Prevent iteration by functional index for Tarantool < 2.8.4

expirationd.start fails with an error for a functional index if
a Tarantool instance version is less than 2.8.4. It can be disabled
using option.force_broken.

Closes #101

expirationd.lua

@@ -450,7 +450,12 @@ end
 --     configured upstream, it's an option `box.cfg.replication_source`
 --     (`box.cfg.replication` for Tarantool 1.7.6+). The option `force` let a
 --     user control where to start task processing and where don't.
---
+-- @boolean[opt] options.force_broken
+--     By default expirationd returns an error on broken cases:
+--     - Iteration by a functional index may lead to a crash for Tarantool
+--     < 2.8.4, see https://github.com/tarantool/expirationd/issues/101
+--     You can skip the error using the option if you know what you are doing
+--     (implement your own `iterate_with` as example).
 -- @number[opt] options.full_scan_delay
 --     Sleep time between full scans (in seconds). It is allowed to pass an FFI
 --     number: `1LL`, `1ULL` etc. Default value is 1 sec.
@@ -603,6 +608,7 @@ local function expirationd_run_task(name, space_id, is_tuple_expired, options)
         args = '?',
         atomic_iteration = '?boolean',
         force = '?boolean',
+        force_broken = '?boolean',
         full_scan_delay = '?number|cdata',
         full_scan_time = '?number|cdata',
         index = '?number|string',
@@ -650,6 +656,28 @@ local function expirationd_run_task(name, space_id, is_tuple_expired, options)
         if expire_index.type ~= "TREE" and expire_index.type ~= "HASH" then
             error("Not supported index type, expected TREE or HASH")
         end
+        local engine = box.space[space_id].engine
+        if engine == "memtx" and expire_index.func ~= nil then
+            local supported = false
+            local sdk = rawget(_G, "_TARANTOOL")
+            local major_minor_patch = sdk:split('-', 1)[1]
+            local major_minor_patch_parts = major_minor_patch:split('.', 2)
+
+            local major = tonumber(major_minor_patch_parts[1])
+            local minor = tonumber(major_minor_patch_parts[2])
+            local patch = tonumber(major_minor_patch_parts[3])
+            -- https://github.com/tarantool/expirationd/issues/101
+            -- fixed since 2.8.4 and 2.10
+            if (major == 2 and minor == 8 and patch >= 4)
+               or (major == 2 and minor >= 10) or (major > 2) then
+                 supported = true
+            end
+            local force_broken = options.force_broken or false
+            if not supported and not force_broken then
+                error("Functional indices are not supported for" ..
+                      " Tarantool < 2.8.4, see options.force_broken")
+            end
+        end
     end
     task.index = expire_index
 

test/helper.lua

@@ -262,4 +262,12 @@ function helpers.vinyl_is_broken()
     return broken_v1_10 or broken_v2
 end
 
+function helpers.memtx_func_index_is_broken()
+    local major, minor, patch = helpers.tarantool_version()
+    if major > 2 or (major == 2 and minor == 8 and patch >= 4) or (major == 2 and minor >= 10) then
+        return false
+    end
+    return true
+end
+
 return helpers

test/unit/custom_index_test.lua

@@ -204,8 +204,50 @@ function g.test_tree_index_multikey(cg)
     task:kill()
 end
 
+function g.test_memtx_tree_functional_index_broken(cg)
+    t.skip_if(_TARANTOOL < "2" or not helpers.memtx_func_index_is_broken(),
+              "Unsupported Tarantool version")
+    t.skip_if(cg.params.index_type ~= 'TREE', 'Unsupported index type')
+    t.skip_if(cg.params.engine == 'vinyl', 'Unsupported engine')
+    local expected = "Functional indices are not supported for Tarantool < 2.8.4," ..
+                     " see options.force_broken"
+
+    t.assert_error_msg_contains(expected, expirationd.start, "clean_all", cg.space.id,
+            helpers.is_expired_debug, {index = "functional_index"})
+end
+
+function g.test_memtx_tree_functional_index_force_broken(cg)
+    t.skip_if(_TARANTOOL < "2" or not helpers.memtx_func_index_is_broken(),
+              "Unsupported Tarantool version")
+    t.skip_if(cg.params.index_type ~= 'TREE', 'Unsupported index type')
+    t.skip_if(cg.params.engine == 'vinyl', 'Unsupported engine')
+
+    helpers.iteration_result = {}
+
+    cg.space:insert({1, "1", nil, nil, nil, nil, nil, "12"})
+    cg.space:insert({2, "2", nil, nil, nil, nil, nil, "21"})
+
+    local select_with = function(task)
+        return pairs(task.index:select({}, {iterator = "ALL"}))
+    end
+
+    local task = expirationd.start("clean_all", cg.space.id, helpers.is_expired_debug,
+            {index = "functional_index", force_broken = true, iterate_with = select_with})
+
+    -- wait for tuples expired
+    helpers.retrying({}, function()
+        -- sort by second character to eighth field
+        t.assert_equals(helpers.iteration_result, {
+            {2, "2", nil, nil, nil, nil, nil, "21"},
+            {1, "1", nil, nil, nil, nil, nil, "12"}
+        })
+    end)
+    task:kill()
+end
+
 function g.test_memtx_tree_functional_index(cg)
-    t.skip_if(_TARANTOOL < "2", "Unsupported Tarantool version")
+    t.skip_if(_TARANTOOL < "2" or helpers.memtx_func_index_is_broken(),
+              "Unsupported Tarantool version")
     t.skip_if(cg.params.index_type ~= 'TREE', 'Unsupported index type')
     t.skip_if(cg.params.engine == 'vinyl', 'Unsupported engine')