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[2/7] Telemetry Infrastructure: CircuitBreaker and FeatureFlagCache #325

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[2/7] Telemetry Infrastructure: CircuitBreaker and FeatureFlagCache #325

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db640fa
Add telemetry infrastructure: CircuitBreaker and FeatureFlagCache
samikshya-db Jan 28, 2026
211f91c
Add authentication support for REST API calls
samikshya-db Jan 29, 2026
c3779af
Fix feature flag and telemetry export endpoints
samikshya-db Jan 29, 2026
a105777
Match JDBC telemetry payload format
samikshya-db Jan 29, 2026
1cdb716
Fix lint errors
samikshya-db Jan 29, 2026
689e561
Add missing getAuthHeaders method to ClientContextStub
samikshya-db Jan 29, 2026
2d41e2d
Fix prettier formatting
samikshya-db Jan 29, 2026
e474256
Add DRIVER_NAME constant for nodejs-sql-driver
samikshya-db Jan 30, 2026
a3c9042
Add missing telemetry fields to match JDBC
samikshya-db Jan 30, 2026
6110797
Fix TypeScript compilation: add missing fields to system_configuratio…
samikshya-db Jan 30, 2026
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13 changes: 13 additions & 0 deletions lib/DBSQLClient.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ import thrift from 'thrift';
import Int64 from 'node-int64';

import { EventEmitter } from 'events';
import { HeadersInit } from 'node-fetch';
import TCLIService from '../thrift/TCLIService';
import { TProtocolVersion } from '../thrift/TCLIService_types';
import IDBSQLClient, { ClientOptions, ConnectionOptions, OpenSessionRequest } from './contracts/IDBSQLClient';
Expand Down Expand Up @@ -291,4 +292,16 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
public async getDriver(): Promise<IDriver> {
return this.driver;
}

public async getAuthHeaders(): Promise<HeadersInit> {
if (this.authProvider) {
try {
return await this.authProvider.authenticate();
} catch (error) {
this.logger.log(LogLevel.debug, `Error getting auth headers: ${error}`);
return {};
}
}
return {};
}
}
8 changes: 8 additions & 0 deletions lib/contracts/IClientContext.ts
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
import { HeadersInit } from 'node-fetch';
import IDBSQLLogger from './IDBSQLLogger';
import IDriver from './IDriver';
import IConnectionProvider from '../connection/contracts/IConnectionProvider';
Expand Down Expand Up @@ -43,4 +44,11 @@ export default interface IClientContext {
getClient(): Promise<IThriftClient>;

getDriver(): Promise<IDriver>;

/**
* Gets authentication headers for HTTP requests.
* Used by telemetry and feature flag fetching to authenticate REST API calls.
* @returns Promise resolving to headers object with authentication, or empty object if no auth
*/
getAuthHeaders(): Promise<HeadersInit>;
}
235 changes: 235 additions & 0 deletions lib/telemetry/CircuitBreaker.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,235 @@
/**
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@jadewang-db jadewang-db Feb 2, 2026

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try use some existing library for circuitbreaker

* Copyright (c) 2025 Databricks Contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

import IClientContext from '../contracts/IClientContext';
import { LogLevel } from '../contracts/IDBSQLLogger';

/**
* States of the circuit breaker.
*/
export enum CircuitBreakerState {
/** Normal operation, requests pass through */
CLOSED = 'CLOSED',
/** After threshold failures, all requests rejected immediately */
OPEN = 'OPEN',
/** After timeout, allows test requests to check if endpoint recovered */
HALF_OPEN = 'HALF_OPEN',
}

/**
* Configuration for circuit breaker behavior.
*/
export interface CircuitBreakerConfig {
/** Number of consecutive failures before opening the circuit */
failureThreshold: number;
/** Time in milliseconds to wait before attempting recovery */
timeout: number;
/** Number of consecutive successes in HALF_OPEN state to close the circuit */
successThreshold: number;
}

/**
* Default circuit breaker configuration.
*/
export const DEFAULT_CIRCUIT_BREAKER_CONFIG: CircuitBreakerConfig = {
failureThreshold: 5,
timeout: 60000, // 1 minute
successThreshold: 2,
};

/**
* Circuit breaker for telemetry exporter.
* Protects against failing telemetry endpoint with automatic recovery.
*
* States:
* - CLOSED: Normal operation, requests pass through
* - OPEN: After threshold failures, all requests rejected immediately
* - HALF_OPEN: After timeout, allows test requests to check if endpoint recovered
*/
export class CircuitBreaker {
private state: CircuitBreakerState = CircuitBreakerState.CLOSED;

private failureCount = 0;

private successCount = 0;

private nextAttempt?: Date;

private readonly config: CircuitBreakerConfig;

constructor(private context: IClientContext, config?: Partial<CircuitBreakerConfig>) {
this.config = {
...DEFAULT_CIRCUIT_BREAKER_CONFIG,
...config,
};
}

/**
* Executes an operation with circuit breaker protection.
*
* @param operation The operation to execute
* @returns Promise resolving to the operation result
* @throws Error if circuit is OPEN or operation fails
*/
async execute<T>(operation: () => Promise<T>): Promise<T> {
const logger = this.context.getLogger();

// Check if circuit is open
if (this.state === CircuitBreakerState.OPEN) {
if (this.nextAttempt && Date.now() < this.nextAttempt.getTime()) {
throw new Error('Circuit breaker OPEN');
}
// Timeout expired, transition to HALF_OPEN
this.state = CircuitBreakerState.HALF_OPEN;
this.successCount = 0;
logger.log(LogLevel.debug, 'Circuit breaker transitioned to HALF_OPEN');
}

try {
const result = await operation();
this.onSuccess();
return result;
} catch (error) {
this.onFailure();
throw error;
}
}

/**
* Gets the current state of the circuit breaker.
*/
getState(): CircuitBreakerState {
return this.state;
}

/**
* Gets the current failure count.
*/
getFailureCount(): number {
return this.failureCount;
}

/**
* Gets the current success count (relevant in HALF_OPEN state).
*/
getSuccessCount(): number {
return this.successCount;
}

/**
* Handles successful operation execution.
*/
private onSuccess(): void {
const logger = this.context.getLogger();

// Reset failure count on any success
this.failureCount = 0;

if (this.state === CircuitBreakerState.HALF_OPEN) {
this.successCount += 1;
logger.log(
LogLevel.debug,
`Circuit breaker success in HALF_OPEN (${this.successCount}/${this.config.successThreshold})`,
);

if (this.successCount >= this.config.successThreshold) {
// Transition to CLOSED
this.state = CircuitBreakerState.CLOSED;
this.successCount = 0;
this.nextAttempt = undefined;
logger.log(LogLevel.debug, 'Circuit breaker transitioned to CLOSED');
}
}
}

/**
* Handles failed operation execution.
*/
private onFailure(): void {
const logger = this.context.getLogger();

this.failureCount += 1;
this.successCount = 0; // Reset success count on failure

logger.log(LogLevel.debug, `Circuit breaker failure (${this.failureCount}/${this.config.failureThreshold})`);

if (this.failureCount >= this.config.failureThreshold) {
// Transition to OPEN
this.state = CircuitBreakerState.OPEN;
this.nextAttempt = new Date(Date.now() + this.config.timeout);
logger.log(LogLevel.debug, `Circuit breaker transitioned to OPEN (will retry after ${this.config.timeout}ms)`);
}
}
}

/**
* Manages circuit breakers per host.
* Ensures each host has its own isolated circuit breaker to prevent
* failures on one host from affecting telemetry to other hosts.
*/
export class CircuitBreakerRegistry {
private breakers: Map<string, CircuitBreaker>;

constructor(private context: IClientContext) {
this.breakers = new Map();
}

/**
* Gets or creates a circuit breaker for the specified host.
*
* @param host The host identifier (e.g., "workspace.cloud.databricks.com")
* @param config Optional configuration overrides
* @returns Circuit breaker for the host
*/
getCircuitBreaker(host: string, config?: Partial<CircuitBreakerConfig>): CircuitBreaker {
let breaker = this.breakers.get(host);
if (!breaker) {
breaker = new CircuitBreaker(this.context, config);
this.breakers.set(host, breaker);
const logger = this.context.getLogger();
logger.log(LogLevel.debug, `Created circuit breaker for host: ${host}`);
}
return breaker;
}

/**
* Gets all registered circuit breakers.
* Useful for testing and diagnostics.
*/
getAllBreakers(): Map<string, CircuitBreaker> {
return new Map(this.breakers);
}

/**
* Removes a circuit breaker for the specified host.
* Useful for cleanup when a host is no longer in use.
*
* @param host The host identifier
*/
removeCircuitBreaker(host: string): void {
this.breakers.delete(host);
const logger = this.context.getLogger();
logger.log(LogLevel.debug, `Removed circuit breaker for host: ${host}`);
}

/**
* Clears all circuit breakers.
* Useful for testing.
*/
clear(): void {
this.breakers.clear();
}
}
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