Class GraphHandler

src/tsd/GraphHandler.java:65–1073

Stateless handler of HTTP graph requests (the /q endpoint).

 * Stateless handler of HTTP graph requests (the {@code /q} endpoint).
 */
final class GraphHandler implements HttpRpc {

  private static final Logger LOG =
    LoggerFactory.getLogger(GraphHandler.class);

  private static final boolean IS_WINDOWS =
    System.getProperty("os.name", "").contains("Windows");

  private static Pattern RANGE_VALIDATOR = Pattern.compile(
      "\\[\\\"?-?\\d+\\.?(\\d+)?([eE]-?\\d+)?\\\"?:\\\"?-?(\\d+\\.?\\d+?)?([eE]-?\\d+)?\\\"?\\]");
  private static Pattern LABEL_VALIDATOR = Pattern.compile("[a-zA-z0-9 \\-_]");
  private static Pattern KEY_VALIDATOR = Pattern.compile(
      "(out|left|top|center|right|horiz|box|bottom)?\\s?");
  private static Pattern STYLE_VALIDATOR = Pattern.compile("(linespoint|points|circles|dots)");
  private static Pattern COLOR_VALIDATOR = Pattern.compile("(x|X)[a-fA-F0-9]{6}");
  private static Pattern SMOOTH_VALIDATOR = Pattern.compile("unique|frequency|fnormal|cumulative|cnormal|bins|csplines|acsplines|mcsplines|bezier|sbezier|unwrap|zsort");
  // NOTE: This one should be tightened for only time based formatters.
  private static Pattern FORMAT_VALIDATOR = Pattern.compile("(%[a-zA-Z])+[:\\/]?\\s?");
  private static Pattern WXH_VALIDATOR = Pattern.compile("^\\d+x\\d+$");
  /** Number of times we had to do all the work up to running Gnuplot. */
  private static final AtomicInteger graphs_generated
    = new AtomicInteger();
  /** Number of times a graph request was served from disk, no work needed. */
  private static final AtomicInteger graphs_diskcache_hit
    = new AtomicInteger();

  /** Keep track of the latency of graphing requests. */
  private static final Histogram graphlatency =
    new Histogram(16000, (short) 2, 100);

  /** Keep track of the latency (in ms) introduced by running Gnuplot. */
  private static final Histogram gnuplotlatency =
    new Histogram(16000, (short) 2, 100);

  /** Executor to run Gnuplot in separate bounded thread pool. */
  private final ThreadPoolExecutor gnuplot;

  /**
   * Constructor.
   */
  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 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();
    gnuplot = new ThreadPoolExecutor(
      ncores, ncores,  // Thread pool of a fixed size.
      /* 5m = */ 300000, MILLISECONDS,        // How long to keep idle threads.
      new ArrayBlockingQueue<Runnable>(20 * ncores),  // XXX Don't hardcode?
      thread_factory);
    // ArrayBlockingQueue does not scale as much as LinkedBlockingQueue in terms
    // of throughput but we don't need high throughput here.  We use ABQ instead
    // of LBQ because it creates far fewer references.
  }