feat(logs): add before_send_log

examples/example.c

@@ -158,6 +158,33 @@ discarding_before_transaction_callback(sentry_value_t tx, void *user_data)
     return tx;
 }
 
+static sentry_value_t
+before_send_log_callback(sentry_value_t log, void *user_data)
+{
+    (void)user_data;
+    sentry_value_t attribute = sentry_value_new_object();
+    sentry_value_set_by_key(
+        attribute, "value", sentry_value_new_string("little"));
+    sentry_value_set_by_key(
+        attribute, "type", sentry_value_new_string("string"));
+    sentry_value_set_by_key(sentry_value_get_by_key(log, "attributes"),
+        "coffeepot.size", attribute);
+    return log;
+}
+
+static sentry_value_t
+discarding_before_send_log_callback(sentry_value_t log, void *user_data)
+{
+    (void)user_data;
+    if (sentry_value_is_null(
+            sentry_value_get_by_key(sentry_value_get_by_key(log, "attributes"),
+                "sentry.message.template"))) {
+        sentry_value_decref(log);
+        return sentry_value_new_null();
+    }
+    return log;
+}
+
 static void
 print_envelope(sentry_envelope_t *envelope, void *unused_state)
 {
@@ -374,6 +401,16 @@ main(int argc, char **argv)
             options, discarding_before_transaction_callback, NULL);
     }
 
+    if (has_arg(argc, argv, "before-send-log")) {
+        sentry_options_set_before_send_log(
+            options, before_send_log_callback, NULL);
+    }
+
+    if (has_arg(argc, argv, "discarding-before-send-log")) {
+        sentry_options_set_before_send_log(
+            options, discarding_before_send_log_callback, NULL);
+    }
+
     if (has_arg(argc, argv, "traces-sampler")) {
         sentry_options_set_traces_sampler(options, traces_sampler_callback);
     }
@@ -424,6 +461,9 @@ main(int argc, char **argv)
 
     // TODO incorporate into test
     if (sentry_options_get_enable_logs(options)) {
+        if (has_arg(argc, argv, "capture-log")) {
+            sentry_log_debug("I'm a log message!");
+        }
         if (has_arg(argc, argv, "logs-timer")) {
             for (int i = 0; i < 10; i++) {
                 sentry_log_info("Informational log nr.%d", i);

include/sentry.h

@@ -1883,6 +1883,23 @@ SENTRY_EXPERIMENTAL_API void sentry_log_warn(const char *message, ...);
 SENTRY_EXPERIMENTAL_API void sentry_log_error(const char *message, ...);
 SENTRY_EXPERIMENTAL_API void sentry_log_fatal(const char *message, ...);
 
+/**
+ * Type of the `before_send_log` callback.
+ *
+ * The callback takes ownership of the `log`, and should usually return
+ * that same log. In case the log should be discarded, the
+ * callback needs to call `sentry_value_decref` on the provided log, and
+ * return a `sentry_value_new_null()` instead.
+ */
+typedef sentry_value_t (*sentry_before_send_log_function_t)(
+    sentry_value_t log, void *user_data);
+
+/**
+ * Sets the `before_send_log` callback.
+ */
+SENTRY_EXPERIMENTAL_API void sentry_options_set_before_send_log(
+    sentry_options_t *opts, sentry_before_send_log_function_t func, void *data);
+
 #ifdef SENTRY_PLATFORM_LINUX
 
 /**

src/sentry_logs.c

@@ -328,12 +328,13 @@ skip_length(const char *fmt_ptr)
     return fmt_ptr;
 }
 
-static void
+// returns how many parameters were added to the attributes object
+static int
 populate_message_parameters(
     sentry_value_t attributes, const char *message, va_list args)
 {
     if (!message || sentry_value_is_null(attributes)) {
-        return;
+        return 0;
     }
 
     const char *fmt_ptr = message;
@@ -375,6 +376,7 @@ populate_message_parameters(
     }
 
     va_end(args_copy);
+    return param_index;
 }
 
 static void
@@ -494,18 +496,21 @@ construct_log(sentry_level_t level, const char *message, va_list args)
         "string", "sentry.sdk.name");
     add_attribute(attributes, sentry_value_new_string(sentry_sdk_version()),
         "string", "sentry.sdk.version");
-    add_attribute(attributes, sentry_value_new_string(message), "string",
-        "sentry.message.template");
 
     // Parse variadic arguments and add them to attributes
-    populate_message_parameters(attributes, message, args_copy_3);
+    if (populate_message_parameters(attributes, message, args_copy_3)) {
+        // only add message template if we have parameters
+        add_attribute(attributes, sentry_value_new_string(message), "string",
+            "sentry.message.template");
+    }
     va_end(args_copy_3);
 
     sentry_value_set_by_key(log, "attributes", attributes);
 
     return log;
 }
 
+// TODO change to int return
 void
 sentry__logs_log(sentry_level_t level, const char *message, va_list args)
 {
@@ -514,9 +519,24 @@ sentry__logs_log(sentry_level_t level, const char *message, va_list args)
         if (options->enable_logs)
             enable_logs = true;
     }
+    int discarded = false;
     if (enable_logs) {
         // create log from message
         sentry_value_t log = construct_log(level, message, args);
+        SENTRY_WITH_OPTIONS (options) {
+            if (options->before_send_log_func) {
+                log = options->before_send_log_func(
+                    log, options->before_send_log_data);
+                if (sentry_value_is_null(log)) {
+                    SENTRY_DEBUG(
+                        "log was discarded by the `before_send_log` hook");
+                    discarded = true;
+                }
+            }
+        }
+        if (discarded) {
+            return;
+        }
         if (!enqueue_log_single(log)) {
             sentry_value_decref(log);
         }

src/sentry_options.c

@@ -153,6 +153,14 @@ sentry_options_set_before_transaction(
     opts->before_transaction_data = user_data;
 }
 
+void
+sentry_options_set_before_send_log(sentry_options_t *opts,
+    sentry_before_send_log_function_t func, void *user_data)
+{
+    opts->before_send_log_func = func;
+    opts->before_send_log_data = user_data;
+}
+
 void
 sentry_options_set_dsn_n(
     sentry_options_t *opts, const char *raw_dsn, size_t raw_dsn_len)

src/sentry_options.h

@@ -52,6 +52,8 @@ struct sentry_options_s {
     void *on_crash_data;
     sentry_transaction_function_t before_transaction_func;
     void *before_transaction_data;
+    sentry_before_send_log_function_t before_send_log_func;
+    void *before_send_log_data;
 
     /* Experimentally exposed */
     double traces_sample_rate;

tests/test_integration_http.py

@@ -1382,3 +1382,66 @@ def test_logs_threaded(cmake, httpserver):
         total_count += envelope.items[0].headers["item_count"]
     print(f"Total amount of captured logs: {total_count}")
     assert total_count >= 100
+
+
+def test_before_send_log(cmake, httpserver):
+    tmp_path = cmake(["sentry_example"], {"SENTRY_BACKEND": "none"})
+
+    httpserver.expect_oneshot_request(
+        "/api/123456/envelope/",
+        headers={"x-sentry-auth": auth_header},
+    ).respond_with_data("OK")
+    env = dict(os.environ, SENTRY_DSN=make_dsn(httpserver), SENTRY_RELEASE="🤮🚀")
+
+    run(
+        tmp_path,
+        "sentry_example",
+        ["log", "enable-logs", "capture-log", "before-send-log"],
+        check=True,
+        env=env,
+    )
+
+    assert len(httpserver.log) == 1
+    req = httpserver.log[0][0]
+    body = req.get_data()
+
+    envelope = Envelope.deserialize(body)
+
+    # Show what the envelope looks like if the test fails.
+    envelope.print_verbose()
+
+    # Extract the log item
+    (log_item,) = envelope.items
+
+    assert log_item.headers["type"] == "log"
+    payload = log_item.payload.json
+
+    # Get the first log item from the logs payload
+    log_entry = payload["items"][0]
+    attributes = log_entry["attributes"]
+
+    # Check that the before_send_log callback added the expected attribute
+    assert "coffeepot.size" in attributes
+    assert attributes["coffeepot.size"]["value"] == "little"
+    assert attributes["coffeepot.size"]["type"] == "string"
+
+
+def test_before_send_log_discard(cmake, httpserver):
+    tmp_path = cmake(["sentry_example"], {"SENTRY_BACKEND": "none"})
+
+    httpserver.expect_oneshot_request(
+        "/api/123456/envelope/",
+        headers={"x-sentry-auth": auth_header},
+    ).respond_with_data("OK")
+    env = dict(os.environ, SENTRY_DSN=make_dsn(httpserver), SENTRY_RELEASE="🤮🚀")
+
+    run(
+        tmp_path,
+        "sentry_example",
+        ["log", "enable-logs", "capture-log", "discarding-before-send-log"],
+        check=True,
+        env=env,
+    )
+
+    # log should have been discarded
+    assert len(httpserver.log) == 0