diff --git a/vendor/github.com/hashicorp/serf/CHANGELOG.md b/vendor/github.com/hashicorp/serf/CHANGELOG.md
new file mode 100644
index 000000000..d90ec957a
--- /dev/null
+++ b/vendor/github.com/hashicorp/serf/CHANGELOG.md
@@ -0,0 +1,423 @@
+## 0.8.2 (UNRELEASED)
+
+FEATURES:
+
+IMPROVEMENTS:
+
+* agent: Fixed a missing case where gossip would stop flowing to dead nodes for a short while. [GH-451]
+* agent: Uses the go-sockaddr library to look for private IP addresses, which prefers non-loopback private addresses over loopback ones when trying to automatically determine the advertise address. [GH-451]
+* agent: Properly seeds Go's random number generator using the seed library. [GH-451]
+* agent: Serf is now built with Go 1.10.x. [GH-520]
+* agent: Improved address comparison during conflict resolution. [GH-433]
+* agent: Updated memberlist to latest to pull several cleanups and fixes. [GH-491]
+* agent: Improved handling of leave intent messages to make sure they propagate and are processed correctly. [GH-510]
+* agent: Added CLI option to disable compression for debugging messages. [GH-529]
+* library: Moved close of shutdown channel until after network resorces are released. [GH-453]
+* library: Fixed several race conditions with QueryResponse [GH-460]
+* library: Made snapshot writing asyncronous and will less aggressive compaction on large clusters to avoid blocking message handler on disk IO [GH-524][GH-525]
+
+
+BUG FIXES:
+
+* agent: Added defenses against invalid network coordinates with NaN and Inf values. [GH-468]
+* agent: Fixed an issue on Windows where "wsarecv" errors were logged when clients accessed the RPC interface. [GH-479]
+* agent: Fixed an issue where calling the serf Stats function could result in a deadlock. [[Consul Issue 4011](https://github.com/hashicorp/consul/issues/4011)]
+
+## 0.8.1 (February 6, 2017)
+
+IMPROVEMENTS:
+
+ * agent: Added support for relaying query responses through N other nodes for redundancy. [GH-439]
+ * agent: Added the ability to tune the broadcast timeout, which might be necessary in very large clusters that experience very large, simultaneous changes to the cluster. [GH-412]
+ * agent: Added a checksum to UDP gossip messages to guard against packet corruption. [GH-432]
+ * agent: Added a short window where gossip will still flow to dead nodes so that they can more quickly refute. [GH-440]
+ * build: Serf now builds with Go 1.7.5. [GH-443]
+
+## 0.8 (September 14, 2016)
+
+FEATURES:
+
+ * **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 flapping in other, healthy nodes. This feature tunes itself automatically and requires no configuration. [GH-394]
+
+IMRPOVEMENTS:
+
+ * Modified management of intents to be per-node to avoid intent queue overflow errors in large clusters. [GH-402]
+ * Joins based on a DNS lookup will use TCP and attempt to join with the full list of returned addresses. [GH-387]
+ * Serf's Go dependencies are now vendored using govendor. [GH-383]
+ * Updated all of Serf's dependencies. [GH-387] [GH-401]
+ * Moved dist build into a Docker container. [GH-409]
+
+BUG FIXES:
+
+ * Updated memberlist to pull in a fix for leaking goroutines when performing TCP fallback pings. This affected users with frequent UDP connectivity problems. [GH-381]
+
+## 0.7 (December 21, 2015)
+
+FEATURES:
+
+ * Added new network tomography subsystem that computes network coordinates for
+   nodes in the cluster which can be used to estimate network round trip times
+   between any two nodes; exposes new `GetCoordinate` API as as well as a
+   a new `serf rtt` command to query RTT interactively
+
+IMPROVEMENTS:
+
+ * Added support for configuring query request size and query response size [GH-346]
+ * Syslog messages are now filtered by the configured log-level
+ * New `statsd_addr` for sending metrics via UDP to statsd
+ * Added support for sending telemetry to statsite
+ * `serf info` command now displays event handlers [GH-312]
+ * Added a `MemberLeave` message to the `EventCh` for a force-leave so higher-
+   level applications can handle the leave event
+ * Lots of documentation updates
+
+BUG FIXES:
+
+ * Fixed updating cached protocol version of a node when an update event
+   fires [GH-335]
+ * Fixed a bug where an empty remote state message would cause a crash in
+   `MergeRemoteState`
+
+## 0.6.4 (Febuary 12, 2015)
+
+IMPROVEMENTS:
+
+ * Added merge delegate to Serf library to support application
+   specific logic in cluster merging.
+ * `SERF_RPC_AUTH` environment variable can be used in place of CLI flags.
+ * Display if encryption is enabled in Serf stats
+ * Improved `join` behavior when using DNS resolution
+
+BUG FIXES:
+
+ * Fixed snapshot file compaction on Windows
+ * Fixed device binding on Windows
+ * Fixed bug with empty keyring
+ * Fixed parsing of ports in some cases
+ * Fixing stability issues under high churn
+
+MISC:
+
+* Increased user event size limit to 512 bytes (previously 256)
+
+## 0.6.3 (July 10, 2014)
+
+IMPROVEMENTS:
+
+* Added `statsite_addr` configuration to stream to statsite
+
+BUG FIXES:
+
+* Fixed issue with mDNS flooding when using IPv4 and IPv6
+* Fixed issue with reloading event handlers
+
+MISC:
+
+* Improved failure detection reliability under load
+* Reduced fsync() use in snapshot file
+* Improved snapshot file performance
+* Additional logging to help debug flapping
+
+## 0.6.2 (June 16, 2014)
+
+IMPROVEMENTS:
+
+* Added `syslog_facility` configuration to set facility
+
+BUG FIXES:
+
+* Fixed memory leak in in-memory stats system
+* Fixed issue that would cause syslog to deadlock
+
+MISC:
+
+* Fixed missing prefixes on some log messages
+* Docs fixes
+
+## 0.6.1 (May 29, 2014)
+
+BUG FIXES:
+
+* On Windows, a "failed to decode request header" error will no
+  longer be shown on every RPC request.
+
+* Avoiding holding a lock which can cause monitor/stream commands to
+  fail when an event handler is blocking
+
+* Fixing conflict response decoding errors
+
+IMPROVEMENTS:
+
+* Improved agent CLI usage documentation
+
+* Warn if an event handler is slow, potentially blocking other events
+
+## 0.6.0 (May 8, 2014)
+
+FEATURES:
+
+ * Support for key rotation when using encryption. This adds a new
+ `serf keys` command, and a `-keyring-file` configuration. Thanks
+ to @ryanuber.
+
+ * New `-tags-file` can be specified to persist changes to tags made
+ via the RPC interface. Thanks to @ryanuber.
+
+ * New `serf info` command to provide operator debugging information,
+ and to get info about the local node.
+
+ * Adding `-retry-join` flag to agent which enables retrying the join
+ until success or `-retry-max` attempts have been made.
+
+IMPROVEMENTS:
+
+ * New `-rejoin` flag can be used along with a snapshot file to
+ automatically rejoin a cluster.
+
+ * Agent uses circular buffer to invoke handlers, guards against unbounded
+ output lengths.
+
+ * Adding support for logging to syslog
+
+ * The SERF_RPC_ADDR environment variable can be used instead of the
+ `-rpc-addr` flags. Thanks to @lalyos [GH-209].
+
+ * `serf query` can now output the results in a JSON format.
+
+ * Unknown configuration directives generate an error [GH-186].
+ Thanks to @vincentbernat.
+
+BUG FIXES:
+
+ * Fixing environmental variables with invalid characters. [GH-200].
+ Thanks to @arschles.
+
+ * Fixing issue with tag changes with hard restart before
+   failure detection.
+
+ * Fixing issue with reconnect when using dynamic ports.
+
+MISC:
+
+ * Improved logging of various error messages
+
+ * Improved debian packaging. Thanks to @vincentbernat.
+
+## 0.5.0 (March 12, 2014)
+
+FEATURES:
+
+ * New `query` command provides a request/response mechanism to do realtime
+ queries across the cluster. [GH-139]
+
+ * Automatic conflict resolution. Serf will detect name conflicts, and use an
+ internal query to determine which node is in the minority and perform a shutdown.
+ [GH-167] [GH-119]
+
+ * New `reachability` command can be used to help diagnose network and configuration
+ issues.
+
+ * Added `member-reap` event to get notified of when Serf removes a failed or left
+ node from the cluster. The reap interval is controlled by `reconnect_timeout` and
+ `tombstone_timeout` respectively. [GH-172]
+
+IMPROVEMENTS:
+
+ * New Recipes section on the site to share Serf tips. Thanks to @ryanuber. [GH-177]
+
+ * `members` command has new `-name` filter flag. Thanks to @ryanuber [GH-164]
+
+ * New RPC command "members-filtered" to move filtering logic to the agent.
+ Thanks to @ryanuber. [GH-149]
+
+ * `reconnect_interval` and `reconnect_timeout` can be provided to configure
+ agent behavior for attempting to reconnect to failed nodes. [GH-155]
+
+ * `tombstone_interval` can be provided to configure the reap time for nodes
+ that have gracefully left. [GH_172]
+
+ * Agent can be provided `rpc_auth` config to require that RPC is authenticated.
+ All commands can take a `-rpc-auth` flag now. [GH-148]
+
+BUG FIXES:
+
+ * Fixed config folder in Upstart script. Thanks to @llchen223. [GH-174]
+
+ * Event handlers are correctly invoked when BusyBox is the shell. [GH-156]
+
+ * Event handlers were not being invoked with the correct SERF_TAG_* values
+ if tags were changed using the `tags` command. [GH-169]
+
+MISC:
+
+  * Support for protocol version 1 (Serf 0.2) has been removed. Serf 0.5 cannot
+  join a cluster that has members running version 0.2.
+
+## 0.4.5 (February 25, 2014)
+
+FEATURES:
+
+ * New `tags` command is available to dynamically update tags without
+ reloading the agent. Thanks to @ryanuber. [GH-126]
+
+IMPROVEMENTS:
+
+ * Upstart receipe logs output thanks to @breerly [GH-128]
+
+ * `members` can filter on any tag thanks to @hmrm [GH-124]
+
+ * Added vagrant demo to make a simple cluster
+
+ * `members` now columnizes the output thanks to @ryanuber [GH-138]
+
+ * Agent passes its own environment variables through thanks to @mcroydon [GH-142]
+
+ * `-iface` flag can be used to bind to interfaces [GH-145]
+
+BUG FIXES:
+
+ * -config-dir would cause protocol to be set to 0 if there are no
+ configuration files in the directory [GH-129]
+
+ * Event handlers can filter on 'member-update'
+
+ * User event handler appends new line, this was being omitted
+
+## 0.4.1 (February 3, 2014)
+
+IMPROVEMENTS:
+
+ * mDNS service uses the advertise address instead of bind address
+
+## 0.4.0 (January 31, 2014)
+
+FEATURES:
+
+ * Static `role` has been replaced with dynamic tags. Each agent can have
+ multiple key/value tags associated using `-tag`. Tags can be updated using
+ a SIGHUP and are advertised to the cluster, causing the `member-update` event
+ to be triggered. [GH-111] [GH-98]
+
+ * Serf can automatically discover peers uing mDNS when provided the `-discover`
+ flag. In network environments supporting multicast, no explicit join is needed
+ to find peers. [GH-53]
+
+ * Serf collects telemetry information and simple runtime profiling. Stats can
+ be dumped to stderr by sending a `USR1` signal to Serf. Windows users must use
+ the `BREAK` signal instead. [GH-103]
+
+ * `advertise` flag can be used to set an advertise address different
+ from the bind address. Used for NAT traversal. Thanks to @benagricola [GH-93]
+
+ * `members` command now takes `-format` flag to specify either text or JSON
+ output. Fixed by @ryanuber [GH-97]
+
+IMPROVEMENTS:
+
+ * User payload always appends a newline when invoking a shell script
+
+ * Severity of "Potential blocking operation" reduced to debug to prevent
+ spurious messages on slow or busy machines.
+
+BUG FIXES:
+
+ * If an agent is restarted with the same bind address but new name, it
+ will not respond to the old name, causing the old name to enter the
+ `failed` state, instead of having duplicate entries in the `alive` state.
+
+ * `leave_on_interrupt` set to false when not specified, if
+ any config file is provided. This flag is deprecated for
+ `skip_leave_on_interrupt` instead. [GH-94]
+
+MISC:
+
+  * `-role` configuration has been deprecated in favor of `-tag role=foo`.
+  The flag is still supported but will generate warnings.
+
+  * Support for protocol version 0 (Serf 0.1) has been removed. Serf 0.4 cannot
+  join a cluster that has members running version 0.1.
+
+## 0.3.0 (December 5, 2013)
+
+FEATURES:
+
+  * Dynamic port support, cluster wide consistent config not necessary
+  * Snapshots to automaticaly rejoin cluster after failure and prevent replays [GH-84] [GH-71]
+  * Adding `profile` config to agent, to support WAN, LAN, and Local modes
+  * MsgPack over TCP RPC protocol which can be used to control Serf, send events, and
+  receive events with low latency.
+  * New `leave` CLI command and RPC endpoint to control graceful leaves
+  * Signal handling is controlable, graceful leave behavior on SIGINT/SIGTERM
+  can be specified
+  * SIGHUP can be used to reload configuration
+
+IMPROVEMENTS:
+
+  * Event handler provides lamport time of user events via SERF_USER_LTIME [GH-68]
+  * Memberlist encryption overhead has been reduced
+  * Filter output of `members` using regular expressions on role and status
+  * `replay_on_join` parameter to control replay with `start_join`
+  * `monitor` works even if the client is behind a NAT
+  * Serf generates warning if binding to public IP without encryption
+
+BUG FIXES:
+
+  * Prevent unbounded transmit queues [GH-78]
+  * IPv6 addresses can be bound to [GH-72]
+  * Serf join won't hang on a slow/dead node [GH-70]
+  * Serf Leave won't block Shutdown [GH-1]
+
+## 0.2.1 (November 6, 2013)
+
+BUG FIXES:
+
+  * Member role and address not updated on re-join [GH-58]
+
+## 0.2.0 (November 1, 2013)
+
+FEATURES:
+
+  * Protocol versioning features so that upgrades can be done safely.
+    See the website on upgrading Serf for more info.
+  * Can now configure Serf with files or directories of files by specifying
+    the `-config-file` and/or `-config-dir` flags to the agent.
+  * New command `serf force-leave` can be used to force a "failed" node
+    to the "left" state.
+  * Serf now supports message encryption and verification so that it can
+    be used on untrusted networks [GH-25]
+  * The `-join` flag on `serf agent` can be used to join a cluster when
+    starting an agent. [GH-42]
+
+IMPROVEMENTS:
+
+  * Random staggering of periodic routines to avoid cluster-wide
+    synchronization
+  * Push/Pull timer automatically slows down as cluster grows to avoid
+    congestion
+  * Messages are compressed to reduce bandwidth utilization
+  * `serf members` now provides node roles in output
+  * Joining a cluster will no longer replay all the old events by default,
+    but it can using the `-replay` flag.
+  * User events are coalesced by default, meaning duplicate events (by name)
+    within a short period of time are merged. [GH-8]
+
+BUG FIXES:
+
+  * Event handlers work on Windows now by executing commands through
+    `cmd /C` [GH-37]
+  * Nodes that previously left and rejoin won't get stuck in 'leaving' state.
+    [GH-18]
+  * Fixing alignment issues on i386 for atomic operations [GH-20]
+  * "trace" log level works [GH-31]
+
+## 0.1.1 (October 23, 2013)
+
+BUG FIXES:
+
+  * Default node name is outputted when "serf agent" is called with no args.
+  * Remove node from reap list after join so a fast re-join doesn't lose the
+    member.
+
+## 0.1.0 (October 23, 2013)
+
+* Initial release
diff --git a/vendor/github.com/hashicorp/serf/GNUmakefile b/vendor/github.com/hashicorp/serf/GNUmakefile
new file mode 100644
index 000000000..a938fd839
--- /dev/null
+++ b/vendor/github.com/hashicorp/serf/GNUmakefile
@@ -0,0 +1,64 @@
+GOTOOLS = github.com/mitchellh/gox github.com/kardianos/govendor
+VERSION = $(shell awk -F\" '/^const Version/ { print $$2; exit }' cmd/serf/version.go)
+GITSHA:=$(shell git rev-parse HEAD)
+GITBRANCH:=$(shell git symbolic-ref --short HEAD 2>/dev/null)
+
+default:: test
+
+# bin generates the releasable binaries
+bin:: tools
+	@sh -c "'$(CURDIR)/scripts/build.sh'"
+
+# cov generates the coverage output
+cov:: tools
+	gocov test ./... | gocov-html > /tmp/coverage.html
+	open /tmp/coverage.html
+
+# dev creates binaries for testing locally - these are put into ./bin and
+# $GOPATH
+dev::
+	@SERF_DEV=1 sh -c "'$(CURDIR)/scripts/build.sh'"
+
+# dist creates the binaries for distibution
+dist::
+	@sh -c "'$(CURDIR)/scripts/dist.sh' $(VERSION)"
+
+get-tools::
+	go get -u -v $(GOTOOLS)
+
+# subnet sets up the require subnet for testing on darwin (osx) - you must run
+# this before running other tests if you are on osx.
+subnet::
+	@sh -c "'$(CURDIR)/scripts/setup_test_subnet.sh'"
+
+# test runs the test suite
+test:: subnet tools
+	@go list ./... | grep -v -E '^github.com/hashicorp/serf/(vendor|cmd/serf/vendor)' | xargs -n1 go test $(TESTARGS)
+
+# testrace runs the race checker
+testrace:: subnet
+	go test -race `govendor list -no-status +local` $(TESTARGS)
+
+tools::
+	@which gox 2>/dev/null ; if [ $$? -eq 1 ]; then \
+		$(MAKE) get-tools; \
+	fi
+
+# updatedeps installs all the dependencies needed to test, build, and run
+updatedeps:: tools
+	govendor list -no-status +vendor | xargs -n1 go get -u
+	govendor update +vendor
+
+vet:: tools
+	@echo "--> Running go tool vet $(VETARGS) ."
+	@govendor list -no-status +local \
+		| cut -d '/' -f 4- \
+		| xargs -n1 \
+			go tool vet $(VETARGS) ;\
+	if [ $$? -ne 0 ]; then \
+		echo ""; \
+		echo "Vet found suspicious constructs. Please check the reported constructs"; \
+		echo "and fix them if necessary before submitting the code for reviewal."; \
+	fi
+
+.PHONY: default bin cov dev dist get-tools subnet test testrace tools updatedeps vet
diff --git a/vendor/github.com/hashicorp/serf/README.md b/vendor/github.com/hashicorp/serf/README.md
new file mode 100644
index 000000000..36e5b77fe
--- /dev/null
+++ b/vendor/github.com/hashicorp/serf/README.md
@@ -0,0 +1,121 @@
+# Serf [![Build Status](https://travis-ci.org/hashicorp/serf.png)](https://travis-ci.org/hashicorp/serf) [![Join the chat at https://gitter.im/hashicorp-serf/Lobby](https://badges.gitter.im/hashicorp-serf/Lobby.svg)](https://gitter.im/hashicorp-serf/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
+* Website: https://www.serf.io
+* Chat: [Gitter](https://gitter.im/hashicorp-serf/Lobby)
+* Mailing list: [Google Groups](https://groups.google.com/group/serfdom/)
+
+Serf is a decentralized solution for service discovery and orchestration
+that is lightweight, highly available, and fault tolerant.
+
+Serf runs on Linux, Mac OS X, and Windows. An efficient and lightweight gossip
+protocol is used to communicate with other nodes. Serf can detect node failures
+and notify the rest of the cluster. An event system is built on top of
+Serf, letting you use Serf's gossip protocol to propagate events such
+as deploys, configuration changes, etc. Serf is completely masterless
+with no single point of failure.
+
+Here are some example use cases of Serf, though there are many others:
+
+* Discovering web servers and automatically adding them to a load balancer
+* Organizing many memcached or redis nodes into a cluster, perhaps with
+  something like [twemproxy](https://github.com/twitter/twemproxy) or
+  maybe just configuring an application with the address of all the
+  nodes
+* Triggering web deploys using the event system built on top of Serf
+* Propagating changes to configuration to relevant nodes.
+* Updating DNS records to reflect cluster changes as they occur.
+* Much, much more.
+
+## Quick Start
+
+First, [download a pre-built Serf binary](https://www.serf.io/downloads.html)
+for your operating system, [compile Serf yourself](#developing-serf), or install
+using `go get -u github.com/hashicorp/serf/cmd/serf`.
+
+Next, let's start a couple Serf agents. Agents run until they're told to quit
+and handle the communication of maintenance tasks of Serf. In a real Serf
+setup, each node in your system will run one or more Serf agents (it can
+run multiple agents if you're running multiple cluster types. e.g. web
+servers vs. memcached servers).
+
+Start each Serf agent in a separate terminal session so that we can see
+the output of each. Start the first agent:
+
+```
+$ serf agent -node=foo -bind=127.0.0.1:5000 -rpc-addr=127.0.0.1:7373
+...
+```
+
+Start the second agent in another terminal session (while the first is still
+running):
+
+```
+$ serf agent -node=bar -bind=127.0.0.1:5001 -rpc-addr=127.0.0.1:7374
+...
+```
+
+At this point two Serf agents are running independently but are still
+unaware of each other. Let's now tell the first agent to join an existing
+cluster (the second agent). When starting a Serf agent, you must join an
+existing cluster by specifying at least one existing member. After this,
+Serf gossips and the remainder of the cluster becomes aware of the join.
+Run the following commands in a third terminal session.
+
+```
+$ serf join 127.0.0.1:5001
+...
+```
+
+If you're watching your terminals, you should see both Serf agents
+become aware of the join. You can prove it by running `serf members`
+to see the members of the Serf cluster:
+
+```
+$ serf members
+foo    127.0.0.1:5000    alive
+bar    127.0.0.1:5001    alive
+...
+```
+
+At this point, you can ctrl-C or force kill either Serf agent, and they'll
+update their membership lists appropriately. If you ctrl-C a Serf agent,
+it will gracefully leave by notifying the cluster of its intent to leave.
+If you force kill an agent, it will eventually (usually within seconds)
+be detected by another member of the cluster which will notify the
+cluster of the node failure.
+
+## Documentation
+
+Full, comprehensive documentation is viewable on the Serf website:
+
+https://www.serf.io/docs
+
+## Developing Serf
+
+If you wish to work on Serf itself, you'll first need [Go](https://golang.org)
+installed (version 1.8+ is _required_). Make sure you have Go properly
+[installed](https://golang.org/doc/install),
+including setting up your [GOPATH](https://golang.org/doc/code.html#GOPATH).
+
+Next, clone this repository into `$GOPATH/src/github.com/hashicorp/serf` and
+then just type `make`. In a few moments, you'll have a working `serf` executable:
+
+```
+$ make
+...
+$ bin/serf
+...
+```
+
+*NOTE: `make` will also place a copy of the executable under `$GOPATH/bin/`*
+
+Serf is first and foremost a library with a command-line interface, `serf`. The
+Serf library is independent of the command line agent, `serf`.  The `serf`
+binary is located under `cmd/serf` and can be installed stand alone by issuing
+the command `go get -u github.com/hashicorp/serf/cmd/serf`.  Applications using
+the Serf library should only need to include `github.com/hashicorp/serf`.
+
+Tests can be run by typing `make test`.
+
+If you make any changes to the code, run `make format` in order to automatically
+format the code according to Go [standards](https://golang.org/doc/effective_go.html#formatting).
diff --git a/vendor/github.com/hashicorp/serf/serf/broadcast.go b/vendor/github.com/hashicorp/serf/serf/broadcast.go
index d20728f3f..751cf184b 100644
--- a/vendor/github.com/hashicorp/serf/serf/broadcast.go
+++ b/vendor/github.com/hashicorp/serf/serf/broadcast.go
@@ -16,6 +16,9 @@ func (b *broadcast) Invalidates(other memberlist.Broadcast) bool {
 	return false
 }
 
+// implements memberlist.UniqueBroadcast
+func (b *broadcast) UniqueBroadcast() {}
+
 func (b *broadcast) Message() []byte {
 	return b.msg
 }
diff --git a/vendor/github.com/hashicorp/serf/serf/delegate.go b/vendor/github.com/hashicorp/serf/serf/delegate.go
index 871b72e50..567c7fe4a 100644
--- a/vendor/github.com/hashicorp/serf/serf/delegate.go
+++ b/vendor/github.com/hashicorp/serf/serf/delegate.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/armon/go-metrics"
 	"github.com/hashicorp/go-msgpack/codec"
+	"github.com/hashicorp/memberlist"
 )
 
 // delegate is the memberlist.Delegate implementation that Serf uses.
@@ -13,6 +14,8 @@ type delegate struct {
 	serf *Serf
 }
 
+var _ memberlist.Delegate = &delegate{}
+
 func (d *delegate) NodeMeta(limit int) []byte {
 	roleBytes := d.serf.encodeTags(d.serf.config.Tags)
 	if len(roleBytes) > limit {
diff --git a/vendor/github.com/hashicorp/serf/serf/keymanager.go b/vendor/github.com/hashicorp/serf/serf/keymanager.go
index fd53182fc..bea038cd2 100644
--- a/vendor/github.com/hashicorp/serf/serf/keymanager.go
+++ b/vendor/github.com/hashicorp/serf/serf/keymanager.go
@@ -189,4 +189,4 @@ func (k *KeyManager) ListKeysWithOptions(opts *KeyRequestOptions) (*KeyResponse,
 	defer k.l.RUnlock()
 
 	return k.handleKeyRequest("", listKeysQuery, opts)
-}
\ No newline at end of file
+}
diff --git a/vendor/github.com/hashicorp/serf/serf/serf.go b/vendor/github.com/hashicorp/serf/serf/serf.go
index 548807a9d..bb6c22fe7 100644
--- a/vendor/github.com/hashicorp/serf/serf/serf.go
+++ b/vendor/github.com/hashicorp/serf/serf/serf.go
@@ -1331,7 +1331,7 @@ func (s *Serf) handleQueryResponse(resp *messageQueryResponse) {
 
 // handleNodeConflict is invoked when a join detects a conflict over a name.
 // This means two different nodes (IP/Port) are claiming the same name. Memberlist
-// will reject the "new" node mapping, but we can still be notified
+// will reject the "new" node mapping, but we can still be notified.
 func (s *Serf) handleNodeConflict(existing, other *memberlist.Node) {
 	// Log a basic warning if the node is not us...
 	if existing.Name != s.config.NodeName {
diff --git a/vendor/github.com/hashicorp/serf/serf/snapshot.go b/vendor/github.com/hashicorp/serf/serf/snapshot.go
index 9f5adebe6..d2eda0ea2 100644
--- a/vendor/github.com/hashicorp/serf/serf/snapshot.go
+++ b/vendor/github.com/hashicorp/serf/serf/snapshot.go
@@ -25,10 +25,34 @@ nodes to re-join, as well as restore our clock values to avoid replaying
 old events.
 */
 
-const flushInterval = 500 * time.Millisecond
-const clockUpdateInterval = 500 * time.Millisecond
-const tmpExt = ".compact"
-const snapshotErrorRecoveryInterval = 30 * time.Second
+const (
+	// flushInterval is how often we force a flush of the snapshot file
+	flushInterval = 500 * time.Millisecond
+
+	// clockUpdateInterval is how often we fetch the current lamport time of the cluster and write to the snapshot file
+	clockUpdateInterval = 500 * time.Millisecond
+
+	// tmpExt is the extention we use for the temporary file during compaction
+	tmpExt = ".compact"
+
+	// snapshotErrorRecoveryInterval is how often we attempt to recover from
+	// errors writing to the snapshot file.
+	snapshotErrorRecoveryInterval = 30 * time.Second
+
+	// eventChSize is the size of the event buffers between Serf and the
+	// consuming application. If this is exhausted we will block Serf and Memberlist.
+	eventChSize = 2048
+
+	// shutdownFlushTimeout is the time limit to write pending events to the snapshot during a shutdown
+	shutdownFlushTimeout = 250 * time.Millisecond
+
+	// snapshotBytesPerNode is an estimated bytes per node to snapshot
+	snapshotBytesPerNode = 128
+
+	// snapshotCompactionThreshold is the threshold we apply to
+	// the snapshot size estimate (nodes * bytes per node) before compacting.
+	snapshotCompactionThreshold = 2
+)
 
 // Snapshotter is responsible for ingesting events and persisting
 // them to disk, and providing a recovery mechanism at start time.
@@ -38,6 +62,7 @@ type Snapshotter struct {
 	fh                      *os.File
 	buffered                *bufio.Writer
 	inCh                    <-chan Event
+	streamCh                chan Event
 	lastFlush               time.Time
 	lastClock               LamportTime
 	lastEventClock          LamportTime
@@ -45,7 +70,7 @@ type Snapshotter struct {
 	leaveCh                 chan struct{}
 	leaving                 bool
 	logger                  *log.Logger
-	maxSize                 int64
+	minCompactSize          int64
 	path                    string
 	offset                  int64
 	outCh                   chan<- Event
@@ -72,13 +97,14 @@ func (p PreviousNode) String() string {
 // Setting rejoinAfterLeave makes leave not clear the state, and can be used
 // if you intend to rejoin the same cluster after a leave.
 func NewSnapshotter(path string,
-	maxSize int,
+	minCompactSize int,
 	rejoinAfterLeave bool,
 	logger *log.Logger,
 	clock *LamportClock,
 	outCh chan<- Event,
 	shutdownCh <-chan struct{}) (chan<- Event, *Snapshotter, error) {
-	inCh := make(chan Event, 1024)
+	inCh := make(chan Event, eventChSize)
+	streamCh := make(chan Event, eventChSize)
 
 	// Try to open the file
 	fh, err := os.OpenFile(path, os.O_RDWR|os.O_APPEND|os.O_CREATE, 0644)
@@ -101,12 +127,13 @@ func NewSnapshotter(path string,
 		fh:               fh,
 		buffered:         bufio.NewWriter(fh),
 		inCh:             inCh,
+		streamCh:         streamCh,
 		lastClock:        0,
 		lastEventClock:   0,
 		lastQueryClock:   0,
 		leaveCh:          make(chan struct{}),
 		logger:           logger,
-		maxSize:          int64(maxSize),
+		minCompactSize:   int64(minCompactSize),
 		path:             path,
 		offset:           offset,
 		outCh:            outCh,
@@ -122,6 +149,7 @@ func NewSnapshotter(path string,
 	}
 
 	// Start handling new commands
+	go snap.teeStream()
 	go snap.stream()
 	return inCh, snap, nil
 }
@@ -171,11 +199,69 @@ func (s *Snapshotter) Leave() {
 	}
 }
 
+// teeStream is a long running routine that is used to copy events
+// to the output channel and the internal event handler.
+func (s *Snapshotter) teeStream() {
+	flushEvent := func(e Event) {
+		// Forward to the internal stream, do not block
+		select {
+		case s.streamCh <- e:
+		default:
+		}
+
+		// Forward the event immediately, do not block
+		if s.outCh != nil {
+			select {
+			case s.outCh <- e:
+			default:
+			}
+		}
+	}
+
+OUTER:
+	for {
+		select {
+		case e := <-s.inCh:
+			flushEvent(e)
+		case <-s.shutdownCh:
+			break OUTER
+		}
+	}
+
+	// Drain any remaining events before exiting
+	for {
+		select {
+		case e := <-s.inCh:
+			flushEvent(e)
+		default:
+			return
+		}
+	}
+}
+
 // stream is a long running routine that is used to handle events
 func (s *Snapshotter) stream() {
 	clockTicker := time.NewTicker(clockUpdateInterval)
 	defer clockTicker.Stop()
 
+	// flushEvent is used to handle writing out an event
+	flushEvent := func(e Event) {
+		// Stop recording events after a leave is issued
+		if s.leaving {
+			return
+		}
+		switch typed := e.(type) {
+		case MemberEvent:
+			s.processMemberEvent(typed)
+		case UserEvent:
+			s.processUserEvent(typed)
+		case *Query:
+			s.processQuery(typed)
+		default:
+			s.logger.Printf("[ERR] serf: Unknown event to snapshot: %#v", e)
+		}
+	}
+
 	for {
 		select {
 		case <-s.leaveCh:
@@ -193,31 +279,32 @@ func (s *Snapshotter) stream() {
 				s.logger.Printf("[ERR] serf: failed to sync leave to snapshot: %v", err)
 			}
 
-		case e := <-s.inCh:
-			// Forward the event immediately
-			if s.outCh != nil {
-				s.outCh <- e
-			}
-
-			// Stop recording events after a leave is issued
-			if s.leaving {
-				continue
-			}
-			switch typed := e.(type) {
-			case MemberEvent:
-				s.processMemberEvent(typed)
-			case UserEvent:
-				s.processUserEvent(typed)
-			case *Query:
-				s.processQuery(typed)
-			default:
-				s.logger.Printf("[ERR] serf: Unknown event to snapshot: %#v", e)
-			}
+		case e := <-s.streamCh:
+			flushEvent(e)
 
 		case <-clockTicker.C:
 			s.updateClock()
 
 		case <-s.shutdownCh:
+			// Setup a timeout
+			flushTimeout := time.After(shutdownFlushTimeout)
+
+			// Snapshot the clock
+			s.updateClock()
+
+			// Clear out the buffers
+		FLUSH:
+			for {
+				select {
+				case e := <-s.streamCh:
+					flushEvent(e)
+				case <-flushTimeout:
+					break FLUSH
+				default:
+					break FLUSH
+				}
+			}
+
 			if err := s.buffered.Flush(); err != nil {
 				s.logger.Printf("[ERR] serf: failed to flush snapshot: %v", err)
 			}
@@ -321,12 +408,25 @@ func (s *Snapshotter) appendLine(l string) error {
 
 	// Check if a compaction is necessary
 	s.offset += int64(n)
-	if s.offset > s.maxSize {
+	if s.offset > s.snapshotMaxSize() {
 		return s.compact()
 	}
 	return nil
 }
 
+// snapshotMaxSize computes the maximum size and is used to force periodic compaction.
+func (s *Snapshotter) snapshotMaxSize() int64 {
+	nodes := int64(len(s.aliveNodes))
+	estSize := nodes * snapshotBytesPerNode
+	threshold := estSize * snapshotCompactionThreshold
+
+	// Apply a minimum threshold to avoid frequent compaction
+	if threshold < s.minCompactSize {
+		threshold = s.minCompactSize
+	}
+	return threshold
+}
+
 // Compact is used to compact the snapshot once it is too large
 func (s *Snapshotter) compact() error {
 	defer metrics.MeasureSince([]string{"serf", "snapshot", "compact"}, time.Now())
diff --git a/vendor/vendor.json b/vendor/vendor.json
index c7aa93b74..5b9b98392 100644
--- a/vendor/vendor.json
+++ b/vendor/vendor.json
@@ -221,8 +221,9 @@
 		{"path":"github.com/hashicorp/net-rpc-msgpackrpc","checksumSHA1":"qnlqWJYV81ENr61SZk9c65R1mDo=","revision":"a14192a58a694c123d8fe5481d4a4727d6ae82f3"},
 		{"path":"github.com/hashicorp/raft","checksumSHA1":"ujL3Sc5iqc28/En2ndmc2R7oUQM=","revision":"9c733b2b7f53115c5ef261a90ce912a1bb49e970","revisionTime":"2019-01-04T13:37:20Z"},
 		{"path":"github.com/hashicorp/raft-boltdb","checksumSHA1":"QAxukkv54/iIvLfsUP6IK4R0m/A=","revision":"d1e82c1ec3f15ee991f7cc7ffd5b67ff6f5bbaee","revisionTime":"2015-02-01T20:08:39Z"},
-		{"path":"github.com/hashicorp/serf/coordinate","checksumSHA1":"0PeWsO2aI+2PgVYlYlDPKfzCLEQ=","revision":"80ab48778deee28e4ea2dc4ef1ebb2c5f4063996","revisionTime":"2018-05-07T23:19:28Z"},
-		{"path":"github.com/hashicorp/serf/serf","checksumSHA1":"QrT+nzyXsD/MmhTjjhcPdnALZ1I=","revision":"80ab48778deee28e4ea2dc4ef1ebb2c5f4063996","revisionTime":"2018-05-07T23:19:28Z"},
+		{"path":"github.com/hashicorp/serf","checksumSHA1":"9omt7lEuhBNSdgT32ThEzXn/aTU=","revision":"c7f3bc96b40972e67dfbe007c1fa825cf59ac8c2","revisionTime":"2019-01-04T15:39:47Z"},
+		{"path":"github.com/hashicorp/serf/coordinate","checksumSHA1":"0PeWsO2aI+2PgVYlYlDPKfzCLEQ=","revision":"c7f3bc96b40972e67dfbe007c1fa825cf59ac8c2","revisionTime":"2019-01-04T15:39:47Z"},
+		{"path":"github.com/hashicorp/serf/serf","checksumSHA1":"siLn7zwVHQk070rpd99BTktGfTs=","revision":"c7f3bc96b40972e67dfbe007c1fa825cf59ac8c2","revisionTime":"2019-01-04T15:39:47Z"},
 		{"path":"github.com/hashicorp/vault/api","checksumSHA1":"DP7dd8OErZVF0q+XfPo0RGkDcLk=","revision":"6e8d91a59c34bd9f323397c30be9651422295c65","revisionTime":"2018-09-19T17:09:49Z"},
 		{"path":"github.com/hashicorp/vault/helper/compressutil","checksumSHA1":"bSdPFOHaTwEvM4PIvn0PZfn75jM=","revision":"8575f8fedcf8f5a6eb2b4701cb527b99574b5286","revisionTime":"2018-09-06T17:45:45Z"},
 		{"path":"github.com/hashicorp/vault/helper/consts","checksumSHA1":"QNGGvSYtwk6VCkj4laZPjM2301E=","revision":"8575f8fedcf8f5a6eb2b4701cb527b99574b5286","revisionTime":"2018-09-06T17:45:45Z"},