Got lots of warning logs (java.lang.NoSuchFieldError: timestampMs) when timestamp field is unset

Hi Prometheus,

This is Yang from OpenCensus. Last year we added an OpenCensus Prometheus exporter that exports metrics to Prometheus end points. I saw you added an optional "timestamp" value as part of metric sample in https://github.com/prometheus/client_java/pull/337 - on OpenCensus we haven’t updated our exporter to set this field. However, when our users were using the OpenCensus Prometheus exporter, they got a bunch of warning logs saying (original issue: https://github.com/census-instrumentation/opencensus-java/issues/1215):

[WARNING] 
java.lang.NoSuchFieldError: timestampMs
    at io.prometheus.client.exporter.common.TextFormat.write004 (TextFormat.java:49)
    at io.prometheus.client.exporter.HTTPServer$HTTPMetricHandler.handle (HTTPServer.java:59)
    at com.sun.net.httpserver.Filter$Chain.doFilter (Filter.java:77)
    at sun.net.httpserver.AuthFilter.doFilter (AuthFilter.java:82)
    at com.sun.net.httpserver.Filter$Chain.doFilter (Filter.java:80)
    at sun.net.httpserver.ServerImpl$Exchange$LinkHandler.handle (ServerImpl.java:685)
    at com.sun.net.httpserver.Filter$Chain.doFilter (Filter.java:77)
    at sun.net.httpserver.ServerImpl$Exchange.run (ServerImpl.java:657)
    at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1167)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:641)
    at java.lang.Thread.run (Thread.java:844)

Since "timestamp" is an optional field, would it be better to reduce such warning logs when it is unset in the metric sample?

[songy23]

Closing for now, this could be resolved by using a consistent version of Prometheus simple client for the library and users’ application.

[songy23]

@pavanbhosle Back then I used v0.3.0 for both simpleclient and simpleclient_common. I’d assume as long as you use a consistent version for both jars, it should work fine.