Provide an API to get storages initialization state

There is an issue with using CRUD functionality if not all storages are
up. New function is added to get the information about storages
state: initialized or not. So, a user can poll state and wait for
storages to be initialized before making CRUD calls.

Resolves #229

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [Unreleased]
 
 ### Added
+* `crud.storage_info` function to get storages status (#229).
 
 ### Changed
 

README.md

@@ -32,6 +32,7 @@ It also provides the `crud-storage` and `crud-router` roles for
   - [Cut extra objects](#cut-extra-objects)
   - [Truncate](#truncate)
   - [Len](#len)
+  - [Storage info](#storage-info)
   - [Count](#count)
   - [Call options for crud methods](#call-options-for-crud-methods)
   - [Statistics](#statistics)
@@ -1074,6 +1075,43 @@ crud.len('customers')
 ...
 ```
 
+### Storage info
+
+```lua
+-- Get storages status
+local result, err = crud.storage_info(opts)
+```
+
+where:
+
+* `opts`:
+  * `timeout` (`?number`) -  maximum time (in seconds) to wait for response from
+  cluster instances.
+
+Returns storages status by instance UUID or nil with error. "status" field contains
+a string representing the status:
+* "running" - storage is initialized.
+* "uninitialized" - storage is not initialized or disabled.
+* "error" - error getting the status from a remote instance. Connection error, for example. 
+
+
+**Example:**
+
+```lua
+crud.storage_info()
+```
+```
+---
+- 5c3392a3-ce89-4aec-83f3-6cb5f18e60c3:
+    status: error
+  376435fc-7871-4686-9817-75df1a093e41:
+    status: running
+  afe7f578-943f-4bd9-b636-6356760f6586:
+    status: uninitialized
+...
+```
+
+
 ### Count
 
 `CRUD` supports multi-conditional count, treating a cluster as a single space.

crud.lua

@@ -138,6 +138,10 @@ crud.stats = stats.get
 -- @function reset_stats
 crud.reset_stats = stats.reset
 
+-- @refer utils.storage_info
+-- @function storage_info
+crud.storage_info = utils.storage_info
+
 --- Initializes crud on node
 --
 -- Exports all functions that are used for calls
@@ -165,6 +169,8 @@ function crud.init_storage()
     count.init()
     borders.init()
     sharding_metadata.init()
+
+    _G._crud.is_initialized = function() return true end
 end
 
 function crud.init_router()

crud/common/call.lua

@@ -5,6 +5,7 @@ local dev_checks = require('crud.common.dev_checks')
 local utils = require('crud.common.utils')
 local sharding_utils = require('crud.common.sharding.utils')
 local fiber_clock = require('fiber').clock
+local const = require('crud.common.const')
 
 local BaseIterator = require('crud.common.map_call_cases.base_iter')
 local BasePostprocessor = require('crud.common.map_call_cases.base_postprocessor')
@@ -13,8 +14,6 @@ local CallError = errors.new_class('CallError')
 
 local call = {}
 
-call.DEFAULT_VSHARD_CALL_TIMEOUT = 2
-
 function call.get_vshard_call_name(mode, prefer_replica, balance)
     dev_checks('string', '?boolean', '?boolean')
 
@@ -84,7 +83,7 @@ function call.map(func_name, func_args, opts)
         return nil, err
     end
 
-    local timeout = opts.timeout or call.DEFAULT_VSHARD_CALL_TIMEOUT
+    local timeout = opts.timeout or const.DEFAULT_VSHARD_CALL_TIMEOUT
 
     local iter = opts.iter
     if iter == nil then
@@ -149,7 +148,7 @@ function call.single(bucket_id, func_name, func_args, opts)
         return nil, err
     end
 
-    local timeout = opts.timeout or call.DEFAULT_VSHARD_CALL_TIMEOUT
+    local timeout = opts.timeout or const.DEFAULT_VSHARD_CALL_TIMEOUT
 
     local res, err = vshard.router[vshard_call_name](bucket_id, func_name, func_args, {
         timeout = timeout,
@@ -171,7 +170,7 @@ function call.any(func_name, func_args, opts)
         timeout = '?number',
     })
 
-    local timeout = opts.timeout or call.DEFAULT_VSHARD_CALL_TIMEOUT
+    local timeout = opts.timeout or const.DEFAULT_VSHARD_CALL_TIMEOUT
 
     local replicasets, err = vshard.router.routeall()
     if replicasets == nil then

crud/common/const.lua

@@ -8,4 +8,6 @@ const.SHARDING_RELOAD_RETRIES_NUM = 1
 const.NEED_SCHEMA_RELOAD   = 0x0001000
 const.NEED_SHARDING_RELOAD = 0x0001001
 
+const.DEFAULT_VSHARD_CALL_TIMEOUT = 2
+
 return const

crud/common/utils.lua

@@ -3,6 +3,7 @@ local ffi = require('ffi')
 local vshard = require('vshard')
 local fun = require('fun')
 local bit = require('bit')
+local log = require('log')
 
 local const = require('crud.common.const')
 local schema = require('crud.common.schema')
@@ -15,6 +16,8 @@ local ShardingError = errors.new_class('ShardingError', {capture_stack = false})
 local GetSpaceFormatError = errors.new_class('GetSpaceFormatError', {capture_stack = false})
 local FilterFieldsError = errors.new_class('FilterFieldsError', {capture_stack = false})
 local NotInitializedError = errors.new_class('NotInitialized')
+local GetReplicaStateError = errors.new_class('GetStorageStateError')
+local fiber_clock = require('fiber').clock
 
 local utils = {}
 
@@ -748,4 +751,64 @@ function utils.list_slice(list, start_index, end_index)
     return slice
 end
 
+--- Polls replicas for storage state
+--
+-- @function storage_info
+--
+-- @tparam ?number opts.timeout
+--  Function call timeout
+--
+-- @return a table of storage states by replica uuid.
+function utils.storage_info(opts)
+    local replicasets, err = vshard.router.routeall()
+    if replicasets == nil then
+        return nil, GetReplicaStateError:new("Failed to get all replicasets: %s", err.err)
+    end
+
+    opts = opts or {}
+
+    local futures_by_replicas = {}
+    local replica_state_by_uuid = {}
+    local async_opts = {is_async = true}
+    local timeout = opts.timeout or const.DEFAULT_VSHARD_CALL_TIMEOUT
+
+    for _, replicaset in pairs(replicasets) do
+        for replica_uuid, replica in pairs(replicaset.replicas) do
+            replica_state_by_uuid[replica_uuid] = {status = "error"}
+            local ok, res = pcall(replica.conn.call, replica.conn, "_crud.is_initialized",
+                                  {}, async_opts)
+            if ok then
+                futures_by_replicas[replica_uuid] = res
+            elseif res ~= nil then
+                log.error("Error getting storage info for %s: %s", replica_uuid, res)
+            end
+        end
+    end
+
+    local deadline = fiber_clock() + timeout
+    for replica_uuid, future in pairs(futures_by_replicas) do
+        local wait_timeout = deadline - fiber_clock()
+        if wait_timeout < 0 then
+            wait_timeout = 0
+        end
+
+        local result, err = future:wait_result(wait_timeout)
+        if result == nil then
+            future:discard()
+            if err ~= nil then
+                local str_err = tostring(err)
+                if (string.find(str_err, " is not defined") ~= nil) then
+                    replica_state_by_uuid[replica_uuid].status = "uninitialized"
+                else
+                    log.error("Error getting storage info for %s: %s", replica_uuid, err)
+                end
+            end
+        else
+            replica_state_by_uuid[replica_uuid].status = result[1] and "running" or "uninitialized"
+        end
+    end
+
+    return replica_state_by_uuid
+end
+
 return utils

test/integration/storages_state_test.lua

@@ -0,0 +1,89 @@
+local fio = require('fio')
+
+local t = require('luatest')
+
+local helpers = require('test.helper')
+
+local fiber = require("fiber")
+
+local pgroup = t.group('replicas_state', {
+    {engine = 'memtx'}
+})
+
+local all_storages_initialized = false
+
+local function wait_storages_init(g)
+    local storages_initialized = false
+    local attempts_left = 5
+    local wait_for_init_timeout = 1
+    while (attempts_left > 0 and not storages_initialized) do
+        local results, err = g.cluster.main_server.net_box:call("crud.storage_info", {})
+        t.assert_equals(err, nil, "Error getting storage status")
+        storages_initialized = true
+        for _,v in pairs(results) do
+            if v.status ~= "running" then
+                storages_initialized = false
+            end
+        end
+        if not storages_initialized then
+            fiber.sleep(wait_for_init_timeout)
+            attempts_left = attempts_left-1
+        end
+    end
+    return storages_initialized
+end
+
+pgroup.before_all(function(g)
+    g.cluster = helpers.Cluster:new({
+        datadir = fio.tempdir(),
+        server_command = helpers.entrypoint('srv_select'),
+        use_vshard = true,
+        replicasets = helpers.get_test_replicasets(),
+        env = {
+            ['ENGINE'] = g.params.engine,
+        },
+    })
+    g.cluster:start()
+
+    -- wait for storages to initialize
+    all_storages_initialized = wait_storages_init(g)
+end)
+
+pgroup.after_all(function(g)
+    helpers.stop_cluster(g.cluster)
+    fio.rmtree(g.cluster.datadir)
+end)
+
+pgroup.test_crud_storage_status_of_stopped_servers = function(g)
+    t.assert_equals(all_storages_initialized, true)
+
+    g.cluster:server("s2-replica"):stop()
+
+    local results, err = g.cluster.main_server.net_box:call("crud.storage_info", {})
+    t.assert_equals(err, nil, "Error getting storags states")
+
+    t.assert_equals(results[helpers.uuid('b', 1)].status, "running")
+    t.assert_equals(results[helpers.uuid('c', 1)].status, "running")
+    t.assert_equals(results[helpers.uuid('c', 2)].status, "error") -- peer closed
+end
+
+pgroup.test_disabled_storage_role = function(g)
+    t.assert_equals(all_storages_initialized, true)
+
+    -- stop crud storage role on one replica
+    local server = g.cluster:server("s1-replica")
+    local results = server.net_box:eval([[
+        local serviceregistry = require("cartridge.service-registry")
+        serviceregistry.get("crud-storage").stop()
+        return true
+    ]])
+
+    t.assert_not_equals(results, nil, "Fail to disable storage role")
+
+    local results, err = g.cluster.main_server.net_box:call("crud.storage_info", {})
+    t.assert_equals(err, nil, "Error getting storags states")
+
+    t.assert_equals(results[helpers.uuid('b', 1)].status, "running")
+    t.assert_equals(results[helpers.uuid('b', 2)].status, "uninitialized")
+    t.assert_equals(results[helpers.uuid('c', 1)].status, "running")
+end