feat: Add a start_backend command for ct and start db-backend from same executable

Author: pxor

src/ct/codetracerconf.nim

@@ -53,6 +53,7 @@ type
     # summary,
     # `report-bug`,
     `trace-metadata`, # TODO .hidden?
+    start_backend,
 
 type
   # the following TODOs are for changes in confutils
@@ -478,6 +479,18 @@ type
         name: "test",
         defaultValue: false,
       .}: bool
+    of start_backend:
+      backendKind* {.
+        argument
+        desc: "This is the backend kind - either 'db' or 'rr'"
+      .}: string
+      isStdio* {.
+        name: "stdio",
+        defaultValue: false,
+      .}: bool
+      socketPath* {.
+        name: "socket-path",
+      .}: Option[string]
 
 proc customValidateConfig*(conf: CodetracerConf) =
   case conf.cmd:

src/ct/launch/backends.nim

@@ -1,12 +1,51 @@
 import
-  std/[strformat, strutils, osproc, posix, posix_utils],
-  ../../common/[start_utils, types, trace_index],
+  std/[strformat, strutils, osproc, posix, posix_utils, os, options],
+  ../../common/[start_utils, types, trace_index, paths, config],
   ../utilities/[env],
   ../cli/[logging],
   cleanup
 
 var coreProcessId* = -1
 
+proc startBackend*(backendKind: string, isStdio: bool, socketPath: Option[string]) =
+  let backendExe =
+    if backendKind == "db":
+      dbBackendExe
+    elif backendKind == "rr":
+      let ctConfig = loadConfig(folder=getCurrentDir(), inTest=false)
+      if ctConfig.rrBackend.enabled:
+        ctConfig.rrBackend.path
+      else:
+        echo "ERROR: rr backend not enabled!"
+        quit(1)
+    else:
+      echo "ERROR: Backend kind not recognized, needs to be 'rr' or 'db'"
+      quit(1)
+
+  let args =
+    if isStdio:
+      @["--stdio"]
+    elif socketPath.isSome:
+      @[socketPath.get()]
+    else: 
+      echo "ERRROR: Needs to have either --stdio or a valid socket path"
+      quit(1)
+
+  let process = startProcess(
+    backendExe,
+    args = args,
+    options = { poParentStreams }
+  )
+
+  coreProcessId = process.processId
+  onSignal(SIGTERM):
+    if coreProcessId != -1:
+      echo "ct: stopping core process"
+      sendSignal(coreProcessId.Pid, SIGTERM)
+
+  let code = waitForExit(process)
+  quit(code)
+
 proc startCore*(traceArg: string, callerPid: int, test: bool) =
   # start_core <trace-program-pattern> <caller-pid> [--test]
   let recordCore = envLoadRecordCore()

src/ct/launch/launch.nim

@@ -182,3 +182,5 @@ proc runInitial*(conf: CodetracerConf) =
         conf.traceMetadataRecent,
         conf.traceMetadataRecentLimit,
         conf.traceMetadataTest)
+    of StartupCommand.start_backend:
+      startBackend(conf.backendKind, conf.isStdio, conf.socketPath)