reliable-get

Reliable HTTP get wrapper (cache and circuit breaker), best wrapped around things you dont trust very much.

Basic usage

var ReliableGet = require('reliable-get');
var config = {
  cache:{
    engine:'memorycache'
  },
  circuitbreaker:{
    includePath: true
  }
};
var rg = new ReliableGet();
rg.on('log', function(level, message, data) {
  // Wire up to your favourite logger
});
rg.on('stat', function(type, key, value) {
 // Wire up to your favourite stats library (e.g. statsd)
});
rg.get({url:'http://www.google.com'}, function(err, response) {
   console.log(response.content);
});

Configuration options

When you create an instance of reliable-get you need to specify the cache and circuit breaker behaviour. This then applies across all requests.

var config = {
  cache:{
    engine:'redis',
    url:'redis://localhost:6379?db=0'
  },
  circuitbreaker:{
    windowDuration:5000,
    numBuckets: 5,
    errorThreshold: 20,
    volumeThreshold: 3,
    includePath: true
  }
};

Property	Description	Example / Default	Required
cache.engine	Cache to use, redis/memorycache/nocache	nocache	No
cache.engine.url	URL to redis	localhost:6379	No
circuitbreaker.windowDuration	Window duration to collect errors over	10000	No
circuitbreaker.numBuckets	Number of segments within window	10	No
circuitbreaker.errorThreshold	Percentage of buckets in error before CB opens	50	No
circuitbreaker.volumeThreshold	Number of errored requests before CB opens	10	No

To disable the circuit breaker, simply delete the circuitbreaker configuration.

GET options

When making a get request, you need to provide a basic options object:

rg.get({url:'http://www.google.com'}, function(err, response) {
   console.log(response.content);
});

Property	Description	Example / Default	Required
url	Service to get	http://my-service.tes.co.uk	Yes
timeout	Timeout for service	5000	No
cacheKey	Key to store cached value against	my-service_tes_co_uk	No
cacheTTL	TTL of cached value	1 minute	No
explicitNoCache	Do not cache under any circumstances	false	No
headers	Headers to send with request		No
tracer	Unique value to pass with request		No
type	Type of request, used for statsd and logging		No
statsdKey	Key that statsd events will be posted to		No
eventHandler	Object (see below) for logging and stats		No

Example from a Compoxure backend request:

var options = {
          url: targetUrl,
          cacheKey: targetCacheKey,
          cacheTTL: targetCacheTTL,
          timeout: utils.timeToMillis(backend.timeout || DEFAULT_LOW_TIMEOUT),
          headers: backendHeaders,
          tracer: req.tracer,
          statsdKey: 'backend_' + utils.urlToCacheKey(host)
};

From a compoxure fragment request:

var options = {
      url: url,
      timeout: timeout,
      cacheKey: cacheKey,
      cacheTTL: cacheTTL,
      explicitNoCache: explicitNoCache,
      headers: optionsHeaders,
      tracer: req.tracer,
      statsdKey: statsdKey
  }