jetcd-launcher: allow starting Etcd Container via non-root user on Linux

jetcd-launcher/src/main/java/io/etcd/jetcd/launcher/Etcd.java

@@ -58,6 +58,7 @@ public static class Builder {
         private List<String> additionalArgs;
         private Network network;
         private boolean shouldMountDataDirectory = true;
+        private String user;
 
         public Builder withClusterName(String clusterName) {
             this.clusterName = clusterName;
@@ -114,12 +115,18 @@ public EtcdCluster build() {
                 debug,
                 additionalArgs,
                 network != null ? network : Network.SHARED,
-                shouldMountDataDirectory);
+                shouldMountDataDirectory,
+                user);
         }
 
         public Builder withMountedDataDirectory(boolean shouldMountDataDirectory) {
             this.shouldMountDataDirectory = shouldMountDataDirectory;
             return this;
         }
+
+        public Builder withUser(String user) {
+            this.user = user;
+            return this;
+        }
     }
 }

jetcd-launcher/src/main/java/io/etcd/jetcd/launcher/EtcdClusterImpl.java

@@ -43,7 +43,8 @@ public EtcdClusterImpl(
         boolean debug,
         Collection<String> additionalArgs,
         Network network,
-        boolean shouldMountDataDirectory) {
+        boolean shouldMountDataDirectory,
+        String user) {
 
         this.clusterName = clusterName;
         this.endpoints = IntStream.range(0, nodes)
@@ -57,7 +58,8 @@ public EtcdClusterImpl(
                 .withDebug(debug)
                 .withAdditionalArgs(additionalArgs)
                 .withNetwork(network)
-                .withShouldMountDataDirectory(shouldMountDataDirectory))
+                .withShouldMountDataDirectory(shouldMountDataDirectory)
+                .withUser(user))
             .collect(toList());
     }
 

jetcd-launcher/src/main/java/io/etcd/jetcd/launcher/EtcdContainer.java

@@ -63,6 +63,7 @@ public class EtcdContainer extends GenericContainer<EtcdContainer> {
     private Path dataDirectory;
     private Collection<String> additionalArgs;
     private boolean shouldMountDataDirectory = true;
+    private String user;
 
     public EtcdContainer(String image, String node, Collection<String> nodes) {
         super(image);
@@ -102,6 +103,18 @@ public EtcdContainer withAdditionalArgs(Collection<String> additionalArgs) {
         return self();
     }
 
+    /**
+     * Optional values are {@code [ user | user:group | uid | uid:gid | user:gid | uid:group ]}.
+     * See <a href="https://docs.docker.com/engine/reference/run/#user">User</a> .
+     *
+     * @param  user Refer to {@link com.github.dockerjava.api.command.CreateContainerCmd#withUser(String)}
+     * @return      self container.
+     */
+    public EtcdContainer withUser(String user) {
+        this.user = user;
+        return self();
+    }
+
     @Override
     protected void configure() {
         if (!configured.compareAndSet(false, true)) {
@@ -120,9 +133,13 @@ protected void configure() {
         withEnv("ETCD_LOG_LEVEL", this.debug ? "debug" : "info");
         withEnv("ETCD_LOGGER", "zap");
 
-        String user = System.getenv("TC_USER");
-        if (user != null) {
-            withCreateContainerCmdModifier(c -> c.withUser(user));
+        String tempUser = this.user;
+        if (tempUser == null) {
+            tempUser = System.getenv("TC_USER");
+        }
+        if (tempUser != null) {
+            String finalUser = tempUser;
+            withCreateContainerCmdModifier(c -> c.withUser(finalUser));
         }
 
         if (ssl) {

jetcd-test/src/main/java/io/etcd/jetcd/test/EtcdClusterExtension.java

@@ -168,6 +168,11 @@ public Builder withMountDirectory(boolean mountDirectory) {
             return this;
         }
 
+        public Builder withUser(String user) {
+            builder.withUser(user);
+            return this;
+        }
+
         public EtcdClusterExtension build() {
             return new EtcdClusterExtension(builder.build());
         }