package com.codahale.metrics.servlet;
import com.codahale.metrics.Counter;
import com.codahale.metrics.Meter;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.Timer;
import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.IOException;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import static com.codahale.metrics.MetricRegistry.name;
/**
* {@link Filter} implementation which captures request information and a breakdown of the response
* codes being returned.
*/
public abstract class AbstractInstrumentedFilter implements Filter {
static final String METRIC_PREFIX = "name-prefix";
private final String otherMetricName;
private final Map<Integer, String> meterNamesByStatusCode;
private final String registryAttribute;
// initialized after call of init method
private ConcurrentMap<Integer, Meter> metersByStatusCode;
private Meter otherMeter;
private Counter activeRequests;
private Timer requestTimer;
/**
* Creates a new instance of the filter.
*
* @param registryAttribute the attribute used to look up the metrics registry in the
* servlet context
* @param meterNamesByStatusCode A map, keyed by status code, of meter names that we are
* interested in.
* @param otherMetricName The name used for the catch-all meter.
*/
protected AbstractInstrumentedFilter(String registryAttribute,
Map<Integer, String> meterNamesByStatusCode,
String otherMetricName) {
this.registryAttribute = registryAttribute;
this.otherMetricName = otherMetricName;
this.meterNamesByStatusCode = meterNamesByStatusCode;
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
final MetricRegistry metricsRegistry = getMetricsFactory(filterConfig);
String metricName = filterConfig.getInitParameter(METRIC_PREFIX);
if(metricName == null || metricName.isEmpty()) {
metricName = getClass().getName();
}
this.metersByStatusCode = new ConcurrentHashMap<Integer, Meter>(meterNamesByStatusCode
.size());
for (Entry<Integer, String> entry : meterNamesByStatusCode.entrySet()) {
metersByStatusCode.put(entry.getKey(),
metricsRegistry.meter(name(metricName, entry.getValue())));
}
this.otherMeter = metricsRegistry.meter(name(metricName,
otherMetricName));
this.activeRequests = metricsRegistry.counter(name(metricName,
"activeRequests"));
this.requestTimer = metricsRegistry.timer(name(metricName,
"requests"));
}
private MetricRegistry getMetricsFactory(FilterConfig filterConfig) {
final MetricRegistry metricsRegistry;
final Object o = filterConfig.getServletContext().getAttribute(this.registryAttribute);
if (o instanceof MetricRegistry) {
metricsRegistry = (MetricRegistry) o;
} else {
metricsRegistry = new MetricRegistry();
}
return metricsRegistry;
}
@Override
public void destroy() {
}
@Override
public void doFilter(ServletRequest request,
ServletResponse response,
FilterChain chain) throws IOException, ServletException {
final StatusExposingServletResponse wrappedResponse =
new StatusExposingServletResponse((HttpServletResponse) response);
activeRequests.inc();
final Timer.Context context = requestTimer.time();
try {
chain.doFilter(request, wrappedResponse);
} finally {
context.stop();
activeRequests.dec();
markMeterForStatusCode(wrappedResponse.getStatus());
}
}
private void markMeterForStatusCode(int status) {
final Meter metric = metersByStatusCode.get(status);
if (metric != null) {
metric.mark();
} else {
otherMeter.mark();
}
}
private static class StatusExposingServletResponse extends HttpServletResponseWrapper {
// The Servlet spec says: calling setStatus is optional, if no status is set, the default is 200.
private int httpStatus = 200;
public StatusExposingServletResponse(HttpServletResponse response) {
super(response);
}
@Override
public void sendError(int sc) throws IOException {
httpStatus = sc;
super.sendError(sc);
}
@Override
public void sendError(int sc, String msg) throws IOException {
httpStatus = sc;
super.sendError(sc, msg);
}
@Override
public void setStatus(int sc) {
httpStatus = sc;
super.setStatus(sc);
}
@Override
public void setStatus(int sc, String sm) {
httpStatus = sc;
super.setStatus(sc, sm);
}
public int getStatus() {
return httpStatus;
}
}
}