mirror of https://github.com/status-im/consul.git
67 lines
3.8 KiB
Plaintext
67 lines
3.8 KiB
Plaintext
---
|
|
layout: intro
|
|
page_title: Consul vs. SmartStack
|
|
sidebar_title: 'SmartStack'
|
|
sidebar_current: vs-other-smartstack
|
|
description: >-
|
|
SmartStack is a tool which tackles the service discovery problem. It has a
|
|
rather unique architecture and has 4 major components: ZooKeeper, HAProxy,
|
|
Synapse, and Nerve. The ZooKeeper servers are responsible for storing cluster
|
|
state in a consistent and fault-tolerant manner. Each node in the SmartStack
|
|
cluster then runs both Nerves and Synapses. The Nerve is responsible for
|
|
running health checks against a service and registering with the ZooKeeper
|
|
servers. Synapse queries ZooKeeper for service providers and dynamically
|
|
configures HAProxy. Finally, clients speak to HAProxy, which does health
|
|
checking and load balancing across service providers.
|
|
---
|
|
|
|
# Consul vs. SmartStack
|
|
|
|
SmartStack is a tool which tackles the service discovery problem. It has a rather
|
|
unique architecture and has 4 major components: ZooKeeper, HAProxy, Synapse, and Nerve.
|
|
The ZooKeeper servers are responsible for storing cluster state in a consistent and
|
|
fault-tolerant manner. Each node in the SmartStack cluster then runs both Nerves and
|
|
Synapses. The Nerve is responsible for running health checks against a service and
|
|
registering with the ZooKeeper servers. Synapse queries ZooKeeper for service providers
|
|
and dynamically configures HAProxy. Finally, clients speak to HAProxy, which does
|
|
health checking and load balancing across service providers.
|
|
|
|
Consul is a much simpler and more contained system as it does not rely on any external
|
|
components. Consul uses an integrated [gossip protocol](/docs/internals/gossip.html)
|
|
to track all nodes and perform server discovery. This means that server addresses
|
|
do not need to be hardcoded and updated fleet-wide on changes, unlike SmartStack.
|
|
|
|
Service registration for both Consul and Nerves can be done with a configuration file,
|
|
but Consul also supports an API to dynamically change the services and checks that are
|
|
in use.
|
|
|
|
For discovery, SmartStack clients must use HAProxy, requiring that Synapse be
|
|
configured with all desired endpoints in advance. Consul clients instead
|
|
use the DNS or HTTP APIs without any configuration needed in advance. Consul
|
|
also provides a "tag" abstraction, allowing services to provide metadata such
|
|
as versions, primary/secondary designations, or opaque labels that can be used for
|
|
filtering. Clients can then request only the service providers which have
|
|
matching tags.
|
|
|
|
The systems also differ in how they manage health checking. Nerve performs local health
|
|
checks in a manner similar to Consul agents. However, Consul maintains separate catalog
|
|
and health systems. This division allows operators to see which nodes are in each service
|
|
pool and provides insight into failing checks. Nerve simply deregisters nodes on failed
|
|
checks, providing limited operational insight. Synapse also configures HAProxy to perform
|
|
additional health checks. This causes all potential service clients to check for
|
|
liveness. With large fleets, this N-to-N style health checking may be prohibitively
|
|
expensive.
|
|
|
|
Consul generally provides a much richer health checking system. Consul supports
|
|
Nagios-style plugins, enabling a vast catalog of checks to be used. Consul allows for
|
|
both service- and host-level checks. There is even a "dead man's switch" check that allows
|
|
applications to easily integrate custom health checks. Finally, all of this is integrated
|
|
into a Health and Catalog system with APIs enabling operators to gain insight into the
|
|
broader system.
|
|
|
|
In addition to the service discovery and health checking, Consul also provides
|
|
an integrated key/value store for configuration and multi-datacenter support.
|
|
While it may be possible to configure SmartStack for multiple datacenters,
|
|
the central ZooKeeper cluster would be a serious impediment to a fault-tolerant
|
|
deployment.
|