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7a1ad33 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 | /**
* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
export type ModelId = string;
type TerminalUnavailabilityReason = 'quota' | 'capacity';
export type TurnUnavailabilityReason = 'retry_once_per_turn';
export type UnavailabilityReason =
| TerminalUnavailabilityReason
| TurnUnavailabilityReason
| 'unknown';
export type ModelHealthStatus = 'terminal' | 'sticky_retry';
type HealthState =
| {
status: 'terminal';
reason: TerminalUnavailabilityReason;
markedAt?: number;
}
| {
status: 'sticky_retry';
reason: TurnUnavailabilityReason;
consumed: boolean;
attempts: number;
};
export interface ModelAvailabilitySnapshot {
available: boolean;
reason?: UnavailabilityReason;
}
export interface ModelSelectionResult {
selectedModel: ModelId | null;
attempts?: number;
skipped: Array<{
model: ModelId;
reason: UnavailabilityReason;
}>;
}
import { normalizeModelId } from '../utils/modelUtils.js';
export class ModelAvailabilityService {
private readonly health = new Map<ModelId, HealthState>();
private getHealth(
model: ModelId,
ttlMs: number = 30000,
): HealthState | undefined {
const state = this.health.get(model);
if (
state &&
state.status === 'terminal' &&
state.reason === 'capacity' &&
state.markedAt !== undefined
) {
const elapsed = Date.now() - state.markedAt;
if (elapsed >= ttlMs) {
this.clearState(model);
return undefined;
}
}
return state;
}
markTerminal(modelId: ModelId, reason: TerminalUnavailabilityReason) {
const model = normalizeModelId(modelId);
this.setState(model, {
status: 'terminal',
reason,
markedAt: Date.now(),
});
}
markHealthy(modelId: ModelId) {
const model = normalizeModelId(modelId);
this.clearState(model);
}
markRetryOncePerTurn(modelId: ModelId, attempts: number = 1) {
const model = normalizeModelId(modelId);
const currentState = this.getHealth(model);
// Do not override a terminal failure with a transient one.
if (currentState?.status === 'terminal') {
return;
}
// Only reset consumption if we are not already in the sticky_retry state.
// This prevents infinite loops if the model fails repeatedly in the same turn.
let consumed = false;
if (currentState?.status === 'sticky_retry') {
consumed = currentState.consumed;
}
this.setState(model, {
status: 'sticky_retry',
reason: 'retry_once_per_turn',
consumed,
attempts,
});
}
consumeStickyAttempt(modelId: ModelId) {
const model = normalizeModelId(modelId);
const state = this.getHealth(model);
if (state?.status === 'sticky_retry') {
this.setState(model, { ...state, consumed: true });
}
}
snapshot(modelId: ModelId, ttlMs: number = 30000): ModelAvailabilitySnapshot {
const model = normalizeModelId(modelId);
const state = this.getHealth(model, ttlMs);
if (!state) {
return { available: true };
}
if (state.status === 'terminal') {
return { available: false, reason: state.reason };
}
if (state.status === 'sticky_retry' && state.consumed) {
return { available: false, reason: state.reason };
}
return { available: true };
}
selectFirstAvailable(modelIds: ModelId[]): ModelSelectionResult {
const skipped: ModelSelectionResult['skipped'] = [];
for (const modelId of modelIds) {
const model = normalizeModelId(modelId);
const snapshot = this.snapshot(model);
if (snapshot.available) {
const state = this.getHealth(model);
// A sticky model is being attempted, so note that.
const attempts =
state?.status === 'sticky_retry' ? state.attempts : undefined;
return { selectedModel: model, skipped, attempts };
} else {
skipped.push({ model, reason: snapshot.reason ?? 'unknown' });
}
}
return { selectedModel: null, skipped };
}
resetTurn() {
for (const [model, state] of this.health.entries()) {
if (state.status === 'sticky_retry') {
this.setState(model, { ...state, consumed: false });
}
}
}
reset() {
this.health.clear();
}
private setState(model: ModelId, nextState: HealthState) {
this.health.set(model, nextState);
}
private clearState(model: ModelId) {
this.health.delete(model);
}
}
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