NSR : nsr server code generation patch

The NSR-server with this patch, appoints the first node
on every replica subvolume, as the leader for that subvolume.
On receiving a 'write' fop, the leader first checks if there is
quorum in the replica subvolume to proceeed. In case there isn't
it fails with EROFS.

If there is quorum, the leader forwards the fop to the
followers. The followers on receiving the fop, perform the
operation, and based on the success or failure of the outcome
send a +ve or a -ve ack to the leader.

The leader after receiving acks from the followers performs a
quorum check of the acks, to see if it should even try to perform
the fop. If quorum is not being met, and the leader's outcome
wouldn't affect quorum, then it would send -ve ack to the client
without even performing the fop. If quorum is being met, the leader
will then try the fop on itself, and based on it's outcome perform
a quorum check of all the acks received (this time, including it's
own). Based on the result of the quorum check (irrespective of the
outcome on the leader), a +ve or -ve ack is send back to the client.

Change-Id: I860654b74c53e9b139b37dba43848e5504df6dce
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/12705
Smoke: Gluster Build System <jenkins@build.gluster.com>
Tested-by: Jeff Darcy <jdarcy@redhat.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>

1 files changed, 429 insertions, 0 deletions

diff --git a/xlators/experimental/nsr-server/src/all-templates.c b/xlators/experimental/nsr-server/src/all-templates.c
new file mode 100644
index 00000000000..300abea959d
--- /dev/null
+++ b/xlators/experimental/nsr-server/src/all-templates.c
@@ -0,0 +1,429 @@
+/*
+ * You can put anything here - it doesn't even have to be a comment - and it
+ * will be ignored until we reach the first template-name comment.
+ */
+
+
+/* template-name read-fop */
+int32_t
+nsr_@NAME@ (call_frame_t *frame, xlator_t *this,
+            @LONG_ARGS@)
+{
+        nsr_private_t   *priv   = this->private;
+        gf_boolean_t in_recon = _gf_false;
+        int32_t recon_term, recon_index;
+
+        /* allow reads during reconciliation       *
+         * TBD: allow "dirty" reads on non-leaders *
+         */
+        if (xdata &&
+            (dict_get_int32(xdata, RECON_TERM_XATTR, &recon_term) == 0) &&
+            (dict_get_int32(xdata, RECON_INDEX_XATTR, &recon_index) == 0)) {
+                in_recon = _gf_true;
+        }
+
+        if ((!priv->leader) && (in_recon == _gf_false)) {
+                goto err;
+        }
+
+        STACK_WIND (frame, default_@NAME@_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->@NAME@,
+                    @SHORT_ARGS@);
+        return 0;
+
+err:
+        STACK_UNWIND_STRICT (@NAME@, frame, -1, EREMOTE,
+                             @ERROR_ARGS@);
+        return 0;
+}
+
+/* template-name read-dispatch */
+/* No "dispatch" function needed for @NAME@ */
+
+/* template-name read-fan-in */
+/* No "fan-in" function needed for @NAME@ */
+
+/* template-name read-continue */
+/* No "continue" function needed for @NAME@ */
+
+/* template-name read-complete */
+/* No "complete" function needed for @NAME@ */
+
+/* template-name write-fop */
+int32_t
+nsr_@NAME@ (call_frame_t *frame, xlator_t *this,
+            @LONG_ARGS@)
+{
+        nsr_local_t     *local          = NULL;
+        nsr_private_t   *priv           = this->private;
+        gf_boolean_t     result         = _gf_false;
+        int             op_errno        = ENOMEM;
+        int             from_leader;
+        int             from_recon;
+        uint32_t        ti = 0;
+
+        /*
+         * Our first goal here is to avoid "split brain surprise" for users who
+         * specify exactly 50% with two- or three-way replication.  That means
+         * either a more-than check against half the total replicas or an
+         * at-least check against half of our peers (one less).  Of the two,
+         * only an at-least check supports the intuitive use of 100% to mean
+         * all replicas must be present, because "more than 100%" will never
+         * succeed regardless of which count we use.  This leaves us with a
+         * slightly non-traditional definition of quorum ("at least X% of peers
+         * not including ourselves") but one that's useful enough to be worth
+         * it.
+         *
+         * Note that n_children and up_children *do* include the local
+         * subvolume, so we need to subtract one in each case.
+         */
+        if (priv->leader) {
+                result = fop_quorum_check (this, (double)(priv->n_children - 1),
+                                   (double)(priv->up_children - 1));
+
+                if (result == _gf_false) {
+                        /* Emulate the AFR client-side-quorum behavior. */
+                        op_errno = EROFS;
+                        goto err;
+                }
+        } else {
+                if (xdata) {
+                        from_leader = !!dict_get(xdata, NSR_TERM_XATTR);
+                        from_recon = !!dict_get(xdata, RECON_TERM_XATTR)
+                                  && !!dict_get(xdata, RECON_INDEX_XATTR);
+                } else {
+                        from_leader = from_recon = _gf_false;
+                }
+
+                /* follower/recon path        *
+                 * just send it to local node *
+                 */
+                if (!from_leader && !from_recon) {
+                        op_errno = EREMOTE;
+                        goto err;
+                }
+        }
+
+        local = mem_get0(this->local_pool);
+        if (!local) {
+                goto err;
+        }
+#if defined(NSR_CG_NEED_FD)
+        local->fd = fd_ref(fd);
+#else
+        local->fd = NULL;
+#endif
+        INIT_LIST_HEAD(&local->qlinks);
+        frame->local = local;
+
+        /*
+         * If we let it through despite not being the leader, then we just want
+         * to pass it on down without all of the additional xattrs, queuing, and
+         * so on.  However, nsr_*_complete does depend on the initialization
+         * immediately above this.
+         */
+        if (!priv->leader) {
+                STACK_WIND (frame, nsr_@NAME@_complete,
+                            FIRST_CHILD(this), FIRST_CHILD(this)->fops->@NAME@,
+                            @SHORT_ARGS@);
+                return 0;
+        }
+
+        if (!xdata) {
+                xdata = dict_new();
+                if (!xdata) {
+                        gf_msg (this->name, GF_LOG_ERROR, ENOMEM,
+                                N_MSG_MEM_ERR, "failed to allocate xdata");
+                        goto err;
+                }
+        }
+
+        if (dict_set_int32(xdata, NSR_TERM_XATTR, priv->current_term) != 0) {
+                gf_msg (this->name, GF_LOG_ERROR, 0,
+                        N_MSG_DICT_FLR, "failed to set nsr-term");
+                goto err;
+        }
+
+        LOCK(&priv->index_lock);
+        ti = ++(priv->index);
+        UNLOCK(&priv->index_lock);
+        if (dict_set_int32(xdata, NSR_INDEX_XATTR, ti) != 0) {
+                gf_msg (this->name, GF_LOG_ERROR, 0,
+                        N_MSG_DICT_FLR, "failed to set index");
+                goto err;
+        }
+
+        local->stub = fop_@NAME@_stub (frame, nsr_@NAME@_continue,
+                                       @SHORT_ARGS@);
+        if (!local->stub) {
+                goto err;
+        }
+
+
+#if defined(NSR_CG_QUEUE)
+        nsr_inode_ctx_t         *ictx   = nsr_get_inode_ctx(this, fd->inode);
+
+        if (!ictx) {
+                op_errno = EIO;
+                goto err;
+        }
+        LOCK(&ictx->lock);
+                if (ictx->active) {
+                        gf_msg_debug (this->name, 0,
+                                      "queuing request due to conflict");
+                        /*
+                         * TBD: enqueue only for real conflict
+                         *
+                         * Currently we just act like all writes are in
+                         * conflict with one another.  What we should really do
+                         * is check the active/pending queues and defer only if
+                         * there's a conflict there.
+                         *
+                         * It's important to check the pending queue because we
+                         * might have an active request X which conflicts with
+                         * a pending request Y, and this request Z might
+                         * conflict with Y but not X.  If we checked only the
+                         * active queue then Z could jump ahead of Y, which
+                         * would be incorrect.
+                         */
+                        local->qstub = fop_@NAME@_stub (frame,
+                                                        nsr_@NAME@_dispatch,
+                                                        @SHORT_ARGS@);
+                        if (!local->qstub) {
+                                UNLOCK(&ictx->lock);
+                                goto err;
+                        }
+                        list_add_tail(&local->qlinks, &ictx->pqueue);
+                        ++(ictx->pending);
+                        UNLOCK(&ictx->lock);
+                        return 0;
+                } else {
+                        list_add_tail(&local->qlinks, &ictx->aqueue);
+                        ++(ictx->active);
+                }
+        UNLOCK(&ictx->lock);
+#endif
+
+        return nsr_@NAME@_dispatch (frame, this, @SHORT_ARGS@);
+
+err:
+        if (local) {
+                if (local->stub) {
+                        call_stub_destroy(local->stub);
+                }
+                if (local->qstub) {
+                        call_stub_destroy(local->qstub);
+                }
+                if (local->fd) {
+                        fd_unref(local->fd);
+                }
+                mem_put(local);
+        }
+        STACK_UNWIND_STRICT (@NAME@, frame, -1, op_errno,
+                             @ERROR_ARGS@);
+        return 0;
+}
+
+/* template-name write-dispatch */
+int32_t
+nsr_@NAME@_dispatch (call_frame_t *frame, xlator_t *this,
+                     @LONG_ARGS@)
+{
+        nsr_local_t     *local  = frame->local;
+        nsr_private_t   *priv   = this->private;
+        xlator_list_t   *trav;
+
+        /*
+         * TBD: unblock pending request(s) if we fail after this point but
+         * before we get to nsr_@NAME@_complete (where that code currently
+         * resides).
+         */
+
+        local->call_count = priv->n_children - 1;
+        local->successful_acks = 0;
+        for (trav = this->children->next; trav; trav = trav->next) {
+                STACK_WIND (frame, nsr_@NAME@_fan_in,
+                            trav->xlator, trav->xlator->fops->@NAME@,
+                            @SHORT_ARGS@);
+        }
+
+        /* TBD: variable Issue count */
+        return 0;
+}
+
+/* template-name write-fan-in */
+int32_t
+nsr_@NAME@_fan_in (call_frame_t *frame, void *cookie, xlator_t *this,
+                   int32_t op_ret, int32_t op_errno,
+                   @LONG_ARGS@)
+{
+        nsr_local_t     *local  = frame->local;
+        uint8_t         call_count;
+
+        gf_msg_trace (this->name, 0, "op_ret = %d, op_errno = %d\n",
+                      op_ret, op_errno);
+
+        LOCK(&frame->lock);
+        call_count = --(local->call_count);
+        if (op_ret != -1) {
+                /* Increment the number of successful acks *
+                 * received for the operation.             *
+                 */
+                (local->successful_acks)++;
+                local->successful_op_ret = op_ret;
+        }
+        gf_msg_debug (this->name, 0, "succ_acks = %d, op_ret = %d, op_errno = %d\n",
+                      op_ret, op_errno, local->successful_acks);
+        UNLOCK(&frame->lock);
+
+        /* TBD: variable Completion count */
+        if (call_count == 0) {
+                call_resume(local->stub);
+        }
+
+        return 0;
+}
+
+/* template-name write-continue */
+int32_t
+nsr_@NAME@_continue (call_frame_t *frame, xlator_t *this,
+                     @LONG_ARGS@)
+{
+        int32_t          ret = -1;
+        gf_boolean_t     result   = _gf_false;
+        nsr_local_t     *local    = NULL;
+        nsr_private_t   *priv     = NULL;
+
+        GF_VALIDATE_OR_GOTO ("nsr", this, out);
+        GF_VALIDATE_OR_GOTO (this->name, frame, out);
+        priv = this->private;
+        local = frame->local;
+        GF_VALIDATE_OR_GOTO (this->name, priv, out);
+        GF_VALIDATE_OR_GOTO (this->name, local, out);
+
+        /* Perform quorum check to see if the leader needs     *
+         * to perform the operation. If the operation will not *
+         * meet quorum irrespective of the leader's result     *
+         * there is no point in the leader performing the fop  *
+         */
+        result = fop_quorum_check (this, (double)priv->n_children,
+                                   (double)local->successful_acks + 1);
+        if (result == _gf_false) {
+                STACK_UNWIND_STRICT (@NAME@, frame, -1, EROFS,
+                                     @ERROR_ARGS@);
+        } else {
+                STACK_WIND (frame, nsr_@NAME@_complete,
+                            FIRST_CHILD(this), FIRST_CHILD(this)->fops->@NAME@,
+                            @SHORT_ARGS@);
+        }
+
+        ret = 0;
+out:
+        return ret;
+}
+
+/* template-name write-complete */
+int32_t
+nsr_@NAME@_complete (call_frame_t *frame, void *cookie, xlator_t *this,
+                     int32_t op_ret, int32_t op_errno,
+                     @LONG_ARGS@)
+{
+        gf_boolean_t     result         = _gf_false;
+        nsr_private_t   *priv           = this->private;
+
+        nsr_local_t *local = frame->local;
+
+        /* If the fop failed on the leader, then reduce one succesful ack
+         * before calculating the fop quorum
+         */
+        LOCK(&frame->lock);
+        if (op_ret == -1)
+                (local->successful_acks)--;
+        UNLOCK(&frame->lock);
+
+#if defined(NSR_CG_QUEUE)
+        nsr_inode_ctx_t *ictx;
+        nsr_local_t     *next;
+
+        if (local->qlinks.next != &local->qlinks) {
+                list_del(&local->qlinks);
+                ictx = nsr_get_inode_ctx(this, local->fd->inode);
+                if (ictx) {
+                        LOCK(&ictx->lock);
+                                if (ictx->pending) {
+                                        /*
+                                         * TBD: dequeue *all* non-conflicting
+                                         * reqs
+                                         *
+                                         * With the stub implementation there
+                                         * can only be one request active at a
+                                         * time (zero here) so it's not an
+                                         * issue.  In a real implementation
+                                         * there might still be other active
+                                         * requests to check against, and
+                                         * multiple pending requests that could
+                                         * continue.
+                                         */
+                                        gf_msg_debug (this->name, 0,
+                                                     "unblocking next request");
+                                        --(ictx->pending);
+                                        next = list_entry (ictx->pqueue.next,
+                                                           nsr_local_t, qlinks);
+                                        list_del(&next->qlinks);
+                                        list_add_tail(&next->qlinks,
+                                                      &ictx->aqueue);
+                                        call_resume(next->qstub);
+                                } else {
+                                        --(ictx->active);
+                                }
+                        UNLOCK(&ictx->lock);
+                }
+        }
+#endif
+
+#if defined(NSR_CG_FSYNC)
+        nsr_mark_fd_dirty(this, local);
+#endif
+
+#if defined(NSR_CG_NEED_FD)
+        fd_unref(local->fd);
+#endif
+
+        /* After the leader completes the fop, a quorum check is      *
+         * performed, taking into account the outcome of the fop      *
+         * on the leader. Irrespective of the fop being successful    *
+         * or failing on the leader, the result of the quorum will    *
+         * determine if the overall fop is successful or not. For     *
+         * example, a fop might have succeeded on every node except   *
+         * the leader, in which case as quorum is being met, the fop  *
+         * will be treated as a successful fop, even though it failed *
+         * on the leader. On follower nodes, no quorum check should   *
+         * be done, and the result is returned to the leader as is.   *
+         */
+        if (priv->leader) {
+                result = fop_quorum_check (this, (double)priv->n_children,
+                                           (double)local->successful_acks + 1);
+                if (result == _gf_false) {
+                        op_ret = -1;
+                        op_errno = EROFS;
+                        gf_msg_debug (this->name, 0,
+                                      "Quorum is not met. The operation has failed.");
+                } else {
+#if defined(NSR_CG_NEED_FD)
+                        op_ret = local->successful_op_ret;
+#else
+                        op_ret = 0;
+#endif
+                        op_errno = 0;
+                        gf_msg_debug (this->name, 0,
+                                      "Quorum has met. The operation has succeeded.");
+                }
+        }
+
+        STACK_UNWIND_STRICT (@NAME@, frame, op_ret, op_errno,
+                             @SHORT_ARGS@);
+
+
+        return 0;
+
+}