ServiceStack.Redis | .NET 's leading C # Redis Client | Performance Testing library

Context:

I'm trying to understand the motivation behind existence of WaitBeforeForcingMasterFailover property (and the code associated with it) inside of ServiceStack.Redis.RedisSentinel.

If I interpreted the code right - the meaning behind this property seems to cover cases like:

1. We have a connection to a healthy sentinel that tells us that a master is at host X
2. When we try to establish a connection to the master at host X - we fail due to some reason.

So the logic will be - if we continuously fail to create a connection to X for WaitBeforeForcingMasterFailover period - initiate a force failover.

The failover does not need to reach a quorum and can elect a new master just with 1 sentinel available.

SENTINEL FAILOVER Force a failover as if the master was not reachable, and without asking for agreement to other Sentinels (however a new version of the configuration will be published so that the other Sentinels will update their configurations).

Source: https://redis.io/topics/sentinel#sentinel-api

The way it seems to me - this feature can be beneficial in some cases and troublesome in other cases.

For example in case of a network partition if a client is left connected to a minority of sentinels (they can't reach a quorum) and these sentinels point to a master that is no longer reachable - this force failover option will trigger a failover within reachable partition, thus potentially creating a split brain situation.

Coming from Java background I also haven't seen such features available in popular redis clients such as Jedis and Lettuce.

This got me wondering on the following questions:

1. Are there strong reasons for this feature to be enabled by default? (I understand that you can effectively disable it if you want to by setting a huge value in it). Do they really worth the risk of interfering with natural sentinels workflow and potentially introducing problems like the one I've mentioned before?

2. Will the library work fine with this option disabled? Are there are cases that I might have missed and turning this feature off will lead to problems even with some happy paths (no network partition, just regular failovers because of a deployment or a sudden node failure)?

Description:

I'm curious what is the relationship between RedisSentinelWorker and RedisPubSubServer.

From what I've observed the library holds at most 1 active sentinel connection even if there are more sentinel hosts available. That sentinel connection is wrapped in RedisSentinelWorker, which wraps RedisPubSubServer under the hood.

What bothers me is that RedisSentinelWorker and RedisPubSubServer might actually represent connections to two different sentinels.

Here is why this is happening:

The problem:

It is not obvious how to correctly authenticate with:

• sentinels
• redis instances themselves

when using the ServiceStack.Redis solution.

According to the docs a proper way to provide a password for redis/sentinel is to set it via URLs in the following manner:

I'm using ServiceStack.Redis v5.10.4 and trying to set the TTL using the following code:

Note: mClientsManager = IRedisClientsManager ttl = TimeSpan?

I'm attempting to use ServiceStack.Redis to connect to a cloud based Redis instance using SSL Certificates. The ServiceStack documentation provides information on how to connect to an Azure based Redis using SSL, but has no information or examples on how to connect to a non Azure Redis instance.

I've got a pem, crt, and key file but nothing I do with them seems to actually pass them across to the service. I've set ssl=true&sslprotocols=tls12 in the connectionstring which seems like the first step, but beyond that I'm not sure what I should be doing to correctly pass across the certificate for verification

EDIT: Current Code

I'm using ServiceStack.Redis in my application, I have a get method that goes to redis (cache) to get some information, but if redis is disconnected, I call the repository to get from the real database

I created a Visual Studio (Community 2019) project with C# using ServiceStack.Redis. Since it is C#, I use Windows 10 (there is a Redis version for Windows but it is really old and as I know, it is unofficial so I am afraid that might be the problem). Here is an excerpt from my code:

Let's say I'm building a cards game (I'm using an analogy as I can't disclose the original project details). Consider the following structure:

I am testing out the Redis "full duplex" communication as shown here, and reading the docs, I thought that the PooledRedisClientManager as well as RedisManagerPool have a pool of clients, and thus being able to process several MQ messages in parallel.

However, in the test project, found here on Github, it seems to me that this is not the case, or I am missing something. The solution consists of:

• EventPublisher: .NET Core WinForms application for publishing Hello DTOs to the MQ
• EventConsumer: .NET Core WinFOrms application that has Service impl for handling Hello DTOs

I added a Thread.Sleep inside the HelloService Any(Hello req) and when I from the EventPublisher send several Hello DTOs quickly, I was expecting them to be handled concurrently in the EventConsumer, as I thought the pool of clients would be used. This, however, doesn't seem to be the case.

The HelloResponses are handled one after the other, on the same thread it seems. Please take a look at this short video:

http://somup.com/cYheY8iNml

Here, I fire off three Hello DTOs to the MQ in quick succession, and in the Output window in VS, you can see that the three DTOs are handled one after each other.

I did not find a setting in PooledRedisClientManager nor RedisManagerPool where I could specify the pool size.