[tor-bugs] #14006 [Core Tor/Tor]: Hidden service error: "We'd like to launch a circuit to handle a connection, but we already have 32 general-purpose client circuits..."

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#14006: Hidden service error: "We'd like to launch a circuit to handle a
connection, but we already have 32 general-purpose client circuits..."
-----------------------------------------------+---------------------------
 Reporter:  asn                                |          Owner:
     Type:  defect                             |         Status:  new
 Priority:  Medium                             |      Milestone:  Tor:
                                               |  unspecified
Component:  Core Tor/Tor                       |        Version:
 Severity:  Normal                             |     Resolution:
 Keywords:  tor-hs, tor-03-unspecified-201612  |  Actual Points:
Parent ID:                                     |         Points:
 Reviewer:                                     |        Sponsor:
-----------------------------------------------+---------------------------

Comment (by asn):

 Replying to [comment:4 alecmuffett]:
 > Hi All!
 >
 > I am using Donncha's OnionBalance to scrape the descriptors of 72x Tor
 Onion Services (spread over 6x machines) for a series of massive bandwidth
 experiments.
 >
 > I, too, am getting this message, on a separate, standalone
 machine/daemon:
 >
 > Dec 19 12:32:09.000 [notice] We'd like to launch a circuit to handle a
 connection, but we already have 32 general-purpose client circuits
 pending. Waiting until some finish. [1675 similar message(s) suppressed in
 last 600 seconds]
 > Dec 19 12:42:10.000 [notice] We'd like to launch a circuit to handle a
 connection, but we already have 32 general-purpose client circuits
 pending. Waiting until some finish. [1375 similar message(s) suppressed in
 last 600 seconds]
 > Dec 19 12:52:10.000 [notice] We'd like to launch a circuit to handle a
 connection, but we already have 32 general-purpose client circuits
 pending. Waiting until some finish. [1256 similar message(s) suppressed in
 last 600 seconds]
 >
 > Is there a number I can bump, please?


 Here is the code:

 {{{
     const int n_pending = count_pending_general_client_circuits();

     /* Do we have too many pending circuits? */
     if (n_pending >= options->MaxClientCircuitsPending) {
       static ratelim_t delay_limit = RATELIM_INIT(10*60);
       char *m;
       if ((m = rate_limit_log(&delay_limit, approx_time()))) {
         log_notice(LD_APP, "We'd like to launch a circuit to handle a "
                    "connection, but we already have %d general-purpose
 client "
                    "circuits pending. Waiting until some finish.%s",
                    n_pending, m);
         tor_free(m);
       }
       return 0;
     }
 }}}

 You can try bumping `MaxClientCircuitsPending` from 32 to something
 bigger.

 However, without understanding what these pending circuits are and why
 they are there, it's hard to fix the root cause of this issue. Perhaps
 with some tactical logging we can get more information about the nature of
 these circuits.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/14006#comment:6>
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