2 * Copyright (c) 2017 Cisco and/or its affiliates.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at:
7 * http://www.apache.org/licenses/LICENSE-2.0
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
22 #include "vom/client_db.hpp"
27 The VPP Object Model (VOM) library.
29 Before we begin, a glossary of terms:
30 - Agent or client: A user mode process that links to and uses the VOM library
32 - VPP: A running instance of VPP
33 - High Availability (HA): Scenarios where the client and/or VPP restart with
34 minimal service interruption.
35 - CReate, Update, Delete (CRUD): An API style where the producer issues
36 notifications to changes to objects
38 The VOM is a C++ library that models entities in VPP as C++ classes. The
39 relationships between VOM objects and VPP entities is not always 1:1. Some
40 effort has been made to construct a higher level, more abstract API to VPP
42 The client programming model is simple (or at least I intended it to be..). The
43 client deals in ‘desired’ state, that is, it expresses the objects it wants to
44 exists (in VPP) and the properties that the object should have, i.e**;
45 Interface af1(“my-af-packet-1”, AFPACKET, admin::UP);
46 Then the client ‘writes’ this object into the ‘model’
47 OM::write(“clients-thing-1”, af1);
49 “clients-thing-1” is a description of the entity within the client’s domain that
50 ‘owns’ (or has locked or has a reference to) the VOM object. There can be many
51 owners of each VOM object. It will be the last owner’s update that will be
52 programmed in VPP. This model means that the client is not burdened with
53 maintaining which of its objects have created which VOM objects. If the client
54 is itself driven by a CRUD API, then create notifications are implemented as
55 above. Update notifications add two extra statements;
56 OM::mark(“clients-thing-1”);
58 OM::sweep(“clients-thing-1”);
59 These ‘mark’ and ‘sweep’ statements are indications to OM that firstly, indicate
60 that all the objects owned by “clients-thing-1” are now stale, i.e that the
61 client may no longer need them. If one of the subsequent writes should update a
62 stale object, then it is no longer stale. The sweep statement will ‘remove’ all
63 the remaining stale objects. In this model, the client does not need to maintain
64 the mapping of VOM objects to its own objects – it can simply express what it
66 The delete notification is simply:
67 OM::remove(“clients-thing-1”);
68 Which will remove all the objects in VOM that are owned by “clients-thing-1”.
69 Where ‘remove’ in this sense means unlock and unreference, the VOM object, and
70 VPP state, will only be truly removed once there are no more owners. This is
71 equivalent to a mark & sweep with no intermediate writes.
73 To provide this client side model the VOM is a stateful library, meaning that
74 for each entity it creates in VPP, VOM maintains its own representation of that
75 object. VOM can therefore be memory hungry. The desired state is expressed by
76 the client, the ‘actual’ state is maintained by VOM. VOM will consolidate the
77 two states when the client writes to the OM and thus issue VPP only the changes
80 The concepts of ownership and statefulness also allow the support for HA
82 VPP restart: When VPP restarts, VOM will reconnect and ‘replay’ its state, in
83 dependency order, to VPP. The client does not need to regenerate its desired
85 Client restart: when the client restarts, VOM will read/dump the current state
86 of all VPP objects and store them in the OM owned by the special owner “boot”.
87 As the client reprogrammes its desired state, objects will become owned by both
88 the boot process and the client. At the point in time, as determined by the
89 client, all stale state, that owned only by boot, can be purged. Hence the
90 system reaches the correct final state, with no interruption to VPP forwarding.
95 Each object in VOM (i.e. an interface, route, bridge-domain, etc) is stored in a
96 per-type object database, with an object-type specific key. This ‘singular’ DB
97 has a value-type of a weak pointer to the object. I use the term ‘singular’ to
98 refer to the instance of the object stored in these databases, to be distinct
99 from the instances the client constructs to represent desired state.
100 The ‘client’ DB maintains the mapping of owner to object. The value type of the
101 client DB is a shared pointer to the singular instance of the owned object.
102 Once all the owners are gone, and all the shared pointers are destroyed, the
103 singular instance is also destroyed.
105 Each VOM object has some basic behaviour:
106 update: issue to VPP an update to this object’s state. This could include the
108 sweep: delete the VPP entity – called when the object is destroyed.
109 replay: issue to VPP all the commands needed to re-programme (VPP restart HA
111 populate: read state from VPP and add it to the OM (client restart HA
114 The object code is boiler-plate, in some cases (like the ACLs) even template.
115 The objects are purposefully left as simple, functionality free as possible.
117 Communication with VPP is through a ‘queue’ of ‘commands’. A command is
118 essentially an object wrapper around a VPP binary API call (although we do use
119 the VAPI C++ bindings too). Commands come in three flavours:
121 DUMP: give me all of these things; here you go
122 EVENT; tell me about these events; here’s one …. Here’s one…. Oh here’s
125 RPC and DUMP commands are handled synchronously. Therefore on return from
126 OM::write(…) VPP has been issued with the request and responded. EVENTs are
127 asynchronous and will be delivered to the listeners in a different thread – so
130 * As such VOM provides some level of insulation to the changes to the VPP
132 ** some of the type names are shorten for brevity’s sake.
137 * The interface to writing objects into VPP OM.
143 * A class providing the RAII pattern for mark and sweep
149 * Constructor - will call mark on the key
151 mark_n_sweep(const client_db::key_t& key);
154 * Destructor - will call sweep on the key
162 mark_n_sweep(const mark_n_sweep& ms) = delete;
165 * The client whose state we are guarding.
167 client_db::key_t m_key;
176 * populate the OM with state read from HW.
178 static void populate(const client_db::key_t& key);
181 * Mark all state owned by this key as stale
183 static void mark(const client_db::key_t& key);
186 * Sweep all the key's objects that are stale
188 static void sweep(const client_db::key_t& key);
191 * Replay all of the objects to HW.
193 static void replay(void);
196 * Make the State in VPP reflect the expressed desired state.
197 * But don't call the HW - use this whilst processing dumped
200 template <typename OBJ>
201 static rc_t commit(const client_db::key_t& key, const OBJ& obj)
206 rc = OM::write(key, obj);
213 * Make the State in VPP reflect the expressed desired state.
214 * After processing all the objects in the queue, in FIFO order,
215 * any remaining state owned by the client_db::key_t is purged.
216 * This is a template function so the object's update() function is
217 * always called with the derived type.
219 template <typename OBJ>
220 static rc_t write(const client_db::key_t& key, const OBJ& obj)
225 * Find the singular instance another owner may have created.
226 * this always returns something.
228 std::shared_ptr<OBJ> inst = obj.singular();
231 * Update the existing object with the new desired state
236 * Find if the object already stored on behalf of this key.
237 * and mark them stale
239 object_ref_list& objs = m_db->find(key);
242 * Iterate through this list to find a matchin' object
243 * to the one requested.
245 auto match_ptr = [inst](const object_ref& oref) {
246 return (inst == oref.obj());
248 auto it = std::find_if(objs.begin(), objs.end(), match_ptr);
250 if (it != objs.end()) {
252 * yes, this key already owns this object.
257 * Add the singular instance to the owners list
259 objs.insert(object_ref(inst));
262 return (HW::write());
266 * Remove all object in the OM referenced by the key
268 static void remove(const client_db::key_t& key);
271 * Print each of the object in the DB into the stream provided
273 static void dump(const client_db::key_t& key, std::ostream& os);
276 * Print each of the KEYS
278 static void dump(std::ostream& os);
281 * Class definition for listeners to OM events
286 listener() = default;
287 virtual ~listener() = default;
290 * Handle a populate event
292 virtual void handle_populate(const client_db::key_t& key) = 0;
295 * Handle a replay event
297 virtual void handle_replay() = 0;
300 * Get the sortable Id of the listener
302 virtual dependency_t order() const = 0;
305 * less than operator for set sorting
307 bool operator<(const listener& listener) const
309 return (order() < listener.order());
314 * Register a listener of events
316 static bool register_listener(listener* listener);
320 * Database of object state created for each key
322 static client_db* m_db;
325 * Comparator to keep the pointers to listeners in sorted order
327 struct listener_comparator_t
329 bool operator()(const listener* l1, const listener* l2) const
331 return (l1->order() < l2->order());
336 * convenient typedef for the sorted set of listeners
338 typedef std::multiset<listener*, listener_comparator_t> listener_list;
341 * The listeners for events
343 static std::unique_ptr<listener_list> m_listeners;
348 * fd.io coding-style-patch-verification: ON
351 * eval: (c-set-style "mozilla")