Implement alloc-osd (allocate a new OSD number) command

src/CMakeLists.txt

@@ -153,7 +153,7 @@ target_link_libraries(vitastor-nbd
 
 # vitastor-cli
 add_executable(vitastor-cli
-	cli.cpp cli_ls.cpp cli_create.cpp cli_modify.cpp cli_flatten.cpp cli_merge.cpp cli_rm.cpp cli_snap_rm.cpp
+	cli.cpp cli_alloc_osd.cpp cli_ls.cpp cli_create.cpp cli_modify.cpp cli_flatten.cpp cli_merge.cpp cli_rm.cpp cli_snap_rm.cpp
 )
 target_link_libraries(vitastor-cli
 	vitastor_client

src/cli.cpp

@@ -130,6 +130,9 @@ void cli_tool_t::help()
         "  <to> must be a child of <from> and <target> may be one of the layers between\n"
         "  <from> and <to>, including <from> and <to>.\n"
         "\n"
+        "%s alloc-osd\n"
+        "  Allocate a new OSD number and reserve it by creating empty /osd/stats/<n> key.\n"
+        "\n"
         "GLOBAL OPTIONS:\n"
         "  --etcd_address <etcd_address>\n"
         "  --iodepth N         Send N operations in parallel to each OSD when possible (default 32)\n"
@@ -139,7 +142,7 @@ void cli_tool_t::help()
         "  --no-color          Disable colored output\n"
         "  --json              JSON output\n"
         ,
-        exe_name, exe_name, exe_name, exe_name, exe_name, exe_name, exe_name, exe_name, exe_name
+        exe_name, exe_name, exe_name, exe_name, exe_name, exe_name, exe_name, exe_name, exe_name, exe_name
     );
     exit(0);
 }
@@ -268,6 +271,11 @@ void cli_tool_t::run(json11::Json cfg)
         // Remove multiple snapshots and rebase their children
         action_cb = start_snap_rm(cfg);
     }
+    else if (cmd[0] == "alloc-osd")
+    {
+        // Allocate a new OSD number
+        action_cb = start_alloc_osd(cfg);
+    }
     else
     {
         fprintf(stderr, "unknown command: %s\n", cmd[0].string_value().c_str());

src/cli.h

@@ -50,11 +50,12 @@ public:
     friend struct snap_flattener_t;
     friend struct snap_remover_t;
 
-    std::function<bool(void)> start_ls(json11::Json cfg);
-    std::function<bool(void)> start_create(json11::Json cfg);
-    std::function<bool(void)> start_modify(json11::Json cfg);
+    std::function<bool(void)> start_ls(json11::Json);
+    std::function<bool(void)> start_create(json11::Json);
+    std::function<bool(void)> start_modify(json11::Json);
     std::function<bool(void)> start_rm(json11::Json);
     std::function<bool(void)> start_merge(json11::Json);
     std::function<bool(void)> start_flatten(json11::Json);
     std::function<bool(void)> start_snap_rm(json11::Json);
+    std::function<bool(void)> start_alloc_osd(json11::Json cfg, uint64_t *out = NULL);
 };

src/cli_alloc_osd.cpp

@@ -0,0 +1,141 @@
+// Copyright (c) Vitaliy Filippov, 2019+
+// License: VNPL-1.1 (see README.md for details)
+
+#include <ctype.h>
+#include "cli.h"
+#include "cluster_client.h"
+#include "base64.h"
+
+#include <algorithm>
+
+// Safely allocate an OSD number
+struct alloc_osd_t
+{
+    cli_tool_t *parent;
+
+    json11::Json result;
+    uint64_t new_id = 1;
+
+    int state = 0;
+
+    bool is_done()
+    {
+        return state == 100;
+    }
+
+    void loop()
+    {
+        if (state == 1)
+            goto resume_1;
+        while (true)
+        {
+            etcd_txn(json11::Json::object {
+                { "compare", json11::Json::array {
+                    json11::Json::object {
+                        { "target", "VERSION" },
+                        { "version", 0 },
+                        { "key", base64_encode(
+                            parent->cli->st_cli.etcd_prefix+"/osd/stats/"+std::to_string(new_id)
+                        ) },
+                    },
+                } },
+                { "success", json11::Json::array {
+                    json11::Json::object {
+                        { "request_put", json11::Json::object {
+                            { "key", base64_encode(
+                                parent->cli->st_cli.etcd_prefix+"/osd/stats/"+std::to_string(new_id)
+                            ) },
+                            { "value", base64_encode("{}") },
+                        } },
+                    },
+                } },
+                { "failure", json11::Json::array {
+                    json11::Json::object {
+                        { "request_range", json11::Json::object {
+                            { "key", base64_encode(parent->cli->st_cli.etcd_prefix+"/osd/stats/") },
+                            { "range_end", base64_encode(parent->cli->st_cli.etcd_prefix+"/osd/stats0") },
+                            { "keys_only", true },
+                        } },
+                    },
+                } },
+            });
+        resume_1:
+            state = 1;
+            if (parent->waiting > 0)
+                return;
+            if (!result["succeeded"].bool_value())
+            {
+                std::vector<osd_num_t> used;
+                for (auto kv: result["responses"][0]["response_range"]["kvs"].array_items())
+                {
+                    std::string key = base64_decode(kv["key"].string_value());
+                    osd_num_t cur_osd;
+                    char null_byte = 0;
+                    sscanf(key.c_str() + parent->cli->st_cli.etcd_prefix.length(), "/osd/stats/%lu%c", &cur_osd, &null_byte);
+                    if (!cur_osd || null_byte != 0)
+                    {
+                        fprintf(stderr, "Invalid key in etcd: %s\n", key.c_str());
+                        continue;
+                    }
+                    used.push_back(cur_osd);
+                }
+                std::sort(used.begin(), used.end());
+                if (used[used.size()-1] == used.size())
+                {
+                    new_id = used.size()+1;
+                }
+                else
+                {
+                    int s = 0, e = used.size();
+                    while (e > s+1)
+                    {
+                        int c = (s+e)/2;
+                        if (used[c] == c+1)
+                            s = c;
+                        else
+                            e = c;
+                    }
+                    new_id = used[e-1]+1;
+                }
+            }
+        }
+        state = 100;
+    }
+
+    void etcd_txn(json11::Json txn)
+    {
+        parent->waiting++;
+        parent->cli->st_cli.etcd_txn(txn, ETCD_SLOW_TIMEOUT, [this](std::string err, json11::Json res)
+        {
+            parent->waiting--;
+            if (err != "")
+            {
+                fprintf(stderr, "Error reading from etcd: %s\n", err.c_str());
+                exit(1);
+            }
+            this->result = res;
+            parent->ringloop->wakeup();
+        });
+    }
+};
+
+std::function<bool(void)> cli_tool_t::start_alloc_osd(json11::Json cfg, uint64_t *out)
+{
+    json11::Json::array cmd = cfg["command"].array_items();
+    auto alloc_osd = new alloc_osd_t();
+    alloc_osd->parent = this;
+    return [alloc_osd, &out]()
+    {
+        alloc_osd->loop();
+        if (alloc_osd->is_done())
+        {
+            if (out)
+                *out = alloc_osd->new_id;
+            else if (alloc_osd->new_id)
+                printf("%lu\n", alloc_osd->new_id);
+            delete alloc_osd;
+            return true;
+        }
+        return false;
+    };
+}