feat(CSOT) - feature branch #4095

W-A-James · 2024-04-23T20:36:58Z

Description

What is changing?

New Error

Added MongoOperationTimeoutError class that is thrown when a CSOT timeout is encountered

Changes to `Timeout`

Add Timeout.throwIfExpired() method
Add Timeout.remainingTime getter method

Updates to `AbstractOperation`

Add timeout field
- timeout is set at construction if the timeoutMS option is provided

Implementing CSOT behaviour for server selection

Update Topology.selectServer to accept a timeout option which it will use determine whether it has timed out when defined. Otherwise, constructs a Timeout using the serverSelectionMS option as before
Update Topology.selectServer to throw a MongoOperationTimeoutError on timeout when options.timeout is provided and retain previous error behaviour otherwise.
Update Topology._connect to pass down timeout to Server.command call used to execute ping on first connection

Implementing CSOT behaviour for connection checkout

Update Server.command to accept timeout option.
Update ConnectionPool.checkOut to accept timeout option
- only uses the passed in timeout if the configured serverSelectionTimeoutMS is greater than the duration on the timeout, otherwise, computes the time elapsed since server selection completed and creates timeout for the serverSelectionTimeoutMS deadline

Test changes

Implement Server Selection prose tests from CSOT spec. Left out last two since they require implementation of the connection creation cancellation behaviour that was decided against in DRIVERS-2347
Implement unit tests from CSOT spec related to server selection and connection checkout. Skipped tests with appropriate messages

Misc changes

Update resolveOptions to handle timeoutMS option propagation
- Add csotMin helper method that implements the CSOT min algorithm described here

Is there new documentation needed for these changes?

What is the motivation for this change?

Release Highlight

Fill in title or leave empty for no highlight

Double check the following

Ran npm run check:lint script
Self-review completed using the steps outlined here
PR title follows the correct format: type(NODE-xxxx)[!]: description
- Example: feat(NODE-1234)!: rewriting everything in coffeescript
Changes are covered by tests
New TODOs have a related JIRA ticket

src/cmap/connect.ts

src/cmap/connection.ts

src/cmap/connection_pool.ts

src/error.ts

src/operations/operation.ts

src/timeout.ts

W-A-James · 2024-05-03T21:40:54Z

src/admin.ts

+ readPreference: options?.readPreference,
+ timeoutMS: options?.timeoutMS ?? this.s.db.timeoutMS


NOTE FOR REVIEWERS: Needed to do this to ensure that unit tests using ping work

W-A-James · 2024-05-03T22:19:43Z

Evergreen link

baileympearson

left some small comments. I'm out this week, so don't consider them blocking!

baileympearson · 2024-05-05T22:45:22Z

src/sdam/server.ts

+ return await Promise.race([
+ finalOptions.operationTimeout,
+ conn.command(ns, cmd, finalOptions)
+ ]);


I don't recall any CSOT requirement that states we should time out the entirety of command execution at the connection layer. Instead, each step of connection-layer command execution has its own rules (your PR description mentions that this PR does not implement this logic.

Is this only added to facilitate testing? Or is there a CSOT requirement I'm missing?

Good catch here. Meant to remove this change, but missed it.

src/sdam/server.ts

src/operations/operation.ts

src/sdam/topology.ts

src/operations/execute_operation.ts

aditi-khare-mongoDB · 2024-05-06T17:33:07Z

Bookkeeping:
Waiting for Warren to respond to Bailey's comments and will proceed with review then.

src/sdam/topology.ts

test/integration/client-side-operations-timeout/client_side_operations_timeout.unit.test.ts

src/sdam/server.ts

src/sdam/topology.ts

W-A-James · 2024-05-07T20:00:49Z

@aditi-khare-mongoDB @nbbeeken should we conditionally clear the timeout on success/a non-timeout failure based on whether or not we created the timeout inside the function that we race the timeout with?
I ask because we don't always own Timeout instance we're using in Topology.selectServer or in ConnectionPool.checkOut.

src/cmap/connection_pool.ts

nbbeeken

looks pretty good

src/operations/operation.ts

src/cmap/connection.ts

src/cmap/connection_pool.ts

nbbeeken · 2024-05-08T15:47:39Z

src/sdam/server.ts

+ if (options.operationTimeout) {
+ conn = await this.pool.checkOut({ timeout: options.operationTimeout });
+ } else {
+ conn = await this.pool.checkOut();
+ }


Suggested change

if (options.operationTimeout) {

conn = await this.pool.checkOut({ timeout: options.operationTimeout });

} else {

conn = await this.pool.checkOut();

}

conn = await this.pool.checkOut({ timeout: options.operationTimeout });

TS supports just calling this because the timeout is optional

I feel Warren's current code is easier to read (and easier for someone editing the code later to not accidentally make the code not CSOT spec-compliant) , but if we do end up going with this suggestion can we leave a clarifying comment?

I am surprised because breaking this up into two calls to checkOut based on a condition that does matter is more to read without more meaningful context given. Whether or not timeout exists, there is no change to how checkOut is, practically, invoked because the typescript reports that field as optional.

I would actually take this further:

conn = await this.pool.checkOut(options);

Why do we need to make a new object here? passing through options should be fine right? Less branching paths the less there is to debug

Can you elaborate on what may accidentally break the spec without a test warning us?

src/cmap/connection_pool.ts

nbbeeken · 2024-05-10T16:12:18Z

src/cmap/connection_pool.ts

+ // Determine if we're using the timeout passed in or a new timeout
+ if (options.timeout.duration > 0 || serverSelectionTimeoutMS > 0) {
+ if (
+ csotMin(options.timeout.duration, serverSelectionTimeoutMS) === serverSelectionTimeoutMS


This is still and equals check, sorry I think we discussed it but didn't leave a comment, if duration is the same then we'll create a new timeout when we can use the existing one.

src/sdam/topology.ts

src/operations/operation.ts

src/sdam/topology.ts

…ver selection

W-A-James force-pushed the NODE-6090 branch 2 times, most recently from 5688ba8 to b878c6c Compare April 26, 2024 23:48