If the server fails, nbdinfo can write partial output before the error message (albeit on different channels). Here is an example: $ nbdkit eval open='echo EIO fail >&2; exit 1' --run 'nbdinfo --json "$uri"' { "protocol": "newstyle-fixed", "TLS": false, nbdkit: eval[1]: error: /tmp/nbdkitii3pZW/open: fail nbdkit: eval[1]: error: /tmp/nbdkitii3pZW/open: fail nbdinfo: nbd_opt_go: server replied with error to opt_go request: No such file or directory Notice the partial JSON document, and the error message from nbdinfo. With this commit nbdinfo tries to produce either the complete output or the error message. --- info/Makefile.am | 1 + info/info-atomic-output.sh | 32 ++++++ info/nbdinfo.c | 194 ++++++++++++++++++++++--------------- 3 files changed, 147 insertions(+), 80 deletions(-) diff --git a/info/Makefile.am b/info/Makefile.am index 9557f59..f0edec6 100644 --- a/info/Makefile.am +++ b/info/Makefile.am @@ -32,6 +32,7 @@ info_sh_files = \ info-map-base-allocation.sh \ info-map-base-allocation-json.sh \ info-map-qemu-dirty-bitmap.sh \ + info-atomic-output.sh \ $(NULL) EXTRA_DIST = \ diff --git a/info/info-atomic-output.sh b/info/info-atomic-output.sh new file mode 100755 index 0000000..11b2ab3 --- /dev/null +++ b/info/info-atomic-output.sh @@ -0,0 +1,32 @@ +#!/usr/bin/env bash +# nbd client library in userspace +# Copyright (C) 2020 Red Hat Inc. +# +# This library is free software; you can redistribute it and/or +# modify it under the terms of the GNU Lesser General Public +# License as published by the Free Software Foundation; either +# version 2 of the License, or (at your option) any later version. +# +# This library is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +# Lesser General Public License for more details. +# +# You should have received a copy of the GNU Lesser General Public +# License along with this library; if not, write to the Free Software +# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + +. ../tests/functions.sh + +set -e +set -x + +requires nbdkit --version +requires nbdkit eval --version + +out=info-atomic-output.out +cleanup_fn rm -f $out + +nbdkit -U - eval open='echo EIO fail >&2; exit 1' \ + --run '$VG nbdinfo --size "nbd+unix:///?socket=$unixsocket"' > $out ||: +test ! -s $out diff --git a/info/nbdinfo.c b/info/nbdinfo.c index 31e2508..24ec129 100644 --- a/info/nbdinfo.c +++ b/info/nbdinfo.c @@ -32,6 +32,7 @@ #include <libnbd.h> static const char *progname; +static FILE *fp; static bool list_all = false; static bool probe_content, content_flag, no_content_flag; static bool json_output = false; @@ -121,6 +122,8 @@ main (int argc, char *argv[]) int64_t size; const char *protocol; int tls_negotiated; + char *output = NULL; + size_t output_len = 0; progname = argv[0]; @@ -207,6 +210,17 @@ main (int argc, char *argv[]) if (map) probe_content = false; + /* Try to write output atomically. We spool output into a + * memstream, pointed to by fp, and write it all at once at the end. + * On error nothing should be printed on stdout. + */ + fp = open_memstream (&output, &output_len); + if (fp == NULL) { + fprintf (stderr, "%s: ", progname); + perror ("open_memstream"); + exit (EXIT_FAILURE); + } + /* Open the NBD side. */ nbd = nbd_create (); if (nbd == NULL) { @@ -250,7 +264,7 @@ main (int argc, char *argv[]) exit (EXIT_FAILURE); } - printf ("%" PRIi64 "\n", size); + fprintf (fp, "%" PRIi64 "\n", size); } else if (map) { /* --map (!list_all) */ uint64_t offset, prev_offset; @@ -269,7 +283,7 @@ main (int argc, char *argv[]) exit (EXIT_FAILURE); } - if (json_output) printf ("[\n"); + if (json_output) fprintf (fp, "[\n"); for (offset = 0; offset < size;) { prev_offset = offset; if (nbd_block_status (nbd, size - offset, offset, @@ -288,7 +302,7 @@ main (int argc, char *argv[]) exit (EXIT_FAILURE); } } - if (json_output) printf ("\n]\n"); + if (json_output) fprintf (fp, "\n]\n"); } else { /* not --size or --map */ /* Print per-connection fields. */ @@ -297,22 +311,22 @@ main (int argc, char *argv[]) if (!json_output) { if (protocol) { - printf ("protocol: %s", protocol); + fprintf (fp, "protocol: %s", protocol); if (tls_negotiated >= 0) - printf (" %s TLS", tls_negotiated ? "with" : "without"); - printf ("\n"); + fprintf (fp, " %s TLS", tls_negotiated ? "with" : "without"); + fprintf (fp, "\n"); } } else { - printf ("{\n"); + fprintf (fp, "{\n"); if (protocol) { - printf ("\"protocol\": "); + fprintf (fp, "\"protocol\": "); print_json_string (protocol); - printf (",\n"); + fprintf (fp, ",\n"); } if (tls_negotiated >= 0) - printf ("\"TLS\": %s,\n", tls_negotiated ? "true" : "false"); + fprintf (fp, "\"TLS\": %s,\n", tls_negotiated ? "true" : "false"); } if (!list_all) @@ -321,7 +335,7 @@ main (int argc, char *argv[]) list_all_exports (nbd, argv[optind]); if (json_output) - printf ("}\n"); + fprintf (fp, "}\n"); } for (i = 0; i < export_list.len; i++) { @@ -333,6 +347,19 @@ main (int argc, char *argv[]) nbd_opt_abort (nbd); nbd_shutdown (nbd, 0); nbd_close (nbd); + + /* Close the output stream and copy it to the real stdout. */ + if (fclose (fp) == EOF) { + fprintf (stderr, "%s: ", progname); + perror ("fclose"); + exit (EXIT_FAILURE); + } + if (puts (output) == EOF) { + fprintf (stderr, "%s: ", progname); + perror ("puts"); + exit (EXIT_FAILURE); + } + exit (EXIT_SUCCESS); } @@ -451,126 +478,133 @@ list_one_export (struct nbd_handle *nbd, const char *desc, content = get_content (nbd, size); if (!json_output) { - printf ("export="); + fprintf (fp, "export="); /* Might as well use the JSON function to get an escaped string here ... */ print_json_string (export_name); - printf (":\n"); + fprintf (fp, ":\n"); if (desc && *desc) - printf ("\tdescription: %s\n", desc); - printf ("\texport-size: %" PRIi64 "\n", size); + fprintf (fp, "\tdescription: %s\n", desc); + fprintf (fp, "\texport-size: %" PRIi64 "\n", size); if (content) - printf ("\tcontent: %s\n", content); + fprintf (fp, "\tcontent: %s\n", content); if (show_context) { - printf ("\tcontexts:\n"); + fprintf (fp, "\tcontexts:\n"); for (struct context_list *next = contexts; next; next = next->next) - printf ("\t\t%s\n", next->name); + fprintf (fp, "\t\t%s\n", next->name); } if (is_rotational >= 0) - printf ("\t%s: %s\n", "is_rotational", is_rotational ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "is_rotational", + is_rotational ? "true" : "false"); if (is_read_only >= 0) - printf ("\t%s: %s\n", "is_read_only", is_read_only ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "is_read_only", + is_read_only ? "true" : "false"); if (can_cache >= 0) - printf ("\t%s: %s\n", "can_cache", can_cache ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "can_cache", can_cache ? "true" : "false"); if (can_df >= 0) - printf ("\t%s: %s\n", "can_df", can_df ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "can_df", can_df ? "true" : "false"); if (can_fast_zero >= 0) - printf ("\t%s: %s\n", "can_fast_zero", can_fast_zero ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "can_fast_zero", + can_fast_zero ? "true" : "false"); if (can_flush >= 0) - printf ("\t%s: %s\n", "can_flush", can_flush ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "can_flush", can_flush ? "true" : "false"); if (can_fua >= 0) - printf ("\t%s: %s\n", "can_fua", can_fua ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "can_fua", can_fua ? "true" : "false"); if (can_multi_conn >= 0) - printf ("\t%s: %s\n", "can_multi_conn", can_multi_conn ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "can_multi_conn", + can_multi_conn ? "true" : "false"); if (can_trim >= 0) - printf ("\t%s: %s\n", "can_trim", can_trim ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "can_trim", can_trim ? "true" : "false"); if (can_zero >= 0) - printf ("\t%s: %s\n", "can_zero", can_zero ? "true" : "false"); + fprintf (fp, "\t%s: %s\n", "can_zero", can_zero ? "true" : "false"); if (block_minimum > 0) - printf ("\t%s: %" PRId64 "\n", "block_size_minimum", block_minimum); + fprintf (fp, "\t%s: %" PRId64 "\n", "block_size_minimum", block_minimum); if (block_preferred > 0) - printf ("\t%s: %" PRId64 "\n", "block_size_preferred", block_preferred); + fprintf (fp, "\t%s: %" PRId64 "\n", "block_size_preferred", + block_preferred); if (block_maximum > 0) - printf ("\t%s: %" PRId64 "\n", "block_size_maximum", block_maximum); + fprintf (fp, "\t%s: %" PRId64 "\n", "block_size_maximum", block_maximum); } else { if (first) - printf ("\"exports\": [\n"); - printf ("\t{\n"); + fprintf (fp, "\"exports\": [\n"); + fprintf (fp, "\t{\n"); - printf ("\t\"export-name\": "); + fprintf (fp, "\t\"export-name\": "); print_json_string (export_name); - printf (",\n"); + fprintf (fp, ",\n"); if (desc && *desc) { - printf ("\t\"description\": "); + fprintf (fp, "\t\"description\": "); print_json_string (desc); - printf (",\n"); + fprintf (fp, ",\n"); } if (content) { - printf ("\t\"content\": "); + fprintf (fp, "\t\"content\": "); print_json_string (content); - printf (",\n"); + fprintf (fp, ",\n"); } if (show_context) { - printf ("\t\"contexts\": [\n"); + fprintf (fp, "\t\"contexts\": [\n"); for (struct context_list *next = contexts; next; next = next->next) { - printf ("\t\t"); + fprintf (fp, "\t\t"); print_json_string (next->name); if (next->next) - putchar(','); - putchar('\n'); + fputc (',', fp); + fputc ('\n', fp); } - printf ("\t],\n"); + fprintf (fp, "\t],\n"); } if (is_rotational >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "is_rotational", is_rotational ? "true" : "false"); if (is_read_only >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "is_read_only", is_read_only ? "true" : "false"); if (can_cache >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "can_cache", can_cache ? "true" : "false"); if (can_df >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "can_df", can_df ? "true" : "false"); if (can_fast_zero >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "can_fast_zero", can_fast_zero ? "true" : "false"); if (can_flush >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "can_flush", can_flush ? "true" : "false"); if (can_fua >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "can_fua", can_fua ? "true" : "false"); if (can_multi_conn >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "can_multi_conn", can_multi_conn ? "true" : "false"); if (can_trim >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "can_trim", can_trim ? "true" : "false"); if (can_zero >= 0) - printf ("\t\"%s\": %s,\n", + fprintf (fp, "\t\"%s\": %s,\n", "can_zero", can_zero ? "true" : "false"); if (block_minimum > 0) - printf ("\t\"%s\": %" PRId64 ",\n", "block_size_minimum", block_minimum); + fprintf (fp, "\t\"%s\": %" PRId64 ",\n", "block_size_minimum", + block_minimum); if (block_preferred > 0) - printf ("\t\"%s\": %" PRId64 ",\n", "block_size_preferred", + fprintf (fp, "\t\"%s\": %" PRId64 ",\n", "block_size_preferred", block_preferred); if (block_maximum > 0) - printf ("\t\"%s\": %" PRId64 ",\n", "block_size_maximum", block_maximum); + fprintf (fp, "\t\"%s\": %" PRId64 ",\n", "block_size_maximum", + block_maximum); /* Put this one at the end because of the stupid comma thing in JSON. */ - printf ("\t\"export-size\": %" PRIi64 "\n", size); + fprintf (fp, "\t\"export-size\": %" PRIi64 "\n", size); if (last) - printf ("\t} ]\n"); + fprintf (fp, "\t} ]\n"); else - printf ("\t},\n"); + fprintf (fp, "\t},\n"); } while (contexts) { @@ -590,7 +624,7 @@ list_all_exports (struct nbd_handle *nbd1, const char *uri) size_t i; if (export_list.len == 0 && json_output) - printf ("\"exports\": []\n"); + fprintf (fp, "\"exports\": []\n"); for (i = 0; i < export_list.len; ++i) { const char *name = export_list.names[i]; @@ -635,22 +669,22 @@ list_all_exports (struct nbd_handle *nbd1, const char *uri) static void print_json_string (const char *s) { - putc ('"', stdout); + fputc ('"', fp); for (; *s; s++) { switch (*s) { case '\\': case '"': - putc ('\\', stdout); - putc (*s, stdout); + fputc ('\\', fp); + fputc (*s, fp); break; default: if (*s < ' ') - printf ("\\u%04x", *s); + fprintf (fp, "\\u%04x", *s); else - putc (*s, stdout); + fputc (*s, fp); } } - putc ('"', stdout); + fputc ('"', fp); } /* Run the file(1) command on the first part of the export and save @@ -768,27 +802,27 @@ extent_callback (void *user_data, const char *metacontext, const char *descr = extent_description (map, entries[i+1]); if (!json_output) { - printf ("%10" PRIu64 " " - "%10" PRIu32 " " - "%3" PRIu32, - offset, entries[i], entries[i+1]); + fprintf (fp, "%10" PRIu64 " " + "%10" PRIu32 " " + "%3" PRIu32, + offset, entries[i], entries[i+1]); if (descr) - printf (" %s", descr); - printf ("\n"); + fprintf (fp, " %s", descr); + fprintf (fp, "\n"); } else { if (comma) - printf (",\n"); + fprintf (fp, ",\n"); - printf ("{ \"offset\": %" PRIu64 ", " - "\"length\": %" PRIu32 ", " - "\"type\": %" PRIu32, - offset, entries[i], entries[i+1]); + fprintf (fp, "{ \"offset\": %" PRIu64 ", " + "\"length\": %" PRIu32 ", " + "\"type\": %" PRIu32, + offset, entries[i], entries[i+1]); if (descr) { - printf (", \"description\": "); + fprintf (fp, ", \"description\": "); print_json_string (descr); } - printf ("}"); + fprintf (fp, "}"); comma = true; } -- 2.27.0