Geode | Evolved concurrent neural networks on godot engine | Game Engine library
kandi X-RAY | Geode Summary
kandi X-RAY | Geode Summary
A racing car agent after 66 generations evolving. This project aims to create a framework in Godot engine for fast creating and testing simulations of neural network agents evolved by a genetic algorithm. Logic is written in c++11 and highly uses concuency. Godot version used is 3.0 beta 2 over GNU/Linux x64.
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QUESTION
We have Apache Geode connected to Postgres using an AEQ + AsyncCacheListener configured to write data to Postgres. During async write, we submit the list of events that we want to persist and it asynchronously inserts those events. Let's say I have two client applications which calls processEvents for async writing and both have some events in common which violate some key. But, after client calls processEvents, control is immediately returned to client. In such cases how will client know if some issue occurred? What are the best practices to tackle this?
ANSWER
Answered 2021-May-19 at 22:22What do you mean by the events in common "violate some key"? Like a primary or foreign key constraint, or some other database constraint perhaps (e.g. uniqueness, non-null values, etc)?
Handling a conflict depends on the importance and nature of the data being inserted, or written to the backend (Postgres) database from Geode and its significance to the application, from a requirements and business logic POV.
If 2 (or more) client applications are writing to the same cache/database entries/records, then certainly some type of collision will eventually occur, and how it is handled will depend on the data and the type of operation performed on the data.
In general, handling the violation closer to where and when the violation occurs (e.g. inside the AsyncEventListener itself) maybe preferable or ideal, since then you should have most of the necessary information (e.g. DataAccessException, events, additional capabilities to query the DB) to deal with the situation.
Inside the AEQ Listener, you could employ different strategies depending on the data and operation as determined by the application:
- First update wins (enforced by optimistic locking)
- Perform a merge
- Log [failed] event(s)
- Overwrite value(s) (last update wins).
- ...
You could employ Geode to conflate events stored in the AEQ for the same key, which should minimize collisions/conflicts.
If the client (as in "client" in a client/server topology) needs to be informed, then you could write the failed events to another Region where a client registers a CQ to be notified when entries are written to this (failed events) Region. The client-side handler associated the CQ could then take the appropriate action, such as notifying the end-user, refreshing and then retrying the operation, and so on.
Given the async nature of the initial write, then you can only respond asynchronously once the violation occurs. This is not unlike in a Reactive world (namely with onSuccess/onFailure event handlers).
So, in this situation, I don't think there really is a "best practice" per-say, rather only "recommendations". For example, handling the situation as near to the actual occurrence of the violation as possible, since handling the violation usually involves having the necessary information readily available to make the best possible, informed decision on the right course of action.
Sometimes you can automate the recovery, other times you might need manual intervention. Most definitely, do not guess. Clearly document your application/systems (configured) behavior when it can handle a situation and when it cannot.
I don't think there is a general, 1 size fits all solution in this case.
I hope this gives you some ideas to think about.
QUESTION
I write a .sh script that firstly downloads the source code of a page and secondly executes a Rscript only if the source code downloaded is different from the latter. The page is updated once a day and the URL ends with the actual date. This is all on a server and a cron job would run the .sh every 15 min. So I do this :
...ANSWER
Answered 2021-May-11 at 20:44You should leave a space between if and [.
QUESTION
I have apache geode as inline cache where it is connected to postgres as datasource. Since for getting all keys at once when getall method id invoked from region It calls CacheLoader Sequentially. Is there a way so that i can get all keys and call my datasource at once such as calling in query from Cacheloader.
...ANSWER
Answered 2021-Apr-26 at 10:02I don't there's a way of accomplishing this out of the box using a CacheLoader since, as you already verified, the callback is invoked sequentially on every key not found within the Region. You might be able to pre-populate the Region with all those keys you know must be there, though, but keys not found while executing Region.getAll() will still be retrieved sequentially by invoking the configured CacheLoader.
QUESTION
I am using region getall method to get values for all keys, but what i found is that for the key present in apache geode it gets data quickly but for one which is not present in apache geode. it calls the cache loader one by one. Is there any mechanism so that calling cacheloader can be made parallel.
...ANSWER
Answered 2021-Apr-21 at 16:22I don't think there's a way of achieving this out of the box, at least not while using a single Region.getAll() operation. If I recall correctly, the servers just iterate through the keys and performs a get on every single one, which ends up triggering the CacheLoader execution.
You could, however, achieve some degree of parallelism by splitting the set of keys into multiple sets, and launching different threads to execute the Region.getAll() operation using these smaller sets. The actual size of each set and the number of threads will depend on the ratio of cache hits / misses you expect, and your SLA requirements, of course.
QUESTION
I have an apache geode setup. I have connected geode with external datasource which is postgres. There is a scenario where i have few data present in apache geode and rest all is in postgres. I am using query service to fetch data and when i fire query then i want that apache geode should provide me data present in its server and from postgres as well(for data not present in apache geode ). How can i proceed with that?
I have my cache loaded which loads data if it is not present in Apache Geode.
''' @Service public class QuoteLoader implements CacheLoader {
...ANSWER
Answered 2021-Apr-19 at 15:56The query engine simply executes the OQL and returns the result, no CacheLoader is invoked whatsoever during the query execution. The CacheLoader is only invoked if there's a cache miss while executing a Region.get(key) operation.
This, if you think about it, makes total sense... a query is an arbitrary string that can return any results (including none), so the query engine can't know whether an entry is expected to be part of the result or not if the actual entry is not already present in the Geode region.
QUESTION
I want to have value based on multiple joins between the table so how can i create a materialized view in apache geode.
...ANSWER
Answered 2021-Apr-15 at 08:30Apache Geode is a high available in-memory data store, not a regular RDBMS system, so the "materialized view" concept doesn't even exist out of the box.
I guess you could simulate something by using CacheListeners and/or CacheWriters (see here) to update an extra Region (using a newly created thread to avoid problems). A simpler option would be to use a Function (see here) and simply calculate whatever you need directly on server side each time.
Either way, the actual implementation is highly tied to your use case and SLAs, so I'm not in a good position to recommend which option to use.
Cheers.
QUESTION
I have an apache geode setup where there is one locator and one Server. we have a region employee in that. we were trying to implement in-line cache where a cache miss will lookup into database and will fill apache geode, but after deployment of Jars when i am trying to alter the region . It shows exception
...ANSWER
Answered 2021-Apr-13 at 11:49I've just tried the scenario using Apache Geode 1.13.2 and it works just fine, you can find the example here. Do you have multiple versions of the same jar within the server's class path?, that might be the reason for the exception.
Cheers.
QUESTION
The context is that I am working on a Kubernetes project, where we use a Geode cluster, and Spring Boot, also Spring Boot Data Geode (SBDG). We have developed an app with it, a ClientCache. Also we have a proprietary internal mechanism to generate cluster-internal certificates, this mechanism automatically renews certificates according to the best practices. We convert the PEM formatted certificate in our App code to JKS, and configured Spring with @EnableSSL annotation to take them.
So the issue is, that everything works wonderfully for the first cycle, when the connections were created with the JKS file the App initially started up with, however if the certificate is renewed, say hourly (in cloud this is best practice), Geode fails to be connected with a bunch of Exceptions, sometimes SSLException (readHandshakeRecord), many times with "Unable to connect to any locators in the list" (but I debugged, and it is also a HandshakeException, just wrapper in a connection-exception instead). The locators and servers are up and running (I checked with GFSH), just the App I think tries to connect with the old SSLContext and fails in the SSL handshake.
The only way so far I have found is to restart the App completely, but we would need this system to be automatic, and highly available, so this should not be the only way around this issue.
I think this problem is affecting a lot of Spring/Java projects as I have found this issue all around (Kafka, PGSQL, etc...).
Do any of you have any method to do this? Is there a way to:
- Recreate all the connections without me restarting the App?
- Invalidate the currently used connections somehow, and force the ClientCache to create new ones, re-reading the JKS file?
- Maybe let the Client App timeout the connections and destroy them, and create new ones, with refreshed SSLContext?
I did not find any possibilities for this.
EDIT: Let me add some code, to show how we do things, since we use Spring, it is dead simple:
...ANSWER
Answered 2021-Jan-25 at 00:43I think what you're looking for is very similar to what the Java buildpack does when deploying apps to CloudFoundry. When an app is deployed, the buildpack injects a custom Security Provider which watches various key/trust stores for changes. This allows the certificates to be updated without needing to restart the app (https://docs.cloudfoundry.org/buildpacks/java/).
I'm not sure of the exact implementation details but the code for the Security Provider can be found here https://github.com/cloudfoundry/java-buildpack-security-provider. Hopefully this will give you some ideas on how to implement this for your own needs.
QUESTION
I have a windows desktop application on .NET Framework that a user can interact with. There is a "connect" button that sets up Apache Geode client connection to Geode Server.
When Geode Server is down (Locator - there is only 1) the desktop application hangs indefinitely and needs to be forcefully closed.
This is how we connenect to the server and hangs on last line indefinitely:
...ANSWER
Answered 2021-Mar-24 at 18:16Depending on what version of .NET native client you are using. There is a property in 10.x connect-timeout that should work. Additionally, you can wrap your connection code under try{...}catch{} block and handle an exception for Apache.Geode.Client.TimeoutException and/or ": No locators available".
Example:
QUESTION
I am implementing geode dunit based tests.Each VM executes Callable asynchronously.The logic is having several steps , between which the VMs need to be synced up. Its not possible to separate them into several different callable s because some variables need to be persisted between stages.
Currently the VMs are doing sleep after each stage and this way the VMs are synced. However i am looking for another option which would allow execution without sleep ( semaphore based ).
Is there an option to have a shared resource between VMs that would allow to sync up the VMs , or may be some geode based mechanism that would allow such orchestration of VMs?
BR
Yulian Oifa
...ANSWER
Answered 2021-Feb-18 at 13:52Geode's internal testing framework does this in several places, actually, I'd suggest having a look at the geode-dunit project for examples, specially at the Blackboard java class. Cheers.
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