Mailing List Archive

commit b1db3bf45bef2594cf923a811918b4fe60805775
Author: Dridi Boukelmoune <dridi.boukelmoune@gmail.com>
Date: Wed Oct 28 15:38:42 2020 +0100

vsl: Give up when it's too late to buffer records

When a VUT is slow enough, it might very well be overrun while it is
scanning logs. For our built-in VUTs like varnishncsa or varnishlog
this can happen if writing the output can block waiting for IO ops
or when the output is piped to a slow consumer.

diff --git a/lib/libvarnishapi/vsl_dispatch.c b/lib/libvarnishapi/vsl_dispatch.c
index ebc45123a..2b4336b2a 100644
--- a/lib/libvarnishapi/vsl_dispatch.c
+++ b/lib/libvarnishapi/vsl_dispatch.c
@@ -427,7 +427,7 @@ chunk_shm_to_buf(struct VSLQ *vslq, struct chunk *chunk)
}

/* Append a set of records to a vtx structure */
-static void
+static enum vsl_status
vtx_append(struct VSLQ *vslq, struct vtx *vtx, const struct VSLC_ptr *start,
size_t len)
{
@@ -439,6 +439,9 @@ vtx_append(struct VSLQ *vslq, struct vtx *vtx, const struct VSLC_ptr *start,
AN(start);

i = VSL_Check(vslq->c, start);
+ if (i == vsl_check_e_inval)
+ return (vsl_e_overrun);
+
if (i == vsl_check_valid && !VTAILQ_EMPTY(&vtx->shmchunks_free)) {
/* Shmref it */
chunk = VTAILQ_FIRST(&vtx->shmchunks_free);
@@ -453,7 +456,6 @@ vtx_append(struct VSLQ *vslq, struct vtx *vtx, const struct VSLC_ptr *start,
/* Append to shmref list */
VTAILQ_INSERT_TAIL(&vslq->shmrefs, chunk, shm.shmref);
} else {
- assert(i != vsl_check_e_inval);
/* Buffer it */
chunk = VTAILQ_LAST(&vtx->chunks, chunkhead);
CHECK_OBJ_ORNULL(chunk, CHUNK_MAGIC);
@@ -468,6 +470,7 @@ vtx_append(struct VSLQ *vslq, struct vtx *vtx, const struct VSLC_ptr *start,
}
}
vtx->len += len;
+ return (vsl_more);
}

/* Allocate a new vtx structure */
@@ -1310,8 +1313,9 @@ vslq_next(struct VSLQ *vslq)
AN(vtx);
}
if (vtx != NULL) {
- vtx_append(vslq, vtx, &c->rec, len);
- vtx_scan(vslq, vtx);
+ r = vtx_append(vslq, vtx, &c->rec, len);
+ if (r == vsl_more)
+ vtx_scan(vslq, vtx);
}

return (r);
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