* **Transactional Key/Value API:** A new `/v1/txn` API was added that allows for atomic updates to and fetches from multiple entries in the key/value store inside of an atomic transaction. This including conditional updates based on obtaining a lock. See the [Key/Value Store Endpoint](https://www.consul.io/docs/agent/http/kv.html#txn) for details. [GH-2028]
* **Native ACL Replication:** Added a full replication capability for ACLs. Non-ACL datacenters can now replicate the complete ACL set locally to their state store and fall back to that if there's an outage. Additionally, this provides a good way to make a backup ACL datacenter, or to migrate the ACL datacenter to a different one. See the [ACL Internals Guide](https://www.consul.io/docs/internals/acl.html#replication) for more details. [GH-2237]
* **Server Connection Rebalancing:** Consul agents will now periodically reconnect to available Consul servers in order to redistribute their RPC query load. Consul clients will, by default, attempt to establish a new connection every 120s to 180s unless the size of the cluster is sufficiently large. The rate at which agents begin to query new servers is proportional to the size of the Consul cluster (servers should never receive more than 64 new connections per second per Consul server as a result of rebalancing). Clusters in stable environments who use `allow_stale` should see a more even distribution of query load across all of their Consul servers. [GH-1743]
* **Raft Updates and Consul Operator Interface:** This version of Consul upgrades to "stage one" of the v2 HashiCorp Raft library. This version offers improved handling of cluster membership changes and recovery after a loss of quorum. This version also provides a foundation for new features that will appear in future Consul versions once the remainder of the v2 library is complete. [GH-2222] Consul's default Raft timing is now set to work more reliably on lower-performance servers, which allows small clusters to use lower cost compute at the expense of reduced performance for failed leader detection and leader elections. You will need to configure Consul to get the same performance as before. See the new [Server Performance](https://www.consul.io/docs/guides/performance.html) guide for more details. [GH-2303] Servers will now abort bootstrapping if they detect an existing cluster with configured Raft peers. This will help prevent spurious leader elections when starting new nodes with `bootstrap_expect` enabled. [GH-2319] Added new `consul operator` command, HTTP endpoint, and associated ACL to allow Consul operators to view and update the Raft configuration. This allows for a stale server to be removed without requiring downtime and peers.json recovery file use. See the new [Consul Operator Command](https://www.consul.io/docs/commands/operator.html) and the [Consul Operator Endpoint](https://www.consul.io/docs/agent/http/operator.html) for details. [GH-2312]
* **Raft Updates and Consul Operator Interface:** This version of Consul upgrades to "stage one" of the v2 HashiCorp Raft library. This version offers improved handling of cluster membership changes and recovery after a loss of quorum. This version also provides a foundation for new features that will appear in future Consul versions once the remainder of the v2 library is complete. [GH-2222] <br><br>Consul's default Raft timing is now set to work more reliably on lower-performance servers, which allows small clusters to use lower cost compute at the expense of reduced performance for failed leader detection and leader elections. You will need to configure Consul to get the same performance as before. See the new [Server Performance](https://www.consul.io/docs/guides/performance.html) guide for more details. [GH-2303] <br><br>Servers will now abort bootstrapping if they detect an existing cluster with configured Raft peers. This will help prevent spurious leader elections when starting new nodes with `bootstrap_expect` enabled. [GH-2319]<br><br> Added new `consul operator` command, HTTP endpoint, and associated ACL to allow Consul operators to view and update the Raft configuration. This allows for a stale server to be removed without requiring downtime and peers.json recovery file use. See the new [Consul Operator Command](https://www.consul.io/docs/commands/operator.html) and the [Consul Operator Endpoint](https://www.consul.io/docs/agent/http/operator.html) for details. [GH-2312]
* **Serf Lifeguard Updates:** Implemented a new set of feedback controls for the gossip layer that help prevent degraded nodes that can't meet the soft real-time requirements from erroneously causing `serfHealth` flapping in other, healthy nodes. [GH-2101]
* **Prepared Query Near Parameter:** Prepared queries support baking in the `Near` sorting parameter. This allows results to be sorted by network round trip time based on a static node, or based on the round trip time from the Consul agent where the request originated. This can be used to find a co-located service is one is available, with a transparent fallback to the next best alternate instance. [GH-2137]
* **Automatic Service Deregistration:** Added a new `deregister_critical_service_after` timeout field for health checks which will cause the service associated with that check to get deregistered if the check is critical for longer than the timeout. [GH-679]
James Phillips
8 years ago