Synapse
Synapse is a Service discovery mechanism. It watch servers for services in a backend and report status in a router. This simplify service communication with backends and allow auto discovery & hot reconfiguration of the communication. This provide better services discovery and fault-tolerant communication between services
At BlaBlaCar, we use a synapse for each service node that want to communicate with another service and discover those backend nodes (> 2000). Nerve report node statuses to a Zookeeper and synapse watch it to update a local Hapoxy. All outgoing communication is going through this haproxy.
Airbnb
Go-Synapse is a go rewrite of Airbnb's Synapse with additional features.
Installation
Download the latest version on the release page.
Create a configuration file base on the doc or examples.
Run with ./synapse synapse-config.yml
Building
****
Just clone the repository and run ./gomake
Configuration
It's a YAML file. You can find examples here
Very minimal configuration file with only one service :
routers:
- type: console
eventsBufferDurationInMilli: 500
services:
- serverSort: random # random, name, date
watcher:
type: zookeeper
hosts: ['localhost:2181']
path: /services/api/myapi
serverOptions:
... # depend on router type
routerOptions:
... # depend on router typeRoot attributes:
logLevel: info
apiHost: 127.0.0.1
apiPort: 3454
routers:
...Router config
Router console
Nothing special to configure for this router.
...
routers:
- type: console
services:
- ...Router haproxy
Router have haproxy specific attributes, but there is also services attributes
...
routers:
- type: haproxy
configPath: /tmp/hap.config
reloadCommand: [./examples/haproxy_reload.sh]
reloadTimeoutInMilli: 1000
reloadMinIntervalInMilli: 500
global: # []string
- stats socket /tmp/hap.socket level admin
defaults: # []string
listen: # map[string][]string
stats:
- mode http
- bind 127.0.0.1:1936
- stats enable
services:
- watcher:
...
serverOptions: check inter 2s rise 3 fall 2
routerOptions:
frontend:
- mode tcp
- timeout client 31s
- bind 127.0.0.1:5679
backend:
- mode tcp
- timeout server 2m
- timeout connect 45sserverOptions support minimal templating:
serverOptions: cookie {{sha1String .Name}} check inter 2s rise 3 fall 2
serverOptions: cookie {{randString 10}} check inter 2s rise 3 fall 2
serverOptions: cookie {{.Name}} check inter 2s rise 3 fall 2
Router template
...
routers:
- type: template
destinationFile: /tmp/notexists/templated
templateFile: ./examples/template.tmpl
postTemplateCommand: [/bin/bash, -c, "echo 'ZZ' > /tmp/DDDD"]
services:
- watcher:
...Services
routers:
- type: ...
services:
- name: db-read
watcher:
...
serverCorrelation: # this will remove the first server declared in otherService from this service
type: excludeServer
otherServiceName: db-write
scope: first
Watcher config
zookeeper watcher
routers:
- type: ...
services:
- watcher:
type: zookeeper
hosts: [ 'localhost:2181', 'localhost:2182' ]
path: /services/es/es_site_search
timeoutInMilli: 2000
