Add support for OTEL_EXPORTER_OTLP_COMPRESSION environment variable

Add fallback to the generic OTEL_EXPORTER_OTLP_COMPRESSION environment variable when the metrics-specific variable is not set.

Signed-off-by: Tigran Kavanosyan <allnightlong@allnightlong.ru>

Author: allnightlong

implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpConfig.java

@@ -159,15 +159,21 @@ default AggregationTemporality aggregationTemporality() {
     /**
      * {@link CompressionMode} of the OtlpMeterRegistry. This determines whether the
      * metrics data should be compressed before being sent to the OTLP endpoint. Default
-     * implementation supports the environment variable
+     * implementation supports the environment variables
+     * {@code OTEL_EXPORTER_OTLP_COMPRESSION} and
      * {@code OTEL_EXPORTER_OTLP_METRICS_COMPRESSION} when a value is not provided by
-     * {@link #get(String)}.
+     * {@link #get(String)}. If both are set, {@code OTEL_EXPORTER_OTLP_METRICS_COMPRESSION}
+     * takes precedence.
      * @return the compressionMode; default is OFF
      * @since 1.17.0
      */
     default CompressionMode compressionMode() {
         return getEnum(this, CompressionMode.class, "compressionMode").orElseGet(() -> {
-            String compression = System.getenv().get("OTEL_EXPORTER_OTLP_METRICS_COMPRESSION");
+            Map<String, String> env = System.getenv();
+            String compression = env.get("OTEL_EXPORTER_OTLP_METRICS_COMPRESSION");
+            if (compression == null) {
+                compression = env.get("OTEL_EXPORTER_OTLP_COMPRESSION");
+            }
             if (compression != null) {
                 return CompressionMode.valueOf(compression.toUpperCase(Locale.ROOT));
             }