From 5df684b60993f769db94fb12a6ff9e98d22d10a8 Mon Sep 17 00:00:00 2001
From: Jordan Bancino <jordan@bancino.net>
Date: Sat, 27 May 2023 17:10:07 +0000
Subject: [PATCH] Show human-readable thread ID in log messages.

This helps debug some multithreading issues.
---
 Cytoplasm/src/HttpServer.c   |  3 ---
 Cytoplasm/src/Log.c          |  3 +++
 Cytoplasm/src/Util.c         | 32 ++++++++++++++++++++++++++++++++
 Cytoplasm/src/include/Util.h | 11 +++++++++++
 4 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/Cytoplasm/src/HttpServer.c b/Cytoplasm/src/HttpServer.c
index e620983..78009f7 100644
--- a/Cytoplasm/src/HttpServer.c
+++ b/Cytoplasm/src/HttpServer.c
@@ -79,7 +79,6 @@ struct HttpServerContext
 typedef struct HttpServerWorkerThreadArgs
 {
     HttpServer *server;
-    int id;
     pthread_t thread;
 } HttpServerWorkerThreadArgs;
 
@@ -625,7 +624,6 @@ HttpServerEventThread(void *args)
         }
 
         workerThread->server = server;
-        workerThread->id = i;
 
         if (pthread_create(&workerThread->thread, NULL, HttpServerWorkerThread, workerThread) != 0)
         {
@@ -644,7 +642,6 @@ HttpServerEventThread(void *args)
         int connFd;
         int pollResult;
 
-
         pollResult = poll(pollFds, 1, 500);
 
         if (pollResult < 0)
diff --git a/Cytoplasm/src/Log.c b/Cytoplasm/src/Log.c
index 6a441e0..d5a5799 100644
--- a/Cytoplasm/src/Log.c
+++ b/Cytoplasm/src/Log.c
@@ -24,6 +24,7 @@
 #include <Log.h>
 
 #include <Memory.h>
+#include <Util.h>
 
 #include <string.h>
 #include <time.h>
@@ -316,6 +317,8 @@ Logv(LogConfig * config, int level, const char *msg, va_list argp)
         }
     }
 
+    StreamPrintf(config->out, "(%lu) ", UtilThreadNo());
+
     switch (level)
     {
         case LOG_EMERG:
diff --git a/Cytoplasm/src/Util.c b/Cytoplasm/src/Util.c
index 8a1b62d..78c220a 100644
--- a/Cytoplasm/src/Util.c
+++ b/Cytoplasm/src/Util.c
@@ -244,3 +244,35 @@ UtilGetLine(char **linePtr, size_t * n, Stream * stream)
 {
     return UtilGetDelim(linePtr, n, '\n', stream);
 }
+
+static void
+ThreadNoDestructor(void *p)
+{
+    Free(p);
+}
+
+unsigned long
+UtilThreadNo(void)
+{
+    static pthread_key_t key;
+    static int createdKey = 0;
+    static unsigned long count = 0;
+
+    unsigned long *no;
+
+    if (!createdKey)
+    {
+        pthread_key_create(&key, ThreadNoDestructor);
+        createdKey = 1;
+    }
+
+    no = pthread_getspecific(key);
+    if (!no)
+    {
+        no = Malloc(sizeof(unsigned long));
+        *no = count++;
+        pthread_setspecific(key, no);
+    }
+
+    return *no;
+}
diff --git a/Cytoplasm/src/include/Util.h b/Cytoplasm/src/include/Util.h
index 0a3e02d..55c34a9 100644
--- a/Cytoplasm/src/include/Util.h
+++ b/Cytoplasm/src/include/Util.h
@@ -102,4 +102,15 @@ extern ssize_t UtilGetDelim(char **, size_t *, int, Stream *);
  */
 extern ssize_t UtilGetLine(char **, size_t *, Stream *);
 
+/**
+ * Get a unique number associated with the current thread.
+ * Numbers are assigned in the order that threads call this
+ * function, but are guaranteed to be unique in identifying
+ * the thread in a more human-readable way than just casting
+ * the return value of
+ * .Fn pthread_self
+ * to a number.
+ */
+extern unsigned long UtilThreadNo(void);
+
 #endif                             /* CYTOPLASM_UTIL_H */