nbd-client: drop extra error noise
v2 cover nbd-client: drop extra error noise
This is a counter-proposal to Vladimir's initial post for reducing the noise in iotest 083. The difference is that I dropped error_get_hint, since I couldn't find any useful hint to be traced during transmission phase in the first place, and instead added a trace message for the one place where we do set hints during handshaking phase.
Eric Blake (1):
nbd/client: Trace all server option error messages
Vladimir Sementsov-Ogievskiy (2):
nbd: publish _lookup functions
block/nbd-client: use traces instead of noisy error_report_err
include/block/nbd.h | 5 +++++ nbd/nbd-internal.h | 5 ----- block/nbd-client.c | 23 +++++++++++++++++++---- nbd/client.c | 2 ++ block/trace-events | 4 ++++ nbd/trace-events | 1 + tests/qemu-iotests/083.out | 28 ---------------------------- 7 files changed, 31 insertions(+), 37 deletions(-)
Signature · 1 line
2.17.2
PATCH v2 1/3 nbd: publish _lookup functions
From: Vladimir Sementsov-Ogievskiy <[email protected]>
These functions are used for formatting pretty trace points. We are going to add some in block/nbd-client, so, let's publish all these functions at once. Note, that nbd_reply_type_lookup is already published, and constants, "named" by these functions live in include/block/nbd.h too.
Message-Id: <[email protected]>
--- include/block/nbd.h | 5 +++++ nbd/nbd-internal.h | 5 ----- 2 files changed, 5 insertions(+), 5 deletions(-)
include/block/nbd.h +5 -0
@@ -343,5 +343,10 @@ static inline bool nbd_reply_is_structured(NBDReply *reply) }const char *nbd_reply_type_lookup (uint16_t type); +const char *nbd_opt_lookup (uint32_t opt); +const char *nbd_rep_lookup (uint32_t rep); +const char *nbd_info_lookup (uint16_t info); +const char *nbd_cmd_lookup (uint16_t info); +const char *nbd_err_lookup (int err);#endif
nbd/nbd-internal.h +0 -5
@@ -100,11 +100,6 @@ struct NBDTLSHandshakeData {void nbd_tls_handshake (QIOTask *task,void *opaque); -const char *nbd_opt_lookup (uint32_t opt); -const char *nbd_rep_lookup (uint32_t rep); -const char *nbd_info_lookup (uint16_t info); -const char *nbd_cmd_lookup (uint16_t info); -const char *nbd_err_lookup (int err);int nbd_drop (QIOChannel *ioc,size_t size,Error **errp);
Signature · 1 line
2.17.2
PATCH v2 2/3 nbd/client: Trace all server option error messages
In reply to Eric BlakeNot all servers send free-form text alongside option error replies, but for servers that do (such as qemu), we pass the server's message as a hint alongside our own error reporting. However, it would also be useful to trace such server messages, since we can't guarantee how the hint may be consumed.
--- nbd/client.c | 2 ++ nbd/trace-events | 1 + 2 files changed, 3 insertions(+)
nbd/client.c +2 -0
@@ -171,6 +171,8 @@ static int nbd_handle_reply_err(QIOChannel *ioc, NBDOptionReply *reply, goto cleanup; } msg[reply->length] ='\0' ; +trace_nbd_server_error_msg (reply->type, +nbd_reply_type_lookup (reply->type), msg); }switch (reply->type) {
nbd/trace-events +1 -0
@@ -1,6 +1,7 @@ # nbd/client.c nbd_send_option_request(uint32_t opt, const char *name, uint32_t len) "Sending option request %" PRIu32" (%s), len %" PRIu32 nbd_receive_option_reply(uint32_t option, const char *optname, uint32_t type, const char *typename, uint32_t length) "Received option reply %" PRIu32" (%s), type %" PRIu32" (%s), len %" PRIu32 +nbd_server_error_msg(uint32_t err, const char *type, const char *msg) "server reported error 0x%" PRIx32 " (%s) with additional message: %s" nbd_reply_err_unsup(uint32_t option, const char *name) "server doesn't understand request %" PRIu32 " (%s), attempting fallback" nbd_opt_go_start(const char *name) "Attempting NBD_OPT_GO for export '%s'" nbd_opt_go_success(void) "Export is good to go"
Signature · 1 line
2.17.2
Re: [Qemu-devel] [PATCH v2 2/3] nbd/client: Trace all server option error messages
Quoted 7 lines · Eric Blake
Not all servers send free-form text alongside option error replies, but for servers that do (such as qemu), we pass the server's message as a hint alongside our own error reporting. However, it would also be useful to trace such server messages, since we can't guarantee how the hint may be consumed.
Signed-off-by Eric Blake <[email protected]>
Quoted 31 lines
--- nbd/client.c | 2 ++ nbd/trace-events | 1 + 2 files changed, 3 insertions(+)nbd/client.c +2
-0@@ -171,6 +171,8 @@ static int nbd_handle_reply_err(QIOChannel *ioc, NBDOptionReply *reply, goto cleanup; } msg[reply->length] ='\0' ; +trace_nbd_server_error_msg (reply->type, +nbd_reply_type_lookup (reply->type), msg); }switch (reply->type) {nbd/trace-events +1
-0@@ -1,6 +1,7 @@ # nbd/client.c nbd_send_option_request(uint32_t opt, const char *name, uint32_t len) "Sending option request %" PRIu32" (%s), len %" PRIu32 nbd_receive_option_reply(uint32_t option, const char *optname, uint32_t type, const char *typename, uint32_t length) "Received option reply %" PRIu32" (%s), type %" PRIu32" (%s), len %" PRIu32 +nbd_server_error_msg(uint32_t err, const char *type, const char *msg) "server reported error 0x%" PRIx32 " (%s) with additional message: %s" nbd_reply_err_unsup(uint32_t option, const char *name) "server doesn't understand request %" PRIu32 " (%s), attempting fallback" nbd_opt_go_start(const char *name) "Attempting NBD_OPT_GO for export '%s'" nbd_opt_go_success(void) "Export is good to go"
Signature · 2 lines
Best regards, Vladimir
PATCH v2 3/3 block/nbd-client: use traces instead of noisy error_report_err
In reply to Eric BlakeFrom: Vladimir Sementsov-Ogievskiy <[email protected]>
Reduce extra noise of nbd-client, change 083 correspondingly.
In various commits (be41c100 in 2.10, f140e300 in 2.11, 78a33ab in 2.12), we added spots where qemu as an NBD client would report problems communicating with the server to stderr, because there was no where else to send the error to. However, this is racy, particularly since the most common source of these errors is when either the client or the server abruptly hangs up, leaving one coroutine to report the error only if it wins (or loses) the race as attempting the read from the server before another thread completes its cleanup of a protocol error that caused the disconnect in the first place. The race is also apparent in the fact that differences in the flush behavior of the server can alter the frequency of encountering the race in the client (see commit 6d39db96).
Rather than polluting stderr, it's better to just trace these situations, for use by developers debugging a flaky connection, particularly since the real error that either triggers the abrupt disconnection in the first place, or that results from the EIO when a request can't receive a reply, DOES make it back to the user in the normal Error propagation channels.
Message-Id: <[email protected]>
--- block/nbd-client.c | 23 +++++++++++++++++++---- block/trace-events | 4 ++++ tests/qemu-iotests/083.out | 28 ---------------------------- 3 files changed, 23 insertions(+), 32 deletions(-)
block/nbd-client.c +19 -4
@@ -28,6 +28,8 @@*/ #include "qemu/osdep.h" + +#include "trace.h" #include "qapi/error.h" #include "nbd-client.h"
@@ -79,7 +81,8 @@ static coroutine_fn void nbd_read_reply_entry(void *opaque)assert (s->reply.handle ==0 ); ret =nbd_receive_reply (s->ioc, &s->reply, &local_err);if (local_err) { -error_report_err (local_err); +trace_nbd_read_reply_entry_fail (ret,error_get_pretty (local_err)); +error_free (local_err); }if (ret <=0 ) {break ;
@@ -771,7 +774,11 @@ static int nbd_co_request(BlockDriverState *bs, NBDRequest *request, ret =nbd_co_receive_return_code (client, request->handle, &local_err);if (local_err) { -error_report_err (local_err); +trace_nbd_co_request_fail (request->from, request->len, request->handle, + request->flags, request->type, +nbd_cmd_lookup (request->type), + ret,error_get_pretty (local_err)); +error_free (local_err); }return ret; }
@@ -802,7 +809,11 @@ int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset, ret =nbd_co_receive_cmdread_reply (client, request.handle, offset, qiov, &local_err);if (local_err) { -error_report_err (local_err); +trace_nbd_co_request_fail (request.from, request.len, request.handle, + request.flags, request.type, +nbd_cmd_lookup (request.type), + ret,error_get_pretty (local_err)); +error_free (local_err); }return ret; }
@@ -925,7 +936,11 @@ int coroutine_fn nbd_client_co_block_status(BlockDriverState *bs, ret =nbd_co_receive_blockstatus_reply (client, request.handle, bytes, &extent, &local_err);if (local_err) { -error_report_err (local_err); +trace_nbd_co_request_fail (request.from, request.len, request.handle, + request.flags, request.type, +nbd_cmd_lookup (request.type), + ret,error_get_pretty (local_err)); +error_free (local_err); }if (ret <0 ) {return ret;
block/trace-events +4 -0
@@ -156,3 +156,7 @@ nvme_cmd_map_qiov_iov(void *s, int i, void *page, int pages) "s %p iov[%d] %p pa # block/iscsi.c iscsi_xcopy(void *src_lun, uint64_t src_off, void *dst_lun, uint64_t dst_off, uint64_t bytes, int ret) "src_lun %p offset %"PRIu64" dst_lun %p offset %"PRIu64" bytes %"PRIu64" ret %d" + +# block/nbd-client.c +nbd_read_reply_entry_fail(int ret, const char *err) "ret = %d, err: %s" +nbd_co_request_fail(uint64_t from, uint32_t len, uint64_t handle, uint16_t flags, uint16_t type, const char *name, int ret, const char *err) "Request failed { .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64 ", .flags = 0x%" PRIx16 ", .type = %" PRIu16 " (%s) } ret = %d, err: %s"
tests/qemu-iotests/083.out +0 -28
@@ -41,8 +41,6 @@ can't open device nbd+tcp://127.0.0.1:PORT/foo === Check disconnect after neg2 === -Unable to read from socket: Connection reset by peer -Connection closed read failed: Input/output error === Check disconnect 8 neg2 ===
@@ -55,40 +53,30 @@ can't open device nbd+tcp://127.0.0.1:PORT/foo === Check disconnect before request === -Unable to read from socket: Connection reset by peer -Connection closed read failed: Input/output error === Check disconnect after request === -Connection closed read failed: Input/output error === Check disconnect before reply === -Connection closed read failed: Input/output error === Check disconnect after reply === -Unexpected end-of-file before all bytes were read read failed: Input/output error === Check disconnect 4 reply === -Unexpected end-of-file before all bytes were read -Connection closed read failed: Input/output error === Check disconnect 8 reply === -Unexpected end-of-file before all bytes were read -Connection closed read failed: Input/output error === Check disconnect before data === -Unexpected end-of-file before all bytes were read read failed: Input/output error === Check disconnect after data ===
@@ -118,8 +106,6 @@ can't open device nbd+tcp://127.0.0.1:PORT/ === Check disconnect after neg-classic === -Unable to read from socket: Connection reset by peer -Connection closed read failed: Input/output error === Check disconnect before neg1 ===
@@ -164,8 +150,6 @@ can't open device nbd+unix:///foo?socket=TEST_DIR/nbd.sock === Check disconnect after neg2 === -Unable to read from socket: Connection reset by peer -Connection closed read failed: Input/output error === Check disconnect 8 neg2 ===
@@ -178,40 +162,30 @@ can't open device nbd+unix:///foo?socket=TEST_DIR/nbd.sock === Check disconnect before request === -Unable to read from socket: Connection reset by peer -Connection closed read failed: Input/output error === Check disconnect after request === -Connection closed read failed: Input/output error === Check disconnect before reply === -Connection closed read failed: Input/output error === Check disconnect after reply === -Unexpected end-of-file before all bytes were read read failed: Input/output error === Check disconnect 4 reply === -Unexpected end-of-file before all bytes were read -Connection closed read failed: Input/output error === Check disconnect 8 reply === -Unexpected end-of-file before all bytes were read -Connection closed read failed: Input/output error === Check disconnect before data === -Unexpected end-of-file before all bytes were read read failed: Input/output error === Check disconnect after data ===
@@ -241,8 +215,6 @@ can't open device nbd+unix:///?socket=TEST_DIR/nbd.sock === Check disconnect after neg-classic === -Unable to read from socket: Connection reset by peer -Connection closed read failed: Input/output error *** done
Signature · 1 line
2.17.2
Quoted 6 lines · Eric Blake
This is a counter-proposal to Vladimir's initial post for reducing the noise in iotest 083. The difference is that I dropped
error_get_hint, since I couldn't find any useful hint to be traced during transmission phase in the first place, and instead added a trace message for the one place where we do set hints during handshaking phase.
OK, agree with the idea.
Quoted 17 lines
Eric Blake (1):
nbd/client: Trace all server option error messagesVladimir Sementsov-Ogievskiy (2):
nbd: publish_lookupfunctions
block/nbd-client: use traces instead of noisyerror_report_errinclude/block/nbd.h | 5 +++++ nbd/nbd-internal.h | 5 ----- block/nbd-client.c | 23 +++++++++++++++++++---- nbd/client.c | 2 ++ block/trace-events | 4 ++++ nbd/trace-events | 1 + tests/qemu-iotests/083.out | 28 ---------------------------- 7 files changed, 31 insertions(+), 37 deletions(-)
Signature · 2 lines
Best regards, Vladimir
Quoted 9 lines · Vladimir Sementsov-Ogievskiy
Quoted 6 lines · Eric Blake
This is a counter-proposal to Vladimir's initial post for reducing the noise in iotest 083. The difference is that I dropped
error_get_hint, since I couldn't find any useful hint to be traced during transmission phase in the first place, and instead added a trace message for the one place where we do set hints during handshaking phase.OK, agree with the idea.
Thanks. I'll queue this one through my NBD tree and send a pull request soon (although depending on timing, Peter might not apply it until January...)
Signature · 3 lines
Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org