Support local reads in client

src/cmd/cli.cpp

@@ -185,6 +185,7 @@ static const char* help_text =
     "    --immediate_commit all        Put pool only on OSDs with this or larger immediate_commit (none < small < all)\n"
     "    --level_placement <rules>     Use additional failure domain rules (example: \"dc=112233\")\n"
     "    --raw_placement <rules>       Specify raw PG generation rules (see documentation for details)\n"
+    "    --local_reads primary         Local read policy for replicated pools: primary, nearest or random\n"
     "    --primary_affinity_tags tags  Prefer to put primary copies on OSDs with all specified tags\n"
     "    --scrub_interval <time>       Enable regular scrubbing for this pool. Format: number + unit s/m/h/d/M/y\n"
     "    --used_for_app fs:<name>      Mark pool as used for VitastorFS with metadata in image <name>\n"

src/cmd/cli_pool_cfg.cpp

@@ -91,7 +91,7 @@ std::string validate_pool_config(json11::Json::object & new_cfg, json11::Json ol
         }
         else if (key == "name" || key == "scheme" || key == "immediate_commit" ||
             key == "failure_domain" || key == "root_node" || key == "scrub_interval" || key == "used_for_app" ||
-            key == "used_for_fs" || key == "raw_placement")
+            key == "used_for_fs" || key == "raw_placement" || key == "local_reads")
         {
             if (!value.is_string())
             {
@@ -165,6 +165,10 @@ std::string validate_pool_config(json11::Json::object & new_cfg, json11::Json ol
         new_cfg["used_for_app"] = "fs:"+new_cfg["used_for_fs"].string_value();
         new_cfg.erase("used_for_fs");
     }
+    if (new_cfg.find("local_reads") != new_cfg.end() && new_cfg["local_reads"].string_value() == "primary")
+    {
+        new_cfg.erase("local_reads");
+    }
 
     // Prevent autovivification of object keys. Now we don't modify the config, we just check it
     json11::Json cfg = new_cfg;
@@ -340,5 +344,19 @@ std::string validate_pool_config(json11::Json::object & new_cfg, json11::Json ol
         }
     }
 
+    // local_reads
+    if (!cfg["local_reads"].is_null())
+    {
+        auto lr = cfg["local_reads"].string_value();
+        if (lr != "" && lr != "primary" && lr != "nearest" && lr != "random")
+        {
+            return "local_reads must be '', 'primary', 'nearest' or 'random', but it is "+cfg["local_reads"].string_value();
+        }
+        if (lr != "" && lr != "primary" && scheme != POOL_SCHEME_REPLICATED)
+        {
+            return "EC pools don't support localized reads, please clear local_reads or set it to 'primary'";
+        }
+    }
+
     return "";
 }

src/cmd/cli_pool_ls.cpp

@@ -504,6 +504,7 @@ resume_3:
                 { "failure_domain", "Failure domain" },
                 { "root_node", "Root node" },
                 { "osd_tags_fmt", "OSD tags" },
+                { "local_reads", "Local read policy" },
                 { "primary_affinity_tags_fmt", "Primary affinity" },
                 { "block_size_fmt", "Block size" },
                 { "bitmap_granularity_fmt", "Bitmap granularity" },