Currently, the update/apptask/fullbackup/platformstart take a
global lock and cannot run in parallel. This causes situations
where when a user tries to trigger an apptask, it says "waiting for
backup to finish..." etc
The solution is to let them run in parallel. We need a lock at the
app level as app operations running in parallel would be bad (tm).
In addition, the update task needs a lock just for the update part.
We also need multi-process locks. Running tasks as processes is core
to our "kill" strategy.
Various inter process locks were explored:
* node's IPC mechanism with process.send(). But this only works for direct node.js
children. taskworker is run via sudo and the IPC does not work.
* File lock using O_EXCL. Basic ideas to create lock files. While file creation
can be done atomically, it becomes complicated to clean up lock files when
the tasks crash. We need a way to know what locks were held by the crashing task.
flock and friends are not built-into node.js
* sqlite/redis were options but introduce additional deps
* Settled on MySQL based locking. Initial plan was to have row locks
or table locks. Each row is a kind of lock. While implementing, it was found that
we need many types of locks (and not just update lock and app locks). For example,
we need locks for each task type, so that only one task type is active at a time.
* Instead of rows, we can just lock table and have a json blob in it. This hit a road
block that LOCK TABLE is per session and our db layer cannot handle this easily! i.e
when issing two db.query() it might use two different connections from the pool. We have to
expose the connection, release connection etc.
* Next idea was atomic blob update of the blob checking if old blob was same. This approach,
was finally refined into a version field.
Phew!
ports is REST API input . Map of env var to the host port
portBinding is the database structure. Map of env var to host port, count, type etc
also, rename portCount -> count in various places to keep things consistent
* Always allow the mandatory 2fa setting to be saved
* Show warning for user if they have no 2fa setup and if not external 2fa
* If they get locked out anyway, they have to use CLI tool
* redirect for mandatory 2fa only if not external 2fa as well
cpuShares is the relative weight wrt other apps. This is used when
there is contention for CPU. If we want this, maybe we implement
a UI where we show all the apps and let the user re-order them.
As it stands, it is confusing.
cpuQuota is a more straightforward "hard limit" of the CPU% that you
want the app to consume.
Can be tested with : stress -c 8 -t 20s
Currently, we only have one field for the name. The first part is
first name. The rest is last name. Obviously, this won't work in all
cases but is the best we can do for the moment.
Girish Ramakrishnan