Address review comments

CHANGELOG.md

@@ -7,6 +7,20 @@ Changes by Version
 ### Backend Changes
 
 #### Breaking Changes
+* Configurable ES doc count ([#2453](https://github.com/jaegertracing/jaeger/pull/2453), [@albertteoh](https://github.com/albertteoh))
+
+    The `--es.max-num-spans` flag has been deprecated in favour of `--es.max-doc-count`.
+    `--es.max-num-spans` is marked for removal in v1.21.0 as indicated in the flag description.
+
+    If both `--es.max-num-spans` and `--es.max-doc-count` are set, the lesser of the two will be used.
+
+    The use of `--es.max-doc-count` (which defaults to 10,000) will limit the results from all Elasticsearch
+    queries by the configured value, limiting counts for Jaeger UI:
+
+    * Services
+    * Operations
+    * Dependencies (edges in a dependency graph)
+    * Span fetch size for a trace
 
 #### New Features
 

plugin/storage/es/options.go

@@ -179,7 +179,9 @@ func addFlags(flagSet *flag.FlagSet, nsConfig *namespaceConfig) {
 	flagSet.Int(
 		nsConfig.namespace+suffixMaxNumSpans,
 		nsConfig.MaxDocCount,
-		"(deprecated, will be removed in release v1.21.0. Please use es.max-doc-count). The maximum number of spans to fetch at a time per query in Elasticsearch")
+		"(deprecated, will be removed in release v1.21.0. Please use es.max-doc-count). "+
+			"The maximum number of spans to fetch at a time per query in Elasticsearch. "+
+			"The lesser of es.max-num-spans and es.max-doc-count will be used if both are set.")
 	flagSet.Int64(
 		nsConfig.namespace+suffixNumShards,
 		nsConfig.NumShards,
@@ -288,15 +290,11 @@ func initFromViper(cfg *namespaceConfig, v *viper.Viper) {
 	cfg.CreateIndexTemplates = v.GetBool(cfg.namespace + suffixCreateIndexTemplate)
 	cfg.Version = uint(v.GetInt(cfg.namespace + suffixVersion))
 
-	maxNumSpans := v.GetInt(cfg.namespace + suffixMaxNumSpans)
 	cfg.MaxDocCount = v.GetInt(cfg.namespace + suffixMaxDocCount)
 
-	if maxNumSpans != 0 {
-		if cfg.MaxDocCount != 0 {
-			cfg.MaxDocCount = int(math.Min(float64(maxNumSpans), float64(cfg.MaxDocCount)))
-		} else {
-			cfg.MaxDocCount = maxNumSpans
-		}
+	if v.IsSet(cfg.namespace + suffixMaxNumSpans) {
+		maxNumSpans := v.GetInt(cfg.namespace + suffixMaxNumSpans)
+		cfg.MaxDocCount = int(math.Min(float64(maxNumSpans), float64(cfg.MaxDocCount)))
 	}
 
 	// TODO: Need to figure out a better way for do this.