https://github.com/yotpoltd/resec
ReSeC- Redis Service Consul
https://github.com/yotpoltd/resec
consul consul-locks failover golang ha health-check high-availability redis redis-sentinel sentinel
Last synced: 4 months ago
JSON representation
ReSeC- Redis Service Consul
- Host: GitHub
- URL: https://github.com/yotpoltd/resec
- Owner: YotpoLtd
- License: mit
- Created: 2017-12-25T07:38:11.000Z (almost 8 years ago)
- Default Branch: master
- Last Pushed: 2021-03-21T08:24:52.000Z (over 4 years ago)
- Last Synced: 2025-06-27T23:06:01.764Z (4 months ago)
- Topics: consul, consul-locks, failover, golang, ha, health-check, high-availability, redis, redis-sentinel, sentinel
- Language: Go
- Homepage:
- Size: 7.47 MB
- Stars: 83
- Watchers: 8
- Forks: 28
- Open Issues: 4
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
[](https://gitter.im/redis-service-consul/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge) [](https://goreportcard.com/report/github.com/YotpoLtd/resec) [](https://travis-ci.org/YotpoLtd/resec)
# Resec - Consul based highly available Redis replication agent
## Description
Resec is a successor to [Redis Sentinel](https://redis.io/topics/sentinel) and [redishappy](https://github.com/mdevilliers/redishappy) for handling high availability failover for Redis.
It avoids Redis Sentinel problems of remembering all the sentinels and all the redis servers that ever appeared in the replication cluster.
Resec master election is based on [Consul Locks](https://www.consul.io/docs/commands/lock.html) to provide single redis master instance.
Resec continuously monitors the status of redis instance and if it's alive, It starts 2 following processes:
* Monitor service of *master* for changes
* if lock is not acquired, on every change of master it runs *SLAVE OF `Master.Address`*
* Trying to acquire lock to became master itself
* once lock acquired it stops watching for master service changes
* promotes redis to be *SLAVE OF NO ONE*
### Services and health checks
Resec registers service with [TTL](https://www.consul.io/docs/agent/checkshtml#TTL) health check with TTL twice as big as `HEALTHCHECK_INTERVAL` and updates consul every `HEALTHCHECK_INTERVAL` to maintain service in passing state
There are 2 options to work with services:
* Use `CONSUL_SERVICE_NAME` for tag based master/slave discovery
* `MASTER_TAGS` must be provided for ability to watch master instance for changes.
* Use `CONSUL_SERVICE_PREFIX` for service name only based discovery
* services in consul will look like `CONSUL_SERVICE_PREFIX`-`Replication.Role`
* If `ANNOUNCE_ADDR` is set it will be used for registration in consul, if it's not provided `REDIS_ADDR` will be used for registration in consul.
* If `REDIS_ADDR` is localhost, only port will be announced to the consul.
### Redis Health
* If redis becomes unhealthy resec will stop the leader election. As soon as redis will become healthy again, resec will start the operation from the beginning.
## Usage
### Environment variables
Environment Variables | Default | Description
----------------------| ---------------| -------------------------------------------------
ANNOUNCE_ADDR | | IP:Port of Redis to be announced, by default service will be registered wi
CONSUL_SERVICE_NAME | | Consul service name for tag based service discovery
CONSUL_SERVICE_PREFIX | redis | Name Prefix, will be followed by "-(master/slave)", ignored if CONSUL_SERVICE_NAME is used
CONSUL_LOCK_KEY | resec/.lock | KV lock location, should be overriden if multiple instances running in the same consul DC
CONSUL_LOCK_SESSION_NAME | resec | Lock session Name to distinguish multiple resec masters on one host
CONSUL_LOCK_MONITOR_RETRIES | 3 | Number of retries of lock receives 500 Error from Consul
CONSUL_LOCK_MONITOR_RETRY_INTERVAL | 1s | Retry interval if lock receives 500 Error from Consul
CONSUL_DEREGISTER_SERVICE_AFTER | 72h |
CONSUL_LOCK_TTL | 15s |
MASTER_TAGS | | Comma separated list of tags to be added to master instance. The first tag (index 0) is used to configure the role of the Redis/resec task, and *must* be different from index 0 in `SLAVE_TAGS`.
SLAVE_TAGS | | Comma separated list of tags to be added to slave instance. The first tag (index 0) is used to configure the role of the Redis/resec task, and *must* be different from index 0 in `MASTER_TAGS`.
HEALTHCHECK_INTERVAL | 5s |
HEALTHCHECK_TIMEOUT | 2s |
REDIS_ADDR | 127.0.0.1:6379 |
REDIS_PASSWORD | |
LOG_LEVEL | INFO | Options are "DEBUG", "INFO", "WARN", "ERROR"
##### Environment variables to configure communication with consul are similar to [Consul CLI](https://www.consul.io/docs/commands/index.html#environment-variables)
### Permissions
Resec requires permissions for Consul in order to function correctly.
The Consul ACL token is passed as the environment variable `CONSUL_HTTP_TOKEN` .
#### Consul ACL Token Permissions
If the Consul cluster being used is running ACLs; the following ACL policy will allow Replicator the required access to perform all functions based on its default configuration:
```hcl
key "resec/" {
policy = "write"
}
session "" {
policy = "write"
}
service "" {
policy = "write"
}
```
### Run the application
* with nomad:
```hcl
job "resec" {
datacenters = ["dc1"]
type = "service"
update {
max_parallel = 1
stagger = "10s"
}
group "cache" {
count = 3
task "redis" {
driver = "docker"
config {
image = "redis:alpine"
command = "redis-server"
args = [
"/local/redis.conf"
]
port_map {
db = 6379
}
}
// Let Redis know how much memory he can use not to be killed by OOM
template {
data = <