kvs: remove dropcache

Problem: KVS dropcache code was added very early on in KVS
prototyping for testing.  It is basically not used anymore.  If we
want to test something that requires a "clean" slate for the KVS,
we can just start a new instance and test with that.

Solution: Remove all KVS dropcache code.  Remove all associated
tests.  Update one regression test to be accomplished through two
instances rather than one to emulate an emptying of the cache.

Fixes #6608

Author: chu11

src/modules/kvs/kvs.c

@@ -222,15 +222,6 @@ static int event_subscribe (struct kvs_ctx *ctx, const char *ns)
      */
 
     if (!(ctx->events_init)) {
-
-        /* These belong to all namespaces, subscribe once the first
-         * time we init a namespace */
-
-        if (flux_event_subscribe (ctx->h, "kvs.dropcache") < 0) {
-            flux_log_error (ctx->h, "flux_event_subscribe");
-            goto cleanup;
-        }
-
         /* On rank 0, we need to listen for all of these namespace
          * events, all of the time.  So subscribe to them just once on
          * rank 0. */
@@ -1171,62 +1162,6 @@ static void transaction_check_cb (flux_reactor_t *r,
  * rpc/event callbacks
  */
 
-static void dropcache_request_cb (flux_t *h, flux_msg_handler_t *mh,
-                                  const flux_msg_t *msg, void *arg)
-{
-    struct kvs_ctx *ctx = arg;
-    int size, expcount = 0;
-
-    /* irrelevant if root not initialized, drop cache entries */
-
-    if (flux_request_decode (msg, NULL, NULL) < 0)
-        goto error;
-    size = cache_count_entries (ctx->cache);
-    if ((expcount = cache_expire_entries (ctx->cache, 0)) < 0) {
-        flux_log_error (ctx->h, "%s: cache_expire_entries", __FUNCTION__);
-        goto error;
-    }
-    else {
-        flux_log (h,
-                  LOG_ALERT,
-                  "dropped %d of %d cache entries",
-                  expcount,
-                  size);
-    }
-    if (flux_respond (h, msg, NULL) < 0)
-        flux_log_error (h, "%s: flux_respond", __FUNCTION__);
-    return;
-error:
-    if (flux_respond_error (h, msg, errno, NULL) < 0)
-        flux_log_error (h, "%s: flux_respond_error", __FUNCTION__);
-}
-
-static void dropcache_event_cb (flux_t *h,
-                                flux_msg_handler_t *mh,
-                                const flux_msg_t *msg,
-                                void *arg)
-{
-    struct kvs_ctx *ctx = arg;
-    int size, expcount = 0;
-
-    /* irrelevant if root not initialized, drop cache entries */
-
-    if (flux_event_decode (msg, NULL, NULL) < 0) {
-        flux_log_error (ctx->h, "%s: flux_event_decode", __FUNCTION__);
-        return;
-    }
-    size = cache_count_entries (ctx->cache);
-    if ((expcount = cache_expire_entries (ctx->cache, 0)) < 0)
-        flux_log_error (ctx->h, "%s: cache_expire_entries", __FUNCTION__);
-    else {
-        flux_log (h,
-                  LOG_ALERT,
-                  "dropped %d of %d cache entries",
-                  expcount,
-                  size);
-    }
-}
-
 static int heartbeat_root_cb (struct kvsroot *root, void *arg)
 {
     struct kvs_ctx *ctx = arg;
@@ -2600,18 +2535,6 @@ static const struct flux_msg_handler_spec htab[] = {
         getroot_request_cb,
         FLUX_ROLE_USER
     },
-    {
-        FLUX_MSGTYPE_REQUEST,
-        "kvs.dropcache",
-        dropcache_request_cb,
-        0
-    },
-    {
-        FLUX_MSGTYPE_EVENT,
-        "kvs.dropcache",
-        dropcache_event_cb,
-        0
-    },
     {
         FLUX_MSGTYPE_REQUEST,
         "kvs.disconnect",

t/issues/t1760-kvs-use-after-free.sh

@@ -1,6 +1,34 @@
 #!/bin/sh -e
 # dropcache, do a put that misses a references, unlink a dir, the reference
 # should not be missing.
+#
+# N.B. the reason this test is split across two flux starts is we need the
+# internal KVS cache to be empty
 
-TEST=issue1760
-${FLUX_BUILD_DIR}/t/kvs/issue1760 a
+cat <<-EOF >t1760setup.sh
+#!/bin/sh -e
+
+flux kvs mkdir foo
+
+EOF
+
+cat <<-EOF >t1760test.sh
+#!/bin/sh -e
+
+${FLUX_BUILD_DIR}/t/kvs/issue1760 foo
+
+EOF
+
+chmod +x t1760setup.sh
+chmod +x t1760test.sh
+
+STATEDIR=issue1760-statedir
+mkdir issue1760-statedir
+
+flux start -s 1 \
+    --setattr=statedir=${STATEDIR} \
+    ./t1760setup.sh
+
+flux start -s 1 \
+    --setattr=statedir=${STATEDIR} \
+    ./t1760test.sh

t/kvs/issue1760.c

@@ -8,7 +8,13 @@
  * SPDX-License-Identifier: LGPL-3.0
 \************************************************************/
 
-/* issue1760.c - make kvs module sad */
+/* issue1760.c - make kvs module sad
+ *
+ * - it is assumed the directory passed in under argv[1] has already
+ * been created.  The command line `flux kvs` command does not allow
+ * a put & unlink to be done under a single transaction, thus the need
+ * for this utility test.
+ */
 
 /* Failure mode 1:
 ./issue1760 a
@@ -52,24 +58,6 @@ int main (int argc, char *argv[])
     if (!(h = flux_open (NULL, 0)))
         log_err_exit ("flux_open");
 
-    /* Mkdir <dir>
-     */
-    if (!(txn = flux_kvs_txn_create ()))
-        log_err_exit ("flux_kvs_txn_create");
-    if (flux_kvs_txn_mkdir (txn, 0, dir) < 0)
-        log_err_exit ("flux_kvs_txn_mkdir");
-    if (!(f = flux_kvs_commit (h, NULL, 0, txn)))
-        log_err_exit ("flux_kvs_commit");
-    if (flux_future_get (f, NULL) < 0)
-        log_err_exit ("flux_future_get");
-    flux_future_destroy (f);
-    flux_kvs_txn_destroy (txn);
-
-    /* Expire internal kvs cache
-     */
-    if (flux_kvs_dropcache (h) < 0)
-        log_err_exit ("flux_kvs_dropcache");
-
     /* Commit the following:
      * put <dir>.a
      * unlink <dir>

t/t1000-kvs.t

@@ -1164,17 +1164,6 @@ test_expect_success 'kvs: --sequence on write ops works' '
         test $VER -eq $SEQ
 '
 
-#
-# dropcache tests
-#
-
-test_expect_success 'kvs: dropcache works' '
-	flux kvs dropcache
-'
-test_expect_success 'kvs: dropcache --all works' '
-	flux kvs dropcache --all
-'
-
 #
 # version/wait tests
 #

t/t1005-kvs-security.t

@@ -379,12 +379,6 @@ test_expect_success 'kvs: guest cannot make a symlink in the test ns on rank 1'
 # Basic tests, user can't perform non-namespace operations
 #
 
-test_expect_success 'kvs: dropcache fails (user)' '
-        set_userid 9999 &&
-        ! flux kvs dropcache &&
-        unset_userid
-'
-
 test_expect_success 'kvs: stats works (user)' '
         set_userid 9999 &&
         flux module stats kvs >/dev/null &&