Cache docker containers and images across job runs

Every time a job runs, it runs completely independently of other runs.
While this can be good, it also has significant impacts. The duration of
the run and the disk space taken up will be much longer because there
will be no docker cache.

This change mounts a volume on /var/lib/docker on the job container so
that there will be a cache between runs. For isolation purposes, each
job will have it's own cache volume. This is to prevent possible
unintended behavior and also for security purposes so different jobs
don't have access to each others cache which could have sensitive
information on them such as secrets.

The result of this change should be jobs running quicker and taking up
less space.

src/main/java/conjob/core/job/DockerAdapter.java

@@ -37,7 +37,7 @@ public List<String> listAllVolumeNames() throws DockerException, InterruptedExce
     }
 
     public String createJobRun(JobRunConfig jobRunConfig) throws CreateJobRunException {
-        HostConfig hostConfig = getHostConfig(jobRunConfig.getSecretsVolumeName());
+        HostConfig hostConfig = getHostConfig(jobRunConfig.getDockerCacheVolumeName(), jobRunConfig.getSecretsVolumeName());
 
         ContainerConfig containerConfig = getContainerConfig(
                 jobRunConfig.getJobName(),
@@ -106,8 +106,11 @@ private ContainerConfig getContainerConfig(String jobName, String input, HostCon
         return containerConfigBuilder.build();
     }
 
-    private HostConfig getHostConfig(String secretsVolumeName) {
+    private HostConfig getHostConfig(String dockerCacheVolumeName, String secretsVolumeName) {
         HostConfig.Builder hostConfigBuilder = getHostConfigBuilderFor(containerRuntime);
+
+        hostConfigBuilder.appendBinds(dockerCacheVolumeName + ":" + "/var/lib/docker");
+
         if (secretsVolumeName != null) {
             hostConfigBuilder.appendBinds(
                     secretsVolumeName

src/main/java/conjob/core/job/JobRunConfigCreator.java

@@ -3,12 +3,12 @@
 import conjob.core.job.model.JobRunConfig;
 
 public class JobRunConfigCreator {
-    public JobRunConfig getContainerConfig(String imageName, String input, String secretsVolumeName) {
+    public JobRunConfig getContainerConfig(String imageName, String input, String dockerCacheVolumeName, String secretsVolumeName) {
         JobRunConfig jobRunConfig;
         if (input != null && !input.isEmpty()) {
-            jobRunConfig = new JobRunConfig(imageName, input, secretsVolumeName);
+            jobRunConfig = new JobRunConfig(imageName, input, dockerCacheVolumeName, secretsVolumeName);
         } else {
-            jobRunConfig = new JobRunConfig(imageName, null, secretsVolumeName);
+            jobRunConfig = new JobRunConfig(imageName, null, dockerCacheVolumeName, secretsVolumeName);
         }
 
         return jobRunConfig;

src/main/java/conjob/core/job/config/ConfigUtil.java

@@ -1,7 +1,7 @@
 package conjob.core.job.config;
 
 public class ConfigUtil {
-    public String translateToVolumeName(String imageName) {
+    public String translateToSecretsVolumeName(String imageName) {
         int usernameSeparatorIndex = imageName.indexOf('/');
         int tagSeparatorIndex = imageName.lastIndexOf(':');
         StringBuilder sb = new StringBuilder(imageName);
@@ -12,4 +12,16 @@ public String translateToVolumeName(String imageName) {
 
         return sb.toString();
     }
+
+    public String translateToDockerCacheVolumeName(String imageName) {
+        int usernameSeparatorIndex = imageName.indexOf('/');
+        int tagSeparatorIndex = imageName.lastIndexOf(':');
+        StringBuilder sb = new StringBuilder(imageName);
+        sb.setCharAt(usernameSeparatorIndex, '-');
+        if (tagSeparatorIndex != -1) {
+            sb.setCharAt(tagSeparatorIndex, '-');
+        }
+
+        return "conjob-docker-cache-" + sb;
+    }
 }

src/main/java/conjob/core/job/model/JobRunConfig.java

@@ -7,5 +7,6 @@
 public class JobRunConfig {
     String jobName;
     String input;
+    String dockerCacheVolumeName;
     String secretsVolumeName;
 }

src/main/java/conjob/service/job/JobService.java

@@ -80,11 +80,12 @@ private JobRun runJob(String imageName, String input, PullStrategy pullStrategy)
     }
 
     private JobRunConfig getJobRunConfig(String imageName, String input) throws SecretsStoreException {
-        String correspondingSecretsVolumeName = configUtil.translateToVolumeName(imageName);
+        String correspondingSecretsVolumeName = configUtil.translateToSecretsVolumeName(imageName);
+        String dockerCacheVolumeName = configUtil.translateToDockerCacheVolumeName(imageName);
         String secretsVolumeName = secretsStore
                 .findSecrets(correspondingSecretsVolumeName)
                 .orElse(null);
 
-        return jobRunConfigCreator.getContainerConfig(imageName, input, secretsVolumeName);
+        return jobRunConfigCreator.getContainerConfig(imageName, input, dockerCacheVolumeName, secretsVolumeName);
     }
 }

src/main/java/conjob/service/secrets/SecretsService.java

@@ -36,7 +36,7 @@ public SecretsService(
 
     public void createsSecret(String imageName, String secrets)
             throws IOException {
-        String secretsVolumeName = configUtil.translateToVolumeName(imageName);
+        String secretsVolumeName = configUtil.translateToSecretsVolumeName(imageName);
         // TODO: Could there be a race condition if two of these containers are running at the same time?
         String intermediaryContainerName =
                 uniqueContainerNameGenerator.generate(CONTAINER_NAME_PREFIX);