Switch over to new user cfg system

src/bdev_lsvd.cc

@@ -219,10 +219,10 @@ int bdev_lsvd_create(str img_name, rados_ioctx_t ioctx, lsvd_config cfg)
     return 0;
 }
 
-int bdev_lsvd_create(str pool_name, str image_name, str cfg_path)
+int bdev_lsvd_create(str pool_name, str image_name, str user_cfg)
 {
     auto be = connect_to_pool(pool_name);
-    auto cfg = lsvd_config::from_file(cfg_path);
+    auto cfg = lsvd_config::from_user_cfg(user_cfg);
     PR_RET_IF(!cfg.has_value(), -1, "Failed to read config file");
 
     return bdev_lsvd_create(image_name, be, cfg.value());

src/config.cc

@@ -1,3 +1,5 @@
+#include <fstream>
+#include <iostream>
 #include <nlohmann/json.hpp>
 #include <stdlib.h>
 #include <string>
@@ -7,24 +9,70 @@
 #include "config.h"
 #include "utils.h"
 
-vec<std::string> cfg_path({"lsvd.conf", "/usr/local/etc/lsvd.conf"});
+lsvd_config lsvd_config::get_default() { return lsvd_config(); }
 
-opt<lsvd_config> lsvd_config::from_file(str path)
+opt<lsvd_config> lsvd_config::from_user_cfg(str cfg)
 {
-    // write just a simple braindead parser
-    // syntax: lines of `key = value`
+    auto c = get_default();
+    if (cfg.empty())
+        return c;
+
+    try {
+        c.parse_file("/usr/local/etc/lsvd.json", true);
+        c.parse_file("./lsvd.json", true);
 
-    UNIMPLEMENTED();
+        if (cfg[0] == '{') {
+            c.parse_json(cfg);
+        } else {
+            c.parse_file(cfg, false);
+        }
+        return c;
+    } catch (const std::exception &e) {
+        log_error("Failed to parse config '{}': {}", cfg, e.what());
+        return std::nullopt;
+    }
 }
 
-lsvd_config lsvd_config::get_default() { return lsvd_config(); }
+// https://stackoverflow.com/questions/116038/how-do-i-read-an-entire-file-into-a-stdstring-in-c
+auto read_file(std::string_view path) -> std::string
+{
+    constexpr auto read_size = std::size_t(4096);
+    auto stream = std::ifstream(path.data());
+    stream.exceptions(std::ios_base::badbit);
+
+    if (not stream)
+        throw std::ios_base::failure("file does not exist");
+
+    auto out = std::string();
+    auto buf = std::string(read_size, '\0');
+    while (stream.read(&buf[0], read_size))
+        out.append(buf, 0, stream.gcount());
+    out.append(buf, 0, stream.gcount());
+    return out;
+}
+
+void lsvd_config::parse_file(str path, bool can_be_missing)
+{
+    assert(!path.empty());
+    if (access(path.c_str(), F_OK) == -1) {
+        if (can_be_missing) {
+            log_info("Optional config file missing: {}, continuing...", path);
+            return;
+        }
+        log_error("Config file not found: {}", path);
+        return;
+    }
+
+    auto cfg = read_file(path);
+    parse_json(cfg);
+}
 
 #define JSON_GET_BOOL(key)                                                     \
     do {                                                                       \
         if (js.contains(#key)) {                                               \
             auto v = js[#key];                                                 \
             if (v.is_boolean()) {                                              \
-                cfg.key = js[#key];                                            \
+                this->key = js[#key];                                          \
             } else {                                                           \
                 log_error("Invalid value for key (must be bool): {}", #key);   \
             }                                                                  \
@@ -36,7 +84,7 @@ lsvd_config lsvd_config::get_default() { return lsvd_config(); }
         if (js.contains(#key)) {                                               \
             auto v = js[#key];                                                 \
             if (v.is_number_unsigned()) {                                      \
-                cfg.key = js[#key];                                            \
+                this->key = js[#key];                                          \
             } else {                                                           \
                 log_error("Invalid value for key (must be uint): {}", #key);   \
             }                                                                  \
@@ -48,25 +96,17 @@ lsvd_config lsvd_config::get_default() { return lsvd_config(); }
         if (js.contains(#key)) {                                               \
             auto v = js[#key];                                                 \
             if (v.is_string()) {                                               \
-                cfg.key = js[#key];                                            \
+                this->key = js[#key];                                          \
             } else {                                                           \
                 log_error("Invalid value for key (must be str): {}", #key);    \
             }                                                                  \
         }                                                                      \
     } while (0)
 
-opt<lsvd_config> lsvd_config::from_json(str json)
+void lsvd_config::parse_json(str json)
 {
-    nlohmann::json js;
+    auto js = nlohmann::json::parse(json);
 
-    try {
-        js = nlohmann::json::parse(json);
-    } catch (nlohmann::json::parse_error &e) {
-        log_error("Failed to parse JSON: {}", e.what());
-        return std::nullopt;
-    }
-
-    lsvd_config cfg;
     JSON_GET_STR(rcache_dir);
     JSON_GET_UINT(rcache_bytes);
     JSON_GET_UINT(rcache_fetch_window);
@@ -86,6 +126,4 @@ opt<lsvd_config> lsvd_config::from_json(str json)
     JSON_GET_UINT(gc_threshold_pc);
     JSON_GET_UINT(gc_write_window);
     JSON_GET_BOOL(no_gc);
-
-    return cfg;
 }

src/config.h

@@ -40,10 +40,17 @@ class lsvd_config
         return fspath(wlog_dir) / filename;
     }
 
-    static opt<lsvd_config> from_json(str json);
-    static opt<lsvd_config> from_file(str path);
+    /**
+     * Read LSVD configuration from user-supplied string. The string can be
+     * either a json string containing the configuration, the path to a file
+     * containing the same, or empty, in which case it will be ignored.
+     */
+    static opt<lsvd_config> from_user_cfg(str cfg);
     static lsvd_config get_default();
 
   private:
     lsvd_config() {}
+
+    void parse_json(str js);
+    void parse_file(str path, bool can_be_missing = true);
 };

src/image.cc

@@ -19,7 +19,8 @@ lsvd_image::lsvd_image(std::string name, rados_ioctx_t io, lsvd_config cfg_)
     : imgname(name), cfg(cfg_), io(io)
 {
     objstore = make_rados_backend(io);
-    rcache = get_read_cache_instance(cfg.rcache_dir, cfg.rcache_size, objstore);
+    rcache =
+        get_read_cache_instance(cfg.rcache_dir, cfg.rcache_bytes, objstore);
 
     read_superblock();
     debug("Found checkpoints: {}", checkpoints);

src/spdk_frontend.cc

@@ -181,7 +181,8 @@ static void start_lsvd(void *arg)
     auto trid = get_trid(HOSTNAME, PORT);
 
     // Add lsvd bdev
-    lsvd_config cfg;                    // TODO read this in from a config file
+    auto cfg =
+        lsvd_config::get_default(); // TODO read this in from a config file
     cfg.rcache_bytes = 160 * 1024 * 1024; // small 160mb cache for testing
     auto err = bdev_lsvd_create(args->image_name, io_ctx, cfg);
     assert(err == 0);
@@ -226,7 +227,6 @@ int main(int argc, const char **argv)
         return 1;
     }
 
-
     auto args = (start_lsvd_args){
         .pool_name = argv[1],
         .image_name = argv[2],
@@ -238,7 +238,6 @@ int main(int argc, const char **argv)
 
     debug("Args: pool={}, image={}", args.pool_name, args.image_name);
 
-
     spdk_app_opts opts = {.shutdown_cb = []() {
         log_info("Shutting down LSVD SPDK program ...");
         spdk_app_stop(0);

src/translate.cc

@@ -1111,7 +1111,7 @@ void translate_impl::do_gc(std::stop_token &st)
             workers->put_locked(req);
             lk.unlock();
 
-            while ((int)requests.size() > cfg.gc_write_window &&
+            while (requests.size() > cfg.gc_write_window &&
                    !st.stop_requested()) {
                 auto t = requests.front();
                 t->wait();