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4241d652e4
Open vSwitch has a few different jsonrpc-based protocols that depend on jsonrpc_session to make sure that the connection is up and working. In turn, jsonrpc_session uses the "reconnect" state machine to send probes if nothing is received. This works fine in normal circumstances. In unusual circumstances, though, it can happen that the program is busy and doesn't even try to receive anything for a long time. Then the timer can time out without a good reason; if it had tried to receive something, it would have. There's a solution that the clients of jsonrpc_session could adopt. Instead of first calling jsonrpc_session_run(), which is what calls into "reconnect" to deal with timing out, and then calling into jsonrpc_session_recv(), which is what tries to receive something, they could use the opposite order. That would make sure that the timeout was always based on a recent attempt to receive something. Great. The actual code in OVS that uses jsonrpc_session, though, tends to use the opposite order, and there are enough users and this is a subtle enough issue that it could get flipped back around even if we fixed it now. So this commit takes a different approach. Instead of fixing this in the users of jsonrpc_session, we fix it in the users of reconnect: make them tell when they've tried to receive something (or disable this particular feature). This commit fixes the problem that way. It's kind of hard to reproduce but I'm pretty sure that I've seen it a number of times in testing. Signed-off-by: Ben Pfaff <blp@ovn.org> Acked-by: Ilya Maximets <i.maximets@ovn.org>
124 lines
5.3 KiB
C
124 lines
5.3 KiB
C
/*
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* Copyright (c) 2009, 2010, 2012 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef RECONNECT_H
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#define RECONNECT_H 1
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/* This library implements a finite-state machine for connecting and
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* reconnecting to a network resource with exponential backoff. It also
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* provides optional support for detecting a connection on which the peer is no
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* longer responding.
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*
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* The library does not implement anything networking related, only an FSM for
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* networking code to use.
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*
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* Many "reconnect" functions take a "now" argument. This makes testing easier
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* since there is no hidden state. When not testing, just pass the return
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* value of time_msec() from timeval.h. (Perhaps this design should be
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* revisited later.) */
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#include <stdbool.h>
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struct reconnect *reconnect_create(long long int now);
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void reconnect_destroy(struct reconnect *);
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void reconnect_set_quiet(struct reconnect *, bool quiet);
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const char *reconnect_get_name(const struct reconnect *);
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void reconnect_set_name(struct reconnect *, const char *name);
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/* Defaults, all in msecs. */
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#define RECONNECT_DEFAULT_MIN_BACKOFF 1000
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#define RECONNECT_DEFAULT_MAX_BACKOFF 8000
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#define RECONNECT_DEFAULT_PROBE_INTERVAL 5000
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int reconnect_get_min_backoff(const struct reconnect *);
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int reconnect_get_max_backoff(const struct reconnect *);
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int reconnect_get_probe_interval(const struct reconnect *);
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void reconnect_set_max_tries(struct reconnect *, unsigned int max_tries);
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unsigned int reconnect_get_max_tries(struct reconnect *);
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void reconnect_set_backoff_free_tries(struct reconnect *,
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unsigned int backoff_free_tries);
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void reconnect_set_backoff(struct reconnect *,
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int min_backoff, int max_backoff);
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void reconnect_set_probe_interval(struct reconnect *, int probe_interval);
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bool reconnect_is_passive(const struct reconnect *);
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void reconnect_set_passive(struct reconnect *, bool passive,
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long long int now);
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bool reconnect_is_enabled(const struct reconnect *);
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void reconnect_enable(struct reconnect *, long long int now);
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void reconnect_disable(struct reconnect *, long long int now);
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void reconnect_force_reconnect(struct reconnect *, long long int now);
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void reconnect_skip_backoff(struct reconnect *);
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bool reconnect_is_connected(const struct reconnect *);
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unsigned int reconnect_get_last_connect_elapsed(const struct reconnect *,
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long long int now);
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unsigned int reconnect_get_last_disconnect_elapsed(const struct reconnect *,
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long long int now);
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void reconnect_disconnected(struct reconnect *, long long int now, int error);
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void reconnect_connecting(struct reconnect *, long long int now);
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void reconnect_listening(struct reconnect *, long long int now);
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void reconnect_listen_error(struct reconnect *, long long int now, int error);
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void reconnect_connected(struct reconnect *, long long int now);
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void reconnect_connect_failed(struct reconnect *, long long int now,
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int error);
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void reconnect_activity(struct reconnect *, long long int now);
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void reconnect_receive_attempted(struct reconnect *, long long int now);
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enum reconnect_action {
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RECONNECT_CONNECT = 1,
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RECONNECT_DISCONNECT,
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RECONNECT_PROBE,
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};
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enum reconnect_action reconnect_run(struct reconnect *, long long int now);
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void reconnect_wait(struct reconnect *, long long int now);
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int reconnect_timeout(struct reconnect *, long long int now);
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struct reconnect_stats {
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/* All times and durations in this structure are in milliseconds. */
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long long int creation_time; /* Time reconnect_create() called. */
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long long int last_activity; /* Last call to reconnect_activity(). */
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long long int last_connected; /* Last call to reconnect_connected(). */
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long long int last_disconnected; /* Last call to reconnect_disconnected(). */
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int backoff; /* Current backoff duration. */
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unsigned int seqno; /* # of connections + # of disconnections. */
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bool is_connected; /* Currently connected? */
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unsigned int msec_since_connect; /* Time since last connect. */
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unsigned int msec_since_disconnect; /* Time since last disconnect. */
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unsigned int total_connected_duration; /* Sum of all connections. */
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unsigned int n_attempted_connections;
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unsigned int n_successful_connections;
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/* These should only be provided to a human user for debugging purposes.
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* The client should not attempt to interpret them. */
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const char *state; /* FSM state. */
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unsigned int state_elapsed; /* Time since FSM state entered. */
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};
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void reconnect_get_stats(const struct reconnect *, long long int now,
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struct reconnect_stats *);
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#endif /* reconnect.h */
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