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Fix readwritesplit handling of unexpected responses

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The backend server can send a response even if the client hasn't sent a
request. One case where this occurs is when the server is shutting
down. The internal logic of readwritesplit can't handle unexpected states
gracefully so the safest thing to do is to just ignore them and send the
responses to the client.
This commit is contained in:
Markus Mäkelä
2017-07-31 23:29:48 +03:00
parent 542f3b69db
commit 782b8db2aa
3 changed files with 67 additions and 16 deletions
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45
server/modules/routing/readwritesplit/readwritesplit.cc
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@ -1076,6 +1076,40 @@ static json_t* diagnostics_json(const MXS_ROUTER *instance)
return rval;
}
static void log_unexpected_response(DCB* dcb, GWBUF* buffer)
{
if (mxs_mysql_is_err_packet(buffer))
{
/** This should be the only valid case where the server sends a response
* without the client sending one first. MaxScale does not yet advertise
* the progress reporting flag so we don't need to handle it. */
uint8_t* data = GWBUF_DATA(buffer);
size_t len = MYSQL_GET_PAYLOAD_LEN(data);
uint16_t errcode = MYSQL_GET_ERRCODE(data);
std::string errstr((char*)data + 7, (char*)data + 7 + len - 3);
if (errcode == ER_CONNECTION_KILLED)
{
MXS_INFO("Connection from '%s'@'%s' to '%s' was killed",
dcb->session->client_dcb->user,
dcb->session->client_dcb->remote,
dcb->server->unique_name);
}
else
{
MXS_WARNING("Server '%s' sent an unexpected error: %hu, %s",
dcb->server->unique_name, errcode, errstr.c_str());
}
}
else
{
MXS_ERROR("Unexpected internal state: received response 0x%02hhx from "
"server '%s' when no response was expected",
mxs_mysql_get_command(buffer), dcb->server->unique_name);
ss_dassert(false);
}
}
/**
* @brief Client Reply routine
*
@ -1102,9 +1136,18 @@ static void clientReply(MXS_ROUTER *instance,
SRWBackend backend = get_backend_from_dcb(rses, backend_dcb);
if (backend->get_reply_state() == REPLY_STATE_DONE)
{
/** If we receive an unexpected response from the server, the internal
* logic cannot handle this situation. Routing the reply straight to
* the client should be the safest thing to do at this point. */
log_unexpected_response(backend_dcb, writebuf);
MXS_SESSION_ROUTE_REPLY(backend_dcb->session, writebuf);
return;
}
/** Statement was successfully executed, free the stored statement */
session_clear_stmt(backend_dcb->session);
ss_dassert(backend->get_reply_state() != REPLY_STATE_DONE);
if (reply_is_complete(backend, writebuf))
{