Added feature to upgrade KVStore to WiredTiger (#57)

*Added feature to upgrade KVStore to WiredTiger

* Added always try to upgrade to mongo 4.0

README.md

@@ -226,6 +226,9 @@ a value of `True` when the non-standalone image is built.  Thus we have these im
 * Install user-seed.conf
 * Configure server.conf, inputs.conf with servername
 * Configure convenience indexed fields
+* Configure `storageEngineMigration` in `server.conf` when `migrate_kvstore` is defined (only needed on version 8.x)
+* Always upgrade kvstore from 3.6 to 4.0 (only works on 9.x)
+* Upgrade kvstore to latest version when `upgrade_kvstrore` is defined
 
 [templates/kvstore_disable](roles/docker_image_build/templates/kvstore_disable)
 * Disables KVStore on primary builds (but overrideable)

roles/docker_image_build/templates/base/entrypoint.sh

@@ -1,2 +1,11 @@
 #!/usr/bin/env bash
+{{ splunk_home }}/bin/splunk migrate migrate-kvstore-36-40
+{% if migrate_kvstore is defined %}
+{{ splunk_home }}/bin/splunk start --accept-license --answer-yes --no-prompt
+{{ splunk_home }}/bin/splunk stop
+{{ splunk_home }}/bin/splunk migrate kvstore-storage-engine --target-engine wiredTiger
+{% endif %}
+{% if upgrade_kvstore is defined %}
+{{ splunk_home }}/bin/splunk migrate migrate-kvstore
+{% endif %}
 {{ splunk_home }}/bin/splunk start --nodaemon --accept-license --answer-yes --no-prompt

roles/docker_image_build/templates/base/etc/system/local/server.conf

@@ -0,0 +1,4 @@
+{% if migrate_kvstore is defined %}
+[kvstore]
+storageEngineMigration = true
+{% endif %}