* **LAN Network Segments:** (Consul Enterprise) Added a new [Network Segments](https://www.consul.io/docs/guides/segments.html) capability which allows users to configure Consul to support segmented LAN topologies with multiple, distinct gossip pools. [GH-3431]
* **WAN Join for Cloud Providers:** Added WAN support for retry join for cloud providers via go-discover, including Amazon AWS, Microsoft Azure, Google Cloud, and SoftLayer. This uses the same "provider" syntax supported for `-retry-join` via the `-retry-join-wan` configuration. [GH-3406]
* **RPC Rate Limiter:** Consul agents in client mode have a new [`limits`](https://www.consul.io/docs/agent/options.html#limits) configuration that enables a rate limit on RPC calls the agent makes to Consul servers. [GH-3140]
* agent: When joining a cluster, Consul now skips the unique node ID constraint for Consul members running Consul older than 0.8.5. This makes it easier to upgrade to newer versions of Consul in an existing cluster with non-unique node IDs. [GH-3070]
* agent: Updated memberlist library for deadlock fix. [GH-3396]
* agent: Fixed a panic when retrieving NS or SOA records on Consul clients (non-servers). This also changed the Consul server list to come from the catalog and not the agent's local state when serving these requests, so the results are consistent across a cluster. [GH-3407]
* cli: Updated the CLI library to pull in a fix that prevents all subcommands from being shown when showing the agent's usage list; now just top-level commands are shown. [GH-3448]
* server: Reverted the change that made unauthorized KV queries return 403 instead of 404 because it had a minor bug that affected the operation of Vault, and in addition to fixing the bug, we identified an additional case that needed to be covered. This restores the <= 0.9.0 behavior until we can get a complete fix. [GH-2637]
* **Secure ACL Token Introduction:** It's now possible to manage Consul's ACL tokens without having to place any tokens inside configuration files. This supports introduction of tokens as well as rotating. This is enabled with two new APIs:
* A new [`/v1/agent/token`](https://www.consul.io/api/agent.html#update-acl-tokens) API allows an agent's ACL tokens to be introduced without placing them into config files, and to update them without restarting the agent. See the [ACL Guide](https://www.consul.io/docs/guides/acl.html#create-an-agent-token) for an example. This was extended to ACL replication as well, along with a new [`enable_acl_replication`](https://www.consul.io/docs/agent/options.html#enable_acl_replication) config option. [GH-3324,GH-3357]
* A new [`/v1/acl/bootstrap`](https://www.consul.io/api/acl.html#bootstrap-acls) allows a cluster's first management token to be created without using the `acl_master_token` configuration. See the [ACL Guide](https://www.consul.io/docs/guides/acl.html#bootstrapping-acls) for an example. [GH-3349]
* **Metrics Viewing Endpoint:** A new [`/v1/agent/metrics`](https://www.consul.io/api/agent.html#view-metrics) API displays the current values of internally tracked metrics. [GH-3369]
* agent: Retry Join for Amazon AWS, Microsoft Azure, Google Cloud, and (new) SoftLayer is now handled through the https://github.com/hashicorp/go-discover library. With this all `-retry-join-{ec2,azure,gce}-*` parameters have been deprecated in favor of a unified configuration. See [`-retry-join`](https://www.consul.io/docs/agent/options.html#_retry_join) for details. [GH-3282,GH-3351]
* agent: Added a new `prefix_filter` option in the `telemetry` config to allow fine-grained allowing/blocking the sending of certain metrics by prefix. [GH-3369]
* cli: Added a `-child-exit-code` option to `consul lock` so that it propagates an error code of 2 if the child process exits with an error. [GH-947]
* docs: Added a new [Geo Failover Guide](https://www.consul.io/docs/guides/geo-failover.html) showing how to use prepared queries to implement geo failover policies for services. [GH-3328]
* docs: Added a new [Consul with Containers Guide](https://www.consul.io/docs/guides/consul-containers.html) showing critical aspects of operating a Consul cluster that's run inside containers. [GH-3347]
* server: Added a `RemoveEmptyTags` option to prepared query templates which will strip out any empty strings in the tags list before executing a query. This is useful when interpolating into tags in a way where the tag is optional, and where searching for an empty tag would yield no results from the query. [GH-2151]
* server: Implemented a much faster recursive delete algorithm for the KV store. It has been benchmarked to be up to 100X faster on recursive deletes that affect millions of keys. [GH-1278, GH-3313]
* agent: Added a new [`enable_script_checks`](https://www.consul.io/docs/agent/options.html#_enable_script_checks) configuration option that defaults to `false`, meaning that in order to allow an agent to run health checks that execute scripts, this will need to be configured and set to `true`. This provides a safer out-of-the-box configuration for Consul where operators must opt-in to allow script-based health checks. [GH-3087]
* api: Reworked `context` support in the API client to more closely match the Go standard library, and added context support to write requests in addition to read requests. [GH-3273, GH-2992]
* agent: Added a new [`block_endpoints`](https://www.consul.io/docs/agent/options.html#block_endpoints) configuration option that allows blocking HTTP API endpoints by prefix. This allows operators to completely disallow access to specific endpoints on a given agent. [GH-3252]
* cli: Added a new [`consul catalog`](https://www.consul.io/docs/commands/catalog.html) command for reading datacenters, nodes, and services from the catalog. [GH-3204]
* server: (Consul Enterprise) Added a new [`consul operator area update`](https://www.consul.io/docs/commands/operator/area.html#update) command and corresponding HTTP endpoint to allow for transitioning the TLS setting of network areas at runtime. [GH-3075]
* server: (Consul Enterprise) Added a new `UpgradeVersionTag` field to the Autopilot config to allow for using the migration feature to roll out configuration or cluster changes, without having to upgrade Consul itself.
* agent: Removed registration of the `consul` service from the agent since it's already handled by the leader. This means that Consul servers no longer need to have an `acl_agent_token` with write access to the `consul` service if ACLs are enabled. [GH-3248]
* agent: Changed the `consul exec` ACL resolution logic to use the `acl_agent_token` if it's available. This lets operators configure an `acl_agent_token` with the required `write` privilieges to the `_rexec` prefix of the KV store without giving this to the `acl_token`, which would expose those privileges to users as well. [GH-3160]
* agent: Updated memberlist to get latest LAN gossip tuning based on the [Lifeguard paper published by Hashicorp Research](https://www.hashicorp.com/blog/making-gossip-more-robust-with-lifeguard/). [GH-3287]
* api: Added the ability to pass in a `context` as part of the `QueryOptions` during a request. This provides a way to cancel outstanding blocking queries. [GH-3195]
* api: Changed signature for "done" channels on `agent.Monitor()` and `session.RenewPeriodic` methods to make them more compatible with `context`. [GH-3271]
* docs: Added a complete end-to-end example of ACL bootstrapping in the [ACL Guide](https://www.consul.io/docs/guides/acl.html#bootstrapping-acls). [GH-3248]
* agent: Fixed an issue where watch plans would take up to 10 minutes to close their connections and give up their file descriptors after reloading Consul. [GH-3018]
* agent: (Consul Enterprise) Fixed an issue with the snapshot agent where it could get stuck trying to obtain the leader lock after an extended server outage.
* agent: Fixed log redacting code to properly remove tokens from log lines with ACL tokens in the URL itself: `/v1/acl/clone/:uuid`, `/v1/acl/destroy/:uuid`, `/v1/acl/info/:uuid`. [GH-3276]
* agent: Added `node` read privileges to the `acl_agent_master_token` by default so it can see all nodes, which enables it to be used with operations like `consul members`. [GH-3113]
* agent: Fixed an issue where enabling [`-disable-keyring-file`](https://www.consul.io/docs/agent/options.html#_disable_keyring_file) would cause gossip encryption to be disabled. [GH-3243]
* server: Updated the Raft library to pull in a fix where servers that are very far behind in replication can get stuck in a loop trying to install snapshots. [GH-3201]
* server: Fixed a rare but serious deadlock where the Consul leader routine could get stuck with the Raft internal leader routine while waiting for the initial barrier after a leader election. [GH-3230]
* server: (Consul Enterprise) Fixed an issue where networks areas would not be able to be added when the server restarts if the Raft log contained a specific sequence of adds and deletes for network areas with the same peer datacenter.
* ui: Provided a path to reset the ACL token when the current token is invalid. Previously, the UI would get stuck on the error page and it wasn't possible to get back to the settings. [GH-2370]
* agent: Parse values given to `?passing` for health endpoints. Previously Consul only checked for the existence of the querystring, not the value. That means using `?passing=false` would actually still include passing values. Consul now parses the value given to passing as a boolean. If no value is provided, the old behavior remains. This may be a breaking change for some users, but the old experience was incorrect and caused enough confusion to warrant changing it. [GH-2212, GH-3136]
* agent: The default value of [`-disable-host-node-id`](https://www.consul.io/docs/agent/options.html#_disable_host_node_id) has been changed from false to true. This means you need to opt-in to host-based node IDs and by default Consul will generate a random node ID. A high number of users struggled to deploy newer versions of Consul with host-based IDs because of various edge cases of how the host IDs work in Docker, on specially-provisioned machines, etc. so changing this from opt-out to opt-in will ease operations for many Consul users. [GH-3171]
* agent: Added automatic notify to systemd on Linux after LAN join is complete, which makes it easier to order services that depend on Consul being available. [GH-2121]
* agent: The `http_api_response_headers` config has been moved into a new `http_config` struct, so the old form is still supported but is deprecated. [GH-3142]
* dns: Added support for EDNS(0) size adjustments if set in the request frame. This allows DNS responses via UDP which are larger than the standard 512 bytes max if the requesting client can support it. [GH-1980, GH-3131]
* agent: Fix `consul leave` shutdown race. When shutting down an agent via the `consul leave` command on the command line the output would be `EOF` instead of `Graceful leave completed` [GH-2880]
* agent: Fixed an issue where internally-configured watches were not working because of an incorrect protocol error, and unified internal watch handling during reloads of the Consul agent. [GH-3177]
* agent: Added a method for [transitioning to gossip encryption on an existing cluster](https://www.consul.io/docs/agent/encryption.html#configuring-gossip-encryption-on-an-existing-cluster). [GH-3079]
* agent: Added a method for [transitioning to TLS on an existing cluster](https://www.consul.io/docs/agent/encryption.html#configuring-tls-on-an-existing-cluster). [GH-1705]
* agent: (Consul Enterprise) Added [AWS server side encryption support](http://docs.aws.amazon.com/AmazonS3/latest/dev/UsingServerSideEncryption.html) for S3 snapshots using the snapshot agent.
* agent: Updated [go-sockaddr](https://github.com/hashicorp/go-sockaddr) library to add support for new helper functions in bind address templates (`GetPrivateIPs`, `GetPublicIPs`), new math functions, and to pick up fixes for issues with detecting addresses on multi-homed hosts. [GH-3068]
* agent: Watches now reset their index back to zero after an error, or if the index goes backwards, which allows watches to recover after a server restart with fresh state. [GH-2621]
* agent: Added defensive code to prevent agents from infecting the network coordinates with `NaN` or `Inf` values, and added code to clean up in environments where this has happened. [GH-3023]
* agent: Fixed an issue where NAT-configured agents with a non-routable advertise address would refuse to make RPC connections to Consul servers. This was a regression related to GH-2822 in Consul 0.8.2. [GH-3028]
* api: HttpClient now defaults to nil in the client config and will be generated if left blank. A NewHttpClient function has been added for creating an HttpClient with a custom Transport or TLS config. [GH-2922]
* agent: Added the `ca_path`, `tls_cipher_suites`, and `tls_prefer_server_cipher_suites` options to give more flexibility around configuring TLS. [GH-2963]
* server: Added a new peers.json format that allows outage recovery when using Raft protocol version 3 and higher. Previously, you'd have to set the Raft protocol version back to 2 in order to manually recover a cluster. See https://www.consul.io/docs/guides/outage.html#manual-recovery-using-peers-json for more details. [GH-3003]
* agent: Node IDs derived from host information are now hashed to prevent things like common server hardware from generating IDs with a common prefix across nodes. [GH-2884]
* agent: Added new `-disable-host-node-id` CLI flag and `disable_host_node_id` config option to the Consul agent to prevent it from using information from the host when generating a node ID. This will result in a random node ID, which is useful when running multiple Consul agents on the same host for testing purposes. Having this built-in eases configuring a random node ID when running in containers. [GH-2877]
* agent: Removed useless "==> Caught signal: broken pipe" logging since that often results from problems sending telemetry or broken incoming client connections; operators don't need to be alerted to these. [GH-2768]
* cli: Added TLS options for setting the client/CA certificates to use when communicating with Consul. These can be provided through environment variables or command line flags. [GH-2914]
* server: Fixed an issue where tracking of leadership changes could become incorrect when changes occurred very rapidly. This could manifest as a panic in Autopilot, but could have caused other issues with multiple leader management routines running simultaneously. [GH-2896]
* **Command-Line Interface RPC Deprecation:** The RPC client interface has been removed. All CLI commands that used RPC and the `-rpc-addr` flag to communicate with Consul have been converted to use the HTTP API and the appropriate flags for it, and the `rpc` field has been removed from the port and address binding configs. You will need to remove these fields from your config files and update any scripts that passed a custom `-rpc-addr` to the following commands: `force-leave`, `info`, `join`, `keyring`, `leave`, `members`, `monitor`, `reload`
* **Version 8 ACLs Are Now Opt-Out:** The [`acl_enforce_version_8`](https://www.consul.io/docs/agent/options.html#acl_enforce_version_8) configuration now defaults to `true` to enable [full version 8 ACL support](https://www.consul.io/docs/internals/acl.html#version_8_acls) by default. If you are upgrading an existing cluster with ACLs enabled, you will need to set this to `false` during the upgrade on **both Consul agents and Consul servers**. Version 8 ACLs were also changed so that [`acl_datacenter`](https://www.consul.io/docs/agent/options.html#acl_datacenter) must be set on agents in order to enable the agent-side enforcement of ACLs. This makes for a smoother experience in clusters where ACLs aren't enabled at all, but where the agents would have to wait to contact a Consul server before learning that. [GH-2844]
* **Remote Exec Is Now Opt-In:** The default for [`disable_remote_exec`](https://www.consul.io/docs/agent/options.html#disable_remote_exec) was changed to "true", so now operators need to opt-in to having agents support running commands remotely via [`consul exec`](/docs/commands/exec.html). [GH-2854]
* **Raft Protocol Compatibility:** When upgrading to Consul 0.8.0 from a version lower than 0.7.0, users will need to
set the [`-raft-protocol`](https://www.consul.io/docs/agent/options.html#_raft_protocol) option to 1 in order to maintain backwards compatibility with the old servers during the upgrade. See [Upgrading Specific Versions](https://www.consul.io/docs/upgrade-specific.html) guide for more details.
* **Autopilot:** A set of features has been added to allow for automatic operator-friendly management of Consul servers. For more information about Autopilot, see the [Autopilot Guide](https://www.consul.io/docs/guides/autopilot.html).
- **Dead Server Cleanup:** Dead servers will periodically be cleaned up and removed from the Raft peer set, to prevent them from interfering with the quorum size and leader elections.
- **Server Health Checking:** An internal health check has been added to track the stability of servers. The thresholds of this health check are tunable as part of the [Autopilot configuration](https://www.consul.io/docs/agent/options.html#autopilot) and the status can be viewed through the [`/v1/operator/autopilot/health`](https://www.consul.io/docs/agent/http/operator.html#autopilot-health) HTTP endpoint.
- **New Server Stabilization:** When a new server is added to the cluster, there will be a waiting period where it must be healthy and stable for a certain amount of time before being promoted to a full, voting member. This threshold can be configured using the new [`server_stabilization_time`](https://www.consul.io/docs/agent/options.html#server_stabilization_time) setting.
- **Advanced Redundancy:** (Consul Enterprise) A new [`-non-voting-server`](https://www.consul.io/docs/agent/options.html#_non_voting_server) option flag has been added for Consul servers to configure a server that does not participate in the Raft quorum. This can be used to add read scalability to a cluster in cases where a high volume of reads to servers are needed, but non-voting servers can be lost without causing an outage. There's also a new [`redundancy_zone_tag`](https://www.consul.io/docs/agent/options.html#redundancy_zone_tag) configuration that allows Autopilot to manage separating servers into zones for redundancy. Only one server in each zone can be a voting member at one time. This helps when Consul servers are managed with automatic replacement with a system like a resource scheduler or auto-scaling group. Extra non-voting servers in each zone will be available as hot standbys (that help with read-scaling) that can be quickly promoted into service when the voting server in a zone fails.
- **Upgrade Orchestration:** (Consul Enterprise) Autopilot will automatically orchestrate an upgrade strategy for Consul servers where it will initially add newer versions of Consul servers as non-voters, wait for a full set of newer versioned servers to be added, and then gradually swap into service as voters and swap out older versioned servers to non-voters. This allows operators to safely bring up new servers, wait for the upgrade to be complete, and then terminate the old servers.
* **Network Areas:** (Consul Enterprise) A new capability has been added which allows operators to define network areas that join together two Consul datacenters. Unlike Consul's WAN feature, network areas use just the server RPC port for communication, and pairwise relationships can be made between arbitrary datacenters, so not all servers need to be fully connected. This allows for complex topologies among Consul datacenters like hub/spoke and more general trees. See the [Network Areas Guide](https://www.consul.io/docs/guides/areas.html) for more details.
* **WAN Soft Fail:** Request routing between servers in the WAN is now more robust by treating Serf failures as advisory but not final. This means that if there are issues between some subset of the servers in the WAN, Consul will still be able to route RPC requests as long as RPCs are actually still working. Prior to WAN Soft Fail, any datacenters having connectivity problems on the WAN would mean that all DCs might potentially stop sending RPCs to those datacenters. [GH-2801]
* **WAN Join Flooding:** A new routine was added that looks for Consul servers in the LAN and makes sure that they are joined into the WAN as well. This catches up up newly-added servers onto the WAN as soon as they join the LAN, keeping them in sync automatically. [GH-2801]
* **Validate command:** To provide consistency across our products, the `configtest` command has been deprecated and replaced with the `validate` command (to match Nomad and Terraform). The `configtest` command will be removed in Consul 0.9. [GH-2732]
* cli: Standardized handling of CLI options for connecting to the Consul agent. This makes sure that the same set of flags and environment variables works in all CLI commands (see https://www.consul.io/docs/commands/index.html#environment-variables). [GH-2717]
* cli: The `operator raft` subcommand has had its two modes split into the `list-peers` and `remove-peer` subcommands. The old flags for these will continue to work for backwards compatibility, but will be removed in Consul 0.9.
* server: Changed the internal `EnsureRegistration` RPC endpoint to prevent registering checks that aren't associated with the top-level node being registered. [GH-2846]
* agent: Fixed an issue where checks and services could not sync deregister operations back to the catalog when version 8 ACL support is enabled. [GH-2818]
* agent: Fixed an issue where agents could use the ACL token registered with a service when registering checks for the same service that were registered with a different ACL token. [GH-2829]
* cli: Fixed an issue where prefixing an address with a protocol (such as 'http://' or 'https://') in `-http-addr` or `CONSUL_HTTP_ADDR` would give an error.
* server: Fixed an issue with version 8 ACLs where servers couldn't deregister nodes from the catalog during reconciliation. [GH-2792] This fix was generalized and applied to registering nodes as well. [GH-2826]
* server: Fixed an issue where servers could temporarily roll back changes to a node's metadata or tagged addresses when making updates to the node's health checks. [GH-2826]
* server: Fixed a rare but serious issue where Consul servers could panic when performing a large delete operation followed by a specific sequence of other updates to related parts of the state store (affects KV, sessions, prepared queries, and the catalog). [GH-2724]
* agent: Integrated gopsutil library to use built in host UUID as node ID, if available, instead of a randomly generated UUID. This makes it easier for other applications on the same host to generate the same node ID without coordinating with Consul. [GH-2697]
* agent: Added a `relay-factor` option to keyring operations to allow nodes to relay their response through N randomly-chosen other nodes in the cluster. [GH-2704]
* dns: Add ability to lookup Consul agents by either their Node ID or Node Name through the node interface (e.g. DNS `(node-id|node-name).node.consul`). [GH-2702]
* dns: Fixed an issue where SRV lookups for services on a node registered with non-IP addresses were missing the CNAME record in the additional section of the response. [GH-2695]
* **KV Import/Export CLI:** `consul kv export` and `consul kv import` can be used to move parts of the KV tree between disconnected consul clusters, using JSON as the intermediate representation. [GH-2633]
* **Node Metadata:** Support for assigning user-defined metadata key/value pairs to nodes has been added. This can be viewed when looking up node info, and can be used to filter the results of various catalog and health endpoints. For more information, see the [Catalog](https://www.consul.io/docs/agent/http/catalog.html), [Health](https://www.consul.io/docs/agent/http/health.html), and [Prepared Query](https://www.consul.io/docs/agent/http/query.html) endpoint documentation, as well as the [Node Meta](https://www.consul.io/docs/agent/options.html#_node_meta) section of the agent configuration. [GH-2654]
* **Node Identifiers:** Consul agents can now be configured with a unique identifier, or they will generate one at startup that will persist across agent restarts. This identifier is designed to represent a node across all time, even if the name or address of the node changes. Identifiers are currently only exposed in node-related endpoints, but they will be used in future versions of Consul to help manage Consul servers and the Raft quorum in a more robust manner, as the quorum is currently tracked via addresses, which can change. [GH-2661]
* **Improved Blocking Queries:** Consul's [blocking query](https://www.consul.io/api/index.html#blocking-queries) implementation was improved to provide a much more fine-grained mechanism for detecting changes. For example, in previous versions of Consul blocking to wait on a change to a specific service would result in a wake up if any service changed. Now, wake ups are scoped to the specific service being watched, if possible. This support has been added to all endpoints that support blocking queries, nothing new is required to take advantage of this feature. [GH-2671]
* **GCE auto-discovery:** New `-retry-join-gce` configuration options added to allow bootstrapping by automatically discovering Google Cloud instances with a given tag at startup. [GH-2570]
* **Keyring API:** A new `/v1/operator/keyring` HTTP endpoint was added that allows for performing operations such as list, install, use, and remove on the encryption keys in the gossip keyring. See the [Keyring Endpoint](https://www.consul.io/docs/agent/http/operator.html#keyring) for more details. [GH-2509]
* **Monitor API:** A new `/v1/agent/monitor` HTTP endpoint was added to allow for viewing streaming log output from the agent, similar to the `consul monitor` command. See the [Monitor Endpoint](https://www.consul.io/docs/agent/http/agent.html#agent_monitor) for more details. [GH-2511]
* **Reload API:** A new `/v1/agent/reload` HTTP endpoint was added for triggering a reload of the agent's configuration. See the [Reload Endpoint](https://www.consul.io/docs/agent/http/agent.html#agent_reload) for more details. [GH-2516]
* **Leave API:** A new `/v1/agent/leave` HTTP endpoint was added for causing an agent to gracefully shutdown and leave the cluster (previously, only `force-leave` was present in the HTTP API). See the [Leave Endpoint](https://www.consul.io/docs/agent/http/agent.html#agent_leave) for more details. [GH-2516]
* **Bind Address Templates (beta):** Consul agents now allow [go-sockaddr/template](https://godoc.org/github.com/hashicorp/go-sockaddr/template) syntax to be used for any bind address configuration (`advertise_addr`, `bind_addr`, `client_addr`, and others). This allows for easy creation of immutable images for Consul that can fetch their own address based on an interface name, network CIDR, address family from an actual RFC number, and many other possible schemes. This feature is in beta and we may tweak the template syntax before final release, but we encourage the community to try this and provide feedback. [GH-2563]
* **Complete ACL Coverage (beta):** Consul 0.8 will feature complete ACL coverage for all of Consul. To ease the transition to the new policies, a beta version of complete ACL support was added to help with testing and migration to the new features. Please see the [ACLs Internals Guide](https://www.consul.io/docs/internals/acl.html#version_8_acls) for more details. [GH-2594, GH-2592, GH-2590]
* agent: Updated Circonus metrics library and added new Circonus configration options for Consul for customizing check display name and tags. [GH-2555]
* agent: Check whether a snapshot needs to be taken more often (every 5 seconds instead of 2 minutes) to keep the raft file smaller and to avoid doing huge truncations when writing lots of entries very quickly. [GH-2591]
* cli: Fixed an issue with the `consul kv put` command where a negative value would be interpreted as an argument to read from standard input. [GH-2526]
* Child process reaping support has been removed, along with the `reap` configuration option. Reaping is also done via [dumb-init](https://github.com/Yelp/dumb-init) in the [Consul Docker image](https://github.com/hashicorp/docker-consul), so removing it from Consul itself simplifies the code and eases future maintainence for Consul. If you are running Consul as PID 1 in a container you will need to arrange for a wrapper process to reap child processes. [GH-1988]
* The default for `max_stale` has been increased to a near-indefinite threshold (10 years) to allow DNS queries to continue to be served in the event of a long outage with no leader. A new telemetry counter has also been added at `consul.dns.stale_queries` to track when agents serve DNS queries that are over a certain staleness (>5 seconds). [GH-2481]
* **Snapshot/Restore:** A new /v1/snapshot HTTP endpoint and corresponding set of `consul snapshot` commands were added for easy point-in-time snapshots for disaster recovery. Snapshots include all state managed by Consul's Raft [consensus protocol](/docs/internals/consensus.html), including Key/Value Entries, Service Catalog, Prepared Queries, Sessions, and ACLs. Snapshots can be restored on the fly into a completely fresh cluster. [GH-2396]
* **AWS auto-discovery:** New `-retry-join-ec2` configuration options added to allow bootstrapping by automatically discovering AWS instances with a given tag key/value at startup. [GH-2459]
* The default behavior of `leave_on_terminate` and `skip_leave_on_interrupt` are now dependent on whether or not the agent is acting as a server or client. When Consul is started as a server the defaults for these are `false` and `true`, respectively, which means that you have to explicitly configure a server to leave the cluster. When Consul is started as a client the defaults are the opposite, which means by default, clients will leave the cluster if shutdown or interrupted. [GH-1909] [GH-2320]
* The `allow_stale` configuration for DNS queries to the Consul agent now defaults to `true`, allowing for better utilization of available Consul servers and higher throughput at the expense of weaker consistency. This is almost always an acceptable tradeoff for DNS queries, but this can be reconfigured to use the old default behavior if desired. [GH-2315]
* Output from HTTP checks is truncated to 4k when stored on the servers, similar to script check output. [GH-1952]
* Consul's Go API client will now send ACL tokens using HTTP headers instead of query parameters, requiring Consul 0.6.0 or later. [GH-2233]
* Removed support for protocol version 1, so Consul 0.7 is no longer compatible with Consul versions prior to 0.3. [GH-2259]
* The Raft peers information in `consul info` has changed format and includes information about the suffrage of a server, which will be used in future versions of Consul. [GH-2222]
* New [`translate_wan_addrs`](https://www.consul.io/docs/agent/options.html#translate_wan_addrs) behavior from [GH-2118] translates addresses in HTTP responses and could break clients that are expecting local addresses. A new `X-Consul-Translate-Addresses` header was added to allow clients to detect if translation is enabled for HTTP responses, and a "lan" tag was added to `TaggedAddresses` for clients that need the local address regardless of translation. [GH-2280]
* The behavior of the `peers.json` file is different in this version of Consul. This file won't normally be present and is used only during outage recovery. Be sure to read the updated [Outage Recovery Guide](https://www.consul.io/docs/guides/outage.html) for details. [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]
* **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 includes conditional updates based on obtaining locks, and all other key/value store operations. See the [Key/Value Store Endpoint](https://www.consul.io/docs/agent/http/kv.html#txn) for more details. [GH-2028]
* **Native ACL Replication:** Added a built-in 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] <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> Servers will now abort bootstrapping if they detect an existing cluster with configured Raft peers. This will help prevent safe but spurious leader elections when introducing new nodes with `bootstrap_expect` enabled into an existing cluster. [GH-2319] <br> Added new `consul operator` command, HTTP endpoint, and associated ACL to allow Consul operators to view and update the Raft configuration. This allows a stale server to be removed from the Raft peers 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, as well as the updated [Outage Recovery Guide](https://www.consul.io/docs/guides/outage.html). [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. This feature tunes itself automatically and requires no configuration. [GH-2101]
* **Prepared Query Near Parameter:** Prepared queries support baking in a new `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 instance is one is available, with a transparent fallback to the next best alternate instance otherwise. [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. This is useful for cleanup of health checks registered natively by applications, or in other situations where services may not always be cleanly shutdown. [GH-679]
* **WAN Address Translation Everywhere:** Extended the [`translate_wan_addrs`](https://www.consul.io/docs/agent/options.html#translate_wan_addrs) config option to also translate node addresses in HTTP responses, making it easy to use this feature from non-DNS clients. [GH-2118]
* **RPC Retries:** Consul will now retry RPC calls that result in "no leader" errors for up to 5 seconds. This allows agents to ride out leader elections with a delayed response vs. an error. [GH-2175]
* **Circonus Telemetry Support:** Added support for Circonus as a telemetry destination. [GH-2193]
* agent: Reap time for failed nodes is now configurable via new `reconnect_timeout` and `reconnect_timeout_wan` config options ([use with caution](https://www.consul.io/docs/agent/options.html#reconnect_timeout)). [GH-1935]
* agent: Joins based on a DNS lookup will use TCP and attempt to join with the full list of returned addresses. [GH-2101]
* agent: Consul will now refuse to start with a helpful message if the same UNIX socket is used for more than one listening endpoint. [GH-1910]
* agent: Removed an obsolete warning message when Consul starts on Windows. [GH-1920]
* agent: Defaults bind address to 127.0.0.1 when running in `-dev` mode. [GH-1878]
* agent: Added version information to the log when Consul starts up. [GH-1404]
* agent: Added timing metrics for HTTP requests in the form of `consul.http.<verb>.<path>`. [GH-2256]
* build: Updated all vendored dependencies. [GH-2258]
* build: Consul releases are now built with Go 1.6.3. [GH-2260]
* checks: Script checks now support an optional `timeout` parameter. [GH-1762]
* checks: HTTP health checks limit saved output to 4K to avoid performance issues. [GH-1952]
* cli: Added a `-stale` mode for watchers to allow them to pull data from any Consul server, not just the leader. [GH-2045] [GH-917]
* dns: Consul agents can now limit the number of UDP answers returned via the DNS interface. The default number of UDP answers is `3`, however by adjusting the `dns_config.udp_answer_limit` configuration parameter, it is now possible to limit the results down to `1`. This tunable provides environments where RFC3484 section 6, rule 9 is enforced with an important workaround in order to preserve the desired behavior of randomized DNS results. Most modern environments will not need to adjust this setting as this RFC was made obsolete by RFC 6724\. See the [agent options](https://www.consul.io/docs/agent/options.html#udp_answer_limit) documentation for additional details for when this should be used. [GH-1712]
* dns: Consul now compresses all DNS responses by default. This prevents issues when recursing records that were originally compressed, where Consul would sometimes generate an invalid, uncompressed response that was too large. [GH-2266]
* dns: Added a new `recursor_timeout` configuration option to set the timeout for Consul's internal DNS client that's used for recursing queries to upstream DNS servers. [GH-2321]
* dns: Added a new `-dns-port` command line option so this can be set without a config file. [GH-2263]
* ui: Added a new network tomography visualization to the UI. [GH-2046]
* agent: Fixed an issue where a health check's output never updates if the check status doesn't change after the Consul agent starts. [GH-1934]
* agent: External services can now be registered with ACL tokens. [GH-1738]
* agent: Fixed an issue where large events affecting many nodes could cause infinite intent rebroadcasts, leading to many log messages about intent queue overflows. [GH-1062]
* agent: Gossip encryption keys are now validated before being made persistent in the keyring, avoiding delayed feedback at runtime. [GH-1299]
* dns: Fixed an issue where DNS requests for SRV records could be incorrectly trimmed, resulting in an ADDITIONAL section that was out of sync with the ANSWER. [GH-1931]
* dns: Fixed two issues where DNS requests for SRV records on a prepared query that failed over would report the wrong domain and fail to translate addresses. [GH-2218] [GH-2220]
* server: Fixed a deadlock related to sorting the list of available datacenters by round trip time. [GH-2130]
* server: Fixed an issue with the state store's immutable radix tree that would prevent it from using cached modified objects during transactions, leading to extra copies and increased memory / GC pressure. [GH-2106]
* server: Upgraded Bolt DB to v1.2.1 to fix an issue on Windows where Consul would sometimes fail to start due to open user-mapped sections. [GH-2203]
