81 lines
2.6 KiB
JavaScript
81 lines
2.6 KiB
JavaScript
/**
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* A Promise-like interface for running a sequence of commands.
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*
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* If a network error occurs while running a command, then a reconnect is automatically
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* attempted and the sequence will resume by sending the same command again. Any other errors
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* that occur while running a command will cause the entire sequence of commands to abort.
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*
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* @param {Mongo} conn - a connection to the server
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*/
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function CommandSequenceWithRetries(conn) {
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"use strict";
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if (!(this instanceof CommandSequenceWithRetries)) {
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return new CommandSequenceWithRetries(conn);
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}
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const steps = [];
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function attemptReconnect(conn) {
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try {
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conn.adminCommand({ping: 1});
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} catch (e) {
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return false;
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}
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return true;
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}
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this.then = function then(phase, action) {
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steps.push({phase: phase, action: action});
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return this;
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};
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this.execute = function execute() {
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let i = 0;
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let stepHadNetworkErrorAlready = false;
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while (i < steps.length) {
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try {
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// Treat no explicit return statement inside the action function as returning
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// {shouldStop: false} for syntactic convenience.
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const result = steps[i].action(conn);
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if (result !== undefined && result.shouldStop) {
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return {ok: 0, msg: "giving up after " + steps[i].phase + ": " + result.reason};
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}
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} catch (e) {
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if (!isNetworkError(e)) {
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throw e;
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}
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// We retry running the action function a second time after a network error
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// because it is possible that the node is in the process of stepping down. We
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// won't be able to reconnect to the node until it has finished closing all of
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// its open connections.
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if (stepHadNetworkErrorAlready) {
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return {
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ok: 0,
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msg: "giving up after " + steps[i].phase +
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" because we encountered multiple network errors"
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};
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}
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if (!attemptReconnect(conn)) {
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return {
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ok: 0,
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msg: "giving up after " + steps[i].phase +
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" because attempting to reconnect failed"
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};
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}
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stepHadNetworkErrorAlready = true;
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continue;
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}
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++i;
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stepHadNetworkErrorAlready = false;
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}
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return {ok: 1};
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};
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}
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