PR27859 PATCH: correct 404-latch in connection reuse
Frank Ch. Eigler
fche@redhat.com
Fri May 14 22:51:17 GMT 2021
Hi -
(I'll deploy this fix to one of the public servers to confirm it there.)
Author: Frank Ch. Eigler <fche@redhat.com>
Date: Fri May 14 18:37:30 2021 -0400
PR27859: correct 404-latch bug in debuginfod client reuse
PR27701 implemented curl handle reuse in debuginfod_client objects,
but with an unexpected bug. Server responses returning an error
"latched" because the curl_easy handles for error cases weren't all
systematically removed from the curl multi handle. This prevented
their proper re-addition the next time.
This version of the code simplfies matters by making only the curl
curl_multi handle long-lived. This turns out to be enough, because it
can maintain a pool of long-lived http/https connections and related
data, and lend them out to short-lived curl_easy handles. This mode
handles errors or hung downloads even better, because the easy handles
don't undergo complex state transitions between reuse.
A new test case confirms this correction via the federating debuginfod
instance (cleaning caches between subtests to make sure http* is being
used and reused).
diff --git a/debuginfod/ChangeLog b/debuginfod/ChangeLog
index 249385b6a3f7..21407dc2e524 100644
--- a/debuginfod/ChangeLog
+++ b/debuginfod/ChangeLog
@@ -1,3 +1,11 @@
+2021-05-14 Frank Ch. Eigler <fche@redhat.com>
+
+ PR27859
+ * debuginfod-client.c (debuginfod_client): Retain only
+ long-lived multi handle from PR27701 work.
+ (debuginfo_begin,debuginfod_end): ctor/dtor for surviving field only.
+ (debuginfod_query_server): Rework to reuse multi handle only.
+
2021-04-19 Martin Liska <mliska@suse.cz>
* debuginfod-client.c (debuginfod_query_server): Use startswith.
diff --git a/debuginfod/debuginfod-client.c b/debuginfod/debuginfod-client.c
index cb51c2611796..ee7eda24df9f 100644
--- a/debuginfod/debuginfod-client.c
+++ b/debuginfod/debuginfod-client.c
@@ -119,9 +119,8 @@ struct debuginfod_client
/* File descriptor to output any verbose messages if > 0. */
int verbose_fd;
- /* Count DEBUGINFOD_URLS elements and corresponding curl handles. */
- int num_urls;
- CURL **server_handles;
+ /* Maintain a long-lived curl multi-handle, which keeps a
+ connection/tls/dns cache to recently seen servers. */
CURLM *server_mhandle;
/* Can contain all other context, like cache_path, server_urls,
@@ -541,12 +540,6 @@ debuginfod_query_server (debuginfod_client *c,
/* Is there any server we can query? If not, don't do any work,
just return with ENOSYS. Don't even access the cache. */
- if (c->num_urls == 0)
- {
- rc = -ENOSYS;
- goto out;
- }
-
urls_envvar = getenv(DEBUGINFOD_URLS_ENV_VAR);
if (vfd >= 0)
dprintf (vfd, "server urls \"%s\"\n",
@@ -770,13 +763,20 @@ debuginfod_query_server (debuginfod_client *c,
goto out0;
}
+ /* Count number of URLs. */
+ int num_urls = 0;
+ for (int i = 0; server_urls[i] != '\0'; i++)
+ if (server_urls[i] != url_delim_char
+ && (i == 0 || server_urls[i - 1] == url_delim_char))
+ num_urls++;
+
CURLM *curlm = c->server_mhandle;
assert (curlm != NULL);
/* Tracks which handle should write to fd. Set to the first
handle that is ready to write the target file to the cache. */
CURL *target_handle = NULL;
- struct handle_data *data = malloc(sizeof(struct handle_data) * c->num_urls);
+ struct handle_data *data = malloc(sizeof(struct handle_data) * num_urls);
if (data == NULL)
{
rc = -ENOMEM;
@@ -786,7 +786,7 @@ debuginfod_query_server (debuginfod_client *c,
/* thereafter, goto out1 on error. */
/* Initialize handle_data with default values. */
- for (int i = 0; i < c->num_urls; i++)
+ for (int i = 0; i < num_urls; i++)
{
data[i].handle = NULL;
data[i].fd = -1;
@@ -797,23 +797,20 @@ debuginfod_query_server (debuginfod_client *c,
char *server_url = strtok_r(server_urls, url_delim, &strtok_saveptr);
/* Initialize each handle. */
- for (int i = 0; i < c->num_urls && server_url != NULL; i++)
+ for (int i = 0; i < num_urls && server_url != NULL; i++)
{
if (vfd >= 0)
dprintf (vfd, "init server %d %s\n", i, server_url);
data[i].fd = fd;
data[i].target_handle = &target_handle;
- data[i].handle = c->server_handles[i];
- assert (data[i].handle != NULL);
- curl_easy_reset(data[i].handle); // esp. previously sent http headers
- data[i].client = c;
-
+ data[i].handle = curl_easy_init();
if (data[i].handle == NULL)
{
rc = -ENETUNREACH;
goto out1;
}
+ data[i].client = c;
/* Build handle url. Tolerate both http://foo:999 and
http://foo:999/ forms */
@@ -869,7 +866,7 @@ debuginfod_query_server (debuginfod_client *c,
/* Query servers in parallel. */
if (vfd >= 0)
- dprintf (vfd, "query %d urls in parallel\n", c->num_urls);
+ dprintf (vfd, "query %d urls in parallel\n", num_urls);
int still_running;
long loops = 0;
int committed_to = -1;
@@ -882,7 +879,7 @@ debuginfod_query_server (debuginfod_client *c,
/* If the target file has been found, abort the other queries. */
if (target_handle != NULL)
{
- for (int i = 0; i < c->num_urls; i++)
+ for (int i = 0; i < num_urls; i++)
if (data[i].handle != target_handle)
curl_multi_remove_handle(curlm, data[i].handle);
else
@@ -979,7 +976,7 @@ debuginfod_query_server (debuginfod_client *c,
curl_easy_strerror (msg->data.result));
if (pnl)
c->default_progressfn_printed_p = 0;
- for (int i = 0; i < c->num_urls; i++)
+ for (int i = 0; i < num_urls; i++)
if (msg->easy_handle == data[i].handle)
{
if (strlen (data[i].errbuf) > 0)
@@ -1111,8 +1108,13 @@ debuginfod_query_server (debuginfod_client *c,
/* Perhaps we need not give up right away; could retry or something ... */
}
- curl_multi_remove_handle(curlm, verified_handle);
- assert (verified_handle == target_handle);
+ /* remove all handles from multi */
+ for (int i = 0; i < num_urls; i++)
+ {
+ curl_multi_remove_handle(curlm, data[i].handle); /* ok to repeat */
+ curl_easy_cleanup (data[i].handle);
+ }
+
free (data);
free (server_urls);
@@ -1126,6 +1128,13 @@ debuginfod_query_server (debuginfod_client *c,
/* error exits */
out1:
+ /* remove all handles from multi */
+ for (int i = 0; i < num_urls; i++)
+ {
+ curl_multi_remove_handle(curlm, data[i].handle); /* ok to repeat */
+ curl_easy_cleanup (data[i].handle);
+ }
+
unlink (target_cache_tmppath);
close (fd); /* before the rmdir, otherwise it'll fail */
(void) rmdir (target_cache_dir); /* nop if not empty */
@@ -1174,7 +1183,6 @@ debuginfod_begin (void)
{
debuginfod_client *client;
size_t size = sizeof (struct debuginfod_client);
- const char* server_urls = NULL;
client = (debuginfod_client *) calloc (1, size);
if (client != NULL)
@@ -1187,45 +1195,15 @@ debuginfod_begin (void)
client->verbose_fd = -1;
}
- /* Count the DEBUGINFOD_URLS and create the long-lived curl handles. */
- client->num_urls = 0;
- server_urls = getenv (DEBUGINFOD_URLS_ENV_VAR);
- if (server_urls != NULL)
- for (int i = 0; server_urls[i] != '\0'; i++)
- if (server_urls[i] != url_delim_char
- && (i == 0 || server_urls[i - 1] == url_delim_char))
- client->num_urls++;
-
- client->server_handles = calloc (client->num_urls, sizeof(CURL *));
- if (client->server_handles == NULL)
- goto out1;
-
- // allocate N curl easy handles
- for (int i=0; i<client->num_urls; i++)
- {
- client->server_handles[i] = curl_easy_init ();
- if (client->server_handles[i] == NULL)
- {
- for (i--; i >= 0; i--)
- curl_easy_cleanup (client->server_handles[i]);
- goto out2;
- }
- }
-
// allocate 1 curl multi handle
client->server_mhandle = curl_multi_init ();
if (client->server_mhandle == NULL)
- goto out3;
+ goto out1;
+
+ // extra future initialization
goto out;
- out3:
- for (int i=0; i<client->num_urls; i++)
- curl_easy_cleanup (client->server_handles[i]);
-
- out2:
- free (client->server_handles);
-
out1:
free (client);
client = NULL;
@@ -1259,10 +1237,6 @@ debuginfod_end (debuginfod_client *client)
if (client == NULL)
return;
- // assume that all the easy handles have already been removed from the multi handle
- for (int i=0; i<client->num_urls; i++)
- curl_easy_cleanup (client->server_handles[i]);
- free (client->server_handles);
curl_multi_cleanup (client->server_mhandle);
curl_slist_free_all (client->headers);
free (client->url);
diff --git a/tests/ChangeLog b/tests/ChangeLog
index 4951e14fae67..38e92659f117 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,9 @@
+2021-05-14 Frank Ch. Eigler <fche@redhat.com>
+
+ PR27859
+ * run-debuginfod-find.sh: Test absence of 404-latch bug in client
+ curl handle reuse.
+
2021-04-19 Martin Liska <mliska@suse.cz>
* dwelf_elf_e_machine_string.c (main): Use startswith.
diff --git a/tests/run-debuginfod-find.sh b/tests/run-debuginfod-find.sh
index 64b8290a119e..9183cccb7201 100755
--- a/tests/run-debuginfod-find.sh
+++ b/tests/run-debuginfod-find.sh
@@ -559,12 +559,24 @@ curl -s http://127.0.0.1:$PORT1/metrics | grep 'scanned_bytes_total'
# And generate a few errors into the second debuginfod's logs, for analysis just below
curl -s http://127.0.0.1:$PORT2/badapi > /dev/null || true
-curl -s http://127.0.0.1:$PORT2/buildid/deadbeef/debuginfo > /dev/null || true
+curl -s http://127.0.0.1:$PORT2/buildid/deadbeef/debuginfo > /dev/null || true
+# NB: this error is used to seed the 404 failure for the survive-404 tests
# Confirm bad artifact types are rejected without leaving trace
curl -s http://127.0.0.1:$PORT2/buildid/deadbeef/badtype > /dev/null || true
(curl -s http://127.0.0.1:$PORT2/metrics | grep 'badtype') && false
+# Confirm that reused curl connections survive 404 errors.
+# The rm's force an uncached fetch
+rm -f $DEBUGINFOD_CACHE_PATH/$BUILDID/debuginfo .client_cache*/$BUILDID/debuginfo
+testrun ${abs_top_builddir}/debuginfod/debuginfod-find debuginfo $BUILDID
+rm -f $DEBUGINFOD_CACHE_PATH/$BUILDID/debuginfo .client_cache*/$BUILDID/debuginfo
+testrun ${abs_top_builddir}/debuginfod/debuginfod-find debuginfo $BUILDID
+testrun ${abs_top_builddir}/debuginfod/debuginfod-find debuginfo $BUILDID
+testrun ${abs_top_builddir}/debuginfod/debuginfod-find debuginfo $BUILDID
+rm -f $DEBUGINFOD_CACHE_PATH/$BUILDID/debuginfo .client_cache*/$BUILDID/debuginfo
+testrun ${abs_top_builddir}/debuginfod/debuginfod-find debuginfo $BUILDID
+
# Confirm that some debuginfod client pools are being used
curl -s http://127.0.0.1:$PORT2/metrics | grep 'dc_pool_op.*reuse'
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