CRYOSTAT_PLATFORM takes comma-separated list

Signed-off-by: Andrew Azores <aazores@redhat.com>

README.md

@@ -128,7 +128,7 @@ Cryostat can be configured via the following environment variables:
 * `CRYOSTAT_CORS_ORIGIN`: the origin for CORS to load a different cryostat-web instance. Defaults to the empty string, which disables CORS.
 * `CRYOSTAT_MAX_WS_CONNECTIONS`: the maximum number of websocket client connections allowed (minimum 1, maximum `Integer.MAX_VALUE`, default `Integer.MAX_VALUE`)
 * `CRYOSTAT_AUTH_MANAGER`: the authentication/authorization manager used for validating user accesses. See the `USER AUTHENTICATION / AUTHORIZATION` section for more details. Set to the fully-qualified class name of the auth manager implementation to use, ex. `io.cryostat.net.BasicAuthManager`. Defaults to an AuthManager corresponding to the selected deployment platform, whether explicit or automatic (see below).
-* `CRYOSTAT_PLATFORM`: the platform client used for performing platform-specific actions, such as listing available target JVMs. If `CRYOSTAT_AUTH_MANAGER` is not specified then a default auth manager will also be selected corresponding to the platform, whether that platform is specified by the user or automatically detected. Set to the fully-qualified name of the platform detection strategy implementation to use, ex. `io.cryostat.platform.internal.KubeEnvPlatformStrategy`.
+* `CRYOSTAT_PLATFORM`: the platform clients used for performing platform-specific actions, such as listing available target JVMs. If `CRYOSTAT_AUTH_MANAGER` is not specified then a default auth manager will also be selected corresponding to the highest priority platform, whether those platforms are specified by the user or automatically detected. Set to the fully-qualified names of the platform detection strategy implementations to use, ex. `io.cryostat.platform.internal.KubeEnvPlatformStrategy,io.cryostat.platform.internal.PodmanPlatformStrategy`.
 * `CRYOSTAT_ENABLE_JDP_BROADCAST`: enable the Cryostat JVM to broadcast itself via JDP (Java Discovery Protocol). Defaults to `true`.
 * `CRYOSTAT_JDP_ADDRESS`: the JDP multicast address to send discovery packets. Defaults to `224.0.23.178`.
 * `CRYOSTAT_JDP_PORT`: the JDP multicast port to send discovery packets. Defaults to `7095`.

src/main/java/io/cryostat/platform/PlatformModule.java

@@ -37,6 +37,9 @@
  */
 package io.cryostat.platform;
 
+import java.util.Arrays;
+import java.util.List;
+import java.util.NoSuchElementException;
 import java.util.Objects;
 import java.util.Set;
 import java.util.SortedSet;
@@ -115,8 +118,9 @@ static SortedSet<PlatformDetectionStrategy<?>> provideSelectedPlatformStrategies
                 new TreeSet<>((a, b) -> Integer.compare(b.getPriority(), a.getPriority()));
         Predicate<PlatformDetectionStrategy<?>> fn;
         if (env.hasEnv(Variables.PLATFORM_STRATEGY_ENV_VAR)) {
-            String platform = env.getEnv(Variables.PLATFORM_STRATEGY_ENV_VAR);
-            fn = s -> Objects.equals(platform, s.getClass().getCanonicalName());
+            List<String> platforms =
+                    Arrays.asList(env.getEnv(Variables.PLATFORM_STRATEGY_ENV_VAR).split(","));
+            fn = s -> platforms.contains(s.getClass().getCanonicalName());
         } else if (env.hasEnv(Variables.DISABLE_BUILTIN_DISCOVERY)) {
             fn = s -> false;
         } else {
@@ -146,7 +150,23 @@ static SortedSet<PlatformDetectionStrategy<?>> provideUnselectedPlatformStrategi
     @Provides
     @Singleton
     static PlatformDetectionStrategy<?> providePlatformStrategy(
-            @Named(SELECTED_PLATFORMS) SortedSet<PlatformDetectionStrategy<?>> strategies) {
-        return strategies.stream().findFirst().orElseThrow();
+            @Named(SELECTED_PLATFORMS) SortedSet<PlatformDetectionStrategy<?>> selectedStrategies,
+            Set<PlatformDetectionStrategy<?>> strategies) {
+        return selectedStrategies.stream()
+                .findFirst()
+                .orElseThrow(
+                        () ->
+                                new NoSuchElementException(
+                                        String.format(
+                                                "No selected platforms found. Available platforms:"
+                                                        + " %s",
+                                                strategies.stream()
+                                                        .sorted(
+                                                                (a, b) ->
+                                                                        Integer.compare(
+                                                                                b.getPriority(),
+                                                                                a.getPriority()))
+                                                        .map(s -> s.getClass().getCanonicalName())
+                                                        .toList())));
     }
 }