rfc/patch: debuginfod client $DEBUGINFOD_PROGRESS env var

["Frank Ch. Eigler" <fche@redhat.com>]

    debuginfod: usability tweaks, incl. $DEBUGINFOD_PROGRESS client support
    
    This facility allows a default progress-printing function
    to be installed if the given environment variable is set.
    Some larger usage experience (systemtap/kernels) indicates
    the default timeout is too short, so bumped it to 30s.
    
    Signed-off-by: Frank Ch. Eigler <fche@redhat.com>

diff --git a/debuginfod/ChangeLog b/debuginfod/ChangeLog
index 8aa2944..a9483d0 100644
--- a/debuginfod/ChangeLog
+++ b/debuginfod/ChangeLog
@@ -1,3 +1,13 @@
+2019-12-04  Frank Ch. Eigler  <fche@redhat.com>
+
+	* debuginfod-client.c (default_progressfn): New function.
+	(debuginfod_begin): Use it if $DEBUGINFOD_PROGRESS set.
+	(server_timeout): Bump to 30 seconds.
+	(debuginfod_query_server): Call progressfn -after- rather than
+	before curl ops, to make it likely that a successful transfer
+	results in final a=b call.  Tweak cleanup sequence.
+	* debuginfod.h: Document $DEBUGINFOD_PROGRESS name.
+
 2019-11-26  Mark Wielaard  <mark@klomp.org>
 
 	* Makefile.am (BUILD_STATIC): Add needed libraries for libdw and
diff --git a/debuginfod/debuginfod-client.c b/debuginfod/debuginfod-client.c
index 6e62b86..3ee5e48 100644
--- a/debuginfod/debuginfod-client.c
+++ b/debuginfod/debuginfod-client.c
@@ -40,6 +40,7 @@
 
 #include "config.h"
 #include "debuginfod.h"
+#include "lib/system.h"
 #include <assert.h>
 #include <dirent.h>
 #include <stdio.h>
@@ -107,7 +108,7 @@ static const char url_delim_char = ' ';
 /* Timeout for debuginfods, in seconds.
    This env var must be set for debuginfod-client to run.  */
 static const char *server_timeout_envvar = DEBUGINFOD_TIMEOUT_ENV_VAR;
-static int server_timeout = 5;
+static int server_timeout = 30;
 
 /* Data associated with a particular CURL easy handle. Passed to
    the write callback.  */
@@ -511,6 +512,28 @@ debuginfod_query_server (debuginfod_client *c,
     {
       CURLMcode curl_res;
 
+      /* Wait 1 second, the minimum DEBUGINFOD_TIMEOUT.  */
+      curl_multi_wait(curlm, NULL, 0, 1000, NULL);
+
+      /* If the target file has been found, abort the other queries.  */
+      if (target_handle != NULL)
+        for (int i = 0; i < num_urls; i++)
+          if (data[i].handle != target_handle)
+            curl_multi_remove_handle(curlm, data[i].handle);
+
+      curl_res = curl_multi_perform(curlm, &still_running);
+
+      if (curl_res != CURLM_OK)
+        {
+          switch (curl_res)
+            {
+            case CURLM_CALL_MULTI_PERFORM: continue;
+            case CURLM_OUT_OF_MEMORY: rc = -ENOMEM; break;
+            default: rc = -ENETUNREACH; break;
+            }
+          goto out1;
+        }
+
       if (c->progressfn) /* inform/check progress callback */
         {
           loops ++;
@@ -554,27 +577,6 @@ debuginfod_query_server (debuginfod_client *c,
           if ((*c->progressfn) (c, pa, pb))
             break;
         }
-
-      /* Wait 1 second, the minimum DEBUGINFOD_TIMEOUT.  */
-      curl_multi_wait(curlm, NULL, 0, 1000, NULL);
-
-      /* If the target file has been found, abort the other queries.  */
-      if (target_handle != NULL)
-        for (int i = 0; i < num_urls; i++)
-          if (data[i].handle != target_handle)
-            curl_multi_remove_handle(curlm, data[i].handle);
-
-      curl_res = curl_multi_perform(curlm, &still_running);
-      if (curl_res != CURLM_OK)
-        {
-          switch (curl_res)
-            {
-            case CURLM_CALL_MULTI_PERFORM: continue;
-            case CURLM_OUT_OF_MEMORY: rc = -ENOMEM; break;
-            default: rc = -ENETUNREACH; break;
-            }
-          goto out1;
-        }
     } while (still_running);
 
   /* Check whether a query was successful. If so, assign its handle
@@ -673,9 +675,9 @@ debuginfod_query_server (debuginfod_client *c,
 
   curl_multi_cleanup(curlm);
   unlink (target_cache_tmppath);
+  close (fd); /* before the rmdir, otherwise it'll fail */
   (void) rmdir (target_cache_dir); /* nop if not empty */
   free(data);
-  close (fd);
 
  out0:
   free (server_urls);
@@ -684,6 +686,35 @@ debuginfod_query_server (debuginfod_client *c,
   return rc;
 }
 
+
+/* Activate a basic form of progress tracing */
+static int
+default_progressfn (debuginfod_client *c, long a, long b)
+{
+  (void) c;
+
+  int fd = open(getenv(DEBUGINFOD_PROGRESS_ENV_VAR),
+		O_APPEND|O_WRONLY|O_CREAT, 0666);
+  if (fd < 0)
+    goto out;
+
+  char *msg = NULL;
+  int rc = asprintf(&msg,
+		    "Downloading from debuginfod %ld/%ld%s", a, b,
+		    ((a == b) ? "\n" : "\r")); /* XXX: include URL - stateful */
+  if (rc < 0)
+    goto out1;
+
+  (void) write_retry(fd, msg, rc);
+  free (msg);
+
+  out1:
+    close (fd);
+  out:
+    return 0;
+}
+
+
 /* See debuginfod.h  */
 debuginfod_client  *
 debuginfod_begin (void)
@@ -692,7 +723,12 @@ debuginfod_begin (void)
   size_t size = sizeof (struct debuginfod_client);
   client = (debuginfod_client *) malloc (size);
   if (client != NULL)
-    client->progressfn = NULL;
+    {
+      if (getenv(DEBUGINFOD_PROGRESS_ENV_VAR))
+	client->progressfn = default_progressfn;
+      else
+	client->progressfn = NULL;
+    }
   return client;
 }
 
diff --git a/debuginfod/debuginfod.h b/debuginfod/debuginfod.h
index 6b1b1cc..33fae86 100644
--- a/debuginfod/debuginfod.h
+++ b/debuginfod/debuginfod.h
@@ -33,6 +33,7 @@
 #define DEBUGINFOD_URLS_ENV_VAR "DEBUGINFOD_URLS"
 #define DEBUGINFOD_CACHE_PATH_ENV_VAR "DEBUGINFOD_CACHE_PATH"
 #define DEBUGINFOD_TIMEOUT_ENV_VAR "DEBUGINFOD_TIMEOUT"
+#define DEBUGINFOD_PROGRESS_ENV_VAR "DEBUGINFOD_PROGRESS"
 
 /* Handle for debuginfod-client connection.  */
 typedef struct debuginfod_client debuginfod_client;
diff --git a/doc/ChangeLog b/doc/ChangeLog
index 00a61ac..9542161 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,9 @@
+2019-12-04  Frank Ch. Eigler  <fche@redhat.com>
+
+	* debuginfod-find.1: Bump default timeout to 30.
+	* debuginfod_find_debuginfo.3: Ditto.
+	Document $DEBUGINFOD_PROGRESS.
+
 2019-09-02  Mark Wielaard  <mark@klomp.org>
 
 	* readelf.1 (symbols): Add optional section name.
diff --git a/doc/debuginfod-find.1 b/doc/debuginfod-find.1
index a759ecb..7f14e8c 100644
--- a/doc/debuginfod-find.1
+++ b/doc/debuginfod-find.1
@@ -121,7 +121,7 @@ debuginfod instances.  Alternate URL prefixes are separated by space.
 .B DEBUGINFOD_TIMEOUT
 This environment variable governs the timeout for each debuginfod HTTP
 connection.  A server that fails to respond within this many seconds
-is skipped.  The default is 5.
+is skipped.  The default is 30.
 
 .TP 21
 .B DEBUGINFOD_CACHE_PATH
diff --git a/doc/debuginfod_find_debuginfo.3 b/doc/debuginfod_find_debuginfo.3
index be8eed0..63766b3 100644
--- a/doc/debuginfod_find_debuginfo.3
+++ b/doc/debuginfod_find_debuginfo.3
@@ -165,7 +165,15 @@ debuginfod instances.  Alternate URL prefixes are separated by space.
 .B DEBUGINFOD_TIMEOUT
 This environment variable governs the timeout for each debuginfod HTTP
 connection.  A server that fails to respond within this many seconds
-is skipped.  The default is 5.
+is skipped.  The default is 30.
+
+.TP 21
+.B DEBUGINFOD_PROGRESS
+This environment variable governs the default progress function.  If
+set, and if a progressfn is not explicitly set, then the library will
+configure a default progressfn.  This function will append a simple
+progress message periodically to the given file.  Consider using
+"/dev/stderr" on platforms that support it.  The default is nothing.
 
 .TP 21
 .B DEBUGINFOD_CACHE_PATH
diff --git a/tests/ChangeLog b/tests/ChangeLog
index 6e3923f..d63d0eb 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,7 @@
+2019-12-04  Frank Ch. Eigler  <fche@redhat.com>
+
+	* run-debuinfod-find.sh: Test $DEBUGINFOD_PROGRESS.
+
 2019-11-26  Mark Wielaard  <mark@klomp.org>
 
 	* Makefile.am (BUILD_STATIC): Add libraries needed for libdw.
diff --git a/tests/run-debuginfod-find.sh b/tests/run-debuginfod-find.sh
index 0ade03b..be6d565 100755
--- a/tests/run-debuginfod-find.sh
+++ b/tests/run-debuginfod-find.sh
@@ -153,8 +153,11 @@ cmp $filename F/prog2
 cat vlog
 grep -q Progress vlog
 tempfiles vlog
-filename=`testrun ${abs_top_builddir}/debuginfod/debuginfod-find executable $BUILDID2`
+filename=`testrun env DEBUGINFOD_PROGRESS=vlog2 ${abs_top_builddir}/debuginfod/debuginfod-find executable $BUILDID2`
 cmp $filename F/prog2
+cat vlog2
+grep -q Downloading vlog2
+tempfiles vlog2
 filename=`testrun ${abs_top_builddir}/debuginfod/debuginfod-find source $BUILDID2 ${PWD}/prog2.c`
 cmp $filename ${PWD}/prog2.c