/**
* Sends the given message as a PNG image. <strong>This method will block</strong> while image is
* being generated. It's only recommended for cases where we want to report an error back to the
* user and the user's browser expects a PNG image. Don't abuse it.
*
* @param status The status of the request (e.g. 200 OK or 404 Not Found).
* @param msg The message to send as an image.
* @param max_age The expiration time of this entity, in seconds. This is not a timestamp, it's
* how old the resource is allowed to be in the client cache. See RFC 2616 section 14.9 for
* more information. Use 0 to disable caching.
*/
public void sendAsPNG(final HttpResponseStatus status, final String msg, final int max_age) {
try {
final long now = System.currentTimeMillis() / 1000;
Plot plot = new Plot(now - 1, now);
HashMap<String, String> params = new HashMap<String, String>(1);
StringBuilder buf = new StringBuilder(1 + msg.length() + 18);
buf.append('"');
escapeJson(msg, buf);
buf.append("\" at graph 0.02,0.97");
params.put("label", buf.toString());
buf = null;
plot.setParams(params);
params = null;
final String basepath =
RpcHandler.getDirectoryFromSystemProp("tsd.http.cachedir")
+ Integer.toHexString(msg.hashCode());
GraphHandler.runGnuplot(this, basepath, plot);
plot = null;
sendFile(status, basepath + ".png", max_age);
} catch (Exception e) {
getQueryString().remove("png"); // Avoid recursion.
internalError(
new RuntimeException(
"Failed to generate a PNG with the" + " following message: " + msg, e));
}
}
