Gmail API - 429 rateLimitExceeded with a single request - google-api

Question

I was writing a node application that uses the gmail API when I noticed this error. My understanding of the error is that there are too many concurrent requests. It seems to be prompting me to wait 15 minutes and try again. After the waiting period, I tried to poke the API with the gui over at https://developers.google.com/gmail/api/v1/reference/users/messages/list#response, but the same error appears (with the time incremental 15 minutes). I've looked at my quota usage on the API site in the developer console, but there's no activity other than the errors. Does anyone know why this might be? I'd be extremely appreciative.
{
"error": {
"errors": [
{
"domain": "usageLimits",
"reason": "rateLimitExceeded",
"message": "User-rate limit exceeded. Retry after 2016-07-11T23:51:49.309Z"
}
],
"code": 429,
"message": "User-rate limit exceeded. Retry after 2016-07-11T23:51:49.309Z"
}
}

Answer 1

The Gmail API is subject to a daily usage limit that applies to all requests made from your application, as well as per-user rate limits.
Daily Usage 1,000,000,000 quota units per day Per User Rate
Limit
250 quota units per user per second, moving average (allows
short bursts)
Exceeding a rate limit will cause an HTTP 403 or HTTP 429 Too Many Requests response and your app should respond by retrying with exponential backoff.
Exponential backoff is a standard error handling strategy for network
applications in which the client periodically retries a failed request
over an increasing amount of time. If a high volume of requests or
heavy network traffic causes the server to return errors, exponential
backoff may be a good strategy for handling those errors. Conversely,
it is not a relevant strategy for dealing with errors unrelated to
rate-limiting, network volume or response times, such as invalid
authorization credentials or file not found errors.
Used properly, exponential backoff increases the efficiency of
bandwidth usage, reduces the number of requests required to get a
successful response, and maximizes the throughput of requests in
concurrent environments.