Add new SCRIPT SHOW subcommand to dump script via sha1 (#617)

In some scenarios, the business may not be able to find the
previously used Lua script and only have a SHA signature.
Or there are multiple identical evalsha's args in monitor/slowlog,
and admin is not able to distinguish the script body.

Add a new script subcommmand to show the contents of script
given the scripts sha1. Returns a NOSCRIPT error if the script
is not present in the cache.

Usage: `SCRIPT SHOW sha1`
Complexity: `O(1)`

Closes #604.
Doc PR: valkey-io/valkey-doc#143

---------

Signed-off-by: wei.kukey <wei.kukey@gmail.com>
Signed-off-by: Madelyn Olson <madelyneolson@gmail.com>
Co-authored-by: Madelyn Olson <madelyneolson@gmail.com>
Co-authored-by: Binbin <binloveplay1314@qq.com>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

src/commands.def

@@ -5333,6 +5333,28 @@ struct COMMAND_ARG SCRIPT_LOAD_Args[] = {
 {MAKE_ARG("script",ARG_TYPE_STRING,-1,NULL,NULL,NULL,CMD_ARG_NONE,0,NULL)},
 };
 
+/********** SCRIPT SHOW ********************/
+
+#ifndef SKIP_CMD_HISTORY_TABLE
+/* SCRIPT SHOW history */
+#define SCRIPT_SHOW_History NULL
+#endif
+
+#ifndef SKIP_CMD_TIPS_TABLE
+/* SCRIPT SHOW tips */
+#define SCRIPT_SHOW_Tips NULL
+#endif
+
+#ifndef SKIP_CMD_KEY_SPECS_TABLE
+/* SCRIPT SHOW key specs */
+#define SCRIPT_SHOW_Keyspecs NULL
+#endif
+
+/* SCRIPT SHOW argument table */
+struct COMMAND_ARG SCRIPT_SHOW_Args[] = {
+{MAKE_ARG("sha1",ARG_TYPE_STRING,-1,NULL,NULL,NULL,CMD_ARG_NONE,0,NULL)},
+};
+
 /* SCRIPT command table */
 struct COMMAND_STRUCT SCRIPT_Subcommands[] = {
 {MAKE_CMD("debug","Sets the debug mode of server-side Lua scripts.","O(1)","3.2.0",CMD_DOC_NONE,NULL,NULL,"scripting",COMMAND_GROUP_SCRIPTING,SCRIPT_DEBUG_History,0,SCRIPT_DEBUG_Tips,0,scriptCommand,3,CMD_NOSCRIPT,ACL_CATEGORY_SCRIPTING,SCRIPT_DEBUG_Keyspecs,0,NULL,1),.args=SCRIPT_DEBUG_Args},
@@ -5341,6 +5363,7 @@ struct COMMAND_STRUCT SCRIPT_Subcommands[] = {
 {MAKE_CMD("help","Returns helpful text about the different subcommands.","O(1)","5.0.0",CMD_DOC_NONE,NULL,NULL,"scripting",COMMAND_GROUP_SCRIPTING,SCRIPT_HELP_History,0,SCRIPT_HELP_Tips,0,scriptCommand,2,CMD_LOADING|CMD_STALE,ACL_CATEGORY_SCRIPTING,SCRIPT_HELP_Keyspecs,0,NULL,0)},
 {MAKE_CMD("kill","Terminates a server-side Lua script during execution.","O(1)","2.6.0",CMD_DOC_NONE,NULL,NULL,"scripting",COMMAND_GROUP_SCRIPTING,SCRIPT_KILL_History,0,SCRIPT_KILL_Tips,2,scriptCommand,2,CMD_NOSCRIPT|CMD_ALLOW_BUSY,ACL_CATEGORY_SCRIPTING,SCRIPT_KILL_Keyspecs,0,NULL,0)},
 {MAKE_CMD("load","Loads a server-side Lua script to the script cache.","O(N) with N being the length in bytes of the script body.","2.6.0",CMD_DOC_NONE,NULL,NULL,"scripting",COMMAND_GROUP_SCRIPTING,SCRIPT_LOAD_History,0,SCRIPT_LOAD_Tips,2,scriptCommand,3,CMD_NOSCRIPT|CMD_STALE,ACL_CATEGORY_SCRIPTING,SCRIPT_LOAD_Keyspecs,0,NULL,1),.args=SCRIPT_LOAD_Args},
+{MAKE_CMD("show","Show server-side Lua script in the script cache.","O(1).","8.0.0",CMD_DOC_NONE,NULL,NULL,"scripting",COMMAND_GROUP_SCRIPTING,SCRIPT_SHOW_History,0,SCRIPT_SHOW_Tips,0,scriptCommand,3,CMD_NOSCRIPT,ACL_CATEGORY_SCRIPTING,SCRIPT_SHOW_Keyspecs,0,NULL,1),.args=SCRIPT_SHOW_Args},
 {0}
 };
 

src/commands/script-show.json

@@ -0,0 +1,27 @@
+{
+    "SHOW": {
+        "summary": "Show server-side Lua script in the script cache.",
+        "complexity": "O(1).",
+        "group": "scripting",
+        "since": "8.0.0",
+        "arity": 3,
+        "container": "SCRIPT",
+        "function": "scriptCommand",
+        "command_flags": [
+            "NOSCRIPT"
+        ],
+        "acl_categories": [
+            "SCRIPTING"
+        ],
+        "arguments": [
+            {
+                "name": "sha1",
+                "type": "string"
+            }
+        ],
+        "reply_schema": {
+            "description": "Lua script if sha1 hash exists in script cache.",
+            "type": "string"
+        }
+    }
+}

src/eval.c

@@ -682,6 +682,8 @@ void scriptCommand(client *c) {
 "    Kill the currently executing Lua script.",
 "LOAD <script>",
 "    Load a script into the scripts cache without executing it.",
+"SHOW <sha1>",
+"    Show a script from the scripts cache.",
 NULL
         };
         /* clang-format on */
@@ -735,6 +737,16 @@ NULL
             addReplyError(c, "Use SCRIPT DEBUG YES/SYNC/NO");
             return;
         }
+    } else if (c->argc == 3 && !strcasecmp(c->argv[1]->ptr, "show")) {
+        dictEntry *de;
+        luaScript *ls;
+
+        if (sdslen(c->argv[2]->ptr) == 40 && (de = dictFind(lctx.lua_scripts, c->argv[2]->ptr))) {
+            ls = dictGetVal(de);
+            addReplyBulk(c, ls->body);
+        } else {
+            addReplyErrorObject(c, shared.noscripterr);
+        }
     } else {
         addReplySubcommandSyntaxError(c);
     }

src/server.c

@@ -1814,7 +1814,7 @@ void createSharedObjects(void) {
     shared.syntaxerr = createObject(OBJ_STRING, sdsnew("-ERR syntax error\r\n"));
     shared.sameobjecterr = createObject(OBJ_STRING, sdsnew("-ERR source and destination objects are the same\r\n"));
     shared.outofrangeerr = createObject(OBJ_STRING, sdsnew("-ERR index out of range\r\n"));
-    shared.noscripterr = createObject(OBJ_STRING, sdsnew("-NOSCRIPT No matching script. Please use EVAL.\r\n"));
+    shared.noscripterr = createObject(OBJ_STRING, sdsnew("-NOSCRIPT No matching script.\r\n"));
     createSharedObjectsWithCompat();
     shared.primarydownerr = createObject(
         OBJ_STRING, sdsnew("-MASTERDOWN Link with MASTER is down and replica-serve-stale-data is set to 'no'.\r\n"));

tests/unit/scripting.tcl

@@ -638,6 +638,21 @@ start_server {tags {"scripting"}} {
             [r evalsha b534286061d4b9e4026607613b95c06c06015ae8 0]
     } {b534286061d4b9e4026607613b95c06c06015ae8 loaded}
 
+    test {SCRIPT SHOW - is able to dump scripts from the scripting cache} {
+        r script load "return 'dump'"
+        r script show 4f5a49d7b18244a3b100d159b78b51474e23e081
+    } {return 'dump'}
+
+    test {SCRIPT SHOW - wrong sha1 length or invalid sha1 char return noscript error} {
+        assert_error {NOSCRIPT*} {r script show b534286061d4b06c06015ae8}
+        assert_error {NOSCRIPT*} {r script show AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA}
+    }
+
+    test {SCRIPT SHOW - script not exist return noscript error} {
+        r script flush
+        assert_error {NOSCRIPT*} {r script show 4f5a49d7b18244a3b100d159b78b51474e23e081}
+    }
+
     test "SORT is normally not alpha re-ordered for the scripting engine" {
         r del myset
         r sadd myset 1 2 3 4 10