From 30e81d58f82a9f0e9f8a9746812ed1130268fbdf Mon Sep 17 00:00:00 2001
From: Alexey Rybalchenko <alexryba@gmail.com>
Date: Sat, 27 Mar 2021 13:38:54 +0100
Subject: [PATCH] shmmonitor: allow getting shmids based on session/userid

---
 fairmq/shmem/Common.h       |  9 +++++++--
 fairmq/shmem/runMonitor.cxx | 19 +++++++++++++++++--
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/fairmq/shmem/Common.h b/fairmq/shmem/Common.h
index 6f0109ac..a8a49b58 100644
--- a/fairmq/shmem/Common.h
+++ b/fairmq/shmem/Common.h
@@ -195,9 +195,9 @@ struct RegionBlock
 
 // find id for unique shmem name:
 // a hash of user id + session id, truncated to 8 characters (to accommodate for name size limit on some systems (MacOS)).
-inline std::string makeShmIdStr(const std::string& sessionId)
+inline std::string makeShmIdStr(const std::string& sessionId, const std::string& userId)
 {
-    std::string seed((std::to_string(geteuid()) + sessionId));
+    std::string seed(userId + sessionId);
     // generate a 8-digit hex value out of sha256 hash
     std::vector<unsigned char> hash(4);
     picosha2::hash256(seed.begin(), seed.end(), hash.begin(), hash.end());
@@ -205,6 +205,11 @@ inline std::string makeShmIdStr(const std::string& sessionId)
     return picosha2::bytes_to_hex_string(hash.begin(), hash.end());
 }
 
+inline std::string makeShmIdStr(const std::string& sessionId)
+{
+    return makeShmIdStr(sessionId, std::to_string(geteuid()));
+}
+
 inline uint64_t makeShmIdUint64(const std::string& sessionId)
 {
     std::string shmId = makeShmIdStr(sessionId);
diff --git a/fairmq/shmem/runMonitor.cxx b/fairmq/shmem/runMonitor.cxx
index a128becd..f3cfdd8d 100644
--- a/fairmq/shmem/runMonitor.cxx
+++ b/fairmq/shmem/runMonitor.cxx
@@ -80,6 +80,8 @@ int main(int argc, char** argv)
         bool runAsDaemon = false;
         bool debug = false;
         bool cleanOnExit = false;
+        bool getShmId = false;
+        int userId = -1;
 
         options_description desc("Options");
         desc.add_options()
@@ -91,9 +93,11 @@ int main(int argc, char** argv)
             ("view,v"         , value<bool>(&viewOnly)->implicit_value(true),           "Run in view only mode")
             ("timeout,t"      , value<unsigned int>(&timeoutInMS)->default_value(5000), "Heartbeat timeout in milliseconds")
             ("daemonize,d"    , value<bool>(&runAsDaemon)->implicit_value(true),        "Daemonize the monitor")
-            ("debug,b"        , value<bool>(&debug)->implicit_value(true),             "Debug - Print a list of messages)")
+            ("debug,b"        , value<bool>(&debug)->implicit_value(true),              "Debug - Print a list of messages)")
             ("clean-on-exit,e", value<bool>(&cleanOnExit)->implicit_value(true),        "Perform cleanup on exit")
             ("interval"       , value<unsigned int>(&intervalInMS)->default_value(100), "Output interval for interactive/view-only mode")
+            ("get-shmid"      , value<bool>(&getShmId)->implicit_value(true),           "Translate given session id and user id to a shmem id (uses current user id if none provided)")
+            ("user-id"        , value<int>(&userId)->default_value(-1),                  "User id")
             ("help,h", "Print help");
 
         variables_map vm;
@@ -110,7 +114,18 @@ int main(int argc, char** argv)
             daemonize();
         }
 
-        if (shmId == "") {
+        if (getShmId) {
+            if (userId == -1) {
+                cout << "shmem id for session '" << sessionName << "' and current user id " << geteuid()
+                     << " is: " << makeShmIdStr(sessionName) << endl;
+            } else {
+                cout << "shmem id for session '" << sessionName << "' and user id " << userId
+                     << " is: " << makeShmIdStr(sessionName, to_string(userId)) << endl;
+            }
+            return 0;
+        }
+
+        if (shmId.empty()) {
             shmId = makeShmIdStr(sessionName);
         }