[Libguestfs] [PATCH nbdkit v5 FINAL 09/19] log: Log extents requests.

[Martin Kletzander]

On Thu, Mar 28, 2019 at 04:18:36PM +0000, Richard W.M. Jones wrote:
>Typical output:
>
>2019-03-26 18:22:17.287434 connection=2 Extents id=2 offset=0x0 count=0x40000000 req_one=1 ...
>2019-03-26 18:22:17.290040 connection=2 ...Extents id=2 extents=[{ offset=0x0, length=0x250000, type=0 }, { offset=0x250000, length=0x7db0000, type=3 }, { offset=0x8000000, length=0x8000, type=0 }, { offset=0x8008000, length=0x38000, type=3 }, { offset=0x8040000, length=0x208000, type=0 }, { offset=0x8248000, length=0x7db8000, type=3 }, { offset=0x10000000, length=0x208000, type=0 }, { offset=0x10208000, length=0x7df8000, type=3 }, { offset=0x18000000, length=0x8000, type=0 }, { offset=0x18008000, length=0x38000, type=3 }, { offset=0x18040000, length=0x208000, type=0 }, { offset=0x18248000, length=0x7db8000, type=3 }, { offset=0x20000000, length=0x208000, type=0 }, { offset=0x20208000, length=0x7df8000, type=3 }, { offset=0x28000000, length=0x8000, type=0 }, { offset=0x28008000, length=0x38000, type=3 }, { offset=0x28040000, length=0x208000, type=0 }, { offset=0x28248000, length=0x7db8000, type=3 }, { offset=0x30000000, length=0x208000, type=0 }, { offset=0x30208000, length=0x7df8000, type=3 }, { offset=0x38000000, length=0x8000, type=0 }, { offset=0x38008000, length=0x38000, type=3 }, { offset=0x38040000, length=0x208000, type=0 }, { offset=0x38248000, length=0x7da8000, type=3 }, { offset=0x3fff0000, length=0x10000, type=0 }] return=0
>
>As you can see this is logging the complete information as generated
>by the underlying plugin, not what is returned to the client (which is
>rather hard for the log filter to discern).  It's probably more useful
>for debugging like this.
>---
> filters/log/nbdkit-log-filter.pod |  6 ++---
> filters/log/log.c                 | 45 +++++++++++++++++++++++++++++++
> 2 files changed, 48 insertions(+), 3 deletions(-)
>
>diff --git a/filters/log/nbdkit-log-filter.pod b/filters/log/nbdkit-log-filter.pod
>index cff209e..e391046 100644
>--- a/filters/log/nbdkit-log-filter.pod
>+++ b/filters/log/nbdkit-log-filter.pod
>@@ -46,9 +46,9 @@ the impact of the caching.
> This filter writes to the file specified by the C<logfile=FILE>
> parameter.  All lines include a timestamp, a connection counter, then
> details about the command.  The following actions are logged: Connect,
>-Read, Write, Zero, Trim, Flush, and Disconnect.  Except for Connect
>-and Disconnect, an event is logged across two lines for call and
>-return value, to allow tracking duration and tracing any parallel
>+Read, Write, Zero, Trim, Extents, Flush, and Disconnect.  Except for
>+Connect and Disconnect, an event is logged across two lines for call
>+and return value, to allow tracking duration and tracing any parallel
> execution, using id for correlation (incremented per action on the
> connection).
>
>diff --git a/filters/log/log.c b/filters/log/log.c
>index 9f2e37d..b31d784 100644
>--- a/filters/log/log.c
>+++ b/filters/log/log.c
>@@ -353,6 +353,50 @@ log_zero (struct nbdkit_next_ops *next_ops, void *nxdata,
>   return r;
> }
>
>+/* Extents. */
>+static int
>+log_extents (struct nbdkit_next_ops *next_ops, void *nxdata,
>+             void *handle, uint32_t count, uint64_t offs, uint32_t flags,
>+             struct nbdkit_extents *extents, int *err)
>+{
>+  struct handle *h = handle;
>+  uint64_t id = get_id (h);
>+  int r;
>+
>+  assert (!(flags & ~(NBDKIT_FLAG_REQ_ONE)));
>+  output (h, "Extents", id,
>+          "offset=0x%" PRIx64 " count=0x%x req_one=%d ...",
>+          offs, count, !!(flags & NBDKIT_FLAG_REQ_ONE));
>+  r = next_ops->extents (nxdata, count, offs, flags, extents, err);
>+  if (r == -1)
>+    output_return (h, "...Extents", id, r, err);
>+  else {
>+    FILE *fp;
>+    char *extents_str = NULL;
>+    size_t i, n, len = 0;
>+
>+    fp = open_memstream (&extents_str, &len);
>+    if (fp != NULL) {
>+      n = nbdkit_extents_count (extents);
>+      for (i = 0; i < n; ++i) {
>+        struct nbdkit_extent e = nbdkit_get_extent (extents, i);
>+        if (i > 0)
>+          fprintf (fp, ", ");
>+        fprintf (fp, "{ offset=0x%" PRIx64 ", length=0x%" PRIx64 ", "
>+                 "type=%" PRIu32 " }",
>+                 e.offset, e.length, e.type);

I'm not sure what the consensus in nbdkit is, but it would be nicer to see what
the type is, so that one does not have to go look in the header files.

>+      }
>+
>+      fclose (fp);
>+    }
>+
>+    output (h, "...Extents", id, "extents=[%s] return=0",
>+            extents_str ? extents_str : "(null)");
>+    free (extents_str);
>+  }
>+  return r;
>+}
>+
> static struct nbdkit_filter filter = {
>   .name              = "log",
>   .longname          = "nbdkit log filter",
>@@ -370,6 +414,7 @@ static struct nbdkit_filter filter = {
>   .flush             = log_flush,
>   .trim              = log_trim,
>   .zero              = log_zero,
>+  .extents           = log_extents,
> };
>
> NBDKIT_REGISTER_FILTER(filter)
>-- 
>2.20.1
>
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