Add comments to hocon configuration files

delta/app/src/main/resources/app.conf

@@ -39,6 +39,7 @@ app {
     # this provides 2-3x performance improvement
     rewrite-batch-inserts = true
 
+    # Cache for the underlying Postgres partitions
     cache {
       # The max number of tokens in the partition cache
       max-size = 1000
@@ -50,29 +51,51 @@ app {
     slow-query-threshold = 2 seconds
   }
 
+  # Query configuration for view indexing operations
   elem-query {
+    # Type of behaviour to adopt when all elements have been indexed
+    # - delay: wait for a fixed delay before querying the primary store again
+    # - passivation: based on the `project-last-update` feature. When selected:
+    #   - for active projects, waits for the fixed delay before retrying
+    #   - for inactive projects, waits for `project-last-update` to notify updates
+    #     of the project to resume, decreasing significantly the number of queries to
+    #     the primary store
     type = "delay"
+    # The maximum number of elements to retrieve in a single query
     batch-size = 30
+    # Fixed delay to wait before attempting to fetch new elements when the current ones have
+    # already been processed
     delay = 2s
   }
 
+  # Allows to compute incrementally the last update instant and ordering value for each project
+  # Split in two parts:
+  # - a write one running on a single node to compute and save in the database the new values
+  # - a read one running on all nodes, which retrieves those values and notify back indexing routines
+  # a project is active again
   project-last-update {
+    # Configuration for the write part
     batch {
       # the maximum batching size, corresponding to the maximum number of elements being aggregated
       # at the same time before pushing the update.
       max-elements = 100
-      # the maximum batching duration.
+      # the maximum amount of time before pushing the update
       max-interval = 1 second
     }
+    # Configuration for the read part
     query {
+      # Maximum number of rows to read back
       batch-size = 30
+      # How much time before attempting to get new updates
       refresh-strategy = 1 second
     }
+    # Only projects with a last update instant contained in this interval
     inactive-interval = 10 minutes
   }
 
   # Database export configuration
   export {
+    # how many rows to get per call
     batch-size = 30
     # Limit number of events per files (this default value should give ~1GB files)
     limit-per-file = 32000
@@ -331,7 +354,9 @@ app {
   # projection configuration
   projections {
     cluster {
+      # Number of nodes in the cluster
       size = 1
+      # Index of the current Delta instance in the cluster
       node-index = 0
     }
     batch {

delta/plugins/blazegraph/src/main/resources/blazegraph.conf

@@ -16,6 +16,7 @@ plugins.blazegraph {
 
   # Blazegraph query timeout
   query-timeout = "1 minute"
+
   slow-queries {
     #  How long a query takes before it is considered slow (and hence, logged)
     slow-query-threshold = 30 seconds
@@ -34,11 +35,9 @@ plugins.blazegraph {
   max-view-refs = 20
   #the maximum duration allowed so that synchronous indexing can complete
   sync-indexing-timeout = 10 seconds
-  # In order to disable this feature, set an infinite time ('Inf')
-  # idle-timeout = Inf
   batch {
     # the maximum batching size, corresponding to the maximum number of elements
-    # uploaded on a bulk request.
+    # pushed in Blazegraph in a bulk update request.
     max-elements = 10
     # the maximum batching duration.
     max-interval = 3 seconds

delta/plugins/composite-views/src/main/resources/composite-views.conf

@@ -43,7 +43,11 @@ plugins.composite-views {
   # the interval at which a view will look for requested restarts
   restart-check-interval = 3 seconds
 
+  # Batch configuration to push data to Blazegraph for both sources and projections
+  # Defaults to the one defined in the Blazegraph plugin
   blazegraph-batch = ${plugins.blazegraph.batch}
+
+  # Batch configuration to push data to Elasticsearch for the related projections
   elasticsearch-batch = ${plugins.elasticsearch.batch}
 
   # set to false to disable composite view indexing

delta/plugins/elasticsearch/src/main/resources/elasticsearch.conf

@@ -18,8 +18,6 @@ plugins.elasticsearch {
   prefix = ${app.defaults.indexing.prefix}
   # configuration of the maximum number of view references allowed on an aggregated view
   max-view-refs = 20
-  # In order to disable this feature, set an infinite time ('Inf')
-  # idle-timeout = Inf
   #the maximum duration allowed so that synchronous indexing can complete
   sync-indexing-timeout = 10 seconds
   #the value for `refresh` Elasticsearch parameter for synchronous indexing