[PATCH] chardev: introduce 'reconnect-ms' and deprecate 'reconnect'
The 'reconnect' option only allows to specify the time in seconds, which is way too long for certain workflows. We have a lightweight disk backend server, which takes about 20ms to live update, but due to this limitation in QEMU, previously the guest disk controller would hang for one second because it would take this long for QEMU to reinitialize the socket connection. Introduce a new option called 'reconnect-ms', which is the same as 'reconnect', except the value is treated as milliseconds. These are mutually exclusive and specifying both results in an error. 'reconnect' is also deprecated by this commit to make it possible to remove it in the future as to not keep two options that control the same thing. Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru> --- chardev/char-socket.c | 33 ++++++++++++++++++++++++--------- chardev/char.c | 3 +++ include/chardev/char-socket.h | 2 +- qapi/char.json | 17 +++++++++++++++-- 4 files changed, 43 insertions(+), 12 deletions(-) diff --git a/chardev/char-socket.c b/chardev/char-socket.c index 1ca9441b1b..c24331ac23 100644 --- a/chardev/char-socket.c +++ b/chardev/char-socket.c @@ -74,7 +74,7 @@ static void qemu_chr_socket_restart_timer(Chardev *chr) assert(!s->reconnect_timer); name = g_strdup_printf("chardev-socket-reconnect-%s", chr->label); s->reconnect_timer = qemu_chr_timeout_add_ms(chr, - s->reconnect_time * 1000, + s->reconnect_time_ms, socket_reconnect_timeout, chr); g_source_set_name(s->reconnect_timer, name); @@ -481,7 +481,7 @@ static void tcp_chr_disconnect_locked(Chardev *chr) if (emit_close) { qemu_chr_be_event(chr, CHR_EVENT_CLOSED); } - if (s->reconnect_time && !s->reconnect_timer) { + if (s->reconnect_time_ms && !s->reconnect_timer) { qemu_chr_socket_restart_timer(chr); } } @@ -1080,9 +1080,9 @@ static int tcp_chr_wait_connected(Chardev *chr, Error **errp) } else { Error *err = NULL; if (tcp_chr_connect_client_sync(chr, &err) < 0) { - if (s->reconnect_time) { + if (s->reconnect_time_ms) { error_free(err); - g_usleep(s->reconnect_time * 1000ULL * 1000ULL); + g_usleep(s->reconnect_time_ms * 1000ULL); } else { error_propagate(errp, err); return -1; @@ -1267,13 +1267,13 @@ skip_listen: static int qmp_chardev_open_socket_client(Chardev *chr, - int64_t reconnect, + int64_t reconnect_ms, Error **errp) { SocketChardev *s = SOCKET_CHARDEV(chr); - if (reconnect > 0) { - s->reconnect_time = reconnect; + if (reconnect_ms > 0) { + s->reconnect_time_ms = reconnect_ms; tcp_chr_connect_client_async(chr); return 0; } else { @@ -1371,7 +1371,7 @@ static void qmp_chardev_open_socket(Chardev *chr, bool is_tn3270 = sock->has_tn3270 ? sock->tn3270 : false; bool is_waitconnect = sock->has_wait ? sock->wait : false; bool is_websock = sock->has_websocket ? sock->websocket : false; - int64_t reconnect = sock->has_reconnect ? sock->reconnect : 0; + int64_t reconnect_ms = 0; SocketAddress *addr; s->is_listen = is_listen; @@ -1443,7 +1443,13 @@ static void qmp_chardev_open_socket(Chardev *chr, return; } } else { - if (qmp_chardev_open_socket_client(chr, reconnect, errp) < 0) { + if (sock->has_reconnect) { + reconnect_ms = sock->reconnect * 1000ULL; + } else if (sock->has_reconnect_ms) { + reconnect_ms = sock->reconnect_ms; + } + + if (qmp_chardev_open_socket_client(chr, reconnect_ms, errp) < 0) { return; } } @@ -1509,6 +1515,15 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend, sock->wait = qemu_opt_get_bool(opts, "wait", true); sock->has_reconnect = qemu_opt_find(opts, "reconnect"); sock->reconnect = qemu_opt_get_number(opts, "reconnect", 0); + sock->has_reconnect_ms = qemu_opt_find(opts, "reconnect-ms"); + sock->reconnect_ms = qemu_opt_get_number(opts, "reconnect-ms", 0); + + if (sock->has_reconnect_ms && sock->has_reconnect) { + error_setg(errp, + "'reconnect' and 'reconnect-ms' are mutually exclusive"); + return; + } + sock->tls_creds = g_strdup(qemu_opt_get(opts, "tls-creds")); sock->tls_authz = g_strdup(qemu_opt_get(opts, "tls-authz")); diff --git a/chardev/char.c b/chardev/char.c index ba847b6e9e..35623c78a3 100644 --- a/chardev/char.c +++ b/chardev/char.c @@ -888,6 +888,9 @@ QemuOptsList qemu_chardev_opts = { },{ .name = "reconnect", .type = QEMU_OPT_NUMBER, + },{ + .name = "reconnect-ms", + .type = QEMU_OPT_NUMBER, },{ .name = "telnet", .type = QEMU_OPT_BOOL, diff --git a/include/chardev/char-socket.h b/include/chardev/char-socket.h index 0708ca6fa9..d6d13ad37f 100644 --- a/include/chardev/char-socket.h +++ b/include/chardev/char-socket.h @@ -74,7 +74,7 @@ struct SocketChardev { bool is_websock; GSource *reconnect_timer; - int64_t reconnect_time; + int64_t reconnect_time_ms; bool connect_err_reported; QIOTask *connect_task; diff --git a/qapi/char.json b/qapi/char.json index ef58445cee..7f117438c6 100644 --- a/qapi/char.json +++ b/qapi/char.json @@ -273,7 +273,19 @@ # # @reconnect: For a client socket, if a socket is disconnected, then # attempt a reconnect after the given number of seconds. Setting -# this to zero disables this function. (default: 0) (Since: 2.2) +# this to zero disables this function. The use of this member is +# deprecated, use @reconnect-ms instead. (default: 0) (Since: 2.2) +# +# @reconnect-ms: For a client socket, if a socket is disconnected, +# then attempt a reconnect after the given number of milliseconds. +# Setting this to zero disables this function. This member is +# mutually exclusive with @reconnect. +# (default: 0) (Since: 9.2) +# +# Features: +# +# @deprecated: Member @reconnect is deprecated. Use @reconnect-ms +# instead. # # Since: 1.4 ## @@ -287,7 +299,8 @@ '*telnet': 'bool', '*tn3270': 'bool', '*websocket': 'bool', - '*reconnect': 'int' }, + '*reconnect': { 'type': 'int', 'features': [ 'deprecated' ] }, + '*reconnect-ms': 'int' }, 'base': 'ChardevCommon' } ## -- 2.34.1
On 04.09.24 08:19, Daniil Tatianin wrote:
The 'reconnect' option only allows to specify the time in seconds, which is way too long for certain workflows.
We have a lightweight disk backend server, which takes about 20ms to live update, but due to this limitation in QEMU, previously the guest disk controller would hang for one second because it would take this long for QEMU to reinitialize the socket connection.
Introduce a new option called 'reconnect-ms', which is the same as 'reconnect', except the value is treated as milliseconds. These are mutually exclusive and specifying both results in an error.
'reconnect' is also deprecated by this commit to make it possible to remove it in the future as to not keep two options that control the same thing.
Signed-off-by: Daniil Tatianin<d-tatianin@yandex-team.ru>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> -- Best regards, Vladimir
On Wed, Sep 04, 2024 at 08:19:13 +0300, Daniil Tatianin wrote:
The 'reconnect' option only allows to specify the time in seconds, which is way too long for certain workflows.
We have a lightweight disk backend server, which takes about 20ms to live update, but due to this limitation in QEMU, previously the guest disk controller would hang for one second because it would take this long for QEMU to reinitialize the socket connection.
Introduce a new option called 'reconnect-ms', which is the same as 'reconnect', except the value is treated as milliseconds. These are mutually exclusive and specifying both results in an error.
'reconnect' is also deprecated by this commit to make it possible to remove it in the future as to not keep two options that control the same thing.
Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru> ---
[...]
diff --git a/qapi/char.json b/qapi/char.json index ef58445cee..7f117438c6 100644 --- a/qapi/char.json +++ b/qapi/char.json @@ -273,7 +273,19 @@ # # @reconnect: For a client socket, if a socket is disconnected, then # attempt a reconnect after the given number of seconds. Setting -# this to zero disables this function. (default: 0) (Since: 2.2) +# this to zero disables this function. The use of this member is +# deprecated, use @reconnect-ms instead. (default: 0) (Since: 2.2) +# +# @reconnect-ms: For a client socket, if a socket is disconnected, +# then attempt a reconnect after the given number of milliseconds. +# Setting this to zero disables this function. This member is +# mutually exclusive with @reconnect. +# (default: 0) (Since: 9.2) +# +# Features: +# +# @deprecated: Member @reconnect is deprecated. Use @reconnect-ms +# instead. # # Since: 1.4 ## @@ -287,7 +299,8 @@ '*telnet': 'bool', '*tn3270': 'bool', '*websocket': 'bool', - '*reconnect': 'int' }, + '*reconnect': { 'type': 'int', 'features': [ 'deprecated' ] }, + '*reconnect-ms': 'int' }, 'base': 'ChardevCommon' }
This is a little off-topic: So I wanted to make libvirt use the new parameter to stay ahead deprecation. I've applied this patch to qemu, dumped capabilities and pretty much expected a bunch of test cases in libvirt fail as they'd be using a deprecated field as libvirt is supposed to validate everything. And the test suite passed unexpectedly. I've dug further and noticed that for some reason libvirt doesn't still use JSON parameters for -chardev (which is the pre-requisite for validation). I've also noticed that at some point I attempted to convert it over witnessed by having an (unused) capability named QEMU_CAPS_CHARDEV_JSON that I've introduced. My questions are: 1) Does '-chardev' accept JSON identical to 'chardev-add' QMP command? If yes: 2) Since when can that be used? (What can I use as a witness) 3) Are there any gotchas? I wonder this as I'd love to finish that out, but I really don't fancy digging into qemu to find a gotcha 3/4 of the way there. Anyways, as I've already stated, this patch is okay for libvirt, but I didn't review the implementation, thus, on behalf of libvirt: ACKed-by: Peter Krempa <pkrempa@redhat.com>
Peter Krempa <pkrempa@redhat.com> writes:
This is a little off-topic:
So I wanted to make libvirt use the new parameter to stay ahead deprecation. I've applied this patch to qemu, dumped capabilities and pretty much expected a bunch of test cases in libvirt fail as they'd be using a deprecated field as libvirt is supposed to validate everything.
And the test suite passed unexpectedly. I've dug further and noticed that for some reason libvirt doesn't still use JSON parameters for -chardev (which is the pre-requisite for validation).
I've also noticed that at some point I attempted to convert it over witnessed by having an (unused) capability named QEMU_CAPS_CHARDEV_JSON that I've introduced.
My questions are: 1) Does '-chardev' accept JSON identical to 'chardev-add' QMP command?
Sadly, no. How badly do you want it?
If yes:
If we implemented it:
2) Since when can that be used? (What can I use as a witness)
I figure we'd provide a witness the same way we did when we added JSON support to -device: add a feature @json-cli to chardev-add.
3) Are there any gotchas?
Not aware of any. Can't be 100% sure until we try.
I wonder this as I'd love to finish that out, but I really don't fancy digging into qemu to find a gotcha 3/4 of the way there.
Understandable :)
Anyways, as I've already stated, this patch is okay for libvirt, but I didn't review the implementation, thus, on behalf of libvirt:
ACKed-by: Peter Krempa <pkrempa@redhat.com>
Thanks!
On Sat, Sep 14, 2024 at 10:42:36 +0200, Markus Armbruster wrote:
Peter Krempa <pkrempa@redhat.com> writes:
This is a little off-topic:
So I wanted to make libvirt use the new parameter to stay ahead deprecation. I've applied this patch to qemu, dumped capabilities and pretty much expected a bunch of test cases in libvirt fail as they'd be using a deprecated field as libvirt is supposed to validate everything.
And the test suite passed unexpectedly. I've dug further and noticed that for some reason libvirt doesn't still use JSON parameters for -chardev (which is the pre-requisite for validation).
I've also noticed that at some point I attempted to convert it over witnessed by having an (unused) capability named QEMU_CAPS_CHARDEV_JSON that I've introduced.
My questions are: 1) Does '-chardev' accept JSON identical to 'chardev-add' QMP command?
Sadly, no.
Yeah, in the meanwhile I had a look and also remembered that we spoke about why this was the case. (All the 'wrapper' objects making the schema of 'chardev-add' extremely unpleasant)
How badly do you want it?
So the main motivation is to have just one instance of the code generating the config for qemu. As JSON has type information inside libvirt always generates JSON internally first. This is the case for -object, -device, -netdev, -blockdev, ... For '-chardev' we currently (in tree) have two separate formatters for '-chardev' and QMP 'chardev-add'. I do have a reasonalby looking rework in the works which unifies them (with a few quirky "if (commandline)" blocks). In cases when we need to support the old syntax for any reason we do have a converter that takes JSON and outputs the qemuopts syntax. This is possible for now as we have mostly flat structures and the only difference for now is how the arrays are processed in -device vs -netdev (by callbacks to the converter). For -chardev this will require a bit more logic as we need to avoid the extra wrappers for commandline output and few fields have different names in QMP than on the commandline. My main goal here is to achieve validation against the QMP schema, and it's much easier for us to add test cases via XML than hardcoding them in C. So honestly I don't think we want it too badly. Definitely not so bad that having it with bad design. I reckon that doing the refactor will also simplify things for the future if the QMP design will be changed to e.g. drop the wrappers.
If yes:
If we implemented it:
2) Since when can that be used? (What can I use as a witness)
I figure we'd provide a witness the same way we did when we added JSON support to -device: add a feature @json-cli to chardev-add.
Yup, that'll always work :)
3) Are there any gotchas?
Not aware of any. Can't be 100% sure until we try.
I wonder this as I'd love to finish that out, but I really don't fancy digging into qemu to find a gotcha 3/4 of the way there.
Understandable :)
Anyways, as I've already stated, this patch is okay for libvirt, but I didn't review the implementation, thus, on behalf of libvirt:
ACKed-by: Peter Krempa <pkrempa@redhat.com>
Thanks!
Am 14.09.2024 um 10:42 hat Markus Armbruster geschrieben:
Peter Krempa <pkrempa@redhat.com> writes:
This is a little off-topic:
So I wanted to make libvirt use the new parameter to stay ahead deprecation. I've applied this patch to qemu, dumped capabilities and pretty much expected a bunch of test cases in libvirt fail as they'd be using a deprecated field as libvirt is supposed to validate everything.
And the test suite passed unexpectedly. I've dug further and noticed that for some reason libvirt doesn't still use JSON parameters for -chardev (which is the pre-requisite for validation).
I've also noticed that at some point I attempted to convert it over witnessed by having an (unused) capability named QEMU_CAPS_CHARDEV_JSON that I've introduced.
My questions are: 1) Does '-chardev' accept JSON identical to 'chardev-add' QMP command?
Sadly, no.
How badly do you want it?
I suppose even my old patches to fully QAPIfy -chardev could be revived, which would not only add JSON support, but also make sure that everything that works in JSON also works with keyval syntax, both ways stay in sync in the future and that you can access non-scalar options without JSON: https://repo.or.cz/qemu/kevin.git/shortlog/refs/tags/qapi-alias-chardev-v4 Without QAPI aliases, they will have to contain some ugly code to do the compatibility conversion, but whatever can be generated can also be written manually... Kevin
On 9/4/24 07:19, Daniil Tatianin wrote:
The 'reconnect' option only allows to specify the time in seconds, which is way too long for certain workflows.
We have a lightweight disk backend server, which takes about 20ms to live update, but due to this limitation in QEMU, previously the guest disk controller would hang for one second because it would take this long for QEMU to reinitialize the socket connection.
Introduce a new option called 'reconnect-ms', which is the same as 'reconnect', except the value is treated as milliseconds. These are mutually exclusive and specifying both results in an error.
'reconnect' is also deprecated by this commit to make it possible to remove it in the future as to not keep two options that control the same thing.
Please add it also to docs/about/deprecated.rst Otherwise looks good, thanks! Paolo
Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru> ACKed-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> --- chardev/char-socket.c | 33 ++++++++++++++++++++++++--------- chardev/char.c | 3 +++ include/chardev/char-socket.h | 2 +- qapi/char.json | 17 +++++++++++++++-- 4 files changed, 43 insertions(+), 12 deletions(-)
diff --git a/chardev/char-socket.c b/chardev/char-socket.c index 1ca9441b1b..c24331ac23 100644 --- a/chardev/char-socket.c +++ b/chardev/char-socket.c @@ -74,7 +74,7 @@ static void qemu_chr_socket_restart_timer(Chardev *chr) assert(!s->reconnect_timer); name = g_strdup_printf("chardev-socket-reconnect-%s", chr->label); s->reconnect_timer = qemu_chr_timeout_add_ms(chr, - s->reconnect_time * 1000, + s->reconnect_time_ms, socket_reconnect_timeout, chr); g_source_set_name(s->reconnect_timer, name); @@ -481,7 +481,7 @@ static void tcp_chr_disconnect_locked(Chardev *chr) if (emit_close) { qemu_chr_be_event(chr, CHR_EVENT_CLOSED); } - if (s->reconnect_time && !s->reconnect_timer) { + if (s->reconnect_time_ms && !s->reconnect_timer) { qemu_chr_socket_restart_timer(chr); } } @@ -1080,9 +1080,9 @@ static int tcp_chr_wait_connected(Chardev *chr, Error **errp) } else { Error *err = NULL; if (tcp_chr_connect_client_sync(chr, &err) < 0) { - if (s->reconnect_time) { + if (s->reconnect_time_ms) { error_free(err); - g_usleep(s->reconnect_time * 1000ULL * 1000ULL); + g_usleep(s->reconnect_time_ms * 1000ULL); } else { error_propagate(errp, err); return -1; @@ -1267,13 +1267,13 @@ skip_listen:
static int qmp_chardev_open_socket_client(Chardev *chr, - int64_t reconnect, + int64_t reconnect_ms, Error **errp) { SocketChardev *s = SOCKET_CHARDEV(chr);
- if (reconnect > 0) { - s->reconnect_time = reconnect; + if (reconnect_ms > 0) { + s->reconnect_time_ms = reconnect_ms; tcp_chr_connect_client_async(chr); return 0; } else { @@ -1371,7 +1371,7 @@ static void qmp_chardev_open_socket(Chardev *chr, bool is_tn3270 = sock->has_tn3270 ? sock->tn3270 : false; bool is_waitconnect = sock->has_wait ? sock->wait : false; bool is_websock = sock->has_websocket ? sock->websocket : false; - int64_t reconnect = sock->has_reconnect ? sock->reconnect : 0; + int64_t reconnect_ms = 0; SocketAddress *addr;
s->is_listen = is_listen; @@ -1443,7 +1443,13 @@ static void qmp_chardev_open_socket(Chardev *chr, return; } } else { - if (qmp_chardev_open_socket_client(chr, reconnect, errp) < 0) { + if (sock->has_reconnect) { + reconnect_ms = sock->reconnect * 1000ULL; + } else if (sock->has_reconnect_ms) { + reconnect_ms = sock->reconnect_ms; + } + + if (qmp_chardev_open_socket_client(chr, reconnect_ms, errp) < 0) { return; } } @@ -1509,6 +1515,15 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend, sock->wait = qemu_opt_get_bool(opts, "wait", true); sock->has_reconnect = qemu_opt_find(opts, "reconnect"); sock->reconnect = qemu_opt_get_number(opts, "reconnect", 0); + sock->has_reconnect_ms = qemu_opt_find(opts, "reconnect-ms"); + sock->reconnect_ms = qemu_opt_get_number(opts, "reconnect-ms", 0); + + if (sock->has_reconnect_ms && sock->has_reconnect) { + error_setg(errp, + "'reconnect' and 'reconnect-ms' are mutually exclusive"); + return; + } + sock->tls_creds = g_strdup(qemu_opt_get(opts, "tls-creds")); sock->tls_authz = g_strdup(qemu_opt_get(opts, "tls-authz"));
diff --git a/chardev/char.c b/chardev/char.c index ba847b6e9e..35623c78a3 100644 --- a/chardev/char.c +++ b/chardev/char.c @@ -888,6 +888,9 @@ QemuOptsList qemu_chardev_opts = { },{ .name = "reconnect", .type = QEMU_OPT_NUMBER, + },{ + .name = "reconnect-ms", + .type = QEMU_OPT_NUMBER, },{ .name = "telnet", .type = QEMU_OPT_BOOL, diff --git a/include/chardev/char-socket.h b/include/chardev/char-socket.h index 0708ca6fa9..d6d13ad37f 100644 --- a/include/chardev/char-socket.h +++ b/include/chardev/char-socket.h @@ -74,7 +74,7 @@ struct SocketChardev { bool is_websock;
GSource *reconnect_timer; - int64_t reconnect_time; + int64_t reconnect_time_ms; bool connect_err_reported;
QIOTask *connect_task; diff --git a/qapi/char.json b/qapi/char.json index ef58445cee..7f117438c6 100644 --- a/qapi/char.json +++ b/qapi/char.json @@ -273,7 +273,19 @@ # # @reconnect: For a client socket, if a socket is disconnected, then # attempt a reconnect after the given number of seconds. Setting -# this to zero disables this function. (default: 0) (Since: 2.2) +# this to zero disables this function. The use of this member is +# deprecated, use @reconnect-ms instead. (default: 0) (Since: 2.2) +# +# @reconnect-ms: For a client socket, if a socket is disconnected, +# then attempt a reconnect after the given number of milliseconds. +# Setting this to zero disables this function. This member is +# mutually exclusive with @reconnect. +# (default: 0) (Since: 9.2) +# +# Features: +# +# @deprecated: Member @reconnect is deprecated. Use @reconnect-ms +# instead. # # Since: 1.4 ## @@ -287,7 +299,8 @@ '*telnet': 'bool', '*tn3270': 'bool', '*websocket': 'bool', - '*reconnect': 'int' }, + '*reconnect': { 'type': 'int', 'features': [ 'deprecated' ] }, + '*reconnect-ms': 'int' }, 'base': 'ChardevCommon' }
##
participants (6)
-
Daniil Tatianin -
Kevin Wolf -
Markus Armbruster -
Paolo Bonzini -
Peter Krempa -
Vladimir Sementsov-Ogievskiy