Hi Aginwala, thanks for the testing. The change of this patch will cause
the IDL to avoid connecting to a follower if "leader_only" is set to
"true". It is the same behavior as before when multiple remotes are used,
but now it just does the same even when a single remote is used, because
the single remote could be a VIP, so it is desired  behavior. For
ovn-nbctl, "leader_only" is default to true, so it is expected that it
refuses to connect if the remote is a follower. However, if you are using
daemon mode ovn-nbctl, and if you didn't set "--no-leader-only", it should
keep retrying until it connects to a leader (depends on LB redirecting to
different servers). I agree this may cause some confusion when a user of
ovn-nbctl connects to only a single remote of a cluster, he/she could get
failure if --no-leader-only is not specified, but it is better than let
user believe they are connected to a leader while in reality connected to a
follower. Maybe I can improve the ovn-nbctl/sbctl documentation to emphasis
this to avoid confusion.

On Tue, Aug 13, 2019 at 7:13 PM aginwala <aginw...@asu.edu> wrote:

>
>
> On Tue, Aug 13, 2019 at 7:07 PM aginwala <aginw...@asu.edu> wrote:
>
>> Thanks for the fixes. Found a bug in current code which breaks both nbctl
>> with local socket and daemon mode on follower nodes. Also nbctl daemon mode
>> always tries to connect to leader node by default which also failed to
>> connect.
>> e.g. export OVN_NB_DB=tcp:<lb_vip>:6641; ovn-nbctl  --pidfile --detach.
>>  
>> 2019-08-14T01:07:06Z|00036|ovsdb_idl|INFO|unix:/var/run/openvswitch/ovnnb_db.sock:
>> clustered database server is not cluster leader; trying another server
>> 2019-08-14T01:07:06Z|00037|reconnect|DBG|unix:/var/run/openvswitch/ovnnb_db.sock:
>> entering RECONNECT
>> 2019-08-14T01:07:06Z|00038|ovsdb_idl|DBG|unix:/var/run/openvswitch/ovnnb_db.sock:
>> SERVER_MONITOR_COND_REQUESTED -> RETRY at lib/ovsdb-idl.c:1917
>> 2019-08-14T01:07:06Z|00039|poll_loop|DBG|wakeup due to 0-ms timeout at
>> lib/reconnect.c:643
>> 2019-08-14T01:07:06Z|00040|reconnect|INFO|unix:/var/run/openvswitch/ovnnb_db.sock:
>> connection attempt timed out
>> 2019-08-14T01:07:06Z|00041|reconnect|INFO|unix:/var/run/openvswitch/ovnnb_db.sock:
>> waiting 2 seconds before reconnect
>> 2019-08-14T01:07:06Z|00042|reconnect|DBG|unix:/var/run/openvswitch/ovnnb_db.sock:
>> entering BACKOFF
>>
>> Need to explicitly specify no-leader-only to work around.  ovn-nbctl
>> --pidfile --detach --no-leader-only.
>> For LB VIP, since LB sees all nodes are active, connections are
>> established to all cluster nodes equally. I am using round robin setting
>> for LB VIP for 3 node cluster using raft.
>>
>> Hence, are we always going to avoid this behavior because this is forcing
>> to always connect to leader and not to followers? So if we use this
>> approach, idl will show ovn-nbctl: tcp:<lb_vip>:6641: database connection
>> failed () if requests reaches followers and only processes success if
>> request reaches leader node with this patch.
>>
>>
>> On Tue, Aug 13, 2019 at 9:23 AM Han Zhou <zhou...@gmail.com> wrote:
>>
>>> From: Han Zhou <hzh...@ebay.com>
>>>
>>> When clustered mode is used, the client needs to retry connecting
>>> to new servers when certain failures happen. Today it is allowed to
>>> retry new connection only if multiple remotes are used, which prevents
>>> using LB VIP with clustered nodes. This patch makes sure the retry
>>> logic works when using LB VIP: although same IP is used for retrying,
>>> the LB can actually redirect the connection to a new node.
>>>
>>> Signed-off-by: Han Zhou <hzh...@ebay.com>
>>> ---
>>>  lib/ovsdb-idl.c        | 11 +++-------
>>>  tests/ovsdb-cluster.at | 57
>>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  tests/test-ovsdb.c     |  1 +
>>>  3 files changed, 61 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
>>> index 1a6a4af..190143f 100644
>>> --- a/lib/ovsdb-idl.c
>>> +++ b/lib/ovsdb-idl.c
>>> @@ -657,12 +657,8 @@ ovsdb_idl_state_to_string(enum ovsdb_idl_state
>>> state)
>>>  static void
>>>  ovsdb_idl_retry_at(struct ovsdb_idl *idl, const char *where)
>>>  {
>>> -    if (idl->session && jsonrpc_session_get_n_remotes(idl->session) >
>>> 1) {
>>> -        ovsdb_idl_force_reconnect(idl);
>>> -        ovsdb_idl_transition_at(idl, IDL_S_RETRY, where);
>>> -    } else {
>>> -        ovsdb_idl_transition_at(idl, IDL_S_ERROR, where);
>>> -    }
>>> +    ovsdb_idl_force_reconnect(idl);
>>> +    ovsdb_idl_transition_at(idl, IDL_S_RETRY, where);
>>>  }
>>>
>>>  static void
>>> @@ -1895,8 +1891,7 @@ ovsdb_idl_check_server_db(struct ovsdb_idl *idl)
>>>      if (!database) {
>>>          VLOG_INFO_RL(&rl, "%s: server does not have %s database",
>>>                       server_name, idl->data.class_->database);
>>> -    } else if (!strcmp(database->model, "clustered")
>>> -               && jsonrpc_session_get_n_remotes(idl->session) > 1) {
>>> +    } else if (!strcmp(database->model, "clustered")) {
>>>
>> > I think this check jsonrpc_session_get_n_remotes(idl->session) > 1 is
>> still needed for follower nodes for monitor condition to avoid this bug.
>> Correct me if I am wrong or missed any case.
>>
>>          uint64_t index = database->n_index ? *database->index : 0;
>>>
>>>          if (!database->schema) {
>>> diff --git a/tests/ovsdb-cluster.at b/tests/ovsdb-cluster.at
>>> index 4701272..6a13843 100644
>>> --- a/tests/ovsdb-cluster.at
>>> +++ b/tests/ovsdb-cluster.at
>>> @@ -63,6 +63,63 @@ m4_define([OVSDB_CHECK_EXECUTION],
>>>  EXECUTION_EXAMPLES
>>>
>>>
>>> +AT_BANNER([OVSDB - disconnect from cluster])
>>> +
>>> +# When a node is disconnected from the cluster, the IDL should
>>> disconnect
>>> +# and retry even if it uses a single remote, because the remote IP can
>>> be
>>> +# a VIP on a load-balance.
>>> +AT_SETUP([OVSDB cluster - disconnect from cluster, single remote])
>>> +AT_KEYWORDS([ovsdb server negative unix cluster disconnect])
>>> +
>>> +schema_name=`ovsdb-tool schema-name $abs_srcdir/idltest.ovsschema`
>>> +ordinal_schema > schema
>>> +AT_CHECK([ovsdb-tool '-vPATTERN:console:%c|%p|%m' create-cluster s1.db
>>> $abs_srcdir/idltest.ovsschema unix:s1.raft], [0], [], [stderr])
>>> +cid=`ovsdb-tool db-cid s1.db`
>>> +schema_name=`ovsdb-tool schema-name $abs_srcdir/idltest.ovsschema`
>>> +for i in `seq 2 3`; do
>>> +    AT_CHECK([ovsdb-tool join-cluster s$i.db $schema_name unix:s$i.raft
>>> unix:s1.raft])
>>> +done
>>> +
>>> +on_exit 'kill `cat *.pid`'
>>> +for i in `seq 3`; do
>>> +    AT_CHECK([ovsdb-server -v -vconsole:off -vsyslog:off --detach
>>> --no-chdir --log-file=s$i.log --pidfile=s$i.pid --unixctl=s$i
>>> --remote=punix:s$i.ovsdb s$i.db])
>>> +done
>>> +for i in `seq 3`; do
>>> +    AT_CHECK([ovsdb_client_wait unix:s$i.ovsdb $schema_name connected])
>>> +done
>>> +
>>> +AT_CHECK([ovsdb-client transact unix:s1.ovsdb '[["idltest",
>>> +      {"op": "insert",
>>> +       "table": "simple",
>>> +       "row": {"i": 1}}]]'], [0], [ignore], [ignore])
>>> +
>>> +# Connect to a single remote s3.  Use "wait" to trigger a non-op
>>> transaction so
>>> +# that test-ovsdb will not quit.
>>> +
>>> +on_exit 'pkill test-ovsdb'
>>> +test-ovsdb '-vPATTERN:console:test-ovsdb|%c|%m' -v -t10 idl
>>> unix:s3.ovsdb '[["idltest",
>>> +      {"op": "wait",
>>> +       "table": "simple",
>>> +       "where": [["i", "==", 1]],
>>> +       "columns": ["i"],
>>> +       "until": "==",
>>> +       "rows": [{"i": 1}]}]]' > test-ovsdb.log 2>&1 &
>>> +
>>> +OVS_WAIT_UNTIL([grep "000: i=1" test-ovsdb.log])
>>> +
>>> +# Shutdown the other 2 servers so that s3 is disconnected from the
>>> cluster.
>>> +for i in 2 1; do
>>> +    OVS_APP_EXIT_AND_WAIT_BY_TARGET([`pwd`/s$i], [s$i.pid])
>>> +done
>>> +
>>> +# The test-ovsdb should detect the disconnect and retry.
>>> +OVS_WAIT_UNTIL([grep disconnect test-ovsdb.log])
>>> +
>>> +OVS_APP_EXIT_AND_WAIT_BY_TARGET([`pwd`/s3], [s3.pid])
>>> +
>>> +AT_CLEANUP
>>> +
>>> +
>>>  OVS_START_SHELL_HELPERS
>>>  # ovsdb_cluster_failure_test SCHEMA_FUNC OUTPUT TRANSACTION...
>>>  ovsdb_cluster_failure_test () {
>>> diff --git a/tests/test-ovsdb.c b/tests/test-ovsdb.c
>>> index 187eb28..b1a4be3 100644
>>> --- a/tests/test-ovsdb.c
>>> +++ b/tests/test-ovsdb.c
>>> @@ -2412,6 +2412,7 @@ do_idl(struct ovs_cmdl_context *ctx)
>>>      track = ((struct test_ovsdb_pvt_context *)(ctx->pvt))->track;
>>>
>>>      idl = ovsdb_idl_create(ctx->argv[1], &idltest_idl_class, true,
>>> true);
>>> +    ovsdb_idl_set_leader_only(idl, false);
>>>      if (ctx->argc > 2) {
>>>          struct stream *stream;
>>>
>>> --
>>> 2.1.0
>>>
>>> _______________________________________________
>>> dev mailing list
>>> d...@openvswitch.org
>>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
>>>
>>
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