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EnvironmentDetector.ts
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EnvironmentDetector.ts
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/*
* Copyright 2019 Amazon.com, Inc. or its affiliates.
* 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 { LOG } from '../utils/Logger';
import { DefaultEnvironment } from './DefaultEnvironment';
import { EC2Environment } from './EC2Environment';
import { IEnvironment } from './IEnvironment';
import { LambdaEnvironment } from './LambdaEnvironment';
import config from '../config/Configuration';
import Environments from './Environments';
import { LocalEnvironment } from './LocalEnvironment';
type EnvironmentProvider = () => Promise<IEnvironment>;
const lambdaEnvironment = new LambdaEnvironment();
const ec2Environment = new EC2Environment();
const defaultEnvironment = new DefaultEnvironment();
const environments = [lambdaEnvironment, ec2Environment];
let environment: IEnvironment | undefined = undefined;
const getEnvironmentFromOverride = (): IEnvironment | undefined => {
// short-circuit environment detection and use override
switch (config.environmentOverride) {
case Environments.Agent:
return defaultEnvironment;
case Environments.EC2:
return ec2Environment;
case Environments.Lambda:
return lambdaEnvironment;
case Environments.Local:
return new LocalEnvironment();
case Environments.Unknown:
default:
return undefined;
}
};
const discoverEnvironment = async (): Promise<IEnvironment> => {
LOG(`Discovering environment`);
for (const envUnderTest of environments) {
LOG(`Testing: ${envUnderTest.constructor.name}`);
try {
if (await envUnderTest.probe()) {
return envUnderTest;
}
} catch (e) {
LOG(`Failed probe: ${envUnderTest.constructor.name}`);
}
}
return defaultEnvironment;
};
const _resolveEnvironment: EnvironmentProvider = async (): Promise<IEnvironment> => {
LOG('Resolving environment');
if (environment) {
return environment;
}
if (config.environmentOverride) {
LOG('Environment override supplied', config.environmentOverride);
// this will be falsy if an invalid configuration value is provided
environment = getEnvironmentFromOverride();
if (environment) {
return environment;
} else {
LOG('Invalid environment provided. Falling back to auto-discovery.', config.environmentOverride);
}
}
environment = await discoverEnvironment(); // eslint-disable-line require-atomic-updates
return environment;
};
// pro-actively begin resolving the environment
// this will allow us to kick off any async tasks
// at module load time to reduce any blocking that
// may occur on the initial flush()
const environmentPromise = _resolveEnvironment();
const resolveEnvironment: EnvironmentProvider = async (): Promise<IEnvironment> => {
return environmentPromise;
};
const cleanResolveEnvironment = async (): Promise<IEnvironment> => {
environment = undefined;
return await _resolveEnvironment();
};
export { EnvironmentProvider, resolveEnvironment, cleanResolveEnvironment };