Added a `nocache' query param to force TSD to serve data from HBase.

Closes OpenTSDB#24

Change-Id: I70ef2bd97ce9794a2baf325115f88b596409d31c

src/tsd/GraphHandler.java

@@ -85,9 +85,9 @@ final class GraphHandler implements HttpRpc {
  public GraphHandler() {
  // Gnuplot is mostly CPU bound and does only a little bit of IO at the
  // beginning to read the input data and at the end to write its output.
- // We don't want to avoid running too many Gnuplot instances concurrently
- // as it can steal a significant number of CPU cycles from us. Instead,
- // we allow only one per core, and we nice it (the nicing is done in the
+ // We want to avoid running too many Gnuplot instances concurrently as
+ // it can steal a significant number of CPU cycles from us. Instead, we
+ // allow only one per core, and we nice it (the nicing is done in the
  // shell script we use to start Gnuplot). Similarly, the queue we use
  // is sized so as to have a fixed backlog per core.
  final int ncores = Runtime.getRuntime().availableProcessors();
@@ -116,6 +116,7 @@ private void doGraph(final TSDB tsdb, final HttpQuery query)
  throws IOException {
  final String basepath = getGnuplotBasePath(query);
  final long start_time = getQueryStringDate(query, "start");
+ final boolean nocache = query.hasQueryStringParam("nocache");
  if (start_time == -1) {
  throw BadRequestException.missingParameter("start");
  }
@@ -135,7 +136,7 @@ private void doGraph(final TSDB tsdb, final HttpQuery query)
  final int max_age = (end_time > now ? 0 // (1)
  : (end_time < now - Const.MAX_TIMESPAN ? 86400 // (2)
  : (int) (end_time - start_time) >> 10)); // (3)
- if (isDiskCacheHit(query, max_age, basepath)) {
+ if (!nocache && isDiskCacheHit(query, max_age, basepath)) {
  return;
  }
  Query[] tsdbqueries;