1 files changed, 98 insertions, 0 deletions
diff --git a/src/fluent-bit/plugins/in_tail/tail_signal.h b/src/fluent-bit/plugins/in_tail/tail_signal.h
new file mode 100644
index 000000000..1a81fec64
--- /dev/null
+++ b/src/fluent-bit/plugins/in_tail/tail_signal.h
@@ -0,0 +1,98 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+
+/*  Fluent Bit
+ *  ==========
+ *  Copyright (C) 2015-2022 The Fluent Bit Authors
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#ifndef FLB_TAIL_SIGNAL_H
+#define FLB_TAIL_SIGNAL_H
+
+#include "tail_config.h"
+
+static inline int tail_signal_manager(struct flb_tail_config *ctx)
+{
+    int n;
+    uint64_t val = 0xc001;
+
+    /*
+     * The number of signal reads might be less than the written signals, this
+     * means that some event is still pending in the queue. On that case we
+     * don't need to signal it again.
+     */
+    if (ctx->ch_reads < ctx->ch_writes) {
+        return 1;
+    }
+
+    /* Reset counters: prevent an overflow, unlikely..but let's keep safe */
+    if (ctx->ch_reads == ctx->ch_writes) {
+        ctx->ch_reads = 0;
+        ctx->ch_writes = 0;
+    }
+
+    /* Insert a dummy event into the channel manager */
+    n = flb_pipe_w(ctx->ch_manager[1], (const char *) &val, sizeof(val));
+    if (n == -1) {
+        flb_errno();
+        return -1;
+    }
+    else {
+        ctx->ch_writes++;
+    }
+
+    return n;
+}
+
+static inline int tail_signal_pending(struct flb_tail_config *ctx)
+{
+    int n;
+    uint64_t val = 0xc002;
+
+    /* Insert a dummy event into the 'pending' channel */
+    n = flb_pipe_w(ctx->ch_pending[1], (const char *) &val, sizeof(val));
+
+    /*
+     * If we get EAGAIN, it simply means pending channel is full. As
+     * notification is already pending, it's safe to ignore.
+     */
+    if (n == -1 && !FLB_PIPE_WOULDBLOCK()) {
+        flb_errno();
+        return -1;
+    }
+
+    return n;
+}
+
+static inline int tail_consume_pending(struct flb_tail_config *ctx)
+{
+    int ret;
+    uint64_t val;
+
+    /*
+     * We need to consume the pending bytes. Loop until we would have
+     * blocked (pipe is empty).
+     */
+    do {
+        ret = flb_pipe_r(ctx->ch_pending[0], (char *) &val, sizeof(val));
+        if (ret <= 0 && !FLB_PIPE_WOULDBLOCK()) {
+            flb_errno();
+            return -1;
+        }
+    } while (!FLB_PIPE_WOULDBLOCK());
+
+    return 0;
+}
+
+#endif