VCL_BACKEND
sharddir_pick_be(VRT_CTX, struct sharddir *shardd, uint32_t key, VCL_INT alt,
VCL_REAL warmup, VCL_BOOL rampup, enum healthy_e healthy)
{
VCL_BACKEND be;
struct shard_state state[1];
unsigned picklist_sz;
CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
CHECK_OBJ_NOTNULL(shardd, SHARDDIR_MAGIC);
sharddir_rdlock(shardd);
if (shardd->n_backend == 0) {
shard_err0(ctx, shardd, "no backends");
sharddir_unlock(shardd);
return (NULL);
}
picklist_sz = VBITMAP_SZ(shardd->n_backend);
char picklist_spc[picklist_sz];
memset(state, 0, sizeof(state));
init_state(state, ctx, shardd, vbit_init(picklist_spc, picklist_sz));
be = sharddir_pick_be_locked(ctx, shardd, key, alt, warmup, rampup,
healthy, state);
sharddir_unlock(shardd);
vbit_destroy(state->picklist);
return (be);
}
/*
* core function for the director backend method
*
* while other directors return a reference to their own backend object (on
* which varnish will call the resolve method to resolve to a non-director
* backend), this director immediately reolves in the backend method, to make
* the director choice visible in VCL
*
* consequences:
* - we need no own struct director
* - we can only respect a busy object when being called on the backend side,
* which probably is, for all practical purposes, only relevant when the
* saintmode vmod is used
*
* if we wanted to offer delayed resolution, we'd need something like
* per-request per-director state or we'd need to return a dynamically created
* director object. That should be straight forward once we got director
* refcounting #2072. Until then, we could create it on the workspace, but then
* we'd need to keep other directors from storing any references to our dynamic
* object for longer than the current task
*
*/
VCL_BACKEND
sharddir_pick_be(VRT_CTX, struct sharddir *shardd,
uint32_t key, VCL_INT alt, VCL_REAL warmup, VCL_BOOL rampup,
enum healthy_e healthy)
{
VCL_BACKEND be;
struct shard_state state;
unsigned picklist_sz = VBITMAP_SZ(shardd->n_backend);
char picklist_spc[picklist_sz];
VCL_DURATION chosen_r, alt_r;
CHECK_OBJ_NOTNULL(shardd, SHARDDIR_MAGIC);
CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
AN(ctx->vsl);
memset(&state, 0, sizeof(state));
init_state(&state, ctx, shardd, vbit_init(picklist_spc, picklist_sz));
sharddir_rdlock(shardd);
if(shardd->n_backend == 0) {
shard_err0(ctx, shardd, "no backends");
goto err;
}
assert(shardd->hashcircle);
validate_alt(ctx, shardd, &alt);
state.idx = shard_lookup(shardd, key);
assert(state.idx >= 0);
SHDBG(SHDBG_LOOKUP, shardd, "lookup key %x idx %d host %u",
key, state.idx, shardd->hashcircle[state.idx].host);
if (alt > 0) {
if (shard_next(&state, alt - 1, healthy == ALL ? 1 : 0) == -1) {
if (state.previous.hostid != -1) {
be = sharddir_backend(shardd,
state.previous.hostid);
goto ok;
}
goto err;
}
}
if (shard_next(&state, 0, healthy == IGNORE ? 0 : 1) == -1) {
if (state.previous.hostid != -1) {
be = sharddir_backend(shardd, state.previous.hostid);
goto ok;
}
goto err;
}
be = sharddir_backend(shardd, state.last.hostid);
if (warmup == -1)
warmup = shardd->warmup;
/* short path for cases we dont want ramup/warmup or can't */
if (alt > 0 || healthy == IGNORE || (! rampup && warmup == 0) ||
shard_next(&state, 0, 0) == -1)
goto ok;
assert(alt == 0);
assert(state.previous.hostid >= 0);
assert(state.last.hostid >= 0);
assert(state.previous.hostid != state.last.hostid);
assert(be == sharddir_backend(shardd, state.previous.hostid));
chosen_r = shardcfg_get_rampup(shardd, state.previous.hostid);
alt_r = shardcfg_get_rampup(shardd, state.last.hostid);
SHDBG(SHDBG_RAMPWARM, shardd, "chosen host %d rampup %f changed %f",
state.previous.hostid, chosen_r,
ctx->now - state.previous.changed);
SHDBG(SHDBG_RAMPWARM, shardd, "alt host %d rampup %f changed %f",
state.last.hostid, alt_r,
ctx->now - state.last.changed);
if (ctx->now - state.previous.changed < chosen_r) {
/*
* chosen host is in rampup
* - no change if alternative host is also in rampup or the dice
* has rolled in favour of the chosen host
*/
if (! rampup ||
ctx->now - state.last.changed < alt_r ||
VRND_RandomTestableDouble() * chosen_r <
(ctx->now - state.previous.changed))
goto ok;
} else {
/* chosen host not in rampup - warmup ? */
if (warmup == 0 || VRND_RandomTestableDouble() > warmup)
goto ok;
}
be = sharddir_backend(shardd, state.last.hostid);
ok:
AN(be);
sharddir_unlock(shardd);
vbit_destroy(state.picklist);
return (be);
err:
sharddir_unlock(shardd);
vbit_destroy(state.picklist);
return NULL;
}