[ResponseOps] Slack webapi does not work with proxies

[pmuellr]

We received a support request for Slack not working with a proxy, and the following message logged:

error determining proxy state for invalid url "conversations.list?types=public_channel,private_channel", using default agents

Looking at the relevant code, it looks like the Slack API connector is using axios a bit differently than other connectors. It sets the domain name when creating the axios instance, and passes a domain-less url into the request() function. That url (without the domain) is what we are using to determine whether to use the proxy, and it can't figure it out (the error message), so it doesn't use the proxy.

relevant code:

kibana/x-pack/plugins/stack_connectors/server/connector_types/slack_api/service.ts

Lines 123 to 143 in a18b523

	const axiosInstance = axios.create({
	baseURL: SLACK_URL,
	headers: {
	Authorization: `Bearer ${token}`,
	'Content-type': 'application/json; charset=UTF-8',
	},
	});
	const validChannelId = async (
	channelId: string
	): Promise<ConnectorTypeExecutorResult<ValidChannelResponse | void>> => {
	try {
	const validChannel = (): Promise<AxiosResponse<ValidChannelResponse>> => {
	return request<ValidChannelResponse>({
	axios: axiosInstance,
	configurationUtilities,
	logger,
	method: 'get',
	url: `conversations.info?channel=${channelId}`,
	});
	};

kibana/x-pack/plugins/actions/server/lib/axios_utils.ts

Lines 22 to 48 in a18b523

	export const request = async <T = unknown>({
	axios,
	url,
	logger,
	method = 'get',
	data,
	configurationUtilities,
	headers,
	sslOverrides,
	...config
	}: {
	axios: AxiosInstance;
	url: string;
	logger: Logger;
	method?: Method;
	data?: T;
	configurationUtilities: ActionsConfigurationUtilities;
	headers?: Record<string, AxiosHeaderValue>;
	sslOverrides?: SSLSettings;
	} & AxiosRequestConfig): Promise<AxiosResponse> => {
	const { httpAgent, httpsAgent } = getCustomAgents(
	configurationUtilities,
	logger,
	url,
	sslOverrides
	);
	const { maxContentLength, timeout } = configurationUtilities.getResponseSettings();

kibana/x-pack/plugins/actions/server/lib/get_custom_agents.ts

Lines 82 to 90 in 83dadd4

	// there is a proxy in use, but it's possible we won't use it via custom host
	// proxyOnlyHosts and proxyBypassHosts
	let targetUrl: URL;
	try {
	targetUrl = new URL(url);
	} catch (err) {
	logger.warn(`error determining proxy state for invalid url "${url}", using default agents`);
	return defaultAgents;
	}

If that assumption is correct, this will require a code fix on our part, I don't believe there is a work-around possible.

[elasticmachine]

Pinging @elastic/response-ops (Team:ResponseOps)

[ymao1]

cc @XavierM