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initial syntax & grammar review

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jetstream/leafnodes.md
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# Jetstream in LeafNodes # JetStream in LeafNodes
If you want to see a demonstration of the full range of this functionality, check out our [video](https://youtu.be/0MkS_S7lyHk) If you want to see a demonstration of the full range of this functionality, check out our [video](https://youtu.be/0MkS_S7lyHk)
One of the use cases for leaf nodes is to provide a local nats network even when the connection to a hub or the cloud is down. One of the use cases for leafnodes is to provide a local NATS network even when the connection to a hub or the cloud is down.
To support such a disconnected use case with JetStream, independent JetStream islands are also supported and available through the same nats network. To support such a disconnected use case with JetStream, independent JetStream islands are also supported and available through the same NATS network.
The general issue with multiple, independent JetStreams, accessible from the same client is that you need to be able to tell them apart. The general issue with multiple, independent JetStreams, accessible from the same client is that you need to be able to tell them apart.
As an example, consider a leaf node with a non clustered JetStream in each server. As an example, consider a leafnode with a non-clustered JetStream in each server.
You connect to one of them, but which JetStream responds when you use the JetStream API `$JS.API.>` ? You connect to one of them, but which JetStream responds when you use the JetStream API `$JS.API.>` ?
To disambiguate that, the option `domain` was added to the JetStream configuration block. To disambiguate that, the option `domain` was added to the JetStream configuration block.
@ -19,9 +19,9 @@ Needless to say, domain names need to be unique.
There are reasons to connect system accounts on either end of your leafnode connection. There are reasons to connect system accounts on either end of your leafnode connection.
You probably don't want to connect your cloud and edge device system accounts, but you might connect them when the only reason keeping you from using a super cluster are firewall rules. You probably don't want to connect your cloud and edge device system accounts, but you might connect them when the only reason keeping you from using a super cluster are firewall rules.
The benefits are: The benefits are:
1) monitoring of all connected nats-servers. 1) monitoring of all connected nats-servers
2) nats-account-resolver working on the entire network. 2) nats-account-resolver working on the entire network
3) extended JetStream cluster. 3) extended JetStream cluster
When `domain` is set, JetStream-related traffic on the system account is suppressed. When `domain` is set, JetStream-related traffic on the system account is suppressed.
This is what causes JetStream to not be extended. This is what causes JetStream to not be extended.
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Thus, if the same subject is subscribed to by different streams in the same account in different domains, as long as the underlying leafnode was connected at the time, each stream will store the message. Thus, if the same subject is subscribed to by different streams in the same account in different domains, as long as the underlying leafnode was connected at the time, each stream will store the message.
This can be resolved by using the same account but use different subjects in each domain or use different accounts in each domain or [isolate accounts](https://youtu.be/0MkS_S7lyHk?t=1151) used in leaf nodes. This can be resolved by using the same account but use different subjects in each domain or use different accounts in each domain or [isolate accounts](https://youtu.be/0MkS_S7lyHk?t=1151) used in leaf nodes.
> *known issue*: if you have more than one JetStream enabled leaf node in a different cluster, the cluster you connect to also needs JetStream enabled and a domain set. > *Known issue*: if you have more than one JetStream enabled leafnode in a different cluster, the cluster you connect to also needs JetStream enabled and a domain set.
> *known issue*: when you intend to extend a central JetStream, by not supplying a domain name in leaf nodes, that central JetStream needs to be in clustered mode. > *Known issue*: when you intend to extend a central JetStream, by not supplying a domain name in leafnodes, that central JetStream needs to be in clustered mode.
## Configuration ## Configuration
Below is the config needed to connect two JetStream enabled servers via a leafnode connection. Below is the config needed to connect two JetStream enabled servers via a leafnode connection.
In the example, the system accounts are connected for demonstration purposes (you do not have to do that). In the example, the system accounts are connected for demonstration purposes (you do not have to do that).
### `accounts.conf` imported by both server ### `accounts.conf` Imported by Both Servers
```txt ```txt
accounts { accounts {
@ -428,7 +428,7 @@ accounts {
system_account: SYS system_account: SYS
``` ```
##### Copying via `source` an `mirror` ##### Copying via `source` and `mirror`
Once the servers have been restarted or reloaded, a `mirror` can be created as follows (same applies to `source`): Once the servers have been restarted or reloaded, a `mirror` can be created as follows (same applies to `source`):
On import from a different account the renamed prefix `JS.acc@hub.API` is provided. On import from a different account the renamed prefix `JS.acc@hub.API` is provided.