overleaf/services/web/scripts/delete_orphaned_data_helper.js

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const { ReadPreference } = require('mongodb')
const { db } = require('../app/src/infrastructure/mongodb')
const { promiseMapWithLimit } = require('../app/src/util/promises')
async function getDeletedProject(projectId, readPreference) {
return await db.deletedProjects.findOne(
{ 'deleterData.deletedProjectId': projectId },
{
// There is no index on .project. Pull down something small.
projection: { 'project._id': 1 },
readPreference,
}
)
}
async function getProject(projectId, readPreference) {
return await db.projects.findOne(
{ _id: projectId },
{
// Pulling down an empty object is fine for differentiating with null.
projection: { _id: 0 },
readPreference,
}
)
}
async function checkProjectExistsWithReadPreference(projectId, readPreference) {
// NOTE: Possible race conditions!
// There are two processes which are racing with our queries:
// 1. project deletion
// 2. project restoring
// For 1. we check the projects collection before deletedProjects.
// If a project were to be delete in this very moment, we should see the
// soft-deleted entry which is created before deleting the projects entry.
// For 2. we check the projects collection after deletedProjects again.
// If a project were to be restored in this very moment, it is very likely
// to see the projects entry again.
// Unlikely edge case: Restore+Deletion in rapid succession.
// We could add locking to the ProjectDeleter for ruling ^ out.
if (await getProject(projectId, readPreference)) {
// The project is live.
return true
}
const deletedProject = await getDeletedProject(projectId, readPreference)
if (deletedProject && deletedProject.project) {
// The project is registered for hard-deletion.
return true
}
if (await getProject(projectId, readPreference)) {
// The project was just restored.
return true
}
// The project does not exist.
return false
}
async function checkProjectExistsOnPrimary(projectId) {
return await checkProjectExistsWithReadPreference(
projectId,
ReadPreference.PRIMARY
)
}
async function checkProjectExistsOnSecondary(projectId) {
return await checkProjectExistsWithReadPreference(
projectId,
ReadPreference.SECONDARY
)
}
async function getHardDeletedProjectIds({
projectIds,
READ_CONCURRENCY_PRIMARY,
READ_CONCURRENCY_SECONDARY,
}) {
const doubleCheckProjectIdsOnPrimary = []
async function checkProjectOnSecondary(projectId) {
if (await checkProjectExistsOnSecondary(projectId)) {
// Finding a project with secondary confidence is sufficient.
return
}
// At this point, the secondaries deem this project as having orphaned docs.
doubleCheckProjectIdsOnPrimary.push(projectId)
}
const hardDeletedProjectIds = []
async function checkProjectOnPrimary(projectId) {
if (await checkProjectExistsOnPrimary(projectId)) {
// The project is actually live.
return
}
hardDeletedProjectIds.push(projectId)
}
await promiseMapWithLimit(
READ_CONCURRENCY_SECONDARY,
projectIds,
checkProjectOnSecondary
)
await promiseMapWithLimit(
READ_CONCURRENCY_PRIMARY,
doubleCheckProjectIdsOnPrimary,
checkProjectOnPrimary
)
return hardDeletedProjectIds
}
module.exports = {
getHardDeletedProjectIds,
}