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Date: Wed, 21 Apr 2021 15:25:16 +0200
From: Fabian =?iso-8859-1?q?Gr=FCnbichler?= <f.gruenbichler@proxmox.com>
To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
References: <20210421111539.29261-1-s.reiter@proxmox.com>
<20210421111539.29261-8-s.reiter@proxmox.com>
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Subject: Re: [pve-devel] [PATCH http-server 07/10] support streaming data
form fh to client
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some nits inline, looks good to me otherwise!
On April 21, 2021 1:15 pm, Stefan Reiter wrote:
> Use an explicit AnyEvent::Handle similar to websocket proxying.
>=20
> Needs some special care to make sure we apply backpressure correctly to
> avoid caching too much data. Note that because of AnyEvent restrictions,
> specifying a "fh" to point to a file or a packet-based socket may result
> in unwanted behaviour[0].
>=20
> [0]: https://metacpan.org/pod/AnyEvent::Handle#DESCRIPTION
>=20
> Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
> ---
> PVE/APIServer/AnyEvent.pm | 97 +++++++++++++++++++++++++++++++++++++--
> 1 file changed, 93 insertions(+), 4 deletions(-)
>=20
> diff --git a/PVE/APIServer/AnyEvent.pm b/PVE/APIServer/AnyEvent.pm
> index 60a2a1c..643ae88 100644
> --- a/PVE/APIServer/AnyEvent.pm
> +++ b/PVE/APIServer/AnyEvent.pm
> @@ -189,7 +189,7 @@ sub finish_response {
> }
> =20
> sub response {
> - my ($self, $reqstate, $resp, $mtime, $nocomp, $delay) =3D @_;
> + my ($self, $reqstate, $resp, $mtime, $nocomp, $delay, $stream_fh) =
=3D @_;
> =20
> #print "$$: send response: " . Dumper($resp);
> =20
> @@ -231,7 +231,7 @@ sub response {
> $resp->header('Server' =3D> "pve-api-daemon/3.0");
> =20
> my $content_length;
> - if ($content) {
> + if ($content && !$stream_fh) {
> =20
> $content_length =3D length($content);
> =20
> @@ -258,11 +258,93 @@ sub response {
> #print "SEND(without content) $res\n" if $self->{debug};
> =20
> $res .=3D "\015\012";
> - $res .=3D $content if $content;
> + $res .=3D $content if $content && !$stream_fh;
> =20
> $self->log_request($reqstate, $reqstate->{request});
> =20
> - if ($delay && $delay > 0) {
> + if ($stream_fh) {
nit the code inside these braces might be worthy of becoming its own sub?
> + # write headers and preamble
> + $reqstate->{hdl}->push_write($res);
> +
> + # then attach an AnyEvent::Handle to pass through the data
> + my $buf_size =3D 4*1024*1024;
> +
> + my $on_read;
> + $on_read =3D sub {
> + my ($hdl) =3D @_;
> + my $reqhdl =3D $reqstate->{hdl};
> + return if !$reqhdl;
> +
> + my $wbuf_len =3D length($reqhdl->{wbuf});
> + my $rbuf_len =3D length($hdl->{rbuf});
> + # TODO: Take into account $reqhdl->{wbuf_max} ? Right now
> + # that's unbounded, so just assume $buf_size
> + my $to_read =3D $buf_size - $wbuf_len;
> + $to_read =3D $rbuf_len if $rbuf_len < $to_read;
> + if ($to_read > 0) {
> + my $data =3D substr($hdl->{rbuf}, 0, $to_read, '');
> + $reqhdl->push_write($data);
> + $rbuf_len -=3D $to_read;
> + } elsif ($hdl->{_eof}) {
> + # workaround: AnyEvent gives us a fake EPIPE if we don't consume
> + # any data when called at EOF, so unregister ourselves - data is
> + # flushed by on_eof anyway
> + # see: https://sources.debian.org/src/libanyevent-perl/7.170-2/lib/Any=
Event/Handle.pm/#L1329
> + $hdl->on_read();
> + return;
> + }
> +
> + # apply backpressure so we don't accept any more data into
> + # buffer if the client isn't downloading fast enough
> + # note: read_size can double upon read, and we also need to
> + # account for one more read after start_read, so *4
> + if ($rbuf_len + $hdl->{read_size}*4 > $buf_size) {
> + # stop reading=20
stop reading until write buffer is empty
> + $hdl->on_read();
> + my $prev_on_drain =3D $reqhdl->{on_drain};
> + $reqhdl->on_drain(sub {
> + my ($wrhdl) =3D @_;
> + # write buffer is empty, continue reading
on_drain was called because write_buffer is empty, start reading again
> + $hdl->on_read($on_read);
> + if ($prev_on_drain) {
> + $wrhdl->on_drain($prev_on_drain);
> + $prev_on_drain->($wrhdl);
> + }
> + });
> + }
> + };
> +
> + $reqstate->{proxyhdl} =3D AnyEvent::Handle->new(
> + fh =3D> $stream_fh,
> + rbuf_max =3D> $buf_size,
> + timeout =3D> 0,
> + on_read =3D> $on_read,
> + on_eof =3D> sub {
> + my ($hdl) =3D @_;
> + eval {
> + if (my $reqhdl =3D $reqstate->{hdl}) {
> + $self->log_aborted_request($reqstate);
> + # write out any remaining data
> + $reqhdl->push_write($hdl->{rbuf}) if length($hdl->{rbuf}) > 0;
> + $hdl->{rbuf} =3D "";
> + $reqhdl->push_shutdown();
> + $self->finish_response($reqstate);
> + }
> + };
> + if (my $err =3D $@) { syslog('err', "$err"); }
> + $on_read =3D undef;
> + },
> + on_error =3D> sub {
> + my ($hdl, $fatal, $message) =3D @_;
> + eval {
> + $self->log_aborted_request($reqstate, $message);
> + $self->client_do_disconnect($reqstate);
> + };
> + if (my $err =3D $@) { syslog('err', "$err"); }
> + $on_read =3D undef;
> + },
> + );
> + } elsif ($delay && $delay > 0) {
> my $w; $w =3D AnyEvent->timer(after =3D> $delay, cb =3D> sub {
> undef $w; # delete reference
> $reqstate->{hdl}->push_write($res);
> @@ -322,6 +404,13 @@ sub send_file_start {
> if (ref($download) eq 'HASH') {
> $fh =3D $download->{fh};
> $mime =3D $download->{'content-type'};
> +
> + if ($download->{stream}) {
> + my $header =3D HTTP::Headers->new(Content_Type =3D> $mime);
> + my $resp =3D HTTP::Response->new(200, "OK", $header);
> + $self->response($reqstate, $resp, undef, 1, 0, $fh);
> + return;
> + }
> } else {
> my $filename =3D $download;
> $fh =3D IO::File->new($filename, '<') ||
> --=20
> 2.20.1
>=20
>=20
>=20
> _______________________________________________
> pve-devel mailing list
> pve-devel@lists.proxmox.com
> https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
>=20
>=20
>=20
=