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Signed-off-by: Matthias Hanel <mh@synadia.com>
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Matthias Hanel 2020-02-14 18:37:06 -05:00
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nats-server/configuration/gateways/README.md
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@ -21,11 +21,11 @@ Gateways exist to:
* reduce the number of connections required between servers
* optimize the interest graph propagation
If gateways are to be used in a cluster, **all** servers of this cluster need to have a gateway configuration with the **same name**. Furthermore, every gateway node needs to be able to **connect to every** other gateway node and vice versa. Everything else is considered a misconfiguration.
If gateways are to be used in a cluster, **all** server of this cluster need to have a gateway configuration with the **same name**. Furthermore, every gateway node needs to be able to **connect to any** other gateway node and vice versa. Everything else is considered a misconfiguration.
## Gateway Connections
A nats-server in a gateway role will specify a port where it will accept gateway connections. If the configuration specifies other _external_ `gateways`, the gateway will create one outbound gateway connection for each gateway in it's configuration. It will also gossip other gateways it knows or discovered. Fewer _external_ `gateways` mean less configuration. Ye, the ability to discover more gateways and gateway nodes depends on these servers running. This is similar to _seed server_ in cluster. It is recommended to have all _seed server_ of a cluster listed in the `gateways` section.
A nats-server in a gateway role will specify a port where it will accept gateway connections. If the configuration specifies other _external_ `gateways`, the gateway will create one outbound gateway connection for each gateway in it's configuration. It will also gossip other gateways it knows or discovers. Fewer _external_ `gateways` mean less configuration. Yet, the ability to discover more gateways and gateway nodes depends on these servers running. This is similar to _seed server_ in cluster. It is recommended to have all _seed server_ of a cluster listed in the `gateways` section.
If the local cluster has three gateway nodes, this means there will be three outbound connections to each external gateway.
@ -61,7 +61,7 @@ Messages from clients directly connected to a gateway node will be sent along ou
* Interest-only Mode
* Queue Subscriptions
Local interest permitting, the receiving gateway node sends the messages directly to it's subscribing clients as well as server within the cluster that have subscribing clients.
Local interest permitting, the receiving gateway node sends the messages directly to it's subscribing clients as well as server within the cluster.
### Optimistic Mode
@ -77,7 +77,7 @@ When a gateway on _A_ sends many messages on various subjects for which _B_ has
When a queue subscriber creates a new subscription, the gateway propagates the subscription interest to other gateways. The subscription interest is only propagated _once_ per _Account_ and subject. When the last queue subscriber is gone, the cluster interest is removed.
Queue subscriptions work on _Interest-only Mode_ to honor NATS' queue semantics across the _Super Cluster_. For each queue group, a message is only delivered to a single queue subscriber. Only when a local queue group member is not found, is a message forwarded to a different interested cluster; gateways will always try to serve local queue subscribers first and only failover when a local queue subscriber is not found. The interested cluster is picked based on lowest RTT.
Queue subscriptions work on _Interest-only Mode_ to honor NATS' queue semantics across the _Super Cluster_. For each queue group, a message is only delivered to a single queue subscriber. If the same queue group exists in multiple clusters, the server will pick one member from the queue group in its cluster, only sending to a different cluster if there is no interest in its cluster. In other words, a server will always try to serve local queue subscribers first and only failover when a local queue subscriber is not found. The server will pick the cluster with the lowest RTT.
### Gateway Configuration