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break up refresh/reveal transaction to reduce failure rate, increase retries in general

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This commit is contained in:
Christian Grothoff 2018-08-10 22:32:23 +02:00
parent 1314b5fe20
commit e606f90488
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GPG Key ID: 939E6BE1E29FC3CC
2 changed files with 160 additions and 57 deletions
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2
src/exchange/taler-exchange-httpd_db.c
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@ -30,7 +30,7 @@
* How often should we retry a transaction before giving up
* (for transactions resulting in serialization/dead locks only).
*/
#define MAX_TRANSACTION_COMMIT_RETRIES 2
#define MAX_TRANSACTION_COMMIT_RETRIES 10
/**

215
src/exchange/taler-exchange-httpd_refresh_reveal.c
View File

@ -36,6 +36,13 @@
*/
#define MAX_FRESH_COINS 256
/**
* How often do we at most retry the reveal transaction sequence?
* Twice should really suffice in all cases (as the possible conflict
* cannot happen more than once).
*/
#define MAX_REVEAL_RETRIES 2
/**
* Send a response for "/refresh/reveal".
@ -142,6 +149,14 @@ struct RevealContext
*/
unsigned int num_fresh_coins;
/**
* Result from preflight checks. #GNUNET_NO for no result,
* #GNUNET_YES if preflight found previous successful operation,
* #GNUNET_SYSERR if prefight check failed hard (and generated
* an MHD response already).
*/
int preflight_ok;
};
@ -188,12 +203,57 @@ check_exists_cb (void *cls,
}
/**
* Check if the "/refresh/reveal" was already successful before.
* If so, just return the old result.
*
* @param cls closure of type `struct RevealContext`
* @param connection MHD request which triggered the transaction
* @param session database session to use
* @param[out] mhd_ret set to MHD response status for @a connection,
* if transaction failed (!)
* @return transaction status
*/
static enum GNUNET_DB_QueryStatus
refresh_reveal_preflight (void *cls,
struct MHD_Connection *connection,
struct TALER_EXCHANGEDB_Session *session,
int *mhd_ret)
{
struct RevealContext *rctx = cls;
enum GNUNET_DB_QueryStatus qs;
/* Try to see if we already have given an answer before. */
qs = TEH_plugin->get_refresh_reveal (TEH_plugin->cls,
session,
&rctx->rc,
&check_exists_cb,
rctx);
switch (qs) {
case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
return qs; /* continue normal execution */
case GNUNET_DB_STATUS_SOFT_ERROR:
return qs;
case GNUNET_DB_STATUS_HARD_ERROR:
GNUNET_break (qs);
*mhd_ret = TEH_RESPONSE_reply_internal_db_error (connection,
TALER_EC_REFRESH_REVEAL_DB_FETCH_REVEAL_ERROR);
rctx->preflight_ok = GNUNET_SYSERR;
return GNUNET_DB_STATUS_HARD_ERROR;
case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
default:
/* Hossa, already found our reply! */
GNUNET_assert (NULL != rctx->ev_sigs);
rctx->preflight_ok = GNUNET_YES;
return qs;
}
}
/**
* Execute a "/refresh/reveal". The client is revealing to us the
* transfer keys for @a #TALER_CNC_KAPPA-1 sets of coins. Verify that the
* revealed transfer keys would allow linkage to the blinded coins,
* and if so, return the signed coins for corresponding to the set of
* coins that was not chosen.
* revealed transfer keys would allow linkage to the blinded coins.
*
* IF it returns a non-error code, the transaction logic MUST
* NOT queue a MHD response. IF it returns an hard error, the
@ -218,30 +278,6 @@ refresh_reveal_transaction (void *cls,
struct TALER_EXCHANGEDB_RefreshMelt refresh_melt;
enum GNUNET_DB_QueryStatus qs;
/* Try to see if we already have given an answer before. */
qs = TEH_plugin->get_refresh_reveal (TEH_plugin->cls,
session,
&rctx->rc,
&check_exists_cb,
rctx);
switch (qs) {
case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
/* continue normal execution */
break;
case GNUNET_DB_STATUS_SOFT_ERROR:
return qs;
case GNUNET_DB_STATUS_HARD_ERROR:
GNUNET_break (qs);
*mhd_ret = TEH_RESPONSE_reply_internal_db_error (connection,
TALER_EC_REFRESH_REVEAL_DB_FETCH_REVEAL_ERROR);
return GNUNET_DB_STATUS_HARD_ERROR;
case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
default:
/* Hossa, already found our reply! */
GNUNET_assert (NULL != rctx->ev_sigs);
return qs;
}
/* Obtain basic information about the refresh operation and what
gamma we committed to. */
qs = TEH_plugin->get_melt (TEH_plugin->cls,
@ -394,23 +430,28 @@ refresh_reveal_transaction (void *cls,
return GNUNET_DB_STATUS_HARD_ERROR;
}
}
return GNUNET_DB_STATUS_SUCCESS_NO_RESULTS;
}
/* Client request OK, sign coins */
rctx->ev_sigs = GNUNET_new_array (rctx->num_fresh_coins,
struct TALER_DenominationSignature);
for (unsigned int i=0;i<rctx->num_fresh_coins;i++)
{
rctx->ev_sigs[i].rsa_signature
= GNUNET_CRYPTO_rsa_sign_blinded (rctx->dkis[i]->denom_priv.rsa_private_key,
rctx->rcds[i].coin_ev,
rctx->rcds[i].coin_ev_size);
if (NULL == rctx->ev_sigs[i].rsa_signature)
{
*mhd_ret = TEH_RESPONSE_reply_internal_db_error (connection,
TALER_EC_REFRESH_REVEAL_SIGNING_ERROR);
return GNUNET_DB_STATUS_HARD_ERROR;
}
}
/**
* Persist result of a "/refresh/reveal".
*
* @param cls closure of type `struct RevealContext`
* @param connection MHD request which triggered the transaction
* @param session database session to use
* @param[out] mhd_ret set to MHD response status for @a connection,
* if transaction failed (!)
* @return transaction status
*/
static enum GNUNET_DB_QueryStatus
refresh_reveal_persist (void *cls,
struct MHD_Connection *connection,
struct TALER_EXCHANGEDB_Session *session,
int *mhd_ret)
{
struct RevealContext *rctx = cls;
enum GNUNET_DB_QueryStatus qs;
/* Persist operation result in DB */
{
@ -584,22 +625,84 @@ handle_refresh_reveal_json (struct MHD_Connection *connection,
rctx->num_fresh_coins = num_fresh_coins;
rctx->rcds = rcds;
rctx->dkis = dkis;
/* do transactional work */
if (GNUNET_OK ==
TEH_DB_run_transaction (connection,
"run reveal",
&res,
&refresh_reveal_transaction,
rctx))
{
/* Generate final (positive) response */
GNUNET_assert (NULL != rctx->ev_sigs);
res = reply_refresh_reveal_success (connection,
num_fresh_coins,
rctx->ev_sigs);
/* sign _early_ (optimistic!) to keep out of transaction scope! */
rctx->ev_sigs = GNUNET_new_array (rctx->num_fresh_coins,
struct TALER_DenominationSignature);
for (unsigned int i=0;i<rctx->num_fresh_coins;i++)
{
rctx->ev_sigs[i].rsa_signature
= GNUNET_CRYPTO_rsa_sign_blinded (rctx->dkis[i]->denom_priv.rsa_private_key,
rctx->rcds[i].coin_ev,
rctx->rcds[i].coin_ev_size);
if (NULL == rctx->ev_sigs[i].rsa_signature)
{
GNUNET_break (0);
res = TEH_RESPONSE_reply_internal_db_error (connection,
TALER_EC_REFRESH_REVEAL_SIGNING_ERROR);
goto cleanup;
}
}
/* We try the three transactions a few times, as theoretically
the pre-check might be satisfied by a concurrent transaction
voiding our final commit due to uniqueness violation; naturally,
on hard errors we exit immediately */
for (unsigned int retries=0;retries < MAX_REVEAL_RETRIES;retries++)
{
/* do transactional work */
rctx->preflight_ok = GNUNET_NO;
if ( (GNUNET_OK ==
TEH_DB_run_transaction (connection,
"reveal pre-check",
&res,
&refresh_reveal_preflight,
rctx)) &&
(GNUNET_YES == rctx->preflight_ok) )
{
/* Generate final (positive) response */
GNUNET_assert (NULL != rctx->ev_sigs);
res = reply_refresh_reveal_success (connection,
num_fresh_coins,
rctx->ev_sigs);
GNUNET_break (MHD_NO != res);
goto cleanup; /* aka 'break' */
}
if (GNUNET_SYSERR == rctx->preflight_ok)
{
GNUNET_break (0);
goto cleanup; /* aka 'break' */
}
if (GNUNET_OK !=
TEH_DB_run_transaction (connection,
"run reveal",
&res,
&refresh_reveal_transaction,
rctx))
{
/* reveal failed, too bad */
GNUNET_break_op (0);
goto cleanup; /* aka 'break' */
}
if (GNUNET_OK ==
TEH_DB_run_transaction (connection,
"persist reveal",
&res,
&refresh_reveal_persist,
rctx))
{
/* Generate final (positive) response */
GNUNET_assert (NULL != rctx->ev_sigs);
res = reply_refresh_reveal_success (connection,
num_fresh_coins,
rctx->ev_sigs);
break;
}
} /* end for (retries...) */
GNUNET_break (MHD_NO != res);
cleanup:
GNUNET_break (MHD_NO != res);
/* free resources */
if (NULL != rctx->ev_sigs)
{