Implement Lame Duck Mode Event Handler

[pzajaczkowski]

Resolves #23

I had two ideas for approaching this issue:

• Make WritableServerInfo property and add setter, that will check if LDM has changed to true
• Add a trigger method that writes the event to a channel in NatsConnection and invoke it directly from NatsReadProtocolProcessor after recieving INFO from server with LDM.

I decided to go with first option.

There is one thing i am not sure of: should anything be passed as argument to the LameDuckModeActivated event? Currently, it is an empty string.

[mtmk]

@pzajaczkowski thanks for the PR. long overdue that issue ;)

• Make WritableServerInfo property and add setter, that will check if LDM has changed to true
• Add a trigger method that writes the event to a channel in NatsConnection and invoke it directly from NatsReadProtocolProcessor after recieving INFO from server with LDM.

I decided to go with first option.

I think that's fine.

There is one thing i am not sure of: should anything be passed as argument to the LameDuckModeActivated event? Currently, it is an empty string.

Potentially passing the host might be a interesting. Or a copy of the server info?

EDIT: What do you think about passing Uri of the host similar to the proposal in PR #712

[mtmk]

I'm guessing this test won't run on Windows due to lack of posix signals?

[darkwatchuk]

I believe you can do this instead...

// var command = $"$SYS.REQ.SERVER.{serverId}.LDM";

RequestAsync(command , ....

[Jarema]

Yes, @darkwatchuk is right, with LDM API introduced this is definately an easier way to test it.

[mtmk]

@pzajaczkowski are you ok to change the test to use the API above?

[pzajaczkowski]

Sorry for late response. I tried this approach:

I believe you can do this instead...

// var command = $"$SYS.REQ.SERVER.{serverId}.LDM";

RequestAsync(command , ....

but cannot make it work. When sending event with .LDM suffix i receive error:

{
  "error": {
    "code": 500,
    "description": "no such client id"
  }
}

Also i haven't found any documentation mentioning $SYS.REQ.SERVER.{serverId}.LDM event.
(https://docs.nats.io/running-a-nats-service/configuration/sys_accounts)

I think that the problem is not related to serverId because other examples from docs above like .STATSZ work as intended.

So i need some help please.

[mtmk]

I'll have a look in the morning.