public override UpstreamPeer Pick()
{
if (PeersVersion != CacheVersion)
{
Reset();
}
if (_peers == null || _peers.Count == 0)
{
return(null);
}
if (_peers.Count == 1 && _peers[0].State == ServiceState.Up)
{
return(_peers[0]);
}
var peer = default(UpstreamPeer);
int max = 0;
for (int i = 0; i < _peers.Count; i++)
{
peer = _peers[i];
int r = 0;
//被设为Down后的第一次pick
if (peer.State == ServiceState.Down && peer.Range > 0)
{
r = -1;
}
else if (peer.State == ServiceState.Up && peer.Range < 0)
{
r = 1;
}
if (r != 0)
{
peer.Range *= -1;
ReWeight(i + 1, _peers.Count, peer.Weight * r);
}
if (peer.State == ServiceState.Down)
{
continue;
}
if (max < peer.Range)
{
max = peer.Range;
}
}
if (max == 0)
{
return(null);
}
var best = default(UpstreamPeer);
int bestIdx = 0;
var now = DateTime.Now;
//随机算法可能多次命中无效peer，最多尝试20次
for (int tries = 0; tries < 20 && best == null; tries++)
{
int idx = _random.Next(max);
for (int i = 0; i < _peers.Count; i++)
{
peer = _peers[i];
if (idx < peer.Range)
{
if (TriedMark?.Get(i) ?? false)
{
break;
}
if (peer.FreezedByFails(now))
{
break;
}
best = peer;
bestIdx = i;
break;
}
}
}
//如果多次尝试后还是没有找到，则降级为简单选择一个可用peer
if (best == null)
{
for (int i = 0; i < _peers.Count; i++)
{
peer = _peers[i];
if (TriedMark?.Get(i) ?? false)
{
continue;
}
if (peer.FreezedByFails(now))
{
continue;
}
best = peer;
bestIdx = i;
}
}
if (best != null)
{
TriedMark?.Set(bestIdx, true);
if (now - best.Checked > best.FailTimeout)
{
best.Checked = now;
}
}
#if DEBUG
var cw = _peers.Aggregate(new StringBuilder("0 - "), (a, c) => a.Append(c.Range).Append(" - "));
cw.Remove(cw.Length - 3, 3);
_logger?.LogDebug($"Current weight ranges: ({cw})");
#endif
return(best);
}
public override UpstreamPeer Pick()
{
if (PeersVersion != CacheVersion)
{
Reset();
}
if (_peers == null || _peers.Count == 0)
{
return(null);
}
if (_peers.Count == 1 && _peers[0].State == ServiceState.Up)
{
return(_peers[0]);
}
var best = default(UpstreamPeer);
int bestIdx = 0;
int total = 0;
var now = DateTime.Now;
for (int i = 0; i < _peers.Count; i++)
{
var peer = _peers[i];
if (peer.State == ServiceState.Down)
{
continue;
}
if (TriedMark?.Get(i) ?? false)
{
continue;
}
//请求第一次失败时，可能已经有多个请求使用了相同的peer，导致多个请求失败；
//每当FailTimeout到期时，该peer仅会放行一次，导致一个请求失败（如果该peer还没恢复的话）
if (peer.FreezedByFails(now))
{
continue;
}
total += peer.EffectiveWeight;
peer.CurrentWeight += peer.EffectiveWeight;
if (best == null || best.CurrentWeight < peer.CurrentWeight)
{
best = peer;
bestIdx = i;
}
if (peer.EffectiveWeight < peer.Weight)
{
peer.EffectiveWeight++;
}
else if (peer.EffectiveWeight > peer.Weight)
{
peer.EffectiveWeight--;
}
}
if (best != null)
{
TriedMark?.Set(bestIdx, true);
best.CurrentWeight -= total;
if (now - best.Checked > best.FailTimeout)
{
best.Checked = now;
}
}
#if DEBUG
var cw = _peers.Aggregate(new StringBuilder(), (a, c) => a.Append(c.CurrentWeight).Append(", "));
cw.Remove(cw.Length - 2, 2);
_logger?.LogDebug($"Current weights: ({cw})");
#endif
return(best);
}
