Tests: validate CONFIG REWRITE for all params. (#7764)

This is a catch-all test to confirm that that rewrite produces a valid
output for all parameters and that this process does not introduce
undesired configuration changes.

src/config.c

@@ -1064,6 +1064,8 @@ struct rewriteConfigState {
     sds *lines;           /* Current lines as an array of sds strings */
     int has_tail;         /* True if we already added directives that were
                              not present in the original config file. */
+    int force_all;        /* True if we want all keywords to be force
+                             written. Currently only used for testing. */
 };
 
 /* Append the new line to the current configuration state. */
@@ -1110,6 +1112,7 @@ struct rewriteConfigState *rewriteConfigReadOldFile(char *path) {
     state->numlines = 0;
     state->lines = NULL;
     state->has_tail = 0;
+    state->force_all = 0;
     if (fp == NULL) return state;
 
     /* Read the old file line by line, populate the state. */
@@ -1188,7 +1191,7 @@ void rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *opti
 
     rewriteConfigMarkAsProcessed(state,option);
 
-    if (!l && !force) {
+    if (!l && !force && !state->force_all) {
         /* Option not used previously, and we are not forced to use it. */
         sdsfree(line);
         sdsfree(o);
@@ -1612,15 +1615,18 @@ cleanup:
  *
  * Configuration parameters that are at their default value, unless already
  * explicitly included in the old configuration file, are not rewritten.
+ * The force_all flag overrides this behavior and forces everything to be
+ * written. This is currently only used for testing purposes.
  *
  * On error -1 is returned and errno is set accordingly, otherwise 0. */
-int rewriteConfig(char *path) {
+int rewriteConfig(char *path, int force_all) {
     struct rewriteConfigState *state;
     sds newcontent;
     int retval;
 
     /* Step 1: read the old config into our rewrite state. */
     if ((state = rewriteConfigReadOldFile(path)) == NULL) return -1;
+    if (force_all) state->force_all = 1;
 
     /* Step 2: rewrite every single option, replacing or appending it inside
      * the rewrite state. */
@@ -2427,7 +2433,7 @@ NULL
             addReplyError(c,"The server is running without a config file");
             return;
         }
-        if (rewriteConfig(server.configfile) == -1) {
+        if (rewriteConfig(server.configfile, 0) == -1) {
             serverLog(LL_WARNING,"CONFIG REWRITE failed: %s", strerror(errno));
             addReplyErrorFormat(c,"Rewriting config file: %s", strerror(errno));
         } else {

src/debug.c

@@ -408,6 +408,7 @@ void debugCommand(client *c) {
 "STRUCTSIZE -- Return the size of different Redis core C structures.",
 "ZIPLIST <key> -- Show low level info about the ziplist encoding.",
 "STRINGMATCH-TEST -- Run a fuzz tester against the stringmatchlen() function.",
+"CONFIG-REWRITE-FORCE-ALL -- Like CONFIG REWRITE but writes all configuration options, including keywords not listed in original configuration file or default values.",
 #ifdef USE_JEMALLOC
 "MALLCTL <key> [<val>] -- Get or set a malloc tunning integer.",
 "MALLCTL-STR <key> [<val>] -- Get or set a malloc tunning string.",
@@ -805,6 +806,12 @@ NULL
     {
         stringmatchlen_fuzz_test();
         addReplyStatus(c,"Apparently Redis did not crash: test passed");
+    } else if (!strcasecmp(c->argv[1]->ptr,"config-rewrite-force-all") && c->argc == 2)
+    {
+        if (rewriteConfig(server.configfile, 1) == -1)
+            addReplyError(c, "CONFIG-REWRITE-FORCE-ALL failed");
+        else
+            addReply(c, shared.ok);
 #ifdef USE_JEMALLOC
     } else if(!strcasecmp(c->argv[1]->ptr,"mallctl") && c->argc >= 3) {
         mallctl_int(c, c->argv+2, c->argc-2);

src/sentinel.c

@@ -1954,7 +1954,7 @@ void sentinelFlushConfig(void) {
     int rewrite_status;
 
     server.hz = CONFIG_DEFAULT_HZ;
-    rewrite_status = rewriteConfig(server.configfile);
+    rewrite_status = rewriteConfig(server.configfile, 0);
     server.hz = saved_hz;
 
     if (rewrite_status == -1) goto werr;

src/server.c

@@ -2552,7 +2552,7 @@ int restartServer(int flags, mstime_t delay) {
     /* Config rewriting. */
     if (flags & RESTART_SERVER_CONFIG_REWRITE &&
         server.configfile &&
-        rewriteConfig(server.configfile) == -1)
+        rewriteConfig(server.configfile, 0) == -1)
     {
         serverLog(LL_WARNING,"Can't restart: configuration rewrite process "
                              "failed");

src/server.h

@@ -2101,7 +2101,7 @@ void appendServerSaveParams(time_t seconds, int changes);
 void resetServerSaveParams(void);
 struct rewriteConfigState; /* Forward declaration to export API. */
 void rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *option, sds line, int force);
-int rewriteConfig(char *path);
+int rewriteConfig(char *path, int force_all);
 void initConfigValues();
 
 /* db.c -- Keyspace access API */

tests/unit/introspection.tcl

@@ -147,4 +147,28 @@ start_server {tags {"introspection"}} {
 
         }
     }
+
+    # Do a force-all config rewrite and make sure we're able to parse
+    # it.
+    test {CONFIG REWRITE sanity} {
+        # Capture state of config before
+        set configs {}
+        foreach {k v} [r config get *] {
+            dict set configs $k $v
+        }
+
+        # Rewrite entire configuration, restart and confirm the
+        # server is able to parse it and start.
+        assert_equal [r debug config-rewrite-force-all] "OK"
+        restart_server 0 0
+        assert_equal [r ping] "PONG"
+
+        # Verify no changes were introduced
+        dict for {k v} $configs {
+            assert_equal $v [lindex [r config get $k] 1]
+        }
+    }
+
+    # Config file at this point is at a wierd state, and includes all
+    # known keywords. Might be a good idea to avoid adding tests here.
 }