feat: make it possible to change the httpclient implementation (#1793)

Also document how to use a different implementation instead of the
okhttp one which is the default one and currently, the one we recommend
to use. Vert.X implementation is also coming along nicely. JDK
implementation should work if you're using Java 17 and up, and will work
with 11 when some bug fixes land in 11.

Author: metacosm

caffeine-bounded-cache-support/pom.xml

@@ -54,6 +54,11 @@
       <type>test-jar</type>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>io.fabric8</groupId>
+      <artifactId>kubernetes-httpclient-okhttp</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>

docs/documentation/v4-3-migration.md

@@ -9,16 +9,16 @@ permalink: /docs/v4-3-migration
 
 ## Condition API Change
 
-In Workflows the target of the condition was the managed resource itself, not the target dependent resource. 
+In Workflows the target of the condition was the managed resource itself, not the target dependent resource.
 This changed, now the API contains the dependent resource.
 
 New API:
 
 ```java
 public interface Condition<R, P extends HasMetadata> {
-    
-  boolean isMet(DependentResource<R, P> dependentResource, P primary, Context<P> context);
-  
+
+    boolean isMet(DependentResource<R, P> dependentResource, P primary, Context<P> context);
+
 }
 ```
 
@@ -27,10 +27,24 @@ Former API:
 ```java
 public interface Condition<R, P extends HasMetadata> {
 
-  boolean isMet(P primary, R secondary, Context<P> context);
-  
+    boolean isMet(P primary, R secondary, Context<P> context);
+
 }
 ```
 
-Migration is trivial. Since the secondary resource can be accessed from the dependent resource. So to access the secondary
+Migration is trivial. Since the secondary resource can be accessed from the dependent resource. So to access the
+secondary
 resource just use `dependentResource.getSecondaryResource(primary,context)`.
+
+## HTTP client choice
+
+It is now possible to change the HTTP client used by the Fabric8 client to communicate with the Kubernetes API server.
+By default, the SDK uses the historical default HTTP client which relies on Okhttp and there shouldn't be anything
+needed to keep using this implementation. The `tomcat-operator` sample has been migrated to use the Vert.X based
+implementation. You can see how to change the client by looking at
+that [sample POM file](https://github.com/java-operator-sdk/java-operator-sdk/blob/d259fcd084f7e22032dfd0df3c7e64fe68850c1b/sample-operators/tomcat-operator/pom.xml#L37-L50):
+
+- You need to exclude the default implementation (in this case okhttp) from the `operator-framework` dependency
+- You need to add the appropriate implementation dependency, `kubernetes-httpclient-vertx` in this case, HTTP client
+  implementations provided as part of the Fabric8 client all following the `kubernetes-httpclient-<implementation name>`
+  pattern for their artifact identifier.

operator-framework-core/pom.xml

@@ -68,6 +68,12 @@
     <dependency>
       <groupId>io.fabric8</groupId>
       <artifactId>kubernetes-client</artifactId>
+      <exclusions>
+        <exclusion>
+          <groupId>io.fabric8</groupId>
+          <artifactId>kubernetes-httpclient-okhttp</artifactId>
+        </exclusion>
+      </exclusions>
     </dependency>
     <dependency>
       <groupId>org.slf4j</groupId>

operator-framework/pom.xml

@@ -17,7 +17,10 @@
       <groupId>io.javaoperatorsdk</groupId>
       <artifactId>operator-framework-core</artifactId>
     </dependency>
-
+    <dependency>
+      <groupId>io.fabric8</groupId>
+      <artifactId>kubernetes-httpclient-okhttp</artifactId>
+    </dependency>
     <dependency>
       <groupId>org.apache.commons</groupId>
       <artifactId>commons-lang3</artifactId>

pom.xml

@@ -110,7 +110,7 @@
             </dependency>
             <dependency>
                 <groupId>io.fabric8</groupId>
-                <artifactId>kubernetes-client</artifactId>
+                <artifactId>kubernetes-client-api</artifactId>
                 <version>${fabric8-client.version}</version>
             </dependency>
             <dependency>
@@ -200,6 +200,28 @@
                 <artifactId>caffeine</artifactId>
                 <version>${caffeine.version}</version>
             </dependency>
+            <!-- Kubernetes client HTTP client implementations -->
+            <dependency>
+              <groupId>io.fabric8</groupId>
+              <artifactId>kubernetes-httpclient-okhttp</artifactId>
+              <version>${fabric8-client.version}</version>
+            </dependency>
+            <dependency>
+              <groupId>io.fabric8</groupId>
+              <artifactId>kubernetes-httpclient-vertx</artifactId>
+              <version>${fabric8-client.version}</version>
+            </dependency>
+<!--            We currently only recommend using the legacy okhttp client and the vert.x-based implementation -->
+<!--            <dependency>-->
+<!--              <groupId>io.fabric8</groupId>-->
+<!--              <artifactId>kubernetes-httpclient-jdk</artifactId>-->
+<!--              <version>${fabric8-client.version}</version>-->
+<!--            </dependency>-->
+<!--            <dependency>-->
+<!--              <groupId>io.fabric8</groupId>-->
+<!--              <artifactId>kubernetes-httpclient-jetty</artifactId>-->
+<!--              <version>${fabric8-client.version}</version>-->
+<!--            </dependency>-->
         </dependencies>
     </dependencyManagement>
 

sample-operators/tomcat-operator/pom.xml

@@ -37,6 +37,16 @@
         <dependency>
             <groupId>io.javaoperatorsdk</groupId>
             <artifactId>operator-framework</artifactId>
+            <exclusions>
+                <exclusion>
+                    <groupId>io.fabric8</groupId>
+                    <artifactId>kubernetes-httpclient-okhttp</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>io.fabric8</groupId>
+            <artifactId>kubernetes-httpclient-vertx</artifactId>
         </dependency>
         <dependency>
             <groupId>io.fabric8</groupId>