Make the default DirAuthorityFallbackRate 0.1

This makes clients on the public tor network prefer to bootstrap off fallback
directory mirrors.

This is a follow-up to 24679, which removed weights from the default fallbacks.

Implements ticket 24681.

diff --git a/changes/ticket24681 b/changes/ticket24681
new file mode 100644 (file)
index 0000000..cc0a42b
--- /dev/null
+++ b/changes/ticket24681
@@ -0,0 +1,6 @@
+  o Minor features (fallback directory mirrors):
+    - Make the default DirAuthorityFallbackRate 0.1, so that clients on the
+      public tor network prefer to bootstrap off fallback directory mirrors.
+      This is a follow-up to 24679, which removed weights from the default
+      fallbacks.
+      Implements ticket 24681.

diff --git a/doc/tor.1.txt b/doc/tor.1.txt
index 74915b71199029f3fb50e1f3643094b2e6e6aa29..b286a065637f5f4ea88611fc9757456def862c0a 100644 (file)
--- a/doc/tor.1.txt
+++ b/doc/tor.1.txt
@@ -432,7 +432,8 @@ GENERAL OPTIONS
     When configured to use both directory authorities and fallback
     directories, the directory authorities also work as fallbacks. They are
     chosen with their regular weights, multiplied by this number, which
-    should be 1.0 or less. (Default: 1.0)
+    should be 1.0 or less. The default is less than 1, to reduce load on
+    authorities. (Default: 0.1)
 
 [[AlternateDirAuthority]] **AlternateDirAuthority** [__nickname__] [**flags**] __address__:__port__ __fingerprint__ +
 

diff --git a/src/or/config.c b/src/or/config.c
index 557790a81e91834720f8aa712f4102af0aab361e..2a0d091a2152477dddd9148567c799470708e43f 100644 (file)
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -225,7 +225,14 @@ static config_var_t option_vars_[] = {
   VAR("DirReqStatistics",        BOOL,     DirReqStatistics_option, "1"),
   VAR("DirAuthority",            LINELIST, DirAuthorities, NULL),
   V(DirCache,                    BOOL,     "1"),
-  V(DirAuthorityFallbackRate,    DOUBLE,   "1.0"),
+  /* A DirAuthorityFallbackRate of 0.1 means that 0.5% of clients try an
+   * authority when all fallbacks are up, and 2% try an authority when 25% of
+   * fallbacks are down. (We rebuild the list when 25% of fallbacks are down).
+   *
+   * We want to reduce load on authorities, but keep these two figures within
+   * an order of magnitude, so there isn't too much load shifting to authorities
+   * when fallbacks go down. */
+  V(DirAuthorityFallbackRate,    DOUBLE,   "0.1"),
   V(DisableAllSwap,              BOOL,     "0"),
   V(DisableDebuggerAttachment,   BOOL,     "1"),
   V(DisableIOCP,                 BOOL,     "1"),