I am developing a location based application. And i need a trustable source for getting geolocation.
right now i am using this geocoder plugin.
and i am gettin
This is probably bound to happen with any web based service. You might want to consider sending these tasks to a background job manager (such as Resque or Delayed Job) which will retry failed jobs without disrupting users. They also make your application seem faster since your user will not have to wait for third party (and possibly intermittent) web applications to respond.
You should geocode client side (in javascript) you won't be hit by the limits :
Server-side geocoding, through the Geocoding Web Service has a quota of 2,500 requests per IP per day, so all requests in one day count against the quota. In addition, the Web Service is rate-limited, so that requests that come in too quickly result in blocking. Client-side geocoding through the browser is rate limited per map session, so the geocoding is distributed across all your users and scales with your userbase. Geocoding quotas and rate limits drive the strategies outlined in this article.
When to Use Client-Side Geocoding
The basic answer is "almost always". As geocoding limits are per IP address, that limit counts against the consumer of your application. It's going to be very rare that someone is going to enter more than 2,500 addresses a day sitting at their computer. Therefore, running client-side geocoding, you generally don't have to worry about your quota.
http://code.google.com/apis/maps/articles/geocodestrat.html
Try using maxmind.com - this will do a geo lookup based on IP address. They have a free or paid for database that your store on your server. They have a Ruby API. I use this in a production system and the lookups are typically sub-millisecond as the data is cached.