Exporter Pushgateway runtime issue in versions 1.3.4 and above

[rafauu]

Version 1.3.3 works correctly
I believe it is caused by #1190
I am using default format in pushgateway which I think is protobuf.

Dependencies in pom.xml:

<dependency>
  <groupId>io.prometheus</groupId>
  <artifactId>prometheus-metrics-core</artifactId>
  <version>1.3.4</version>
</dependency>
<dependency>
  <groupId>io.prometheus</groupId>
  <artifactId>prometheus-metrics-exporter-pushgateway</artifactId>
  <version>1.3.4</version>
</dependency>

Runtime issue from shaded jar:

Exception in thread (...) java.lang.ExceptionInInitializerError
Caused by: java.lang.RuntimeException: class io.prometheus.metrics.expositionformats.PrometheusProtobufWriter is not available
at io.prometheus.metrics.exporter.pushgateway.PushGateway.<init>(PushGateway.java:99)
at io.prometheus.metrics.exporter.pushgateway.PushGateway.<init>(PushGateway.java:77)
at io.prometheus.metrics.exporter.pushgateway.PushGateway$Builder.build(PushGateway.java:456)
(...)
Caused by: java.lang.ExceptionInInitializerError: Exception java.lang.RuntimeException: class io.prometheus.metrics.expositionformats.PrometheusProtobufWriter is not available

So I guess it complains about
https://github.com/prometheus/client_java/blob/main/prometheus-metrics-exporter-pushgateway/src/main/java/io/prometheus/metrics/exporter/pushgateway/PushGateway.java#L9
or
https://github.com/prometheus/client_java/blob/main/prometheus-metrics-exporter-pushgateway/src/main/java/io/prometheus/metrics/exporter/pushgateway/PushGateway.java#L114

[zeitlinger]

From the description it looks exactly like https://github.com/prometheus/client_java/tree/main/integration-tests/it-pushgateway

Please include a full example that demonstrates the bug.

[rafauu]

Thanks for answering, yeah I started comparing your example with my codebase and I think I've found what causes the issue. So 1 difference I've found is that I'm using minimizeJar tag under configuration in maven-shade-plugin.

When minimizeJar is set to true then we have runtime issue and calling jar tf myJar.jar | grep PrometheusProtobufWriter yields

io/prometheus/metrics/expositionformats/PrometheusProtobufWriter.class

When minimizeJar is set to false then it works and calling command (jar tf...) yields

io/prometheus/metrics/expositionformats/PrometheusProtobufWriter.class
io/prometheus/metrics/expositionformats/internal/PrometheusProtobufWriterImpl.class

I'm gonna create full repro with minimal example soon.

[rafauu]

Here is repro of the issue: https://github.com/rafauu/prometheus-pushgateway/tree/main

So pom.xml contains minimizeJar tag. When you compile and run it you will get

Exception in thread "main" java.lang.RuntimeException: class io.prometheus.metrics.expositionformats.PrometheusProtobufWriter is not available
	at io.prometheus.metrics.exporter.pushgateway.PushGateway.<init>(PushGateway.java:102)
	at io.prometheus.metrics.exporter.pushgateway.PushGateway.<init>(PushGateway.java:77)
	at io.prometheus.metrics.exporter.pushgateway.PushGateway$Builder.build(PushGateway.java:483)
	at PushGatewayApp.runSimpleTest(PushGatewayApp.java:15)
	at PushGatewayApp.main(PushGatewayApp.java:10)

You can get it working either with setting minimizeJar to false or downgrading dependencies down to 1.3.3 version. It looks like minimizeJar from maven shade plugin messes somehow with reflection introduced in 1.3.4.

[rafauu]

I can see it was addressed before prometheus/jmx_exporter#1133
edit: although issue is a little bit different, it is still related to shading

[rafauu]

Hi @zeitlinger, any new insights on that?

[zeitlinger]

To reproduce:

mvn -X package

The class that is missing is now loaded via reflection - and I guess this is not detected when minimizing:

client_java/prometheus-metrics-exposition-textformats/src/main/java/io/prometheus/metrics/expositionformats/PrometheusProtobufWriter.java

Line 26 in 66f4dc8

"io.prometheus.metrics.expositionformats.internal.PrometheusProtobufWriterImpl")

This change below adds the class back according to the build output

[DEBUG] io.prometheus.metrics.expositionformats.internal.PrometheusProtobufWriterImpl not removed because it was specifically included

It still is not included it the final jar - maybe that's a bug in the shade plugin.

Index: pom.xml
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/pom.xml b/pom.xml
--- a/pom.xml	(revision 73a722f42a9de5ad02bd31b9433a53f5d7949f87)
+++ b/pom.xml	(date 1750760862248)
@@ -41,6 +41,14 @@
                   <mainClass>com.company.prometheus.PushGatewayApp</mainClass>
                 </transformer>
               </transformers>
+              <filters>
+                <filter>
+                  <artifact>io.prometheus:prometheus-metrics-exposition-formats-no-protobuf</artifact>
+                  <includes>
+                    <include>io/prometheus/metrics/expositionformats/internal/PrometheusProtobufWriterImpl</include>
+                  </includes>
+                </filter>
+              </filters>
             </configuration>
           </execution>
         </executions>

[rafauu]

@zeitlinger I was playing with this maven shade filtering. Interestingly enough when you change (in your approach)
<include>io/prometheus/metrics/expositionformats/internal/PrometheusProtobufWriterImpl</include>
into
<include>**</include>
it starts working. I'm not sure why tbh but as long as it works I'm good.

Then I thought I would update version to the newest one, I changed version to 1.3.9 and it stopped working again (fix from 1.3.8 does not work in 1.3.9). Have you changed something regarding shading in 1.3.9?

[rafauu]

Ok, I've figured out how to make it work in versions 1.3.9 and 1.3.10. Such filtering is required:

<filters>
  <filter>
    <artifact>io.prometheus:prometheus-metrics-exposition-formats</artifact>
    <includes>
      <include>io/prometheus/metrics/expositionformats/**</include>
      <include>io/prometheus/metrics/shaded/**</include>
    </includes>
  </filter>
</filters>

prometheus-metrics-exposition-formats has to be used instead of prometheus-metrics-exposition-formats-no-protobuf. Is it in accordance with how it is supposed to be? I don't know, you can tell me :d.

[zeitlinger]

prometheus-metrics-exposition-formats has to be used instead of prometheus-metrics-exposition-formats-no-protobuf. Is it in accordance with how it is supposed to be? I don't know, you can tell me :d.

Yes, this is the result of the #1411 bug fix.
A docs PR would be highly welcome 😄