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LocalTransportAgent: added transmission of child's SyncReport 

The SyncReport is transmitted via an additional socket pair. This is
necessary because the one for messages is shut down to notify the peer
of a premature shutdown.

The parent uses the information obtained from the SyncReport to update
its own status: first the error is logged (thus also setting the
"first error seen" part of the parent), then an exception with a bad child
status is thrown (interrupting anything the parent was doing and, if it
was the first error, setting the overall status of the sync).
This commit is contained in:
Patrick Ohly 2010-11-03 12:10:15 +01:00
parent dc2ce796cb
commit 51111bea95
2 changed files with 153 additions and 33 deletions
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168
src/syncevo/LocalTransportAgent.cpp
View File

@ -21,6 +21,8 @@
#include <syncevo/SyncContext.h>
#include <syncevo/SyncML.h>
#include <syncevo/LogRedirect.h>
#include <syncevo/StringDataBlob.h>
#include <syncevo/IniConfigNode.h>
#include <stddef.h>
#include <sys/socket.h>
@ -45,12 +47,20 @@ LocalTransportAgent::LocalTransportAgent(SyncContext *server,
m_clientContext(SyncConfig::normalizeConfigString(clientContext)),
m_loop(static_cast<GMainLoop *>(loop)),
m_status(INACTIVE),
m_messageFD(-1),
m_statusFD(-1),
m_pid(0)
{
}
LocalTransportAgent::~LocalTransportAgent()
{
if (m_statusFD >= 0) {
close(m_statusFD);
}
if (m_messageFD >= 0) {
close(m_messageFD);
}
if (m_pid) {
SE_LOG_DEBUG(NULL, NULL, "starting to wait for child process %ld in destructor", (long)m_pid);
int status;
@ -61,7 +71,7 @@ LocalTransportAgent::~LocalTransportAgent()
void LocalTransportAgent::start()
{
int sockets[2];
int sockets[2][2];
// compare normalized context names to detect forbidden sync
// within the same context; they could be set up, but are more
@ -77,31 +87,49 @@ void LocalTransportAgent::start()
SE_THROW(StringPrintf("invalid local sync inside context '%s', need second context with different databases", context.c_str()));
}
if (socketpair(AF_LOCAL,
SOCK_STREAM,
0, sockets)) {
m_server->throwError("socketpair()", errno);
}
memset(sockets, 0, sizeof(sockets));
try {
if (socketpair(AF_LOCAL,
SOCK_STREAM,
0, sockets[0]) ||
socketpair(AF_LOCAL,
SOCK_STREAM,
0, sockets[1])) {
m_server->throwError("socketpair()", errno);
}
pid_t pid = fork();
switch (pid) {
case -1:
m_server->throwError("fork()", errno);
break;
case 0:
// child
close(sockets[0]);
m_messageFD = sockets[1];
run();
break;
default:
// parent
close(sockets[1]);
m_messageFD = sockets[0];
// first message must come from child
m_status = ACTIVE;
m_pid = pid;
break;
pid_t pid = fork();
switch (pid) {
case -1:
m_server->throwError("fork()", errno);
break;
case 0:
// child
close(sockets[0][0]);
m_messageFD = sockets[0][1];
close(sockets[1][0]);
m_statusFD = sockets[1][1];
run();
break;
default:
// parent
close(sockets[0][1]);
m_messageFD = sockets[0][0];
close(sockets[1][1]);
m_statusFD = sockets[1][0];
// first message must come from child
m_status = ACTIVE;
m_pid = pid;
break;
}
} catch (...) {
for (int *fd = &sockets[0][0];
fd < &sockets[2][2];
++fd) {
if (*fd) {
close(*fd);
}
}
}
}
@ -197,6 +225,30 @@ void LocalTransportAgent::run()
m_clientReport.setStatus(status);
}
// send final report
try {
if (m_messageFD >= 0) {
close(m_messageFD);
m_messageFD = -1;
}
// matches parent's code in shutdown()
boost::shared_ptr<std::string> data(new std::string);
boost::shared_ptr<StringDataBlob> dump(new StringDataBlob("buffer", data, false));
IniHashConfigNode node(dump);
node << m_clientReport;
SE_LOG_DEBUG(NULL, NULL, "client: sending report (%s/ERROR '%s'):\n%s",
Status2String(m_clientReport.getStatus()).c_str(),
m_clientReport.getError().c_str(),
data->c_str());
node.flush();
writeMessage(m_statusFD, Message::MSG_SYNC_REPORT, data->c_str(), data->size());
} catch (...) {
SyncMLStatus status = m_clientReport.getStatus();
Exception::handle(&status, redirect);
m_clientReport.setStatus(status);
}
if (redirect) {
redirect->flush();
}
@ -221,16 +273,60 @@ void LocalTransportAgent::setContentType(const std::string &type)
void LocalTransportAgent::shutdown()
{
if (m_pid) {
// TODO: get sync report, then wait for exit in child.
if (m_messageFD) {
// close message transports, tells peer to shut down
close(m_messageFD);
m_messageFD = -1;
}
if (m_pid) {
// parent: receive SyncReport
receiveChildReport();
// join forked process
int status;
SE_LOG_DEBUG(NULL, NULL, "starting to wait for child process %ld in shutdown()", (long)m_pid);
pid_t res = waitpid(m_pid, &status, 0);
SE_LOG_DEBUG(NULL, NULL, "child %ld completed, status %d", (long)res, status);
m_pid = 0;
// now relay the result from our child, will be added to
// our own sync report if it doesn't have an error already
checkChildReport();
} else {
close(m_messageFD);
// child: sends SyncReport at the end of run()
}
}
void LocalTransportAgent::receiveChildReport()
{
SE_LOG_DEBUG(NULL, NULL, "parent: receiving report");
m_receiveBuffer.m_used = 0;
readMessage(m_statusFD, m_receiveBuffer);
boost::shared_ptr<std::string> data(new std::string);
data->assign(m_receiveBuffer.m_message->m_data, m_receiveBuffer.m_message->getDataLength());
boost::shared_ptr<StringDataBlob> dump(new StringDataBlob("buffer", data, false));
IniHashConfigNode node(dump);
node >> m_clientReport;
SE_LOG_DEBUG(NULL, NULL, "parent: received report (%s/ERROR '%s'):\n%s",
Status2String(m_clientReport.getStatus()).c_str(),
m_clientReport.getError().c_str(),
data->c_str());
}
void LocalTransportAgent::checkChildReport()
{
std::string childError = "child process failed";
if (!m_clientReport.getError().empty()) {
childError += ": ";
childError += m_clientReport.getError();
SE_LOG_ERROR(NULL, NULL, "%s", childError.c_str());
}
if (m_clientReport.getStatus() != STATUS_HTTP_OK &&
m_clientReport.getStatus() != STATUS_OK) {
SE_THROW_EXCEPTION_STATUS(TransportStatusException,
childError,
m_clientReport.getStatus());
}
}
@ -304,9 +400,8 @@ TransportAgent::Status LocalTransportAgent::wait(bool noReply)
{
switch (m_status) {
case ACTIVE:
// need next message; for noReply == true, it is the SyncReport (TODO)
// need next message; for noReply == true we are done
if (noReply) {
// TODO: remove this code and send SyncReport as last message in client
m_status = INACTIVE;
return m_status;
}
@ -380,8 +475,17 @@ void LocalTransportAgent::readMessage(int fd, Buffer &buffer)
SE_THROW_EXCEPTION(TransportException,
StringPrintf("message receive: %s", strerror(errno)));
} else if (!recvd) {
SE_THROW_EXCEPTION(TransportException,
"client has died unexpectedly");
if (m_pid) {
// Child died. Try to get its sync report to find out why.
receiveChildReport();
checkChildReport();
// if no exception yet, raise a generic one
SE_THROW_EXCEPTION(TransportException,
"child has died unexpectedly");
} else {
SE_THROW_EXCEPTION(TransportException,
"parent has died unexpectedly");
}
}
buffer.m_used += recvd;
break;

18
src/syncevo/LocalTransportAgent.h
View File

@ -48,7 +48,8 @@ struct Message
MSG_SYNCML_XML,
MSG_SYNCML_WBXML,
MSG_PASSWORD_REQUEST,
MSG_PASSWORD_RESPONSE
MSG_PASSWORD_RESPONSE,
MSG_SYNC_REPORT
} m_type;
/** length including header */
@ -150,6 +151,15 @@ class LocalTransportAgent : public TransportAgent
*/
int m_messageFD;
/**
* Second read/write stream socket for transferring final
* status. Same communication method as for m_messageFD.
* Necessary because the regular communication
* channel needs to be closed in case of a failure, to
* notify the peer.
*/
int m_statusFD;
/** 0 in client, child PID in server */
pid_t m_pid;
@ -170,6 +180,12 @@ class LocalTransportAgent : public TransportAgent
* complete message is not overwritten.
*/
void readMessage(int fd, Buffer &buffer);
/** utility function for parent: copy child's report into m_clientReport */
void receiveChildReport();
/** utility function for parent: check m_clientReport and log/throw errors */
void checkChildReport();
};
SE_END_CXX