+ * Inspect response headers for any sign of server overload and respect any
+ * 'retry-after' directive
+ *
+ * @see https://github.com/Ensembl/ensembl-rest/wiki/Rate-Limits
+ * @param connection
+ */
+ void checkRateLimits(HttpURLConnection connection)
+ {
+ // number of requests allowed per time interval:
+ String limit = connection.getHeaderField("X-RateLimit-Limit");
+ // length of quota time interval in seconds:
+ // String period = connection.getHeaderField("X-RateLimit-Period");
+ // seconds remaining until usage quota is reset:
+ String reset = connection.getHeaderField("X-RateLimit-Reset");
+ // number of requests remaining from quota for current period:
+ String remaining = connection.getHeaderField("X-RateLimit-Remaining");
+ // number of seconds to wait before retrying (if remaining == 0)
+ String retryDelay = connection.getHeaderField("Retry-After");
+
+ // to test:
+ // retryDelay = "5";
+
+ if (retryDelay != null)
+ {
+ System.err.println("Ensembl REST service rate limit exceeded, wait "
+ + retryDelay + " seconds before retrying");
+ try
+ {
+ retryAfter = System.currentTimeMillis()
+ + (1000 * Integer.valueOf(retryDelay));
+ } catch (NumberFormatException e)
+ {
+ System.err.println("Unexpected value for Retry-After: "
+ + retryDelay);
+ }
+ }
+ else
+ {
+ retryAfter = 0;
+ // debug:
+ // System.out.println(String.format(
+ // "%s Ensembl requests remaining of %s (reset in %ss)",
+ // remaining, limit, reset));
+ }
+ }
+ /**