
traffic. Write fall-back logic that uses cached results when a manual
scaling instance is unavailable.
Instance Uptime
I'm on a Corda V2 project (but will be migrating to V3 shortly). Per the docs
Artemis is hidden behind a thin interface...
But I'm exploring some business cases around the queue. Specifically is any of the following exposed for configuration? (Couldn't find anything specific in node config, but about to look at source.) Or would I need to do my own broker and specify with messagingServerAddress?
delivery retry rate
backoff rate
timeout, or when Artemis gives up on delivering the message
Sorry, might be separate question but can the internal queue be queried to see if a node has proposed tx's still waiting to be sent to a different node?
As of Corda 3, these settings are not configurable.
It is recommended not to try and interfere with these settings, as many Corda components do not have timeouts configured.
If your use case absolutely requires configuring these settings, please update to original question to explain why :)
I'm looking to use a message queue system for an ongoing project, which now is relying on a custom (and brittle) message subsystem to interconnect multiple applications. Both the pub/sub and queue patterns are heavily used in my system.
Apache Apollo is one of the message queue systems I'm taking into account, but I don't find information about how can I handle (for instance) an Apollo server failure.
Is there a way to provide failover support in Apollo?
No, as of now this has not been resolved. Apollo is a very good broker, indeed, but lacks some production critical features like fail over. Apollo was an attempt to make a core for the next generation of ActiveMQ. However, the development is no loger active.
Have you considered other brokers like Apache Artemis? It's basically a new attempt to remake ActiveMQ with code from HornetQ, ActiveMQ and Apollo. Development is very active at the moment and there is support for fail over etc.
I work on a few .NET web apps that use Redis heavily for caching along with ServiceStack's Redis client. In all cases I've got Redis running on the same machine. I've used both BasicRedisClientManager and PooledRedisClientManager (always implemented as singletons) and have had some issues with both approaches.
With BasicRedisClientManager, things would work fine for a while, but eventually Redis would start refusing connections. Using netstat we discovered that thousands of TCP connections to the default Redis port were hanging around in TIME_WAIT status.
We then switched to PooledRedisClientManager, which seemed to fix the problem immediately. However, not long after, we started noticing occasional CPU spikes that we narrowed down to thread waiting (System.Threading.Monitor.Wait calls) caused by PooledRedisClientManager.GetClient.
In code, we use a get-in-get-out approach (using ServiceStack's handy ExecAs shortcuts) so in general connections are acquired very frequently but held as briefly as possible.
We get a modest amount of traffic but we're no StackExchange, and I can't help but think the ServiceStack client is up to the job and we're just doing something wrong. Is PooledRedisClientManager the correct approach here? Would it be advisable to simply increase the pool size? Or is that likely just masking a problem with our code?
Just looking for general guidance here, I don't have specific code I need help with at this point. Thanks in advance.
Are you absolutely sure all Redis connections are being disposed?
With ServiceStack, the Redisproperty on Service and ViewPageBase (if you're using SS Razor) do dispose themselves, but any time you request a connection from the pool yourself you must dispose it yourself.
However, despite this, we recently had issues with our pool being exhausted of all connections, too. One of my colleagues discovered that there wasn't proper clean up for Razor pages and made a pull request here - This means that there has only been correct disposal on Razor pages since ServiceStack v4.0.21. I have not checked if that fix has been back-ported to the v3 branch.
My colleague also added TrackingRedisClientsManager that may help you track down the improper disposal. See here
You can also check the stats of a PooledRedisClientManager by using this helper method. We threw it on a little razor page to check the stats as we feel appropriate) but you could write better code around this to monitor the pool health of specific nodes, too.