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TraceLogFilter.java
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TraceLogFilter.java
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package com.example.google_trace_example.filter;
import com.google.cloud.logging.TraceLoggingEnhancer;
import java.io.IOException;
import java.util.UUID;
import javax.inject.Singleton;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import lombok.extern.slf4j.Slf4j;
@Slf4j
@Singleton
public class TraceLogFilter implements Filter {
// Taken from https://cloud.google.com/appengine/docs/flexible/python/reference/request-headers
public static final String GOOGLE_PROJECT_ID_KEY = "GOOGLE_PROJECT_ID_KEY";
// Taken from https://cloud.google.com/appengine/docs/flexible/python/reference/request-headers
// StackDriver will utilize this header to group the logs together
private static final String X_CLOUD_TRACE = "X-Cloud-Trace-Context";
private FilterConfig filterConfig;
@Override
public void init(final FilterConfig filterConfig) {
this.filterConfig = filterConfig;
}
/**
* This method will append a trace id to the request. It will see if there is an existing trace id
* and if not, it will generate one.
*
* @param request
* @param response
* @param chain
* @throws IOException
* @throws ServletException
*/
@Override
public void doFilter(
final ServletRequest request, final ServletResponse response, final FilterChain chain)
throws IOException, ServletException {
// Attempt to find a stack driver trace id to map to the Nginx log
String traceId = (String) request.getAttribute(X_CLOUD_TRACE);
if (traceId == null && request instanceof HttpServletRequest) {
HttpServletRequest httpRequest = (HttpServletRequest) request;
traceId = httpRequest.getHeader(X_CLOUD_TRACE);
if (traceId != null) {
// Get rid of the garbage after the first slash
// EX: c3d69f17521a87095454e6e05bef5f29/f3d69f17521a87095454e6e05bef5f29 and
// we only want c3d69f17521a87095454e6e05bef5f29
int slash = traceId.indexOf('/');
if (slash >= 0) {
traceId = traceId.substring(0, slash);
}
} else {
traceId = UUID.randomUUID().toString();
}
request.setAttribute(X_CLOUD_TRACE, traceId);
} else {
// otherwise pick a random one for this request
traceId = UUID.randomUUID().toString();
}
TraceLoggingEnhancer.setCurrentTraceId(
"projects/" + filterConfig.getInitParameter(GOOGLE_PROJECT_ID_KEY) + "/traces/" + traceId);
log.debug("projects/" + filterConfig.getInitParameter(GOOGLE_PROJECT_ID_KEY) + "/traces/" + traceId);
chain.doFilter(request, response);
TraceLoggingEnhancer.setCurrentTraceId(null);
}
@Override
public void destroy() {}
}