Update fallback config comment for exponential backoff
We modified the fallback behaviour when we merged the exponential backoff code in 0.2.9.1-alpha, and again in #17750 (moved):
/* With the ClientBootstrapConsensus*Download* below:
* Clients with only authorities will try:
* - 3 authorities over 10 seconds, then wait 60 minutes.
* Clients with authorities and fallbacks will try:
* - 2 authorities and 4 fallbacks over 21 seconds, then wait 60 minutes.
* Clients will also retry when an application request arrives.
* After a number of failed reqests, clients retry every 3 days + 1 hour.
*
* Clients used to try 2 authorities over 10 seconds, then wait for
* 60 minutes or an application request.
*
* When clients have authorities and fallbacks available, they use these
* schedules: (we stagger the times to avoid thundering herds) */
V(ClientBootstrapConsensusAuthorityDownloadSchedule, CSV_INTERVAL,
"6, 11, 3600, 10800, 25200, 54000, 111600, 262800" /* 3 days + 1 hour */),
V(ClientBootstrapConsensusFallbackDownloadSchedule, CSV_INTERVAL,
"0, 1, 4, 11, 3600, 10800, 25200, 54000, 111600, 262800"),
/* When clients only have authorities available, they use this schedule: */
V(ClientBootstrapConsensusAuthorityOnlyDownloadSchedule, CSV_INTERVAL,
"0, 3, 7, 3600, 10800, 25200, 54000, 111600, 262800"),
The behaviour is now:
/* With the ClientBootstrapConsensus*Download* below:
* Clients with only authorities will try:
* - at least 3 authorities over 10 seconds, then exponentially backoff,
* with the next attempt 3-21 seconds later,
* Clients with authorities and fallbacks will try:
* - at least 2 authorities and 4 fallbacks over 21 seconds, then
* exponentially backoff, with the next attempts 4-33 seconds later,
* Clients will also retry when an application request arrives.
* After a number of failed requests, clients retry every 3 days + 1 hour.
*
* Clients used to try 2 authorities over 10 seconds, then wait for
* 60 minutes or an application request.