simplifies jsonnet sharding (#3439)

production/ksonnet/loki/config.libsonnet

@@ -140,7 +140,7 @@
       frontend: {
         compress_responses: true,
         log_queries_longer_than: '5s',
-        max_outstanding_per_tenant: if !$._config.queryFrontend.sharded_queries_enabled then 256 else 2048,
+        max_outstanding_per_tenant: if $._config.queryFrontend.sharded_queries_enabled then 1024 else 256,
       },
       frontend_worker: {
         frontend_address: 'query-frontend.%s.svc.cluster.local:9095' % $._config.namespace,
@@ -176,9 +176,11 @@
       limits_config: {
         enforce_metric_name: false,
         // align middleware parallelism with shard factor to optimize one-legged sharded queries.
-        max_query_parallelism: if !$._config.queryFrontend.sharded_queries_enabled then
-          16  // default to 16x parallelism
-        else $._config.queryFrontend.shard_factor << 4,  // For a sharding factor of 16 (default), this is 256, or enough for 16 sharded queries.
+        max_query_parallelism: if $._config.queryFrontend.sharded_queries_enabled then
+          // For a sharding factor of 16 (default), this is 256, or enough for 16 sharded queries.
+          $._config.queryFrontend.shard_factor * 16
+        else
+          16,  // default to 16x parallelism
         reject_old_samples: true,
         reject_old_samples_max_age: '168h',
         max_query_length: '12000h',  // 500 days

production/ksonnet/loki/query-frontend.libsonnet

@@ -16,6 +16,7 @@
     container.mixin.readinessProbe.withInitialDelaySeconds(15) +
     container.mixin.readinessProbe.withTimeoutSeconds(1) +
     $.jaeger_mixin +
+    // sharded queries may need to do a nonzero amount of aggregation on the frontend.
     if $._config.queryFrontend.sharded_queries_enabled then
       $.util.resourcesRequests('2', '2Gi') +
       $.util.resourcesLimits(null, '6Gi') +