Backport changes made to TLogServer in #4616 back to old TLog implementations.
Old implementations were using SpecialCounter, which is string. The new type
is int64_t. Without the change, we can have many events like:
<Event Severity="30" Time="1658165532.958152" DateTime="2022-07-18T17:32:12Z" Type="ScopeEventFieldTypeMismatch" ID="0000000000000000" EventType="TraceEvent.TLogMetrics" FieldName="QueueDiskBytesUsed" OldType="Int64" NewType="String" ThreadID="2451559325190099131" Machine="10.242.248.26:4703" LogGroup="xxxx" Roles="TL" />
* proof of concept
* use code-probe instead of test
* code probe working on gcc
* code probe implemented
* renamed TestProbe to CodeProbe
* fixed refactoring typo
* support filtered output
* print probes at end of simulation
* fix missed probes print
* fix deduplication
* Fix refactoring issues
* revert bad refactor
* make sure file paths are relative
* fix more wrong refactor changes
* Revert "Revert "Refactor: ClusterController driving cluster-recovery state machine""
Major changes includes:
1. Re-revert Sequencer refactor commits listed below (in listed order):
1.a. This reverts commit bb17e194d9c9888e203421290959bd7f2c075d7f.
1.b. This reverts commit d174bb2e06bff01157d16c652073536c54d17f7f.
1.c. This reverts commit 30b05b469c87d9b526b427751c211fb5cf7ff9cd.
2. Update Status.actor to track ClusterController interface to track
recovery status.
3. Introduce a ServerKnob to define "cluster recovery trace event"
prefix; for now keeping it as "Master", however, it should allow
smooth transition to "Cluster" prefix as it seems more appropriate.
At present, cluster recovery process consists of following steps:
1. ClusterController clusterWatchDatabase actor recruits
master/sequencer process.
2. Sequencer process implements the cluster recovery state machine,
responsible to recruit all other processes as well restore the
cluster state.
Patch proposes a scheme where the cluster recovery state machine
is implemented and driven by the ClusterController process instead
of the Sequencer process.
Advantages of the scheme could be:
1. Simplified design where ClusterController recruits "sequencer"
process like other worker processes compared to current scheme
where "sequencer" process gets special treatment. In newer scheme
sequencer is responsible for maintaining/providing
"committed version" (as expected).
2. ClusterController is responsible for worker processes recruitment,
the sequencer though orchestrating the recovery state machine, it
need to reachout to the ClusterController for recruiting worker
processes etc.
NOTE:
Patch has moved the recovery state machine code from
'sequencer' -> 'cluster-controller' process, however, necessary
updates were done for both functionality as well as performance
improvement reasons.
Next Steps:
Cluster recovery documentation will be updated in near future.
We are currently emitting Role transition traces when a role starts and
when it ends. While this is useful for debugging, it doesn't work well
with tools that inject data and might potentially miss some trace lines.
We do decorate each trace lines with the roles assigned to that
particular process, however, this is not sufficient for tools that can
make use of the UID -> Role mapping
