oauth: Track total call count during a client flow

Tracking down the bugs that led to the addition of comb_multiplexer()
and drain_timer_events() was difficult, because an inefficient flow is
not visibly different from one that is working properly. To help
maintainers notice when something has gone wrong, track the number of
calls into the flow as part of debug mode, and print the total when the
flow finishes.

A new test makes sure the total count is less than 100. (We expect
something on the order of 10.) This isn't foolproof, but it is able to
catch several regressions in the logic of the prior two commits, and
future work to add TLS support to the oauth_validator test server should
strengthen it as well.

Backpatch-through: 18
Discussion: https://postgr.es/m/CAOYmi+nDZxJHaWj9_jRSyf8uMToCADAmOfJEggsKW-kY7aUwHA@mail.gmail.com

diff --git a/src/interfaces/libpq-oauth/oauth-curl.c b/src/interfaces/libpq-oauth/oauth-curl.c
index aa5d2bfd96c05a042f3551e7b65f0897c45ae943..aa50b00d053832d9d6c196db98a901cefa479b90 100644 (file)
--- a/src/interfaces/libpq-oauth/oauth-curl.c
+++ b/src/interfaces/libpq-oauth/oauth-curl.c
@@ -278,6 +278,7 @@ struct async_ctx
        bool            user_prompted;  /* have we already sent the authz prompt? */
        bool            used_basic_auth;        /* did we send a client secret? */
        bool            debugging;              /* can we give unsafe developer assistance? */
+       int                     dbg_num_calls;  /* (debug mode) how many times were we called? */
 };
 
 /*
@@ -3021,6 +3022,8 @@ PostgresPollingStatusType
 pg_fe_run_oauth_flow(PGconn *conn)
 {
        PostgresPollingStatusType result;
+       fe_oauth_state *state = conn_sasl_state(conn);
+       struct async_ctx *actx;
 #ifndef WIN32
        sigset_t        osigset;
        bool            sigpipe_pending;
@@ -3049,6 +3052,25 @@ pg_fe_run_oauth_flow(PGconn *conn)
 
        result = pg_fe_run_oauth_flow_impl(conn);
 
+       /*
+        * To assist with finding bugs in comb_multiplexer() and
+        * drain_timer_events(), when we're in debug mode, track the total number
+        * of calls to this function and print that at the end of the flow.
+        *
+        * Be careful that state->async_ctx could be NULL if early initialization
+        * fails during the first call.
+        */
+       actx = state->async_ctx;
+       Assert(actx || result == PGRES_POLLING_FAILED);
+
+       if (actx && actx->debugging)
+       {
+               actx->dbg_num_calls++;
+               if (result == PGRES_POLLING_OK || result == PGRES_POLLING_FAILED)
+                       fprintf(stderr, "[libpq] total number of polls: %d\n",
+                                       actx->dbg_num_calls);
+       }
+
 #ifndef WIN32
        if (masked)
        {

diff --git a/src/test/modules/oauth_validator/t/001_server.pl b/src/test/modules/oauth_validator/t/001_server.pl
index 41672ebd5c6dc5890407d8566f43945691b15bc4..c0dafb8be7642bd7b0fcd77150dc6b52b98ecc0f 100644 (file)
--- a/src/test/modules/oauth_validator/t/001_server.pl
+++ b/src/test/modules/oauth_validator/t/001_server.pl
@@ -418,6 +418,35 @@ $node->connect_fails(
          qr/failed to obtain access token: mutual TLS required for client \(invalid_client\)/
 );
 
+# Count the number of calls to the internal flow when multiple retries are
+# triggered. The exact number depends on many things -- the TCP stack, the
+# version of Curl in use, random chance -- but a ridiculously high number
+# suggests something is wrong with our ability to clear multiplexer events after
+# they're no longer applicable.
+my ($ret, $stdout, $stderr) = $node->psql(
+       'postgres',
+       "SELECT 'connected for call count'",
+       extra_params => ['-w'],
+       connstr => connstr(stage => 'token', retries => 2),
+       on_error_stop => 0);
+
+is($ret, 0, "call count connection succeeds");
+like(
+       $stderr,
+       qr@Visit https://example\.com/ and enter the code: postgresuser@,
+       "call count: stderr matches");
+
+my $count_pattern = qr/\[libpq\] total number of polls: (\d+)/;
+if (like($stderr, $count_pattern, "call count: count is printed"))
+{
+       # For reference, a typical flow with two retries might take between 5-15
+       # calls to the client implementation. And while this will probably continue
+       # to change across OSes and Curl updates, we're likely in trouble if we see
+       # hundreds or thousands of calls.
+       $stderr =~ $count_pattern;
+       cmp_ok($1, '<', 100, "call count is reasonably small");
+}
+
 # Stress test: make sure our builtin flow operates correctly even if the client
 # application isn't respecting PGRES_POLLING_READING/WRITING signals returned
 # from PQconnectPoll().
@@ -428,7 +457,7 @@ my @cmd = (
        connstr(stage => 'all', retries => 1, interval => 1));
 
 note "running '" . join("' '", @cmd) . "'";
-my ($stdout, $stderr) = run_command(\@cmd);
+($stdout, $stderr) = run_command(\@cmd);
 
 like($stdout, qr/connection succeeded/, "stress-async: stdout matches");
 unlike(